Philipp Gutruf

Interests

Research

Our research focuses on creating devices that intimately integrate with biological systems. We combine innovations in soft materials, photonics and electronics to create systems with broad impact on health diagnostics and neuroscience.

Teaching

I am specifically interested in teaching design oriented hands on skills for biomedical engineers.

Courses

Scholarly Contributions

Books

• Zhang, H., Gutruf, P., & Rogers, J. A. (2019). Flexible Inorganic Light Emitting Diodes Enabled by New Materials and Designs, With Examples of Their Use in Neuroscience Research. Wiley.
• Gutruf, P. (2018). Low Power Semiconductor Devices and Processes for Emerging Applications in Communications, Computing, and Sensing. Chapter 12:"Miniaturized Battery-Free Wireless Bio-Integrated Systems": CRC Press.

Chapters

• Burton, A., Stuart, T., Ausra, J., & Gutruf, P. (2020). Smartphone for monitoring basic vital signs: Miniaturized, near-field communication based devices for chronic recording of health. In Smartphone for monitoring basic vital signs: Miniaturized, near-field communication based devices for chronic recording of health(pp 177-208). Elsevier.

Journals/Publications

• Burton, A., Wang, Z., Song, D., Tran, S., Hanna, J., Ahmad, D., Bakall, J., Clausen, D., Anderson, J., Peralta, R., Sandepudi, K., Benedetto, A., Yang, E., Basrai, D., Miller, L. E., Tresch, M. C., & Gutruf, P. (2023). Fully implanted battery-free high power platform for chronic spinal and muscular functional electrical stimulation. Nature communications, 14(1), 7887.
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  Electrical stimulation of the neuromuscular system holds promise for both scientific and therapeutic biomedical applications. Supplying and maintaining the power necessary to drive stimulation chronically is a fundamental challenge in these applications, especially when high voltages or currents are required. Wireless systems, in which energy is supplied through near field power transfer, could eliminate complications caused by battery packs or external connections, but currently do not provide the harvested power and voltages required for applications such as muscle stimulation. Here, we introduce a passive resonator optimized power transfer design that overcomes these limitations, enabling voltage compliances of ± 20 V and power over 300 mW at device volumes of 0.2 cm, thereby improving power transfer 500% over previous systems. We show that this improved performance enables multichannel, biphasic, current-controlled operation at clinically relevant voltage and current ranges with digital control and telemetry in freely behaving animals. Preliminary chronic results indicate that implanted devices remain operational over 6 weeks in both intact and spinal cord injured rats and are capable of producing fine control of spinal and muscle stimulation.
• Stuart, T., Farley, M., Amato, J., Thien, R., Hanna, J., Bhatia, A., Clausen, D. M., & Gutruf, P. (2023). Biosymbiotic platform for chronic long-range monitoring of biosignals in limited resource settings. Proceedings of the National Academy of Sciences of the United States of America, 120(50), e2307952120.
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  Remote patient monitoring is a critical component of digital medicine, and the COVID-19 pandemic has further highlighted its importance. Wearable sensors aimed at noninvasive extraction and transmission of high-fidelity physiological data provide an avenue toward at-home diagnostics and therapeutics; however, the infrastructure requirements for such devices limit their use to areas with well-established connectivity. This accentuates the socioeconomic and geopolitical gap in digital health technology and points toward a need to provide access in areas that have limited resources. Low-power wide area network (LPWAN) protocols, such as LoRa, may provide an avenue toward connectivity in these settings; however, there has been limited work on realizing wearable devices with this functionality because of power and electromagnetic constraints. In this work, we introduce wearables with electromagnetic, electronic, and mechanical features provided by a biosymbiotic platform to realize high-fidelity biosignals transmission of 15 miles without the need for satellite infrastructure. The platform implements wireless power transfer for interaction-free recharging, enabling long-term and uninterrupted use over weeks without the need for the user to interact with the devices. This work presents demonstration of a continuously wearable device with this long-range capability that has the potential to serve resource-constrained and remote areas, providing equitable access to digital health.
• Stuart, T., Jeang, W. J., Slivicki, R. A., Brown, B. J., Burton, A., Brings, V. E., Alarcón-Segovia, L. C., Agyare, P., Ruiz, S., Tyree, A., Pruitt, L., Madhvapathy, S., Niemiec, M., Zhuang, J., Krishnan, S., Copits, B. A., Rogers, J. A., Gereau, R. W., Samineni, V. K., , Bandodkar, A. J., et al. (2023). Wireless, Battery-Free Implants for Electrochemical Catecholamine Sensing and Optogenetic Stimulation. ACS nano, 17(1), 561-574.
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  Neurotransmitters and neuromodulators mediate communication between neurons and other cell types; knowledge of release dynamics is critical to understanding their physiological role in normal and pathological brain function. Investigation into transient neurotransmitter dynamics has largely been hindered due to electrical and material requirements for electrochemical stimulation and recording. Current systems require complex electronics for biasing and amplification and rely on materials that offer limited sensor selectivity and sensitivity. These restrictions result in bulky, tethered, or battery-powered systems impacting behavior and that require constant care of subjects. To overcome these challenges, we demonstrate a fully implantable, wireless, and battery-free platform that enables optogenetic stimulation and electrochemical recording of catecholamine dynamics in real time. The device is nearly 1/10th the size of previously reported examples and includes a probe that relies on a multilayer electrode architecture featuring a microscale light emitting diode (μ-LED) and a carbon nanotube (CNT)-based sensor with sensitivities among the highest recorded in the literature (1264.1 nA μM cm). High sensitivity of the probe combined with a center tapped antenna design enables the realization of miniaturized, low power circuits suitable for subdermal implantation even in small animal models such as mice. A series of and experiments highlight the sensitivity and selectivity of the platform and demonstrate its capabilities in freely moving, untethered subjects. Specifically, a demonstration of changes in dopamine concentration after optogenetic stimulation of the nucleus accumbens and real-time readout of dopamine levels after opioid and naloxone exposure in freely behaving subjects highlight the experimental paradigms enabled by the platform.
• Stuart, T., Yin, X., Chen, S. J., Farley, M., McGuire, D. T., Reddy, N., Thien, R., DiMatteo, S., Fumeaux, C., & Gutruf, P. (2023). Context-aware electromagnetic design for continuously wearable biosymbiotic devices. Biosensors & bioelectronics, 228, 115218.
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  Imperceptible wireless wearable devices are critical to advance digital medicine with the goal to capture clinical-grade biosignals continuously. Design of these systems is complex because of unique interdependent electromagnetic, mechanic and system level considerations that directly influence performance. Typically, approaches consider body location, related mechanical loads, and desired sensing capabilities, however, design for real world application context is not formulated. Wireless power casting eliminates user interaction and the need to recharge batteries, however, implementation is challenging because the use case influences performance. To facilitate a data-driven approach to design, we demonstrate a method for personalized, context-aware antenna, rectifier and wireless electronics design that considers human behavioral patterns and physiology to optimize electromagnetic and mechanical features for best performance across an average day of the target user group. Implementation of these methods result in devices that enable continuous recording of high-fidelity biosignals over weeks without the need for human interaction.
