Euan Mcleod

Interests

Research

My research interests lie at intersection of nano-photonics and soft materials science, in particular the study of systems with many individual components. I tackle both fundamental and applied problems, endeavoring to find solutions that can provide a clear future benefit to society. Two application areas of particular interest are nano-fabrication and microscopic bioimaging.

Teaching

Nanophotonics, biophotonics, microscopy, Fourier optics, surface science.

Courses

Scholarly Contributions

Chapters

• Mcleod, E., Mcleod, E., Ozcan, A., & Ozcan, A. (2015). Wide-field nano-scale imaging on a chip. In Applications of Nanoscience in Photomedicine. Chandos Publishing. doi:10.1533/9781908818782.9
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  : Wide-field imaging facilitates the detection of rare events and reduces imaging time for large-area samples. Nano-scale imaging enables the detection and enumeration of individual nanoparticles and sub-cellular bioparticles. Uniting these two capabilities in a compact and field-portable on-chip imaging platform through lensfree holographic microscopy provides deep submicron resolution with high sensitivity over fields of view in the range 10–1800 mm2 – approximately 150–2700 times larger than a typical 40 × objective field of view. High resolution is achieved via a pixel super-resolution approach, while high sensitivity is obtained via a sample preparation procedure that generates self-assembled nanolenses around individual nanoparticles and viruses. The foundations of these computational imaging approaches, along with their methodology and results, are discussed.
• McLeod, E., Luo, W., Mudanyali, O., Greenbaum, A., & Ozcan, A. (2013). Giga-pixel nanoimaging using computational on-chip microscopy. In 2013 IEEE Photonics Conference.

Journals/Publications

• Xu, Y., Stanko, A. M., Cerione, C. S., Lohrey, T. D., McLeod, E., Stoltz, B. M., & Su, J. (2024).

  Low Part-Per-Trillion, Humidity Resistant Detection of Nitric Oxide Using Microtoroid Optical Resonators

  . ACS Applied Materials & Interfaces, 16(4), 5120-5128. doi:10.1021/acsami.3c16012
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  The nitric oxide radical plays pivotal roles in physiological as well as atmospheric contexts. Although the detection of dissolved nitric oxide in vivo has been widely explored, highly sensitive (i.e. low part-per-trillion level), selective, and humidity resistant detection of gaseous nitric oxide in air remains challenging. In the field, humidity can have dramatic effects on the accuracy and selectivity of gas sensors, confounding data and leading to overestimation of gas concentration. Highly selective and humidity resistant gaseous NO sensors based on laser-induced graphene (LIG) were recently reported, displaying a limit of detection (LOD) of 8.3 ppb. Although highly sensitive (LOD = 590 ppq) single-wall carbon nanotube NO sensors have been reported, these sensors lack selectivity and humidity resistance. In this report, we disclose a highly sensitive (LOD = 2.34 ppt), selective, and humidity resistant nitric oxide sensor based on a whispering-gallery mode (WGM) microtoroid optical resonator. Excellent analyte selectivity was enabled via novel ferrocene-containing polymeric coatings synthesized via RAFT polymerization. Utilizing a Frequency Locked Optical Whispering Evanescent Resonator (FLOWER) system, the microtoroid’s real-time resonance frequency shift response to nitric oxide, was tracked with sub-femtometer resolution. The lowest concentration experimentally detected was 6.4 ppt, which is the lowest reported to date. Additionally, the performance of the sensor remained consistent across different humidity environments. Lastly, the impact of the chemical composition and molecular weight of the novel ferrocene-containing polymeric coatings on sensing performance was evaluated. We anticipate that our results will have impact on a wide variety of fields where NO sensing is important such as medical diagnostics through exhaled breath, determination of planetary habitability, marine science, climate change, air quality monitoring, and treating cardiovascular and neurological disorders.
• Baker, M., & McLeod, E. (2023).

  Lensfree time-gated photoluminescent imaging

  . APL Photonics, 8, 061301. doi:10.1063/5.0148217
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  Fluorescence and, more generally, photoluminescence enable high contrast imaging of targeted regions of interest through the use of photoluminescent probes with high specificity for different targets. Fluorescence can be used for rare cell imaging; however, this often requires a high space-bandwidth product: simultaneous high resolution and large field of view. With bulky traditional microscopes, high space-bandwidth product images require time-consuming mechanical scanning and stitching. Lensfree imaging can compactly and cost-effectively achieve a high space-bandwidth product in a single image through computational reconstruction of images from diffraction patterns recorded over the full field of view of standard image sensors. Many methods of lensfree photoluminescent imaging exist, where the excitation light is filtered before the image sensor, often by placing spectral filters between the sample and sensor. However, the sample-to-sensor distance is one of the limiting factors on resolution in lensfree systems and so more competitive performance can be obtained if this distance is reduced. Here, we show a time-gated lensfree photoluminescent imaging system that can achieve a resolution of 8.77 µm. We use europium chelate fluorophores because of their long lifetime (642 µs) and trigger camera exposure ∼50 µs after excitation. Because the excitation light is filtered temporally, there is no need for physical filters, enabling reduced sample-to-sensor distances and higher resolutions.
• Baker, M., Gollier, F., Melzer, J. E., & McLeod, E. (2023).

  Lensfree Air-Quality Monitoring of Fine and Ultrafine Particulate Matter Using Vapor-Condensed Nanolenses

  . ACS Applied Nano Materials, 6(13), 11166-11174. doi:10.1021/acsanm.3c01154
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  Current commercial air-quality monitoring devices lack a large dynamic range, especially at the small, ultrafine size scale. Furthermore, there is a low density of air-quality monitoring stations, reducing the precision with which local particulate matter hazards can be tracked. Here, we show a low-cost, lensfree, and portable air-quality monitoring device (LPAQD) that can detect and measure micron-sized particles down to 100 nm-sized particles, with the capability to track and measure particles in real time throughout a day and the ability to accurately measure particulate matter densities as low as 3 μg m-3. A vapor-condensed film is deposited onto the coverslip used to collect particles before the LPAQD is deployed at outdoor monitoring sites. The vapor-condensed film increases the scattering cross section of particles smaller than the pixel size, enabling the sub-pixel and sub-diffraction-limit-sized particles to be detected. The high dynamic range, low cost, and portability of this device can enable citizens to monitor their own air quality to hopefully impact user decisions that reduce the risk for particulate matter-related diseases.
• Liu, W., & McLeod, E. (2023).

  Fast and accurate electromagnetic field calculation for substrate-supported metasurfaces using the discrete dipole approximation

