Publications by authors named "Jae-Woong Jeong"

30 Publications

  • Page 1 of 1

Instant, multiscale dry transfer printing by atomic diffusion control at heterogeneous interfaces.

Sci Adv 2021 Jul 9;7(28). Epub 2021 Jul 9.

Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology, Daegu 42988, South Korea.

Transfer printing is a technique that integrates heterogeneous materials by readily retrieving functional elements from a grown substrate and subsequently printing them onto a specific target site. These strategies are broadly exploited to construct heterogeneously integrated electronic devices. A typical wet transfer printing method exhibits limitations related to unwanted displacement and shape distortion of the device due to uncontrollable fluid movement and slow chemical diffusion. In this study, a dry transfer printing technique that allows reliable and instant release of devices by exploiting the thermal expansion mismatch between adjacent materials is demonstrated, and computational studies are conducted to investigate the fundamental mechanisms of the dry transfer printing process. Extensive exemplary demonstrations of multiscale, sequential wet-dry, circuit-level, and biological topography-based transfer printing demonstrate the potential of this technique for many other emerging applications in modern electronics that have not been achieved through conventional wet transfer printing over the past few decades.
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http://dx.doi.org/10.1126/sciadv.abh0040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8270493PMC
July 2021

Outdoor-Useable, Wireless/Battery-Free Patch-Type Tissue Oximeter with Radiative Cooling.

Adv Sci (Weinh) 2021 05 9;8(10):2004885. Epub 2021 Mar 9.

School of Electrical Engineering and Computer Science (EECS) Gwangju Institute of Science and Technology (GIST) 123, Cheomdangwagi-ro, Bukgu Gwangju 61005 Republic of Korea.

For wearable electronics/optoelectronics, thermal management should be provided for accurate signal acquisition as well as thermal comfort. However, outdoor solar energy gain has restricted the efficiency of some wearable devices like oximeters. Herein, wireless/battery-free and thermally regulated patch-type tissue oximeter (PTO) with radiative cooling structures are presented, which can measure tissue oxygenation under sunlight in reliable manner and will benefit athlete training. To maximize the radiative cooling performance, a nano/microvoids polymer (NMVP) is introduced by combining two perforated polymers to both reduce sunlight absorption and maximize thermal radiation. The optimized NMVP exhibits sub-ambient cooling of 6 °C in daytime under various conditions such as scattered/overcast clouds, high humidity, and clear weather. The NMVP-integrated PTO enables maintaining temperature within ≈1 °C on the skin under sunlight relative to indoor measurement, whereas the normally used, black encapsulated PTO shows over 40 °C owing to solar absorption. The heated PTO exhibits an inaccurate tissue oxygen saturation (StO) value of ≈67% compared with StO in a normal state (i.e., ≈80%). However, the thermally protected PTO presents reliable StO of ≈80%. This successful demonstration provides a feasible strategy of thermal management in wearable devices for outdoor applications.
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http://dx.doi.org/10.1002/advs.202004885DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8132059PMC
May 2021

Rapidly-customizable, scalable 3D-printed wireless optogenetic probes for versatile applications in neuroscience.

Adv Funct Mater 2020 Nov 18;30(46). Epub 2020 Sep 18.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.

Optogenetics is an advanced neuroscience technique that enables the dissection of neural circuitry with high spatiotemporal precision. Recent advances in materials and microfabrication techniques have enabled minimally invasive and biocompatible optical neural probes, thereby facilitating optogenetic research. However, conventional fabrication techniques rely on cleanroom facilities, which are not easily accessible and are expensive to use, making the overall manufacturing process inconvenient and costly. Moreover, the inherent time-consuming nature of current fabrication procedures impede the rapid customization of neural probes in between studies. Here, we introduce a new technique stemming from 3D printing technology for the low-cost, mass production of rapidly customizable optogenetic neural probes. We detail the 3D printing production process, on-the-fly design versatility, and biocompatibility of 3D printed optogenetic probes as well as their functional capabilities for wireless optogenetics. Successful studies with 3D printed devices highlight the reliability of this easily accessible and flexible manufacturing approach that, with advances in printing technology, can foreshadow its widespread applications in low-cost bioelectronics in the future.
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http://dx.doi.org/10.1002/adfm.202004285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7942018PMC
November 2020

Design Strategy for Transformative Electronic System toward Rapid, Bidirectional Stiffness Tuning using Graphene and Flexible Thermoelectric Device Interfaces.