• Yin, R. T., Chen, S. W., Benjamin Lee, K., Choi, Y. S., Koo, J., Yang, Q., Napolitano, M. A., Ausra, J., Holleran, T. J., Lapiano, J. B., Alex Waters, E., Brikha, A., Kowalik, G., Miniovich, A. N., Knight, H. S., Russo, B. A., Kiss, A., Murillo-Berlioz, A., Efimova, T., , Haney, C. R., et al. (2023). Open thoracic surgical implantation of cardiac pacemakers in rats. Nature protocols, 18(2), 374-395.
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  Genetic engineering and implantable bioelectronics have transformed investigations of cardiovascular physiology and disease. However, the two approaches have been difficult to combine in the same species: genetic engineering is applied primarily in rodents, and implantable devices generally require larger animal models. We recently developed several miniature cardiac bioelectronic devices suitable for mice and rats to enable the advantages of molecular tools and implantable devices to be combined. Successful implementation of these device-enabled studies requires microsurgery approaches that reliably interface bioelectronics to the beating heart with minimal disruption to native physiology. Here we describe how to perform an open thoracic surgical technique for epicardial implantation of wireless cardiac pacemakers in adult rats that has lower mortality than transvenous implantation approaches. In addition, we provide the methodology for a full biocompatibility assessment of the physiological response to the implanted device. The surgical implantation procedure takes ~40 min for operators experienced in microsurgery to complete, and six to eight surgeries can be completed in 1 d. Implanted pacemakers provide programmed electrical stimulation for over 1 month. This protocol has broad applications to harness implantable bioelectronics to enable fully conscious in vivo studies of cardiovascular physiology in transgenic rodent disease models.
• Ausra, J., Madrid, M., Yin, R. T., Hanna, J., Arnott, S., Brennan, J. A., Peralta, R., Clausen, D., Bakall, J. A., Efimov, I. R., & Gutruf, P. (2022). Wireless, fully implantable cardiac stimulation and recording with on-device computation for closed-loop pacing and defibrillation. Science advances, 8(43), eabq7469.
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  Monitoring and control of cardiac function are critical for investigation of cardiovascular pathophysiology and developing life-saving therapies. However, chronic stimulation of the heart in freely moving small animal subjects, which offer a variety of genotypes and phenotypes, is currently difficult. Specifically, real-time control of cardiac function with high spatial and temporal resolution is currently not possible. Here, we introduce a wireless battery-free device with on-board computation for real-time cardiac control with multisite stimulation enabling optogenetic modulation of the entire rodent heart. Seamless integration of the biointerface with the heart is enabled by machine learning-guided design of ultrathin arrays. Long-term pacing, recording, and on-board computation are demonstrated in freely moving animals. This device class enables new heart failure models and offers a platform to test real-time therapeutic paradigms over chronic time scales by providing means to control cardiac function continuously over the lifetime of the subject.
• Rahman, M. A., Cai, L., Tawfik, S. A., Tucker, S., Burton, A., Perera, G., Spencer, M. J., Walia, S., Sriram, S., Gutruf, P., & Bhaskaran, M. (2022). Nicotine Sensors for Wearable Battery-Free Monitoring of Vaping. ACS sensors, 7(1), 82-88.
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  Nicotine, an addictive substance in tobacco products and electronic cigarettes (e-cigs), is recognized for increasing the risk of cardiovascular and respiratory disorders. Careful real-time monitoring of nicotine exposure is critical in alleviating the potential health impacts of not just smokers but also those exposed to second-hand and third-hand smoke. Monitoring of nicotine requires suitable sensing material to detect nicotine selectively and testing under free-living conditions in the standard environment. Here, we experimentally demonstrate a vanadium dioxide (VO)-based nicotine sensor and explain its conductometric mechanisms with compositional analysis and density functional theory (DFT) calculations. For real-time monitoring of nicotine vapor from e-cigarettes in the air, the sensor is integrated with an epidermal near-field communication (NFC) interface that enables battery-free operation and data transmission to smart electronic devices to record and store sensor data. Collectively, the technique of sensor development and integration expands the use of wearable electronics for real-time monitoring of hazardous elements in the environment and biosignals wirelessly.
• Stuart, T., Hanna, J., & Gutruf, P. (2022). Wearable devices for continuous monitoring of biosignals: Challenges and opportunities. APL bioengineering, 6(2), 021502.
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  The ability for wearable devices to collect high-fidelity biosignals continuously over weeks and months at a time has become an increasingly sought-after characteristic to provide advanced diagnostic and therapeutic capabilities. Wearable devices for this purpose face a multitude of challenges such as formfactors with long-term user acceptance and power supplies that enable continuous operation without requiring extensive user interaction. This review summarizes design considerations associated with these attributes and summarizes recent advances toward continuous operation with high-fidelity biosignal recording abilities. The review also provides insight into systematic barriers for these device archetypes and outlines most promising technological approaches to expand capabilities. We conclude with a summary of current developments of hardware and approaches for embedded artificial intelligence in this wearable device class, which is pivotal for next generation autonomous diagnostic, therapeutic, and assistive health tools.
• Ausra, J., Munger, S. J., Azami, A., Burton, A., Peralta, R., Miller, J. E., & Gutruf, P. (2021). Wireless battery free fully implantable multimodal recording and neuromodulation tools for songbirds. Nature communications, 12(1), 1968.
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  Wireless battery free and fully implantable tools for the interrogation of the central and peripheral nervous system have quantitatively expanded the capabilities to study mechanistic and circuit level behavior in freely moving rodents. The light weight and small footprint of such devices enables full subdermal implantation that results in the capability to perform studies with minimal impact on subject behavior and yields broad application in a range of experimental paradigms. While these advantages have been successfully proven in rodents that move predominantly in 2D, the full potential of a wireless and battery free device can be harnessed with flying species, where interrogation with tethered devices is very difficult or impossible. Here we report on a wireless, battery free and multimodal platform that enables optogenetic stimulation and physiological temperature recording in a highly miniaturized form factor for use in songbirds. The systems are enabled by behavior guided primary antenna design and advanced energy management to ensure stable optogenetic stimulation and thermography throughout 3D experimental arenas. Collectively, these design approaches quantitatively expand the use of wireless subdermally implantable neuromodulation and sensing tools to species previously excluded from in vivo real time experiments.