  . Nanophotonics, 12(22), 4157-4173. doi:10.1515/nanoph-2023-0423
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  Abstract Metasurface design tends to be tedious and time-consuming based on sweeping geometric parameters. Common numerical simulation techniques are slow for large areas, ultra-fine grids, and/or three-dimensional simulations. Simulation time can be reduced by combining the principle of the discrete dipole approximation (DDA) with analytical solutions for light scattered by a dipole near a flat surface. The DDA has rarely been used in metasurface design, and comprehensive benchmarking comparisons are lacking. Here, we compare the accuracy and speed of three DDA methods—substrate discretization, two-dimensional Cartesian Green’s functions, and one-dimensional (1D) cylindrical Green’s functions—against the finite difference time domain (FDTD) method. We find that the 1D cylindrical approach performs best. For example, the s -polarized field scattered from a silica-substrate-supported 600 × 180 × 60 nm gold elliptic nanocylinder discretized into 642 dipoles is computed with 0.78 % pattern error and 6.54 % net power error within 294 s, which is 6 times faster than FDTD. Our 1D cylindrical approach takes advantage of parallel processing and also gives transmitted field solutions, which, to the best of our knowledge, is not found in existing tools. We also examine the differences among four polarizability models: Clausius–Mossotti, radiation reaction, lattice dispersion relation, and digitized Green’s function, finding that the radiation reaction dipole model performs best in terms of pattern error, while the digitized Green’s function has the lowest power error.
• McLeod, E., Li, C., Lohrey, T., Nguyen, P., Min, Z., Tang, Y., Ge, C., Sercel, Z. P., Stoltz, B. M., & Su, J. (2022). Part-per-Trillion Trace Selective Gas Detection Using Frequency Locked Whispering-Gallery Mode Microtoroids. ACS Applied Materials & Interfaces, 14(37), 42430-42440. doi:10.1021/acsami.2c11494
• McLeod, E., Wang, J., Xiong, Z., Hu, Y., & Potter, C. J. (2022). Point-of-care SARS-CoV-2 sensing using lens-free imaging and a deep learning-assisted quantitative agglutination assay. Lab on a Chip, 22(19), 3744-3754. doi:10.1039/d2lc00289b
• Baker, M., Liu, W., & Mcleod, E. (2021). Accurate and fast modeling of scattering from random arrays of nanoparticles using the discrete dipole approximation and angular spectrum method. Optics Express, 29(14), 22761-22777. doi:10.1364/OE.431754
• McLeod, E., Liu, W., & Baker, M. (2021). Accurate and fast modeling of scattering from random arrays of nanoparticles using the discrete dipole approximation and angular spectrum method. Optics Express, 29(14), 22761. doi:10.1364/oe.431754
• McLeod, E., Xiong, Z., & Potter, C. J. (2021). High-Speed Lens-Free Holographic Sensing of Protein Molecules Using Quantitative Agglutination Assays. ACS Sensors, 6(3), 1208-1217. doi:10.1021/acssensors.0c02481
• Melzer, J. E., & Mcleod, E. (2021). Assembly of multicomponent structures from hundreds of micron-scale building blocks using optical tweezers. Microsystems & Nanoengineering, 7(1), 1-9. doi:10.1038/s41378-021-00272-z
• Xiong, Z., Potter, C. J., & Mcleod, E. (2021). High-speed lens-free holographic sensing of protein molecules using quantitative agglutination assays. ACS Sensors, 6(3), 1208-1217. doi:10.1021/acssensors.0c02481
• Zhang, H., Jiao, Z., & Mcleod, E. (2020). Tunable terahertz hyperbolic metamaterial slabs and super-resolving hyperlenses. Applied Optics, 59(22), G64-G70. doi:10.1364/AO.391952
• Chen, L., Li, C., Liu, Y., Su, J., & Mcleod, E. (2020). Three-Dimensional Simulation of Particle-Induced Mode Splitting in Large Toroidal Microresonators. Sensors, 20(18), 5420. doi:10.3390/s20185420
• McLeod, E., & Melzer, J. E. (2020). 3D Nanophotonic device fabrication using discrete components. Nanophotonics, 9(6), 1373-1390. doi:10.1515/nanoph-2020-0161
• Melzer, J. E., & McLeod, E. (2020). 3D Nanophotonic device fabrication using discrete components. Nanophotonics, 9(6), 1373-1390. doi:10.1515/nanoph-2020-0161
• Potter, C. J., & Mcleod, E. (2020). How Covid-19 Diagnostic Tests Work. Nanoscientific.org.
• Xiong, Z., & Mcleod, E. (2020). Quantitative large area binding sensor using a high-speed lens-free holographic microscope. Frontiers in Optics. doi:10.1364/fio.2020.fth1a.4
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  Aggregation of > 104 beads due to specific protein molecules is quantified using microfluidic chips, fast lens-free microscopes, and image processing algorithms. The limit of detection, cost, and size are appropriate for COVID-19 point-of-care testing.
• Chen, L., Li, C., Liu, Y., Su, T. J., & Mcleod, E. (2019). Simulating robust far-field coupling to travelling waves in large three-dimensional nanostructured high-Q microresonators. Photonics Research, 7(9), 967-976.
• Fiedler, K. R., Mcleod, E., & Troian, S. M. (2019). Differential colorimetry measurements of fluctuation growth in nanofilms exposed to large surface thermal gradients. Journal of Applied Physics, 125(6), 065303.
• Li, C., Chen, L., Mcleod, E., & Su, T. J. (2019). Dark mode plasmonic optical microcavity biochemical sensor. Photonics Research, 7(8), 939-947.
• Liu, W., & Mcleod, E. (2019). Accuracy of the skin depth correction for metallic nanoparticle polarizability. Journal of Physical Chemistry C, 123(20), 13009-13014.
• McLeod, E., & Liu, W. (2019). Accuracy of the Skin Depth Correction for Metallic Nanoparticle Polarizability. The Journal of Physical Chemistry C, 123(20), 13009-13014. doi:10.1021/acs.jpcc.9b01672
• McLeod, E., Fiedler, K. R., & Troian, S. M. (2019). Differential colorimetry measurements of fluctuation growth in nanofilms exposed to large surface thermal gradients. Journal of Applied Physics, 125(6), 065303. doi:10.1063/1.5051456
• McLeod, E., & Melzer, J. E. (2018). Fundamental Limits of Optical Tweezer Nanoparticle Manipulation Speeds. ACS Nano, 12(3), 2440-2447. doi:10.1021/acsnano.7b07914
• Mcleod, E., & Ozcan, A. (2018). Microscopy without lenses. Optronics, 37(435), 65.
• Melzer, J. E., & Mcleod, E. (2018). Fundamental limits of optical tweezer nanoparticle manipulation speeds. ACS Nano, 12(3), 2440-2447. doi:10.1021/acsnano.7b07914
• Xiong, Z., Melzer, J. E., Garan, J., & Mcleod, E. (2018). Optimized sensing of sparse and small targets using lens-free holographic microscopy. Optics Express, 26(20), 25676-25692. doi:10.1364/OE.26.025676
• Daloglu, M. U., Ray, A., Gorocs, Z., Xiong, M., Malik, R., Bitan, G., Mcleod, E., & Ozcan, A. (2017). Computational on-chip imaging of nanoparticles and biomolecules using ultraviolet light. Scientific Reports, 7, 44157. doi:10.1038/srep44157
• Mcleod, E. (2017). 3D Nanophotonic Systems for Biosensing and Integrated Photonics. Frontiers in Optics. doi:10.1364/fio.2017.ftu5d.1
• Mcleod, E., & Ozcan, A. (2017). Microscopy without lenses. Physics Today, 70(9), 50. doi:10.1063/PT.3.3693
• Melzer, J. E., Mcleod, E., & Garan, J. (2017). Liquid polymeric materials for optical nano-bio sensing. Proceedings of SPIE, 10100. doi:10.1117/12.2252970
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  Detecting, counting, and sizing nanoparticles is a key problem in biomedical, environmental, and materials synthesis fields. Here we demonstrate a cost-effective and high-performance approach that uses wide-field microscopy enabled by the combination of inline lensfree holography, pixel super-resolution, and vapor-condensed nano-scale lenses (nanolenses). These nanolenses are composed of liquid polyethylene glycol (PEG) that self-assembles in situ around particles of interest. A nanolens around each particle generates a more substantial phase shift than the native object alone, making it more easily detectible in the imaging system. This latest generation of lensfree holographic microscope incorporates more precise temperature control and utilizes a hermetically sealed chamber allowing for a controlled, repeatable environment for simultaneous hologram measurements and nanolens formation. To further enhance the sensitivity of our system, we have compared the performance of two different pixel super-resolution algorithms: shiftand- add and gradient descent. It was found that the gradient descent approach provides the highest resolution. Detection and localization results for 1 μm, 400 nm, and 100 nm particles are presented.
• Ray, A., Daloglu, M. U., Ho, J., Torres, A., Mcleod, E., & Ozcan, A. (2017). Computational sensing of herpes simplex virus using a cost-effective on-chip microscope. Scientific Reports, 7, 4856. doi:10.1038/s41598-017-05124-3
• McLeod, E., & Ozcan, A. (2016). Lensless Imaging and Sensing. Annual Review of Biomedical Engineering, 18(1), 77-102. doi:10.1146/annurev-bioeng-092515-010849
• Mcleod, E. (2016). High-throughput nanoparticle sizing using lensfree holographic microscopy and liquid nanolenses(Conference Presentation). Proceedings of SPIE, 9718. doi:10.1117/12.2211933
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  The sizing of individual nanoparticles and the recovery of the distributions of sizes from populations of nanoparticles provide valuable information in virology, exosome analysis, air and water quality monitoring, and nanomaterials synthesis. Conventional approaches for nanoparticle sizing include those based on costly or low-throughput laboratory-scale equipment such as transmission electron microscopy or nanoparticle tracking analysis, as well as those approaches that only provide population-averaged quantities, such as dynamic light scattering. Some of these limitations can be overcome using a new family of alternative approaches based on quantitative phase imaging that combines lensfree holographic on-chip microscopy with self-assembled liquid nanolenses. In these approaches, the particles of interest are deposited onto a glass coverslip and the sample is coated with either pure liquid polyethylene glycol (PEG) or aqueous solutions of PEG. Due to surface tension, the PEG self-assembles into nano-scale lenses around the particles of interest. These nanolenses enhance the scattering signatures of the embedded particles such that individual nanoparticles as small as 40 nm are clearly visible in phase images reconstructed from captured holograms. The magnitude of the phase quantitatively corresponds to particle size with an accuracy of +/-11 nm. This family of approaches can individually size more than 10^5 particles in parallel, can handle a large dynamic range of particle sizes (40 nm – 100s of microns), and can accurately size multi-modal distributions of particles. Furthermore, the entire approach has been implemented in a compact and cost-effective device suitable for use in the field or in low-resource settings.
• Mcleod, E. (2016). Nanoparticle and Virus Sensing Enabled by Computational Lensfree Imaging. Frontiers in Optics. doi:10.1364/fio.2016.fth4c.1
• Mcleod, E., & Ozcan, A. (2016). Unconventional methods of imaging: computational microscopy and compact implementations. Reports on Progress in Physics, 79(7), 076001. doi:10.1088/0034-4885/79/7/076001
• Ozcan, A., & McLeod, E. (2016). Lensless Imaging and Sensing. Annual Review of Biomedical Engineering, 18, 77-102. doi:10.1146/annurev-bioeng-092515-010849
• G{\"o}r{\"o}cs, Z., McLeod, E., & Ozcan, A. (2015). Enhanced light collection in fluorescence microscopy using self-assembled micro-reflectors. Scientific reports, 5.
• Koydemir, H. C., Gorocs, Z., Tseng, D., Cortazar, B., Feng, S., Chan, R. Y., Burbano, J., McLeod, E., & Ozcan, A. (2015). Rapid imaging, detection and quantification of Giardia lamblia cysts using mobile-phone based fluorescent microscopy and machine learning. Lab on a chip, 15, 1284--1293.
• McLeod, E., Dincer, T. U., Veli, M., Ertas, Y. N., Nguyen, C., Luo, W., Greenbaum, A., Feizi, A., & Ozcan, A. (2015). High-Throughput and Label-Free Single Nanoparticle Sizing Based on Time-Resolved On-Chip Microscopy. ACS nano, 9, 3265--3273.
• McLeod, E., Wei, Q., & Ozcan, A. (2015). Democratization of Nanoscale Imaging and Sensing Tools Using Photonics. Analytical chemistry, 87, 6434--6445.
• McLeod, E., & Ozcan, A. (2014). Nano-imaging enabled via self-assembly. Nano today, 9, 560--573.
• McLeod, E., Nguyen, C., Huang, P., Luo, W., Veli, M., & Ozcan, A. (2014).

  Tunable Vapor-Condensed Nanolenses

  . ACS Nano, 8(7), 7340-7349. doi:10.1021/nn502453h
• McLeod, E., Nguyen, C., Huang, P., Luo, W., Veli, M., & Ozcan, A. (2014). Tunable vapor-condensed nanolenses. ACS nano, 8, 7340--7349.
• Hennequin, Y., Allier, C. P., McLeod, E., Mudanyali, O., Migliozzi, D., Ozcan, A., & Dinten, J. (2013). Optical detection and sizing of single nanoparticles using continuous wetting films. ACS nano, 7, 7601--7609.
• Hennequin, Y., Allier, C., McLeod, E., Mudanyali, O., Migliozzi, D., Ozcan, A., & Dinten, J. (2013).