• Ausra, J., Wu, M., Zhang, X., Vázquez-Guardado, A., Skelton, P., Peralta, R., Avila, R., Murickan, T., Haney, C. R., Huang, Y., Rogers, J. A., Kozorovitskiy, Y., & Gutruf, P. (2021). Wireless, battery-free, subdermally implantable platforms for transcranial and long-range optogenetics in freely moving animals. Proceedings of the National Academy of Sciences of the United States of America, 118(30).
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  Wireless, battery-free, and fully subdermally implantable optogenetic tools are poised to transform neurobiological research in freely moving animals. Current-generation wireless devices are sufficiently small, thin, and light for subdermal implantation, offering some advantages over tethered methods for naturalistic behavior. Yet current devices using wireless power delivery require invasive stimulus delivery, penetrating the skull and disrupting the blood-brain barrier. This can cause tissue displacement, neuronal damage, and scarring. Power delivery constraints also sharply curtail operational arena size. Here, we implement highly miniaturized, capacitive power storage on the platform of wireless subdermal implants. With approaches to digitally manage power delivery to optoelectronic components, we enable two classes of applications: transcranial optogenetic activation millimeters into the brain (validated using motor cortex stimulation to induce turning behaviors) and wireless optogenetics in arenas of more than 1 m in size. This methodology allows for previously impossible behavioral experiments leveraging the modern optogenetic toolkit.
• Burton, A., Won, S. M., Sohrabi, A. K., Stuart, T., Amirhossein, A., Kim, J. U., Park, Y., Gabros, A., Rogers, J. A., Vitale, F., Richardson, A. G., & Gutruf, P. (2021). Wireless, battery-free, and fully implantable electrical neurostimulation in freely moving rodents. Microsystems & nanoengineering, 7, 62.
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  Implantable deep brain stimulation (DBS) systems are utilized for clinical treatment of diseases such as Parkinson's disease and chronic pain. However, long-term efficacy of DBS is limited, and chronic neuroplastic changes and associated therapeutic mechanisms are not well understood. Fundamental and mechanistic investigation, typically accomplished in small animal models, is difficult because of the need for chronic stimulators that currently require either frequent handling of test subjects to charge battery-powered systems or specialized setups to manage tethers that restrict experimental paradigms and compromise insight. To overcome these challenges, we demonstrate a fully implantable, wireless, battery-free platform that allows for chronic DBS in rodents with the capability to control stimulation parameters digitally in real time. The devices are able to provide stimulation over a wide range of frequencies with biphasic pulses and constant voltage control via low-impedance, surface-engineered platinum electrodes. The devices utilize off-the-shelf components and feature the ability to customize electrodes to enable broad utility and rapid dissemination. Efficacy of the system is demonstrated with a readout of stimulation-evoked neural activity in vivo and chronic stimulation of the medial forebrain bundle in freely moving rats to evoke characteristic head motion for over 36 days.
• Cai, L., & Gutruf, P. (2021). Soft, wireless and subdermally implantable recording and neuromodulation tools. Journal of neural engineering, 18(4).
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  Progress in understanding neuronal interaction and circuit behavior of the central and peripheral nervous system (PNS) strongly relies on the advancement of tools that record and stimulate with high fidelity and specificity. Currently, devices used in exploratory research predominantly utilize cables or tethers to provide pathways for power supply, data communication, stimulus delivery and recording, which constrains the scope and use of such devices. In particular, the tethered connection, mechanical mismatch to surrounding soft tissues and bones frustrate the interface leading to irritation and limitation of motion of the subject, which in the case of fundamental and preclinical studies, impacts naturalistic behaviors of animals and precludes the use in experiments involving social interaction and ethologically relevant three-dimensional environments, limiting the use of current tools to mostly rodents and exclude species such as birds and fish. This review explores the current state-of-the-art in wireless, subdermally implantable tools that quantitively expand capabilities in analysis and perturbation of the central and PNS by removing tethers and externalized features of implantable neuromodulation and recording tools. Specifically, the review explores power harvesting strategies, wireless communication schemes, and soft materials and mechanics that enable the creation of such devices and discuss their capabilities in the context of freely-behaving subjects. Highlights of this class of devices includes wireless battery-free and fully implantable operation with capabilities in cell specific recording, multimodal neural stimulation and electrical, optogenetic and pharmacological neuromodulation capabilities. We conclude with a discussion on translation of such technologies, which promises routes towards broad dissemination.
• Cai, L., Burton, A., Gonzales, D. A., Kasper, K. A., Azami, A., Peralta, R., Johnson, M., Bakall, J. A., Barron Villalobos, E., Ross, E. C., Szivek, J. A., Margolis, D. S., & Gutruf, P. (2021). Osseosurface electronics-thin, wireless, battery-free and multimodal musculoskeletal biointerfaces. Nature communications, 12(1), 6707.
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  Bioelectronic interfaces have been extensively investigated in recent years and advances in technology derived from these tools, such as soft and ultrathin sensors, now offer the opportunity to interface with parts of the body that were largely unexplored due to the lack of suitable tools. The musculoskeletal system is an understudied area where these new technologies can result in advanced capabilities. Bones as a sensor and stimulation location offer tremendous advantages for chronic biointerfaces because devices can be permanently bonded and provide stable optical, electromagnetic, and mechanical impedance over the course of years. Here we introduce a new class of wireless battery-free devices, named osseosurface electronics, which feature soft mechanics, ultra-thin form factor and miniaturized multimodal biointerfaces comprised of sensors and optoelectronics directly adhered to the surface of the bone. Potential of this fully implanted device class is demonstrated via real-time recording of bone strain, millikelvin resolution thermography and delivery of optical stimulation in freely-moving small animal models. Battery-free device architecture, direct growth to the bone via surface engineered calcium phosphate ceramic particles, demonstration of operation in deep tissue in large animal models and readout with a smartphone highlight suitable characteristics for exploratory research and utility as a diagnostic and therapeutic platform.
• Gutruf, P., Utzinger, U., & Subbian, V. (2021). Moving from Pedagogy to Andragogy in Biomedical Engineering Design: Strategies for Lab-at-Home and Distance Learning. Biomedical engineering education, 1(2), 301-305.
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  Engineering design courses are particularly challenging to deliver in online or distance modalities because of the hands-on, collaborative nature of the design process and the need for physical resources and work spaces. In this work, we describe how we rapidly transformed two design courses in the middle two years of the biomedical engineering (BME) program to an online format during the 2019 coronavirus pandemic. In addition to time and safety constraints, we identified access to design spaces with biochemistry, computing, electronic, computing, and manufacturing tools, and team-based learning as major challenges to distance learning in BME design courses. To this end, we mapped and translated various course and design activities to an online environment using a combination of customized at-home laboratory kits and distributed team structures. Drawing upon our pilot experience as well as principles from online and adult learning theories, we offer an overview of strategies to retain hands-on and team-based activities and rapidly implement BME design courses in online or distance modalities.
• Stuart, T., Cai, L., Burton, A., & Gutruf, P. (2021). Wireless and battery-free platforms for collection of biosignals. Biosensors & bioelectronics, 178, 113007.
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  Recent progress in biosensors have quantitively expanded current capabilities in exploratory research tools, diagnostics and therapeutics. This rapid pace in sensor development has been accentuated by vast improvements in data analysis methods in the form of machine learning and artificial intelligence that, together, promise fantastic opportunities in chronic sensing of biosignals to enable preventative screening, automated diagnosis, and tools for personalized treatment strategies. At the same time, the importance of widely accessible personal monitoring has become evident by recent events such as the COVID-19 pandemic. Progress in fully integrated and chronic sensing solutions is therefore increasingly important. Chronic operation, however, is not truly possible with tethered approaches or bulky, battery-powered systems that require frequent user interaction. A solution for this integration challenge is offered by wireless and battery-free platforms that enable continuous collection of biosignals. This review summarizes current approaches to realize such device architectures and discusses their building blocks. Specifically, power supplies, wireless communication methods and compatible sensing modalities in the context of most prevalent implementations in target organ systems. Additionally, we highlight examples of current embodiments that quantitively expand sensing capabilities because of their use of wireless and battery-free architectures.
• Stuart, T., Kasper, K. A., Iwerunmor, I. C., McGuire, D. T., Peralta, R., Hanna, J., Johnson, M., Farley, M., LaMantia, T., Udorvich, P., & Gutruf, P. (2021). Biosymbiotic, personalized, and digitally manufactured wireless devices for indefinite collection of high-fidelity biosignals. Science advances, 7(41), eabj3269.
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  [Figure: see text].
• Wei, X., Centeno, M. V., Ren, W., Borruto, A. M., Procissi, D., Xu, T., Jabakhanji, R., Mao, Z., Kim, H., Li, Y., Yang, Y., Gutruf, P., Rogers, J. A., Surmeier, D. J., Radulovic, J., Liu, X., Martina, M., & Apkarian, A. V. (2021). Activation of the dorsal, but not the ventral, hippocampus relieves neuropathic pain in rodents. Pain, 162(12), 2865-2880.
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  Accumulating evidence suggests hippocampal impairment under the chronic pain phenotype. However, it is unknown whether neuropathic behaviors are related to dysfunction of the hippocampal circuitry. Here, we enhanced hippocampal activity by pharmacological, optogenetic, and chemogenetic techniques to determine hippocampal influence on neuropathic pain behaviors. We found that excitation of the dorsal (DH), but not the ventral (VH) hippocampus induces analgesia in 2 rodent models of neuropathic pain (SNI and SNL) and in rats and mice. Optogenetic and pharmacological manipulations of DH neurons demonstrated that DH-induced analgesia was mediated by N-Methyl-D-aspartate and μ-opioid receptors. In addition to analgesia, optogenetic stimulation of the DH in SNI mice also resulted in enhanced real-time conditioned place preference for the chamber where the DH was activated, a finding consistent with pain relief. Similar manipulations in the VH were ineffective. Using chemo-functional magnetic resonance imaging (fMRI), where awake resting-state fMRI was combined with viral vector-mediated chemogenetic activation (PSAM/PSEM89s) of DH neurons, we demonstrated changes of functional connectivity between the DH and thalamus and somatosensory regions that tracked the extent of relief from tactile allodynia. Moreover, we examined hippocampal functional connectivity in humans and observe differential reorganization of its anterior and posterior subdivisions between subacute and chronic back pain. Altogether, these results imply that downregulation of the DH circuitry during chronic neuropathic pain aggravates pain-related behaviors. Conversely, activation of the DH reverses pain-related behaviors through local excitatory and opioidergic mechanisms affecting DH functional connectivity. Thus, this study exhibits a novel causal role for the DH but not the VH in controlling neuropathic pain-related behaviors.
• Won, S. M., Cai, L., Gutruf, P., & Rogers, J. A. (2021). Wireless and battery-free technologies for neuroengineering. Nature biomedical engineering.
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  Tethered and battery-powered devices that interface with neural tissues can restrict natural motions and prevent social interactions in animal models, thereby limiting the utility of these devices in behavioural neuroscience research. In this Review Article, we discuss recent progress in the development of miniaturized and ultralightweight devices as neuroengineering platforms that are wireless, battery-free and fully implantable, with capabilities that match or exceed those of wired or battery-powered alternatives. Such classes of advanced neural interfaces with optical, electrical or fluidic functionality can also combine recording and stimulation modalities for closed-loop applications in basic studies or in the practical treatment of abnormal physiological processes.
• Ausra, J., Munger, S., Azami, A., Burton, A., Peralta, R., Miller, J., & Gutruf, P. (2020). Wireless battery free fully implantable multimodal recording and neuromodulation tools for songbirds.
• Bandodkar, A. J., Lee, S. P., Huang, I., Li, W., Wang, S., Su, C., Jeang, W. J., Hang, T., Mehta, S., & Nyberg, N. (2020). Sweat-activated biocompatible batteries for epidermal electronic and microfluidic systems. Nature Electronics, 3(9), 554-562.
• Burton, A., Obaid, S. N., Vázquez-Guardado, A., Schmit, M. B., Stuart, T., Cai, L., Chen, Z., Kandela, I., Haney, C. R., Waters, E. A., Cai, H., Rogers, J. A., Lu, L., & Gutruf, P. (2020). Wireless, battery-free subdermally implantable photometry systems for chronic recording of neural dynamics. Proceedings of the National Academy of Sciences, 201920073.
• Burton, A., Obaid, S. N., Vázquez-Guardado, A., Schmit, M. B., Stuart, T., Cai, L., Chen, Z., Kandela, I., Haney, C. R., Waters, E. A., Cai, H., Rogers, J. A., Lu, L., & Gutruf, P. (2020). Wireless, battery-free subdermally implantable photometry systems for chronic recording of neural dynamics. Proceedings of the National Academy of Sciences of the United States of America, 117(6), 2835-2845.