  Optical Detection and Sizing of Single Nanoparticles Using Continuous Wetting Films

  . ACS Nano, 7(9), 7601-7609. doi:10.1021/nn403431y
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  The physical interaction between nanoscale objects and liquid interfaces can create unique optical properties, enhancing the signatures of the objects with subwavelength features. Here we show that the evaporation on a wetting substrate of a polymer solution containing submicrometer or nanoscale particles creates liquid microlenses that arise from the local deformations of the continuous wetting film. These microlenses have properties similar to axicon lenses that are known to create beams with a long depth of focus. This enhanced depth of focus allows detection of single nanoparticles using a low-magnification microscope objective lens, achieving a relatively wide field-of-view, while also lifting the constraints on precise focusing onto the object plane. Hence, by creating these liquid axicon lenses through spatial deformations of a continuous thin wetting film, we transfer the challenge of imaging individual nanoparticles to detecting the light focused by these lenses. As a proof of concept, we demonstrate the detection and sizing of single nanoparticles (100 and 200 nm), CpGV granuloviruses, as well as Staphylococcus epidermidis bacteria over a wide field-of-view of 5.10 × 3.75 mm2 using a 5× objective lens with a numerical aperture of 0.15. In addition to conventional lens-based microscopy, this continuous wetting-film-based approach is also applicable to lens-free computational on-chip imaging, which can be used to detect single nanoparticles over a large field-of-view of >20–30 mm2. These results could be especially useful for high-throughput field analysis of nanoscale objects using compact and cost-effective microscope designs.
• McLeod, E., Luo, W., Mudanyali, O., Greenbaum, A., & Ozcan, A. (2013). Toward giga-pixel nanoscopy on a chip: a computational wide-field look at the nano-scale without the use of lenses. Lab on a chip, 13, 2028--2035.
• Mudanyali, O., McLeod, E., Luo, W., Greenbaum, A., Coskun, A. F., Hennequin, Y., Allier, C. P., & Ozcan, A. (2013). Wide-field optical detection of nanoparticles using on-chip microscopy and self-assembled nanolenses. Nature photonics, 7, 247--254.
• Su, T., Choi, I., Feng, J., Huang, K., McLeod, E., & Ozcan, A. (2013).

  Sperm Trajectories Form Chiral Ribbons

  . Scientific Reports, 3, 1664. doi:10.1038/srep01664
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  We report the discovery of an entirely new three-dimensional (3D) swimming pattern observed in human and horse sperms. This motion is in the form of 'chiral ribbons', where the planar swing of the sperm head occurs on an osculating plane creating in some cases a helical ribbon and in some others a twisted ribbon. The latter, i.e., the twisted ribbon trajectory, also defines a minimal surface, exhibiting zero mean curvature for all the points on its surface. These chiral ribbon swimming patterns cannot be represented or understood by already known patterns of sperms or other micro-swimmers. The discovery of these unique patterns is enabled by holographic on-chip imaging of >33,700 sperm trajectories at >90-140 frames/sec, which revealed that only ~1.7% of human sperms exhibit chiral ribbons, whereas it increases to ~27.3% for horse sperms. These results might shed more light onto the statistics and biophysics of various micro-swimmers' 3D motion.
• Su, T., Choi, I., Feng, J., Huang, K., McLeod, E., & Ozcan, A. (2013). Sperm trajectories form chiral ribbons. Scientific reports, 3.
• Wei, Q., McLeod, E., Qi, H., Wan, Z., Sun, R., & Ozcan, A. (2013).

  On-Chip Cytometry using Plasmonic Nanoparticle Enhanced Lensfree Holography

  . Scientific Reports, 3, 1699. doi:10.1038/srep01699
• Wei, Q., McLeod, E., Qi, H., Wan, Z., Sun, R., & Ozcan, A. (2013). On-chip cytometry using plasmonic nanoparticle enhanced lensfree holography. Scientific reports, 3.
• McLeod, E., & Ozcan, A. (2012). Nanofabrication using near-field optical probes. Journal of laboratory automation, 17, 248--254.
• McLeod, E., & Özcan, A. (2012).

  Nanofabrication Using Near-Field Optical Probes

  . Journal of Laboratory Automation, 17(4), 248-254. doi:10.1177/2211068212450289
• McLeod, E., Liu, Y., & Troian, S. M. (2011).

  Experimental Verification of the Formation Mechanism for Pillar Arrays in Nanofilms Subject to Large Thermal Gradients

  . Physical Review Letters, 106, 175501. doi:10.1103/physrevlett.106.175501
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  The free surface of molten nanofilms is known to undergo spontaneous formation of periodic protrusions when exposed to a large transverse thermal gradient. Early time measurements of the array pitch and growth rate in polymer melts confirm a formation process based on a long wavelength thermocapillary instability and not electrostatic attraction or acoustic phonon driven growth as previously believed. We find excellent agreement with theoretical predictions provided the nanofilm out-of-plane thermal conductivity is several times larger than bulk, an enhancement suggestive of polymer chain alignment.
• McLeod, E., Liu, Y., & Troian, S. M. (2011). Experimental verification of the formation mechanism for pillar arrays in nanofilms subject to large thermal gradients. Physical review letters, 106, 175501.
• Fardel, R., McLeod, E., Tsai, Y., & Arnold, C. B. (2010). Nanoscale ablation through optically trapped microspheres. Applied Physics A, 101, 41--46.
• McLeod, E. (2009). Bessel beams in tunable acoustic gradient index lenses and optical trap assisted nanolithography.
• McLeod, E., & Arnold, C. B. (2009). Array-based optical nanolithography using optically trapped microlenses. Optics express, 17, 3640--3650.
• Joy, J., McLeod, E., & Arnold, C. B. (2008). Optical Trap Assisted Nanoscale Laser Direct-Write Patterning. 27th International Congress on Applications of Lasers and Electro-Optics Proceedings.
• Lipp, T., Mermillod-Blondin, A., McLeod, E., & Arnold, C. B. (2008). RAPID BEAM SHAPING AND FOCUSSING USING TUNABLE ACOUSTIC GRADIENT INDEX LENSES.
• McLeod, E., & Arnold, C. B. (2008). Optical analysis of time-averaged multiscale Bessel beams generated by a tunable acoustic gradient index of refraction lens. Applied optics, 47, 3609--3618.
• Mcleod, E., & Arnold, C. B. (2008). Subwavelength direct-write nanopatterning using optically trapped microspheres. Nature nanotechnology, 3, 413--417.
• Mermillod-Blondin, A., McLeod, E., & Arnold, C. B. (2008). Dynamic pulsed-beam shaping using a TAG lens in the near UV. Applied Physics A, 93, 231--234.
• Mermillod-Blondin, A., McLeod, E., & Arnold, C. B. (2008). High-speed varifocal imaging with a tunable acoustic gradient index of refraction lens. Optics letters, 33, 2146--2148.
• Arnold, C. B., & McLeod, E. (2007). A new approach to adaptive optics for materials processing. Photonics Spectra, 41, 78--79.
• McLeod, E., & Arnold, C. B. (2007). Mechanics and refractive power optimization of tunable acoustic gradient lenses. Journal of Applied Physics, 102, 033104.
• McLeod, E., Hopkins, A. B., & Arnold, C. B. (2006). Multiscale Bessel beams generated by a tunable acoustic gradient index of refraction lens. Optics letters, 31, 3155--3157.

Proceedings Publications

• Kim, D., Chalifoux, B. D., Furenlid, L. R., Jessen, P., Jones, J. P., Koshel, J., Lemon, C., Mansuripur, M., & McLeod, E. (2023).

  Optical Sciences Winter School for enabling future students in optics society

  . In SPIE Conference on Education and Training in Optics and Photonics: ETOP, 12723, 127231D.
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  Optical Sciences and Photonics are areas of growing importance that are too often missing from traditional undergraduate science and engineering curricula. Often, aspects of optics and photonics are picked up as side topics in undergraduate and graduate courses along the way to obtaining more traditional STEM (Science, Technology, Engineering and Mathematics) degrees. Since 2016, the annual Optical Sciences Winter School has been held during the winter break of the University of Arizona’s academic calendar. Its annual participants are now approximately 50 – 60 undergraduate students (mostly juniors and seniors) from US (United States) Universities who demonstrate an aptitude and talent for science and research. These students participate in a three- to five-day immersion experience, learning the many opportunities and benefits that choosing optics and photonics for their graduate studies can offer. The Optical Sciences Winter School (OSWS) brings together a motivated group of undergraduate students for a series of overview lectures teaching foundational topics in optics and their relation to current research. It also provides a forum for faculty, alumni, and invited guests to share results, approaches and methodologies in optics and photonics research and education that are unique to the undergraduate setting. This event is not focused on a specific school’s program but tries to highlight the diverse optics programs in the US. Many sessions in the program are filled with various invited faculties and researchers’ presentations from prominent optical physics and engineering undergraduate or graduate institutions.
• McLeod, E. (2023).

  Automated Photonic Material and Device Assembly Using Optical Tweezers

  . In Novel Optical Materials and Applications (NOMA), Advanced Photonics Congress, NoW4C.4.
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  We use optical positioning and linking (OPAL) to assemble heterogeneous micro and nanoparticle building blocks into large, complex structures comprising hundreds of particles. One application of interest is augmenting microtoroid optical chemosensors for robust coupling.
• McLeod, E. (2023).

  Optical Tweezers for 3D Assembly and Enhancement of Optical Chemosensors

  . In Conference on Lasers and Electro-Optics (CLEO), SW4P.3.
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  We use automated optical tweezers to assemble 3D micro- and nano-structured systems out of hundreds of building blocks of various materials. In particular, microtoroid chemosensors can be augmented with particles for improved optical coupling.
• McLeod, E., Potter, C. J., & Baker, M. (2023).

  Biological and Environmental Sensors Based on Lensfree Microscopes

  . In Conference on Lasers and Electro-Optics (CLEO), STu4O.1.
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  Lensfree microscopes offer an ultra-large field of view together with high res-olution and cost-effective, compact hardware. This makes them well suited for the COVID-19 and airborne nanoparticulate matter sensing applications we present here.
• Baker, M., Li, W., & McLeod, E. (2022).

  Improved accuracy and speed of nanoscale digital holographic microscopy

  . In SPIE Photonics West.
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  Scattering from nanoparticles has previously been utilized to achieve sub-wavelength resolution in microscopy, sub-diffraction beam widths in focused laser beams, and improved sensitivity in biological sensing. However, these applications often require time-consuming detailed vectorial simulation of the interaction of incident fields with the nanoparticles to achieve the desired performance. On the other hand, the scalar angular spectrum method is widely used for rapid holographic reconstruction, but can be inaccurate for sub-wavelength features, depending on the light-matter interaction model. Here we establish the domains of accuracy of three scalar light-matter interaction models for arrays of randomly distributed dielectric and metallic nanoparticles.
• Baker, M., Melzer, J. E., Gollier, F., Garan, J., & McLeod, E. (2022).