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  Recording cell-specific neuronal activity while monitoring behaviors of freely moving subjects can provide some of the most significant insights into brain function. Current means for monitoring calcium dynamics in genetically targeted populations of neurons rely on delivery of light and recording of fluorescent signals through optical fibers that can reduce subject mobility, induce motion artifacts, and limit experimental paradigms to isolated subjects in open, two-dimensional (2D) spaces. Wireless alternatives eliminate constraints associated with optical fibers, but their use of head stages with batteries adds bulk and weight that can affect behaviors, with limited operational lifetimes. The systems introduced here avoid drawbacks of both types of technologies, by combining highly miniaturized electronics and energy harvesters with injectable photometric modules in a class of fully wireless, battery-free photometer that is fully implantable subdermally to allow for the interrogation of neural dynamics in freely behaving subjects, without limitations set by fiber optic tethers or operational lifetimes constrained by traditional power supplies. The unique capabilities of these systems, their compatibility with magnetic resonant imaging and computed tomography and the ability to manufacture them with techniques in widespread use for consumer electronics, suggest a potential for broad adoption in neuroscience research.
• Gutruf, P., Utzinger, U., & Subbian, V. (2020). Moving from Pedagogy to Andragogy in Biomedical Engineering Design: Strategies for Lab-at-Home and Distance Learning. Biomedical engineering education, 1-5.
• Han, Y., Zhang, Y., Kim, H., Grayson, V. S., Jovasevic, V., Ren, W., Centeno, M. V., Guedea, A. L., Meyer, M. A., Wu, Y., Gutruf, P., Surmeier, D. J., Gao, C., Martina, M., Apkarian, A. V., Rogers, J. A., & Radulovic, J. (2020). Excitatory VTA to DH projections provide a valence signal to memory circuits. Nature communications, 11(1), 1466.
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  The positive or negative value (valence) of past experiences is normally integrated into neuronal circuits that encode episodic memories and plays an important role in guiding behavior. Here, we show, using mouse behavioral models, that glutamatergic afferents from the ventral tegmental area to the dorsal hippocampus (VTA→DH) signal negative valence to memory circuits, leading to the formation of fear-inducing context memories and to context-specific reinstatement of fear. To a lesser extent, these projections also contributed to opioid-induced place preference, suggesting a role in signaling positive valence as well, and thus a lack of dedicated polarity. Manipulations of VTA terminal activity were more effective in females and paralleled by sex differences in glutamatergic signaling. By prioritizing retrieval of negative and positive over neutral memories, the VTA→DH circuit can facilitate the selection of adaptive behaviors when current and past experiences are valence congruent.
• Hourlier-Fargette, A., Schon, S., Xue, Y., Avila, R., Li, W., Gao, Y., Liu, C., Kim, S. B., Raj, M. S., Fields, K. B., Parsons, B. V., Lee, K., Lee, J. Y., Chung, H. U., Lee, S. P., Johnson, M., Bandodkar, A. J., Gutruf, P., Model, J. B., , Aranyosi, A. J., et al. (2020). Skin-interfaced soft microfluidic systems with modular and reusable electronics for capacitive sensing of sweat loss, rate and conductivity. Lab on a chip.
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  Important insights into human health can be obtained through the non-invasive collection and detailed analysis of sweat, a biofluid that contains a wide range of essential biomarkers. Skin-interfaced microfluidic platforms, characterized by soft materials and thin geometries, offer a collection of capabilities for in situ capture, storage, and analysis of sweat and its constituents. In ambulatory uses cases, the ability to provide real-time feedback on sweat loss, rate and content, without visual inspection of the device, can be important. This paper introduces a low-profile skin-interfaced system that couples disposable microfluidic sampling devices with reusable 'stick-on' electrodes and wireless readout electronics that remain isolated from the sweat. An ultra-thin capping layer on the microfluidic platform permits high-sensitivity, contactless capacitive measurements of both sweat loss and sweat conductivity. This architecture avoids the potential for corrosion of the sensing components and eliminates the need for cleaning/sterilizing the electronics, thereby resulting in a cost-effective platform that is simple to use. Optimized electrode designs follow from a combination of extensive benchtop testing, analytical calculations and FEA simulations for two sensing configurations: (1) sweat rate and loss, and (2) sweat conductivity, which contains information about electrolyte content. Both configurations couple to a flexible, wireless electronics platform that digitizes and transmits information to Bluetooth-enabled devices. On-body field testing during physical exercise validates the performance of the system in scenarios of practical relevance to human health and performance.
• Bandodkar, A. J., Choi, J., Lee, S. P., Jeang, W. J., Agyare, P., Gutruf, P., Wang, S., Sponenburg, R. A., Reeder, J. T., Schon, S., Ray, T. R., Chen, S., Mehta, S., Ruiz, S., & Rogers, J. A. (2019). Soft, Skin-Interfaced Microfluidic Systems with Passive Galvanic Stopwatches for Precise Chronometric Sampling of Sweat. Advanced Materials, 31(32), 1902109.
• Bandodkar, A. J., Gutruf, P., Choi, J., Lee, K., Sekine, Y., Reeder, J. T., Jeang, W. J., Aranyosi, A. J., Lee, S. P., Model, J. B., Ghaffari, R., Su, C., Leshock, J. P., Ray, T., Verrillo, A., Thomas, K., Krishnamurthi, V., Han, S., Kim, J., , Krishnan, S., et al. (2019). Battery-free, skin-interfaced microfluidic/electronic systems for simultaneous electrochemical, colorimetric, and volumetric analysis of sweat. Science Advances, 5(1).
• Gutruf, P., Yin, R. T., Lee, K. B., Ausra, J., Brennan, J. A., Qiao, Y., Xie, Z., Peralta, R., Talarico, O., Murillo, A., Chen, S. W., Leshock, J. P., Haney, C. R., Waters, E. A., Zhang, C., Luan, H., Huang, Y., Trachiotis, G., Efimov, I. R., & Rogers, J. A. (2019). Wireless, battery-free, fully implantable multimodal and multisite pacemakers for applications in small animal models. Nature Communications, 10(1), 5742.
• Ray, T. R., Choi, J., Bandodkar, A. J., Krishnan, S., Gutruf, P., Tian, L., Ghaffari, R., & Rogers, J. A. (2019). Bio-Integrated Wearable Systems: A Comprehensive Review. Chemical Reviews.
• Reeder, J. T., Choi, J., Xue, Y., Gutruf, P., Hanson, J., Liu, M., Ray, T., Bandodkar, A. J., Avila, R., Xia, W., Krishnan, S., Xu, S., Barnes, K., Pahnke, M., Ghaffari, R., Huang, Y., & Rogers, J. A. (2019). Waterproof, electronics-enabled, epidermal microfluidic devices for sweat collection, biomarker analysis, and thermography in aquatic settings. Science Advances, 5(1).
• Yu, X., Xie, Z., Yu, Y., Lee, J., Vazquez-Guardado, A., Luan, H., Ruban, J., Ning, X., Akhtar, A., Li, D., Ji, B., Liu, Y., Sun, R., Cao, J., Huo, Q., Zhong, Y., Lee, C., Kim, S., Gutruf, P., , Zhang, C., et al. (2019). Skin-integrated wireless haptic interfaces for virtual and augmented reality. Nature, 575(7783), 473-479.
• Zhang, H., Gutruf, P., Meacham, K., Montana, M. C., Zhao, X., Chiarelli, A. M., Vázquez-Guardado, A., Norris, A., Lu, L., Guo, Q., Xu, C., Wu, Y., Zhao, H., Ning, X., Bai, W., Kandela, I., Haney, C. R., Chanda, D., Gereau, R. W., & Rogers, J. A. (2019). Wireless, battery-free optoelectronic systems as subdermal implants for local tissue oximetry. Science Advances, 5(3), eaaw0873.
• Zhang, Y., Castro, D. C., Han, Y., Wu, Y., Guo, H., Weng, Z., Xue, Y., Ausra, J., Wang, X., Li, R., Wu, G., Vázquez-Guardado, A., Xie, Y., Xie, Z., Ostojich, D., Peng, D., Sun, R., Wang, B., Yu, Y., , Leshock, J. P., et al. (2019). Battery-free, lightweight, injectable microsystem for in vivo wireless pharmacology and optogenetics. Proceedings of the National Academy of Sciences, 116(43), 21427.