  Vapor-condensed nano-lenses for air-quality monitoring with a lensfree imaging system

  . In Conference on Lasers and Electro-Optics (CLEO).
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  Many air-quality monitoring devices can detect different sizes of particles but cannot quantify individual particle sizes across the range 0.1-10 μm. Here we show such a device that is furthermore cost-effective and portable.
• Li, W., & McLeod, E. (2022).

  Efficiently and accurately engineering substrate-supported nanostructures using the coupled dipole method

  . In SPIE Photonics West.
• McLeod, E. (2022).

  3D assembly using optical tweezers and biomolecular linkers

  . In SPIE Photonics West.
• McLeod, E., Xiong, Z., Baker, M., Potter, C. J., & Li, W. (2022).

  Small particle imaging using lensfree holographic microscopy for protein sensing diagnostics

  . In SPIE Photonics West.
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  Bead-based assays are traditionally difficult to adapt for high-sensitivity quantitative point-of-care diagnostics. Here we use lensfree optical microscopes with automated image processing to quantitatively sense specific proteins in solution via the agglutination of functionalized beads within a microfluidic chip. Simple protocols and compact and inexpensive readout devices make our approach well-suited for point-of-care diagnostics. We sense interferon gamma, a biomarker of infectious and inflammatory disease, as well as NeutrAvidin. Furthermore, we discuss computational methods for improving the identification of small particles in the lensfree images, including sparsity-promoting regularized reconstruction and vectorial Green’s function modeling based on dipole electromagnetic scattering theory.
• Melzer, J. E., & McLeod, E. (2022).

  Optical positioning and linking for additive assembly

  . In SPIE Photonics West.
• Melzer, J. E., Shultz, N. K., & McLeod, E. (2022).

  Microscale Additive Assembly with Optical Tweezers

  . In Conference on Lasers and Electro-Optics (CLEO).
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  The ability to fabricate three-dimensional structures with microscale resolution is critical to many emerging applications. We use an optical tweezers platform with biochemical linking mechanism to assemble 3D structures consisting of hundreds of individual building blocks.
• Sreevatsan, S., Potter, C. J., & McLeod, E. (2022).

  Deep Learning Optimization for Lens-Free Holographic Imaging and SARS-CoV-2 Biosensing

  . In Frontiers in Optics.
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  Rapid biosensing assays to detect SARS-CoV-2 are critical in mitigating the impact of the pandemic. Here, we use a lens-free holographic microscope coupled with deep learning in a rapid and sensitive assay to detect SARS-CoV-2.
• Baker, M., Li, W., & McLeod, E. (2021).

  Methods for computing nanoparticle scattering for improved lens-free digital holographic imaging

  . In SPIE Optics + Photonics.
• Baker, M., Liu, W., & Mcleod, E. (2021). Accurate and fast modeling of scattering from random arrays of nanoparticles using the discrete dipole approximation and angular spectrum method. In Photonics West, 11658, 116580G.
• Liu, W., & Mcleod, E. (2020, May). Accurate electromagnetic field and optical force calculations for metallic nanoparticles. In Conference on Lasers and Electro-Optics (CLEO), FM4Q. 2.
• Mcleod, E., & Liu, W. (2021). Accounting for substrate-particle interactions in metasurfaces using fast discrete dipole approximation simulations. In High Contrast Metastructures X, 11695.
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  Metasurfaces are planar nanostructured optical elements for lensing, wave-front shaping, and polarization control. A general but time-consuming metasurface design tool is the finite difference time domain (FDTD) technique. The discrete dipole approximation (DDA) is a rigorous and fast alternative for computing the electromagnetic field scattered by particles, but has not been widely used in metasurface design because of the complicated numerical difficulties imposed by the nanostructure-substrate interaction. Here we present a substrate-compatible DDA formulation using a 1D Green’s function method under cylindrical coordinates, proving that DDA can be a promising alternative method to design and optimize nanophotonic devices.
• Melzer, J. E., & McLeod, E. (2021).

  Optical positioning and linking for nanoscale assembly

  . In SPIE Optics + Photonics.
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  Three-dimensional (3D) structures with nanoscale building blocks often benefit from light-matter interaction at the nanometer size scale. The most popular existing technologies for the 3D fabrication of these small structures (e.g. direct laser writing) typically encounter significant restrictions. Here we demonstrate our optical positioning and linking (OPAL) platform for the assembly of multi-material 3D devices consisting of nanoscale components. OPAL integrates an optical trapping setup with a computer-controlled motion platform, microfluidic building block delivery apparatus, and imaging feedback system, overcoming the limitations of many traditional nanofabrication approaches, and establishing a versatile tool for the fabrication of complex 3D nanophotonic structures.
• Melzer, J. E., & Mcleod, E. (2021). Multicomponent structure assembly with optical tweezers. In Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XIV, 11696.
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  The optical tweezers platform provides an attractive approach for the fabrication of three-dimensional structures. Existing studies on optical tweezers assembly have mostly focused on the formation of small-scale structures consisting of a single type of dielectric building block. In this work, we demonstrate the potential of our automated optical positioning and linking (OPAL) platform that uses optical trapping for object manipulation and biochemical binding as a linking mechanism. We show a comprehensive analysis of system parameters and fabricate the largest microstructure built to date using this approach. Furthermore, we assemble multicomponent structures consisting of nanoscale building blocks.
• Potter, C. J., Xiong, Z., & Mcleod, E. (2021). Quantitative Large-Area Agglutination Assay Sensing of Protein Molecules in Solution. In Biophotonics Congress, DM1A.7.
• Xiong, Z., & Mcleod, E. (2021). Protein sensing in solution using a high-speed lens-free holographic microscope. In Optical Diagnostics and Sensing XXI: Toward Point-of-Care Diagnostics, 11651.
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  Lens-free holographic microscopy (LFHM) is cost-effective and field-portable, making it a promising diagnostic approach for point-of-care applications. However, LFHM has not yet been applied to protein molecule sensing in solution . Here we develop a quantitative large-area binding sensor by combining a high-speed LFHM with a one-step bead-based agglutination assay, where agglutination of >10^4 2-μm beads in solution undergoing Brownian motion are imaged and quantified. We sense NeutrAvidin molecules and interferon-gamma (an immune system biomarker) in solution, achieving a limit of detection of
• Baker, M. T., Liu, W., & McLeod, E. (2020, September). Accurate and fast modeling of scattering from random arrays of nanoparticles using the discrete dipole approximation and angular spectrum method. In Frontiers in Optics, FW7A. 7.
• McLeod, E., & Melzer, J. E. (2020, May). Optical Manipulation of Nanoparticles for Assembly of 3D Devices and Materials. In Conference on Lasers and Electro-Optics (CLEO), SF1R.3.
• Mcleod, E., & Liu, W. (2020). Rigorous and fast computation of plasmonic particle-substrate interactions. In Plasmonics: Design, Materials, Fabrication, Characterization, and Applications XVIII, 11462.
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  As powerful wave-front shapers, meta-surfaces can be used as planar lenses, polarizers, vortex generators, and other components. A general design approach is the finite difference time domain (FDTD) technique, which is robust but computationally costly. The discrete dipole approximation (DDA) is a rigorous and fast alternative, but has not been widely used in nanophotonic design because of computational complexity resulting from dipole-substrate interactions. Here we present a substrate-compatible DDA formulation using a one-dimensional Green’s function in cylindrical coordinates that accurately handles singularities and high-frequency oscillations. It is significantly faster with similar accuracy compared to several other methods, including FDTD.
• Melzer, J. E., & Mcleod, E. (2020). Assembling nanoscale building blocks in 3D using optical tweezers. In Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XVII.
• Melzer, J. E., & Mcleod, E. (2020). Automated 3D assembly of hundreds of building blocks using optical tweezers. In Optical Trapping and Optical Micromanipulation XVII, 11463.
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  For many micro- and nano-photonic applications, current 3D prototyping approaches are unable to provide the necessary resolution or material integration. Optical tweezers (OT) are a potentially attractive solution due to their ability to manipulate various small objects with high precision. Here we show a custom-built automated OT 3D assembly platform that operates with manipulation speeds up to 0.22 mm/s and positioning accuracy better than 50 nm. Furthermore, to the best of our knowledge, we assemble the largest 3D structure to date using an OT platform, consisting of several hundred objects of multiple compositions.
• Melzer, J. E., & Mcleod, E. (2020, February). Optical tweezers for micro-and nano-assembly. In Photonics West, 11292, 1129209.
• Melzer, J. E., Mcleod, E., & Liu, W. (2020). Directed assembly of 3D nanophotonic systems from building blocks (Conference Presentation). In Photonic and Phononic Properties of Engineered Nanostructures X.
• Melzer, J. E., Nguyen, P., Su, J., & McLeod, E. (2020, September). Assembly of Nanophotonic Structures Using Optical Tweezers. In Frontiers in Optics, FTu6B. 5.
• Xiong, Z., & McLeod, E. (2020, September). Quantitative Large Area Binding Sensor Using A High-speed Lens-free Holographic Microscope. In Frontiers in Optics, FTh1A. 4.
• Xiong, Z., & Mcleod, E. (2020). High-speed lens-free holographic microscope for biomolecular sensing. In Optics and Photonics for Information Processing XIV, 11509.
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  We implemented a lens-free holographic microscope (LFHM) that can image ~105 2-μm microspheres in solution over an ultra-large field-of-view >15 mm2 with sub-micron resolution and enhanced signal-to-noise ratio in less than 1 second. This performance is achieved using a high-speed hardware design for multi-frame pixel super-resolution and a novel sparsity-promoting reconstruction algorithm. We use the microscope as a biomolecular sensor to detect and quantify NeutrAvidin protein molecules. We coat 2-μm microspheres with biotin, which binds strongly to NAv, causing observable bead binding and clustering. This is quantified through an automated image processing algorithm and is used to infer NAv concentrations.
• Chen, L., Li, C., Liu, Y., Su, T. J., & Mcleod, E. (2019, July). Simulating Travelling Waves in Large 3D Whispering Gallery Mode Resonators Decorated with Plasmonic Nanoparticles. In Advanced Photonics Congress, IW1A.4.
• Li, C., Chen, L., Mcleod, E., & Su, T. J. (2019, April). Plasmonic Dark Modes for Enhanced Microcavity Biosensing. In Biophotonics Congress: Optics in the Life Sciences, OW2D.2.
• Li, W., & McLeod, E. (2019).