• Zhang, Y., Mickle, A. D., Gutruf, P., McIlvried, L. A., Guo, H., Wu, Y., Golden, J. P., Xue, Y., Grajales-Reyes, J. G., Wang, X., Krishnan, S., Xie, Y., Peng, D., Su, C., Zhang, F., Reeder, J. T., Vogt, S. K., Huang, Y., Rogers, J. A., & Gereau, R. W. (2019). Battery-free, fully implantable optofluidic cuff system for wireless optogenetic and pharmacological neuromodulation of peripheral nerves. Science Advances, 5(7), eaaw5296.
• Gutruf, P., & Rogers, J. A. (2018). Implantable, wireless device platforms for neuroscience research. Current opinion in neurobiology, 50, 42-49.
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  Recently developed classes of ultraminiaturized wireless devices provide powerful capabilities in neuroscience research, as implantable light sources for simulation/inhibition via optogenetics, as integrated microfluidic systems for programmed pharmacological delivery and as multimodal sensors for physiological measurements. These platforms leverage basic advances in biocompatible materials, semiconductor device designs and systems engineering concepts to afford modes of operation that are qualitatively distinct from those of conventional approaches that tether animals to external hardware by means of optical fibers, electrical cables and/or fluidic tubing. Neuroscience studies that exploit the unique features of these technologies enable insights into neural function through targeted stimulation, inhibition and recording, with spatially and genetically precise manipulation of neural circuit activity. Experimental possibilities include studies in naturalistic, three dimensional environments, investigations of pair-wise or group related social interactions and many other scenarios of interest that cannot be addressed using traditional hardware.
• Gutruf, P., Good, C. H., & Rogers, J. A. (2018). Perspective: Implantable optical systems for neuroscience research in behaving animal models:Current approaches and future directions. APL Photonics, 3(12), 120901.
• Gutruf, P., Krishnamurthi, V., Vázquez-Guardado, A., Xie, Z., Banks, A., Su, C., Xu, Y., Haney, C. R., Waters, E. A., Kandela, I., Krishnan, S. R., Ray, T., Leshock, J. P., Huang, Y., Chanda, D., & Rogers, J. A. (2018). Fully implantable optoelectronic systems for battery-free, multimodal operation in neuroscience research. Nature Electronics, 1(12), 652-660.
• Heo, S. Y., Kim, J., Gutruf, P., Banks, A., Wei, P., Pielak, R., Balooch, G., Shi, Y., Araki, H., Rollo, D., Gaede, C., Patel, M., Kwak, J. W., Peña-Alcántara, A. E., Lee, K., Yun, Y., Robinson, J. K., Xu, S., & Rogers, J. A. (2018). Wireless, battery-free, flexible, miniaturized dosimeters monitor exposure to solar radiation and to light for phototherapy. Science Translational Medicine, 10(470), eaau1643.
• Krishnan, S. R., Ray, T. R., Ayer, A. B., Ma, Y., Gutruf, P., Lee, K., Lee, J. Y., Wei, C., Feng, X., Ng, B., Abecassis, Z. A., Murthy, N., Stankiewicz, I., Freudman, J., Stillman, J., Kim, N., Young, G., Goudeseune, C., Ciraldo, J., , Tate, M., et al. (2018). Epidermal electronics for noninvasive, wireless, quantitative assessment of ventricular shunt function in patients with hydrocephalus. Science Translational Medicine, 10(465).
• Krishnan, S. R., Su, C., Xie, Z., Patel, M., Madhvapathy, S. R., Xu, Y., Freudman, J., Ng, B., Heo, S. Y., Wang, H., Ray, T. R., Leshock, J., Stankiewicz, I., Feng, X., Huang, Y., Gutruf, P., & Rogers, J. A. (2018). Wireless, Battery-Free Epidermal Electronics for Continuous, Quantitative, Multimodal Thermal Characterization of Skin. Small, 0(0), 1803192.
• Lu, L., Gutruf, P., Xia, L., Bhatti, D. L., Wang, X., Vazquez-Guardado, A., Ning, X., Shen, X., Sang, T., Ma, R., Pakeltis, G., Sobczak, G., Zhang, H., Seo, D. O., Xue, M., Yin, L., Chanda, D., Sheng, X., Bruchas, M. R., & Rogers, J. A. (2018). Wireless optoelectronic photometers for monitoring neuronal dynamics in the deep brain. Proceedings of the National Academy of Sciences of the United States of America, 115(7), E1374-E1383.
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  Capabilities for recording neural activity in behaving mammals have greatly expanded our understanding of brain function. Some of the most sophisticated approaches use light delivered by an implanted fiber-optic cable to optically excite genetically encoded calcium indicators and to record the resulting changes in fluorescence. Physical constraints induced by the cables and the bulk, size, and weight of the associated fixtures complicate studies on natural behaviors, including social interactions and movements in environments that include obstacles, housings, and other complex features. Here, we introduce a wireless, injectable fluorescence photometer that integrates a miniaturized light source and a photodetector on a flexible, needle-shaped polymer support, suitable for injection into the deep brain at sites of interest. The ultrathin geometry and compliant mechanics of these probes allow minimally invasive implantation and stable chronic operation. In vivo studies in freely moving animals demonstrate that this technology allows high-fidelity recording of calcium fluorescence in the deep brain, with measurement characteristics that match or exceed those associated with fiber photometry systems. The resulting capabilities in optical recordings of neuronal dynamics in untethered, freely moving animals have potential for widespread applications in neuroscience research.
• Nirantar, S., Ahmed, T., Ren, G., Gutruf, P., Xu, C., Bhaskaran, M., Walia, S., & Sriram, S. (2018). Metal Air Transistors: Semiconductor-Free Field-Emission Air-Channel Nanoelectronics. Nano Letters.
• Araki, H., Kim, J., Zhang, S., Banks, A., Crawford, K. E., Sheng, X., Gutruf, P., Shi, Y., Pielak, R. M., & Rogers, J. A. (2017). Materials and Device Designs for an Epidermal UV Colorimetric Dosimeter with Near Field Communication Capabilities. ADVANCED FUNCTIONAL MATERIALS, 27(2).
• Kim, J., Gutruf, P., Chiarelli, A. M., Heo, S. Y., Cho, K., Xie, Z., Banks, A., Han, S., Jang, K. I., Lee, J. W., Lee, K. T., Feng, X., Huang, Y., Fabiani, M., Gratton, G., Paik, U., & Rogers, J. A. (2017). Miniaturized Battery-Free Wireless Systems for Wearable Pulse Oximetry. Advanced functional materials, 27(1).
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  Development of unconventional technologies for wireless collection, storage and analysis of quantitative, clinically relevant information on physiological status is of growing interest. Soft, biocompatible systems are widely regarded as important because they facilitate mounting on external (e.g. skin) and internal (e.g. heart, brain) surfaces of the body. Ultra-miniaturized, lightweight and battery-free devices have the potential to establish complementary options in bio-integration, where chronic interfaces (i.e. months) are possible on hard surfaces such as the fingernails and the teeth, with negligible risk for irritation or discomfort. Here we report materials and device concepts for flexible platforms that incorporate advanced optoelectronic functionality for applications in wireless capture and transmission of photoplethysmograms, including quantitative information on blood oxygenation, heart rate and heart rate variability. Specifically, reflectance pulse oximetry in conjunction with near-field communication (NFC) capabilities enables operation in thin, miniaturized flexible devices. Studies of the material aspects associated with the body interface, together with investigations of the radio frequency characteristics, the optoelectronic data acquisition approaches and the analysis methods capture all of the relevant engineering considerations. Demonstrations of operation on various locations of the body and quantitative comparisons to clinical gold standards establish the versatility and the measurement accuracy of these systems, respectively.
• Lee, G., Kang, S., Won, S. M., Gutruf, P., Jeong, Y. R., Koo, J., Lee, S., Rogers, J. A., & Ha, J. S. (2017). Fully Biodegradable Microsupercapacitor for Power Storage in Transient Electronics. ADVANCED ENERGY MATERIALS, 7(18).
• Fumeaux, C., Zou, C., Headland, D., Nirantar, S., Gutruf, P., Zou, L., Bhaskaran, M., Sriram, S., & Withayachumnankul, W. (2016). Terahertz and Optical Dielectric Resonator Antennas: Potential and Challenges for Efficient Designs. 2016 10TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP).
• Gutruf, P., Zou, C., Withayachumnankul, W., Bhaskaran, M., Sriram, S., & Fumeaux, C. (2016). Mechanically Tunable Dielectric Resonator Metasurfaces at Visible Frequencies. ACS nano, 10(1), 133-41.
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  Devices that manipulate light represent the future of information processing. Flat optics and structures with subwavelength periodic features (metasurfaces) provide compact and efficient solutions. The key bottleneck is efficiency, and replacing metallic resonators with dielectric resonators has been shown to significantly enhance performance. To extend the functionalities of dielectric metasurfaces to real-world optical applications, the ability to tune their properties becomes important. In this article, we present a mechanically tunable all-dielectric metasurface. This is composed of an array of dielectric resonators embedded in an elastomeric matrix. The optical response of the structure under a uniaxial strain is analyzed by mechanical-electromagnetic co-simulations. It is experimentally demonstrated that the metasurface exhibits remarkable resonance shifts. Analysis using a Lagrangian model reveals that strain modulates the near-field mutual interaction between resonant dielectric elements. The ability to control and alter inter-resonator coupling will position dielectric metasurfaces as functional elements of reconfigurable optical devices.
• Headland, D., Carrasco, E., Nirantar, S., Withayachumnankul, W., Gutruf, P., Schwarz, J., Abbott, D., Bhaskaran, M., Sriram, S., Perruisseau-Carrier, J., & Fumeaux, C. (2016). Dielectric Resonator Reflectarray as High-Efficiency Nonuniform Terahertz Metasurface. ACS PHOTONICS, 3(6), 1019-1026.
• Headland, D., Nirantar, S., Gutruf, P., Abbott, D., Bhaskaran, M., Fumeaux, C., Sriram, S., & Withayachumnankul, W. (2016). Fabrication of micro-scale single-crystal silicon structures for efficient terahertz magnetic mirror. 2016 41ST INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ).
• Wong, W., Gutruf, P., Sriram, S., Bhaskaran, M., Wang, Z., & Tricoli, A. (2016). Strain Engineering of Wave-like Nanofibers for Dynamically Switchable Adhesive/Repulsive Surfaces. ADVANCED FUNCTIONAL MATERIALS, 26(3), 399-407.
• Yan, Z., Zhang, F., Liu, F., Han, M., Ou, D., Liu, Y., Lin, Q., Guo, X., Fu, H., Xie, Z., Gao, M., Huang, Y., Kim, J., Qiu, Y., Nan, K., Kim, J., Gutruf, P., Luo, H., Zhao, A., , Hwang, K. C., et al. (2016). Mechanical assembly of complex, 3D mesostructures from releasable multilayers of advanced materials. Science advances, 2(9), e1601014.
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  Capabilities for assembly of three-dimensional (3D) micro/nanostructures in advanced materials have important implications across a broad range of application areas, reaching nearly every class of microsystem technology. Approaches that rely on the controlled, compressive buckling of 2D precursors are promising because of their demonstrated compatibility with the most sophisticated planar technologies, where materials include inorganic semiconductors, polymers, metals, and various heterogeneous combinations, spanning length scales from submicrometer to centimeter dimensions. We introduce a set of fabrication techniques and design concepts that bypass certain constraints set by the underlying physics and geometrical properties of the assembly processes associated with the original versions of these methods. In particular, the use of releasable, multilayer 2D precursors provides access to complex 3D topologies, including dense architectures with nested layouts, controlled points of entanglement, and other previously unobtainable layouts. Furthermore, the simultaneous, coordinated assembly of additional structures can enhance the structural stability and drive the motion of extended features in these systems. The resulting 3D mesostructures, demonstrated in a diverse set of more than 40 different examples with feature sizes from micrometers to centimeters, offer unique possibilities in device design. A 3D spiral inductor for near-field communication represents an example where these ideas enable enhanced quality () factors and broader working angles compared to those of conventional 2D counterparts.
• Zou, C., Gutruf, P., Withayachumnankul, W., Zou, L., Bhaskaran, M., Sriram, S., & Fumeaux, C. (2016). Nanoscale TiO2 dielectric resonator absorbers. OPTICS LETTERS, 41(15), 3391-3394.
• Gutruf, P., Walia, S., Sriram, S., & Bhaskaran, M. (2015). Visible-Blind UV Imaging with Oxygen-Deficient Zinc Oxide Flexible Devices. ADVANCED ELECTRONIC MATERIALS, 1(12).
• Gutruf, P., Zeller, E., Walia, S., Nili, H., Sriram, S., & Bhaskaran, M. (2015). Stretchable and Tunable Microtectonic ZnO-Based Sensors and Photonics. SMALL, 11(35), 4532-4539.
• Gutruf, P., Zeller, E., Walia, S., Sriram, S., & Bhaskaran, M. (2015). Mechanically Tunable High Refractive-Index Contrast TiO2-PDMS Gratings. ADVANCED OPTICAL MATERIALS, 3(11), 1565-1569.
• Headland, D., Nirantar, S., Withayachumnankul, W., Gutruf, P., Abbott, D., Bhaskaran, M., Fumeaux, C., & Sriram, S. (2015). Terahertz Magnetic Mirror Realized with Dielectric Resonator Antennas. ADVANCED MATERIALS, 27(44), 7137-+.
• Headland, D., Taha, M., Gutruf, P., Withayachumnankul, W., Bhaskaran, M., Fumeaux, C., Abbott, D., & Sriram, S. (2015). Passive electric monopole array for terahertz surface wave launcher. 2015 40TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ).
• Kim, J., Banks, A., Cheng, H., Xie, Z., Xu, S., Jang, K., Lee, J. W., Liu, Z., Gutruf, P., Huang, X., Wei, P., Liu, F., Li, K., Dalal, M., Ghaffari, R., Feng, X., Huang, Y., Gupta, S., Paik, U., & Rogers, J. A. (2015). Epidermal Electronics with Advanced Capabilities in Near-Field Communication. SMALL, 11(8), 906-912.
• Kim, J., Banks, A., Xie, Z., Heo, S. Y., Gutruf, P., Lee, J. W., Xu, S., Jang, K., Liu, F., Brown, G., Choi, J., Kim, J. H., Feng, X., Huang, Y., Paik, U., & Rogers, J. A. (2015). Miniaturized Flexible Electronic Systems with Wireless Power and Near-Field Communication Capabilities. ADVANCED FUNCTIONAL MATERIALS, 25(30), 4761-4767.
• Nili, H., Walia, S., Kandjani, A. E., Ramanathan, R., Gutruf, P., Ahmed, T., Balendhran, S., Bansal, V., Strukov, D. B., Kavehei, O., Bhaskaran, M., & Sriram, S. (2015). Donor-Induced Performance Tuning of Amorphous SrTiO3 Memristive Nanodevices: Multistate Resistive Switching and Mechanical Tunability. ADVANCED FUNCTIONAL MATERIALS, 25(21), 3172-3182.
• Sonsilphong, A., Gutruf, P., Withayachumnankul, W., Abbott, D., Bhaskaran, M., Sriram, S., & Wongkasem, N. (2015). Flexible bi-layer terahertz chiral metamaterials. JOURNAL OF OPTICS, 17(8).
• Walia, S., Shah, C. M., Gutruf, P., Nili, H., Chowdhury, D. R., Withayachumnankul, W., Bhaskaran, M., & Sriram, S. (2015). Flexible metasurfaces and metamaterials: A review of materials and fabrication processes at micro- and nano-scales. APPLIED PHYSICS REVIEWS, 2(1).
• Gutruf, P., Walia, S., Ali, M. N., Sriram, S., & Bhaskaran, M. (2014). Strain response of stretchable micro-electrodes: Controlling sensitivity with serpentine designs and encapsulation. APPLIED PHYSICS LETTERS, 104(2).
• Niu, T., Withayachumnankul, W., Upadhyay, A., Gutruf, P., Abbott, D., Bhaskaran, M., Sriram, S., & Fumeaux, C. (2014). Terahertz reflectarray as a polarizing beam splitter. OPTICS EXPRESS, 22(13), 16148-16160.
• Gutruf, P., Shah, C. M., Walia, S., Nili, H., Zoolfakar, A. S., Karnutsch, C., Kalantar-zadeh, K., Sriram, S., & Bhaskaran, M. (2013). Transparent functional oxide stretchable electronics: micro-tectonics enabled high strain electrodes. NPG ASIA MATERIALS, 5.