  Accurate dipole modeling of forces on a metallic nanoparticle with a larger radius than skin depth

  . In Biophotonics Congress: Optics in the Life Sciences.
• Liu, W., & Mcleod, E. (2019, April). Accurate Dipole Modeling of Forces on a Metallic Nanoparticle With a Larger Radius Than Skin Depth. In Biophotonics Congress: Optics in the Life Sciences, AM3E.4.
• Mcleod, E. (2019). Particulate-based structures for nanoscale imaging and sensing (Conference Presentation). In Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications XVI, 10891.
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  Three major challenges in biological sensing and imaging systems are to improve sensitivity, resolution, and throughput. In this talk, I present results on using structures seeded or constructed by nanoparticles to provide enhancements in these three areas. We present our work in two parts. First, we have used vapor-deposited liquid nanoscale polyethylene glycol lenses to aid in sensing nanoscale particles that serve as seeds for these nanolenses. This approach is combined with lensfree holographic microscopy to image a transparent sample slide with adsorbed nanoparticles. Lensfree holographic microscopy provides an ultra-large field of view >20 mm^2 together with submicron resolution, however its sensitivity to nanoparticles is limited and particles smaller than ~300 nm cannot be inherently distinguished from background noise. The liquid nanolenses we deposit significantly enhance the sensitivity of this system such that >10^5 particles as small as 40 nm can be individually detected, localized, and sized. The second part of this talk focuses on using optical tweezers to assemble nanophotonic structures out of heterogeneous colloidal nanoparticles. The resulting structures can provide superresolution based on transmission line and metamaterial physical principles. Optically-positioned nanoparticles can also be attached to whispering gallery mode microresonators to enhance their sensitivity and facilitate free-space coupling. Finally, we have investigated the speed with which we can position nanoparticles using optical tweezers, and have measured maximum manipulation rates in excess of 150 um/s, which makes optical tweezers a viable approach for rapid prototyping additive manufacturing of nanophotonic structures.
• Melzer, J. E., & Mcleod, E. (2019, April). Theoretical Limits of Nanoparticle Optical Manipulation. In Biophotonics Congress: Optics in the Life Sciences, AM3E.2.
• Melzer, J. E., Mcleod, E., & Liu, W. (2019). Metallic nanoparticles: high-speed optical tweezing and more accurate force calculations (Conference Presentation). In Optical Trapping and Optical Micromanipulation XVI.
• Su, J., Mcleod, E., Li, C., & Chen, L. (2019). Rationally designed nanoantennas coupled to microtoroids for enhanced biochemical sensing (Conference Presentation). In Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications XVI.
• Teimourpour, M. H., Su, J., Mcleod, E., Liu, Y., Li, C., & Chen, L. (2019). Photonic nanostructures for robust far-field coupling to high-Q whispering-gallery mode optical resonators (Conference Presentation). In Photonic and Phononic Properties of Engineered Nanostructures IX.
• Teimourpour, M. H., Su, J., Nguyen, P., Mcleod, E., Li, C., & Chen, L. (2019). Dark mode plasmonic cavity biosensor (Conference Presentation). In Frontiers in Biological Detection: From Nanosensors to Systems XI.
• Xiong, Z., Melzer, J. E., Garan, J., & Mcleod, E. (2019, April). Optimized Reconstruction for Sparse and Small Targets in Lens-free Holographic Microscopy. In Biophotonics Congress: Optics in the Life Sciences, DW1B.7.
• Xiong, Z., Melzer, J. E., Mcleod, E., & Garan, J. D. (2019). Optimization of small target sensing in lensfree microscopes (Conference Presentation). In Computational Imaging IV, 10990.
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  The ability to sense, count, and size microscopic and nanoscopic particles is important in air quality monitoring, biomedical diagnostics, and nanomaterials synthesis. Lensfree holographic microscopy is an attractive sensing platform due to its ultra-large field of view, compact form factor, and cost-effective components. Although submicron resolution has been previously demonstrated using lensfree holographic microscopy, the ability to detect individual microscale and nanoscale objects can pose a challenge due to limited signal to noise ratio (SNR). Previously, we have used vapor-deposited nanoscale polymer lenses to boost the SNR in sensing experiments, however this adds experimental complexity and is not compatible with all types of samples. Here we present a computational approach for boosting SNR in lensfree holographic microscopy. This approach optimizes a sparsity-promoting cost function in conjunction with a pixel superresolution method for synthesizing a high resolution hologram out of multiple low-resolution holograms captured at slightly different angles. The resulting high-resolution hologram can be computationally reconstructed to provide an in-focus image of the sample. We find that a sparsity-promoting cost function yields ~8 dB of improvement over conventional pixel superresolution approaches that involve cardinal neighbor regularization, provided that the surface coverage is below ~4%. The impacts of the sparsity-promoting cost function on image resolution and computational time will be presented, as well as a guide to which regularization parameters work best for given target sizes and coverage densities. These computational approaches can be used to extend the limit of detection of lensfree holographic microscopes in sensing applications.
• Daloglu, M. U., Ray, A., Gorocs, Z., Xiong, M., Malik, R., Bitan, G., Mcleod, E., & Ozcan, A. (2018, February). On-chip ultraviolet holography for high-throughput nanoparticle and biomolecule detection. In SPIE Photonics West, 10485, 1048510.
• Li, C., Teimourpour, M. H., McLeod, E., & Su, J. (2018).

  Enhanced whispering gallery mode sensors

  . In SPIE Defense + Commercial Sensing.
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  Optical whispering gallery mode (WGM) biochemical sensors operate by tracking changes in resonant frequency as materials enter the evanescent near-field of the resonator. To achieve the smallest limit of detection, it is desirable for WGM sensors to exhibit as large a frequency shift as possible for a material of a given size and refractive index, as well as the ability to track as small a frequency shift as possible. Previously, plasmonic nanoantennas have been coupled to WGM resonators to increase the magnitude of resonance shifts via plasmonic enhancement of the electric field, however this approach also results in increased scattering from the WGM, which degrades its quality factor, making it less sensitive to extremely small frequency shifts. This degradation is caused by the ohmic and scattering dissipation caused by metallic nanoantennas. Using simulations, we show here that the precise positioning of nanoantennas coupled to a microtoroid WGM resonator can be used to overcome this drawback and achieve ultrahigh-Q plasmonic cavity modes simultaneously with electric field enhancement. It is shown that a nanoantenna composed of two similarly coupled nanorods supports higher Q modes than a single nanorod antenna. Our results have immediate application in the context of optical sensing.
• Li, C., Teimourpour, M., Mcleod, E., & Su, T. J. (2018, April). Enhanced Whispering Gallery Mode Sensors. In SPIE Defense and Commercial Sensing.
• McLeod, E., & Li, W. (2018).

  Rapid nanophotonic structure design and optimization using a coupled dipole approach (Conference Presentation)