Proceedings Publications

• Nirantar, S., Ahmed, T., Ren, G., Gutruf, P., Xu, C., Bhaskaran, M., Walia, S., & Sriram, S. (2019, 2019). Semiconductor-Free Field-Emission Nanoelectronics: Application in Air-Channel Transistors. In 2019 International Vacuum Electronics Conference (IVEC), 1-2.

Presentations

• Miller, J. E., Gutruf, P., Peralta, R., Burton, A., Azami, A., Ausra, J., Munger, S. J., & Ibrahim, N. (2020, November). Effects of Optogenetic Manipulation on Song in a Zebra Finch Model.. Annual Biomedical Research Conference for Minority Students (ABRCMS)Annual Biomedical Research Conference for Minority Students (ABRCMS).
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  Undergraduate MARC student Naya Ibrahim won a cash prize for her oral presentation in the virtual format.
• Gutruf, P. (2019, 03). Wireless battery free subdermally implantable neuromodulation and recording tools. BIOEL 2019. Kirchberg, Austria.
• Gutruf, P. (2019, 04). Fully Implantable Wireless Battery-Free Optoelectronic Systems for Multimodal Optogenetic Neuromodulation. MRS Spring Phoenix.
• Gutruf, P. (2019, 11). Wireless, subdermally implantable neuromodulation tools for chronic recording and stimulation in freely moving subjects. Neuroscience.
• Gutruf, P. (2019, 12). Soft, wireless and battery free sensors and photonics for broad application in the assessment and stimulation of biological systems. ICBME.