  . In SPIE Photonics West.
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  Currently, many nanophotonic structures are designed based on heuristic principles, for example the design of gratings based on wavevector matching, or the design of a nanoantenna to have a length equal to a half-wavelength. In contrast, automated iterative optimization-based approaches can yield complex nonintuitive structures that provide better performance than heuristically-designed structures. This is especially true for 3D photonic structures, whose behavior can be more dificult to conceptualize than that of 2D structures. The challenge is that multi-parameter optimization routines often require hundreds or thousands of iterations, but a typical full-wave nanophotonic simulation may take hours per iteration. One type of optimization approach that has been applied to nanophotonics is topology optimization (TO). While TO works well for top-down fabrication where structures are fabricated from continuous media, it is not as well-suited for bottom-up, or additive-type fabrication methods based on building blocks of non-negligible size. Here we present a design methodology based around iterative object placement optimization, where the iterative loops are rapidly computed using a coupled dipole approach. The coupled dipole approach cannot capture all of the same physics as full-wave simulation approaches, however it can provide approximate results much more rapidly. We compare the accuracy of the coupled dipole approach to finite-difference time domain simulations. Two application designs will also be presented: compact 3D waveguide couplers and superresolution imaging structures.
• Mcleod, E., & Mcleod, E. (2018). Toward Complex 3D Nanophotonics by the Assembly of Building Blocks. In Advanced Photonics 2018 (BGPP, IPR, NP, NOMA, Sensors, Networks, SPPCom, SOF).
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  Directed nanoparticle assembly provides a way to fabricate complex heteroge-nous 3D nanophotonic devices. We present rapid optimization-based design methods and experimentally investigate the limits on attainable assembly speed using optical tweezers.
• Melzer, J. E., & Mcleod, E. (2018). High velocity micro- and nano-particle optical manipulation (Conference Presentation). In Complex Light and Optical Forces XII, 10549.
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  In contrast to many micromanipulation and microassembly techniques, optical tweezers (OT) are non-contact and are fully capable of 3D positioning. While OT have been used extensively for the ultra-precise measurement of small biomechanical forces and displacements, more recently, OT have been proposed for applications such as cell sorting, tissue engineering, and micro/nano fabrication, which all require larger translation distances and stronger forces. In these applications, manipulation speed is a key specification, but the majority of OT systems do not have the ability to reach the high velocities necessary to compete with other micromanipulation techniques in terms of throughput. In order to create faster OT systems, it is essential to understand the factors that limit the maximum manipulation speeds for different objects. Here, we present our measurements of the maximum lateral transport speeds of polystyrene, gold, and silver spheres ranging from 100 nm to 5 µm in diameter as a function of trapping beam power over a long translation distance of >0.5 mm. In particular, we investigate the behavior at high laser powers, beyond the traditional linear relationship between laser power and maximum manipulation velocity that is predicted by the balance of Stokes’ drag and optical gradient forces. We find that the nonlinear relationship between laser power and maximum velocity depends on the particle size and material, and may be caused by different factors, such as mechanical vibrations or thermal effects. Furthermore, to our knowledge, we demonstrate the fastest recorded object manipulation speed achieved using optical tweezers of 0.22 mm·s-1.
• Melzer, J. E., Melzer, J. E., Mcleod, E., & Mcleod, E. (2018). Maximum manipulation speeds of dielectric and metallic micro and nanoparticles (Conference Presentation). In Optical Trapping and Optical Micromanipulation XV, 10723.
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  Optical tweezers are perhaps most well-known for their ability to make precise measurements of small forces and displacements, but they are also capable of high-speed and long-distance motion. High speed and long distance optical manipulation is necessary for high throughput in applications such as tissue engineering, cell sorting, and the assembly of 3D structures and materials. Here we present the greatest speeds that we have achieved using 3D optical traps to manipulate a variety of particle materials and sizes across millimeter-scale translation distances [1]. In general, higher laser powers enable faster manipulation speeds, and we investigate the high-speed / high-power limit of this relationship. For polystyrene microscale particles with diameters in the range 0.5 µm – 5 µm, we find that we are limited by mechanical stage vibrations to maximum speeds of ~220 µm/s, while for nanoscale gold, silver, and polystyrene particles, we are limited by thermal absorption effects to maximum speeds of 150 µm/s – 170 µm/s. In the low-power regime, we find good agreement with standard theory based on the balance of the optical gradient force with Stokes’ drag. Our results are, to the best of our knowledge, one of the most comprehensive studies of maximum particle manipulation speed, and we have attained the fastest published submicron particle manipulation speed. We think that these results will establish and highlight the high throughput potential for automated pick-and-place processes based on optical tweezers. [1] J. E. Melzer and E. McLeod, ACS Nano, in press (2018), doi: 10.1021/acsnano.7b07914.
• Xiong, Z., Engle, I., Garan, J., Melzer, J. E., & Mcleod, E. (2018, February). Optimized computational imaging methods for small-target sensing in lens-free holographic microscopy. In SPIE Photonics West, 10501, 105010E.
• Garan, J., Melzer, J. E., & Mcleod, E. (2017, February). Liquid polymeric materials for optical nano-bio sensing. In SPIE Photonics West, 10100, 101000N.
• Mcleod, E. (2017, May). On-chip Microscopy and Nano-particle Detection Using Ultraviolet Light. In Conference on Lasers and Electro-Optics (CLEO), ATh1A.5.
• Mcleod, E. (2017, September). 3D Nanophotonic Systems for Biosensing and Integrated Photonics. In Frontiers in Optics, FTu5D.1.
• Koydemir, H. C., Gorocs, Z., Tseng, D., Cortazar, B., Feng, S. W., Chan, R. Y., Burbano, J., Mcleod, E., & Ozcan, A. (2016, February). Rapid and sensitive detection of waterborne pathogens using machine learning on a smartphone based fluorescence microscope. In SPIE Photonics West, 9699, 96990G.
• Gorocs, Z., McLeod, E., Acharya, S., & Ozcan, A. (2015). Self-assembled micro-reflectors for signal enhancement in fluorescence microscopy. In Lasers and Electro-Optics (CLEO), 2015 Conference on.
• Koydemir, H. C., G{\"o}r{\"o}cs, Z., McLeod, E., Tseng, D., & Ozcan, A. (2015). Field portable mobile phone based fluorescence microscopy for detection of Giardia lamblia cysts in water samples. In SPIE BiOS.
• Mcleod, E., Dincer, T. U., Veli, M., Ertas, Y. N., Nguyen, C., Luo, W., Greenbaum, A., Feizi, A., & Ozcan, A. (2015, May). Field-Portable Nanoparticle and Virus Sizing Enabled by On-Chip Microscopy and Vapor-Condensed Nanolenses. In Conference on Lasers and Electro-Optics (CLEO), STu2K.6.
• McLeod, E., Mudanyali, O., Luo, W., Greenbaum, A., Coskun, A. F., Hennequin, Y., Allier, C. P., & Ozcan, A. (2013). Self-assembled nanolens formation for widefield computational imaging of nanoparticles on a chip. In CLEO: Science and Innovations.
• McLeod, E., Mudanyali, O., Luo, W., Greenbaum, A., Coşkun, A. F., Hennequin, Y., Allier, C., & Özcan, A. (2013).

  Self-Assembled Nanolens Formation for Widefield Computational Imaging of Nanoparticles on a Chip

  . In Conference on Lasers and Electro-Optics (CLEO).
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  Individual unlabeled nanoparticles are observed within a >0.2–9 cm2 field-of-view by surrounding particles with self-assembled nanolenses and imaging them with super-resolved lensfree holographic computational microscopy. Nanolens formation, topology, and impact on contrast are discussed.
• Mudanyali, O., McLeod, E., Luo, W., Greenbaum, A., Coskun, A. F., Hennequin, Y., Allier, C. P., & Ozcan, A. (2013). High-throughput imaging of single viruses using self-assembled nano-lenses and on-chip holography. In CLEO: Applications and Technology.
• Mudanyali, O., McLeod, E., Luo, W., Greenbaum, A., Coşkun, A. F., Hennequin, Y., Allier, C., & Özcan, A. (2013).

  High-throughput Imaging of Single Viruses using Self-assembled Nano-lenses and On-Chip Holography

  . In Conference on Lasers and Electro-Optics (CLEO).
• Su, T., Choi, I., Feng, J., Huang, K., McLeod, E., & Ozcan, A. (2013). Lensfree holographic imaging discovers chiral ribbon trajectories of sperms. In Photonics Conference (IPC), 2013 IEEE.
• Wei, Q., McLeod, E., Qi, H., Wan, Z., Sun, R., & Ozcan, A. (2013). Lensfree holographic cytometry using plasmonic nanoparticles. In Photonics Conference (IPC), 2013 IEEE.
• McLeod, E., & Troian, S. (2011). Tracking the Growth Rate of Nanopillar Formations Caused by Large Thermocapillary Forces. In APS Meeting Abstracts, 1.
• McLeod, E., & Troian, S. M. (2011). One step non-contact fabrication of polymer microlens arrays by thermocapillary lithography. In CLEO: Science and Innovations.
• Liu, Y., McLeod, E., & Troian, S. (2010). Experimental Study of Fluid Structure Formation from the Linear to Non-Linear Regime in Polymer Nanofilms Subject to Benard-Like Instability. In APS Division of Fluid Dynamics Meeting Abstracts, 1.
• McLeod, E., Liu, Y., & Troian, S. (2010). Experimental Confirmation of Pillar Array Formation in Polymer Nanofilms by Thermocapillary Instability. In APS Division of Fluid Dynamics Meeting Abstracts, 1.
• Arnold, C. B., & McLeod, E. (2009). Positional Accuracy in Optical Trap-Assisted Nanolithography. In APS Meeting Abstracts, 1.
• McLeod, E., & Arnold, C. B. (2009).

  Parallel Direct-Write Nanolithography Using Arrays of Optically Trapped Microlenses

  . In Conference on Lasers and Electro-Optics (CLEO).
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  We use Bessel beam optical traps to self-position arrays of microsphere objectives near surfaces. Pulsed laser illumination of these objectives is used to perform near-field direct-write subwavelength optical nanopatterning with 100 nm feature sizes.
• McLeod, E., & Arnold, C. B. (2009). Parallel direct-write nanolithography using arrays of optically trapped microlenses. In Conference on Lasers and Electro-Optics.
• Yan, J., Mermillod-Blondin, A., McLeod, E., & Arnold, C. B. (2009). Rapidly tunable acoustic gradient index lenses for pulsed imaging and laser processing. In Conference on Lasers and Electro-Optics.
• Yan, J., Mermillod–Blondin, A., McLeod, E., & Arnold, C. B. (2009).

  RAPIDLY TUNABLE ACOUSTIC GRADIENT INDEX LENSES FOR PULSED IMAGING AND LASER PROCESSING

  . In Conference on Lasers and Electro-Optics (CLEO).
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  A MHz-rate device employing acoustic waves within a fluid is used to reshape and focus an incident laser beam. Rapidly changeable focal lengths and patterns can be formed for pulsed imaging and processing applications.
• Arnold, C., & McLeod, E. (2008). Self-Positioning Optically Trapped Microspheres For Nanoscale Laser Direct Write. In APS Meeting Abstracts, 1.
• Arnold, C., Mermillod-Blondin, A., & McLeod, E. (2008). Rapid Beam Shaping For Pulsed Laser Processing Using Tunable Acoustic Gradient Index Lenses. In APS March Meeting Abstracts, 1.
• McLeod, E., & Arnold, C. B. (2008). Laser direct write near-field nanopatterning using optically trapped microspheres. In Conference on Lasers and Electro-Optics.
• McLeod, E., Mermillod-Blondin, A., & Arnold, C. B. (2008). Rapid beam shaping using tunable acoustic gradient index of refraction lenses. In Conference on Lasers and Electro-Optics.
• Mcleod, E., Joy, J., & Arnold, C. B. (2008). Optical trap assisted nanoscale laser direct-write patterning. In International Congress on Applications of Lasers & Electro-Optics, 2008.
  More info

  Laser direct-write patterning methods are traditionally limited by the diffraction limit to size scales several hundreds of nanometers at the minimum. In this work, we demonstrate a new method of laser based patterning that overcomes these limitations by taking advantage of near-field enhancement at the surface of dielectric microspheres. Polystyrene microspheres are trapped in CW Bessel beam laser traps above a polyimide surface. A second, pulsed ultraviolet laser gets focused through the bead, and produces nanometer scale features on the substrate. The full width, half maximum of the features generated by this technique is measured and analyzed along with Finite Difference Time Domain simulations to predict the effects of bead size and pulsed laser energy. It is demonstrated that using a 0.76 µm sphere to focus the processing laser results in spots with an average size of 130 nm and a standard deviation of 38 nm, showing that spots with sizes below the diffraction limit can be generated.Laser direct-write patterning methods are traditionally limited by the diffraction limit to size scales several hundreds of nanometers at the minimum. In this work, we demonstrate a new method of laser based patterning that overcomes these limitations by taking advantage of near-field enhancement at the surface of dielectric microspheres. Polystyrene microspheres are trapped in CW Bessel beam laser traps above a polyimide surface. A second, pulsed ultraviolet laser gets focused through the bead, and produces nanometer scale features on the substrate. The full width, half maximum of the features generated by this technique is measured and analyzed along with Finite Difference Time Domain simulations to predict the effects of bead size and pulsed laser energy. It is demonstrated that using a 0.76 µm sphere to focus the processing laser results in spots with an average size of 130 nm and a standard deviation of 38 nm, showing that spots with sizes below the diffraction limit can be generated.
• McLeod, E., & Arnold, C. B. (2007).

  Multiscale Bessel Beams from Tunable Acoustic Gradient Index of Refraction Lenses

  . In Conference on Lasers and Electro-Optics (CLEO).
  More info

  A device that uses acoustic waves within a fluid to phase modulate an incident laser beam and form tunable multiscale Bessel beams is presented. This device is both modelled and experimentally characterized.
• McLeod, E., & Arnold, C. B. (2007). Complex beam sculpting with tunable acoustic gradient index lenses. In Integrated Optoelectronic Devices 2007.
• McLeod, E., & Arnold, C. B. (2007). Multiscale Bessel beams from tunable acoustic gradient index of refraction lenses. In Photonic Applications Systems Technologies Conference.
• Tsai, T., McLeod, E., & Arnold, C. B. (2006). Generating Bessel beams with a tunable acoustic gradient index of refraction lens. In SPIE Optics+ Photonics.

Presentations

• Liu, W., & Mcleod, E. (2023). Fast metasurface-based angle sensitive pixel design procedure using the discrete dipole approximation. Photonics West. San Francisco: SPIE.
• Mcleod, E. (2023). Automated photonic material and device assembly using optical tweezers. Novel Optical Materials and Applications (NOMA), Advanced Photonics Congress. Busan, Korea: Optica.
• Mcleod, E. (2023). Nano-bio sensing using lensfree microscopy. Optical Metrology. Munich, Germany: SPIE.
• Mcleod, E. (2023). Optical Tweezers for 3D Assembly and Enhancement of Optical Chemosensors. Conference on Lasers and Electro-Optics (CLEO). San Jose: Optica.
• Mcleod, E. (2023). Optical tweezers for large-scale 3D assembly of micro and nanoscale building blocks. Photonics West. San Francisco: SPIE.
• Mcleod, E. (2023). Soft-material nanophotonic systems in nanofabrication and sensing. Lasers in Micro, Nano, Biosystems. Mt. Snow, VT: Gordon Research Conferences.
• Mcleod, E., Melzer, J. E., Suebka, S., Chen, L., Li, C., & Su, J. (2023). Free-space coupling to microtoroid optical resonator chemosensors. Defense + Commercial Sensing. Orlando: SPIE.
• Mcleod, E., Potter, C. J., & Baker, M. (2023). Biological and Environmental Sensors Based on Lensfree Microscopes. Conference on Lasers and Electro-Optics (CLEO). San Jose: Optica.
• Mcleod, E., Potter, C. J., Hu, Y., Xiong, Z., & Wang, J. (2023). A COVID-19 sensor that combines lens-free microscopy, an agglutination assay, and machine learning. Defense + Commercial Sensing. Orlando: SPIE.
• Mcleod, E., Shultz, N., Sharma, K., & Melzer, J. E. (2023). Fabrication of 3D nano and micro-particle assemblies using optical tweezers. Frontiers in Optics. Tacoma: Optica.
• Potter, C. J., Hu, Y., Xiong, Z., Wang, J., & Mcleod, E. (2023). Point-of-care sensing of SARS-CoV-2 using lens free holographic microscopy and deep learning. Photonics West. San Francisco: SPIE.
• Shultz, N., Melzer, J., & Mcleod, E. (2023). Automated microscale assembly using optical tweezers. Optics + Photonics. San Diego: SPIE.
• Baker, M., Liu, W., & Mcleod, E. (2021). Accurate and fast modeling of scattering from random arrays of nanoparticles using the discrete dipole approximation and angular spectrum method. Photonics West. Virtual: SPIE.
• Baker, M., Liu, W., & Mcleod, E. (2021). Methods for computing nanoparticle scattering for improved lens-free digital holographic imaging. Optics + Photonics. San Diego: SPIE.
• Liu, W., & Mcleod, E. (2021). Accounting for substrate-particle interactions in metasurfaces using fast discrete dipole approximation simulations. Photonics West. Virtual: SPIE.
• Mcleod, E. (2021). Assembly of 3D micro- and nano-photonic structures from building blocks. Fall Industrial Affiliates Workshop & Showcase. University of Arizona: Wyant College of Optical Sciences.
• Mcleod, E. (2021). Low cost and compact protein biomarker sensors based on lensfree microscopy. Virtual BioPhotonics Conference. Virtual: Photonics Media.
• Mcleod, E. (2021). Optical positioning and linking for 3D nanofabrication. Vebleo Webinar. Virtual: Vebleo.
• Melzer, J. E., & Mcleod, E. (2021). Optical positioning and linking for nanoscale assembly. Optics + Photonics. San Diego: SPIE.
• Potter, C. J., Xiong, Z., & Mcleod, E. (2021). Quantitative Large-Area Agglutination Assay Sensing of Protein Molecules in Solution. Biophotonics Congress. Virtual: Optica.
• Xiong, Z., & Mcleod, E. (2021). Protein sensing in solution using a high-speed lens-free holographic microscope. Photonics West. Virtual: SPIE.
• Baker, M. T., Liu, W., & Mcleod, E. (2020, September). Accurate and fast modeling of scattering from random arrays of nanoparticles using the discrete dipole approximation and angular spectrum method. Frontiers in Optics. Virtual: Optical Society of America.
• Liu, W., & McLeod, E. (2020, August). Rigorous and fast computation of plasmonic particle-substrate interactions. Optics + Photonics. Virtual: SPIE.
• Liu, W., & McLeod, E. (2020, May). Accurate electromagnetic field and optical force calculations for metallic nanoparticles. Conference on Lasers and Electro-Optics (CLEO). Virtual: Optical Society of America.
• McLeod, E., Melzer, J. E., & Liu, W. (2020, February). Directed assembly of 3D nanophotonic systems from building blocks. Photonics West. San Francisco: SPIE.
• Mcleod, E. (2020, November). Soft-Material Nanophotonic Systems. Wyant College of Optical Sciences Colloquium. University of Arizona: Wyant College of Optical Sciences.
• Mcleod, E., & Melzer, J. E. (2020, May). Optical Manipulation of Nanoparticles for Assembly of 3D Devices and Materials. Conference on Lasers and Electro-Optics (CLEO). Virtual: Optical Society of America.
• Melzer, J. E., & McLeod, E. (2020, August). Assembling nanoscale building blocks in 3D using optical tweezers. Optics + Photonics. Virtual: SPIE.
• Melzer, J. E., & Mcleod, E. (2020, August). Automated 3D assembly of hundreds of building blocks using optical tweezers. Optics + Photonics. Virtual: SPIE.
• Melzer, J. E., & Mcleod, E. (2020, February). Optical tweezers for micro-and nano-assembly. Photonics West. San Francisco: SPIE.
• Melzer, J. E., Nguyen, P., Su, J., & McLeod, E. (2020, September). Assembly of Nanophotonic Structures Using Optical Tweezers. Frontiers in Optics. Virtual: Optical Society of America.
• Xiong, Z., & Mcleod, E. (2020, August). High-speed lens-free holographic microscope for biomolecular sensing. Optics + Photonics. Virtual: SPIE.
• Xiong, Z., & Mcleod, E. (2020, September). Quantitative Large Area Binding Sensor Using A High-speed Lens-free Holographic Microscope. Frontiers in Optics. Virtual: Optical Society of America.
• Chen, L., Li, C., Liu, Y., Su, T. J., & Mcleod, E. (2019, July). Simulating Travelling Waves in Large 3D Whispering Gallery Mode Resonators Decorated with Plasmonic Nanoparticles. Advanced Photonics Congress. San Francisco: OSA.
• Li, C., Chen, L., Mcleod, E., & Su, T. J. (2019, April). Plasmonic Dark Modes for Enhanced Microcavity Biosensing. Biophotonics Congress: Optics in the Life Sciences. Tucson: OSA.
• Liu, W., & Mcleod, E. (2019, April). Accurate Dipole Modeling of Forces on a Metallic Nanoparticle With a Larger Radius Than Skin Depth. Biophotonics Congress: Optics in the Life Sciences. Tucson: OSA.
• Mcleod, E. (2019, December). Optical solutions for widely deployable environmental particulate sensors. Restruct Built Environment Research Symposium. Tucson: University of Arizona.
• Mcleod, E. (2019, February). Particulate-based structures for nanoscale imaging and sensing. Photonics West. San Francisco: SPIE.
• Mcleod, E. (2019, January). Simple and inexpensive lensfree holographic microscopy. Winter Meeting, American Association of Physics Teachers. Houston: American Association of Physics Teachers.
• Mcleod, E. (2019, July). Optical trapping and sensing of nanoparticles. Departmental seminar. Harbin, China: Harbin Institute of Technology.
• Mcleod, E., Melzer, J. E., & Liu, W. (2019, August). Metallic nanoparticles: high-speed optical tweezing and more accurate force calculations. Optics + Photonics. San Diego: SPIE.
• Mcleod, E., Su, T. J., Liu, Y., Teimourpour, M., Li, C., & Chen, L. (2019, February). Photonic nanostructures for robust far-field coupling to high-Q whispering-gallery mode optical resonators. SPIE Photonics West.
• Melzer, J. E., & Mcleod, E. (2019, April). Theoretical Limits of Nanoparticle Optical Manipulation. Biophotonics Congress: Optics in the Life Sciences. Tucson: OSA.
• Su, T. J., Mcleod, E., Chen, L., & Li, C. (2019, February). Rationally designed nanoantennas coupled to microtoroids for enhanced biochemical sensing. SPIE Photonics West.
• Su, T. J., Mcleod, E., Chen, L., Nguyen, P., Teimourpour, M., & Li, C. (2019, February). Dark mode plasmonic cavity biosensor. SPIE Photonics West.
• Xiong, Z., Melzer, J. E., Garan, J., & Mcleod, E. (2019, April). Optimization of small target sensing in lensfree microscopes. Defense + Commercial Sensing. Baltimore: SPIE.
• Xiong, Z., Melzer, J. E., Garan, J., & Mcleod, E. (2019, April). Optimized Reconstruction for Sparse and Small Targets in Lens-free Holographic Microscopy. Biophotonics Congress: Optics in the Life Sciences. Tucson: OSA.
• Daloglu, M. U., Ray, A., Gorocs, Z., Xiong, M., Malik, R., Bitan, G., Mcleod, E., & Ozcan, A. (2018, February). On-chip ultraviolet holography for high-throughput nanoparticle and biomolecule detection. SPIE Photonics West. San Francisco: SPIE.
• Li, C., Teimourpour, M., Mcleod, E., & Su, T. J. (2018, April). Enhanced Whispering Gallery Mode Sensors. SPIE Defense and Commercial Sensing.
• Mcleod, E. (2018, April). Lensfree Holographic Imaging for In Vitro Diagnostics. Cancer Imaging Program Meeting. Tucson: University of Arizona Cancer Center.
• Mcleod, E. (2018, July). Polymeric and colloidal materials for 3D nanophotonics. Light Conference. Changchun, China: Light: Science and Applications.
• Mcleod, E. (2018, July). Toward 3D nanophotonics by the assembly of building blocks. Advanced Photonics. Zurich: Optical Society of America.
• Mcleod, E., & Liu, W. (2018, February). Rapid nanophotonic structure design and optimization using a coupled dipole approach. SPIE Photonics West. San Francisco: SPIE.
• Mcleod, E., & Melzer, J. E. (2018, August). Maximum manipulation speeds of dielectric and metallic micro and nanoparticles. SPIE Optics + Photonics. San Diego: SPIE.
• Melzer, J. E., & Mcleod, E. (2018, February). High velocity micro- and nano-particle manipulation. SPIE Photonics West. San Francisco: SPIE.
• Xiong, Z., Engle, I., Garan, J., Melzer, J. E., & Mcleod, E. (2018, January). Optimized computational imaging methods for small-target sensing in lens-free holographic microscopy. SPIE Photonics West. San Francisco: SPIE.
• Daloglu, M. U., Ray, A., Gorocs, Z., Xiong, M., Malik, R., Bitan, G., Mcleod, E., & Ozcan, A. (2017, May). On-chip microscopy and nano-particle detection using ultraviolet light. Conference on Lasers and Electro-Optics (CLEO). San Jose, CA: Optical Society of America (OSA).
• Mcleod, E. (2017, December). 3D Nanophotonic Systems for Environmental and Biological Sensing. Seminar at Nanjing University. Nanjing, China: Nanjing University.
• Mcleod, E. (2017, December). 3D Nanophotonic Systems for Environmental and Biological Sensing. Seminar at Shanghai Jiao Tong University. Shanghai, China: Shanghai Jiao Tong University.
• Mcleod, E. (2017, December). 3D Nanophotonic Systems for Environmental and Biological Sensing. Seminar at Southeast University. Nanjing, China: Southeast University, Nanjing.
• Mcleod, E. (2017, January). Liquid polymeric materials for optical nano-bio sensing. SPIE Photonics West. San Francisco, CA: SPIE.
• Mcleod, E. (2017, June). Soft nano-photonic systems: Nanolenses for on-chip holographic imaging of viruses and nanoparticles. Seminar at Beijing Anzhen Hospital. Beijing, China: Beijing Institute of Heart, Lung, and Blood Vessel Diseases, Beijing Anzhen Hospital.
• Mcleod, E. (2017, June). Soft nano-photonic systems: Nanolenses for on-chip holographic imaging of viruses and nanoparticles. Seminar at Beijing University of Posts and Telecommunications. Beijing, China: Institute of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications.
• Mcleod, E. (2017, June). Soft nano-photonic systems: Nanolenses for on-chip holographic imaging of viruses and nanoparticles. Seminar at Peking University. Beijing, China: School of Physics, Peking University.
• Mcleod, E. (2017, June). Soft nano-photonic systems: Nanolenses for on-chip holographic imaging of viruses and nanoparticles. Seminar at the University of Chinese Academy of Sciences. Beijing, China: National Center for Nanoscience and Technology, University of Chinese Academy of Sciences.
• Mcleod, E. (2017, September). 3D Nanophotonic systems for biosensing and integrated photonics. Frontiers in Optics. Washington, DC: Optical Society of America (OSA).
• Ray, A., Ho, H., Daloglu, M., Torres, A., Mcleod, E., & Ozcan, A. (2017, January). Cost-effective and label-free holographic biosensor for detection of herpes simplex virus. SPIE Photonics West. San Francisco, CA: SPIE.
• Mcleod, E. (2016, February). High-throughput nanoparticle sizing using lensfree holographic microscopy and liquid nanolenses. Photonics West. San Francisco: SPIE.
• Mcleod, E. (2016, November). Soft nanophotonic systems for small nanoparticle detection and sizing. Colloquium at Northern Arizona University Physics Dept.. Flagstaff, AZ: Northern Arizona University.
• Mcleod, E. (2016, October). Nanoparticle and Virus Sensing Enabled by Computational Lensfree Imaging. Frontiers in Optics. Rochester, NY: Optical Society of America (OSA).
• Ray, A., Ho, H., Daloglu, M., Mcleod, E., & Ozcan, A. (2016, October). Field-portable holographic microscope for label-free detection of herpes simplex virus. Biomedical Engineering Society Annual Meeting. Minneapolis, MN: Biomedical Engineering Society.
• Gorocs, Z. S., Mcleod, E., Acharya, S., & Ozcan, A. (2015, February). Fluorescent signal enhancement using vapor-condensed microreflectors. Photonics West. San Francisco, CA: SPIE.
• Koydemir, H. C., Gorocs, Z. S., Mcleod, E., Tseng, D., & Ozcan, A. (2015, February). Field portable fluorescence microscopy for detection of Giardia lamblia cysts in water samples. Photonics West. San Francisco, CA: SPIE.
• Mcleod, E. (2015, February). Tunable vapor-condensed nanolenses for label-free nanoscale imaging and sensing. Bustamante group presentation. Berkeley, CA: UC Berkeley.
• Mcleod, E. (2015, January). Self-assembly of liquid nanolenses for holographic on-chip imaging of viruses and nanoparticles. College of Optical Sciences Seminar. Tucson, AZ: University of Arizona.
• Mcleod, E. (2015, July). Fabrication of self-assembled liquid nanolenses for high-throughput bioimaging. Departmental Seminar. Perth, Australia: University of Western Australia.
• Mcleod, E. (2015, June). Cost-effective and label-free virus and nanoparticle imager for biomedical monitoring. Point-of-Care Diagnostics Conference, Molecular Diagnostics Summit. San Digeo, CA: GTCbio.
• Mcleod, E. (2015, September). Self-assembly of liquid nanolenses for holographic on-chip imaging of viruses and nanoparticles. Optical Sciences Colloquium Lecture Series. Tucson, AZ: University of Arizona.
• Mcleod, E., Dincer, T. U., Veli, M., Ertas, Y. N., Nguyen, C., Luo, W., & Ozcan, A. (2015, February). Field-portable and cost-effective holographic device for label-free nanoparticle and virus imaging and sizing. Photonics West. San Francisco, CA: SPIE.
• Mcleod, E., Dincer, T. U., Veli, M., Ertas, Y. N., Nguyen, C., Luo, W., Greenbaum, A., Feizi, A., & Ozcan, A. (2015, May). Field-Portable Nanoparticle and Virus Sizing Enabled by On-Chip Microscopy and Vapor-Condensed Nanolenses. Conference on Lasers and Electro-Optics (CLEO). San Jose, CA: OSA.
• Mcleod, E., Nguyen, C., Huang, P., Luo, W., Veli, M., & Ozcan, A. (2015, February). Tunable vapor-condensed nanolenses for label-free nanoscale imaging and sensing. Photonics West. San Francisco, CA: SPIE.
• Mcleod, E. (2014, December). Self-assembled nanolenses for wide-field on-chip nanoparticle and virus imaging. Seminar at the Laser Biomedical Research Center. Cambridge, MA: Massachusetts Institute of Technology.
• Mcleod, E., & Ozcan, A. (2014, November). Portable healthcare solutions: Bringing bioimaging technology to the field. HillTop. New York, NY: GlobeMed / Columbia University.
• Mcleod, E. (2011, August). Novel surface patterning techniques and high-speed laser beam control. Laboratory Seminar. Berkeley, CA: Lawrence Berkeley National Laboratory.
• Mcleod, E. (2011, September). Novel surface patterning techniques and high-speed laser beam control. Electrical Engineering Departmental Presentation. Los Angeles, CA: UCLA.
• Mcleod, E., & Troian, S. M. (2011, May). Thermal-gradient-induced instability in liquid nanofilms for lithographic applications. Aerospace Engineering Seminar. Pasadena, CA: California Institute of Technology.
• Mcleod, E., & Arnold, C. B. (2009, February). Bessel beams: From adaptive optics to nanolithography. Laboratory Seminar. Livermore, CA: Lawrence Livermore National Laboratory.
• Mcleod, E., & Arnold, C. B. (2008, November). Direct write nanopatterning using near-field focusing by optically trapped microspheres. Princeton Research Symposium. Princeton, NJ: Princeton University.

Poster Presentations

• Mcleod, E., Chen, L., Li, C., Melzer, J. E., Stoltz, B., & Su, T. J. (2019, November). Nanostructuring microtoroid optical chemosensors for mechanically robust and stable sensing. Chemical and Biological Defense Science & Technology Conference. Cincinnati: Defense Threat Reduction Agency (DTRA).
• Mcleod, E. (2018, December). Pixel-level 3D nanophotonic structures for multi-modality image sensors. Nanoscale Science and Engineering Grantees Conference. Alexandria, Virginia: National Science Foundation.
• Xiong, Z., Engle, I., & Mcleod, E. (2018, September). Cancer biomarkers detection using a microfluidic microscope sensor. Cancer Center Fall Retreat. Tucson: University of Arizona Cancer Center.