Adv Mater 2021 Mar 25;33(10):e2007239. Epub 2021 Jan 25.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.

Electronics with tunable shape and stiffness can be applied in broad range of applications because their tunability allows their use in either rigid handheld form or soft wearable form, depending on needs. Previous research has enabled such reconfigurable electronics by integrating a thermally tunable gallium-based platform with flexible/stretchable electronics. However, supercooling phenomenon caused in the freezing process of gallium impedes reliable and rapid bidirectional rigid-soft conversion, limiting the full potential of this type of "transformative" electronics. Here, materials and electronics design strategies are reported to develop a transformative system with a gallium platform capable of fast reversible mechanical switching. In this electronic system, graphene is used as a catalyst to accelerate the heterogeneous nucleation of gallium to mitigate the degree of supercooling. Additionally, a flexible thermoelectric device is integrated as a means to provide active temperature control to further reduce the time for the solid-liquid transition of gallium. Analytical and experimental results establish the fundamentals for the design and optimized operation of transformative electronics for accelerated bidirectional transformation. Proof-of-concept demonstration of a reconfigurable system, which can convert between rigid handheld electronics and a flexible wearable biosensor, demonstrates the potential of this design approach for highly versatile electronics that can support multiple applications.
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http://dx.doi.org/10.1002/adma.202007239DOI Listing
March 2021

Soft subdermal implant capable of wireless battery charging and programmable controls for applications in optogenetics.

Nat Commun 2021 01 22;12(1):535. Epub 2021 Jan 22.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.

Optogenetics is a powerful technique that allows target-specific spatiotemporal manipulation of neuronal activity for dissection of neural circuits and therapeutic interventions. Recent advances in wireless optogenetics technologies have enabled investigation of brain circuits in more natural conditions by releasing animals from tethered optical fibers. However, current wireless implants, which are largely based on battery-powered or battery-free designs, still limit the full potential of in vivo optogenetics in freely moving animals by requiring intermittent battery replacement or a special, bulky wireless power transfer system for continuous device operation, respectively. To address these limitations, here we present a wirelessly rechargeable, fully implantable, soft optoelectronic system that can be remotely and selectively controlled using a smartphone. Combining advantageous features of both battery-powered and battery-free designs, this device system enables seamless full implantation into animals, reliable ubiquitous operation, and intervention-free wireless charging, all of which are desired for chronic in vivo optogenetics. Successful demonstration of the unique capabilities of this device in freely behaving rats forecasts its broad and practical utilities in various neuroscience research and clinical applications.
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http://dx.doi.org/10.1038/s41467-020-20803-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7822865PMC
January 2021

ID1-Mediated BMP Signaling Pathway Potentiates Glucagon-Like Peptide-1 Secretion in Response to Nutrient Replenishment.

Int J Mol Sci 2020 May 28;21(11). Epub 2020 May 28.

Department of Medical Science, BK21 Plus Project for Medical Science, Yonsei University College of Medicine, Seoul 03722, Korea.

Glucagon-like peptide-1 (GLP-1) is a well-known incretin hormone secreted from enteroendocrinal L cells in response to nutrients, such as glucose and dietary fat, and controls glycemic homeostasis. However, the detailed intracellular mechanisms of how L cells control GLP-1 secretion in response to nutrients still remain unclear. Here, we report that bone morphogenetic protein (BMP) signaling pathway plays a pivotal role to control GLP-1 secretion in response to nutrient replenishment in well-established mouse enteroendocrinal L cells (GLUTag cells). Nutrient starvation dramatically reduced cellular respiration and GLP-1 secretion in GLUTag cells. Transcriptome analysis revealed that nutrient starvation remarkably reduced gene expressions involved in BMP signaling pathway, whereas nutrient replenishment rescued BMP signaling to potentiate GLP-1 secretion. Transient knockdown of inhibitor of DNA binding (ID)1, a well-known target gene of BMP signaling, remarkably reduced GLP-1 secretion. Consistently, LDN193189, an inhibitor of BMP signaling, markedly reduced GLP-1 secretion in L cells. In contrast, BMP4 treatment activated BMP signaling pathway and potentiated GLP-1 secretion in response to nutrient replenishment. Altogether, we demonstrated that BMP signaling pathway is a novel molecular mechanism to control GLP-1 secretion in response to cellular nutrient status. Selective activation of BMP signaling would be a potent therapeutic strategy to stimulate GLP-1 secretion in order to restore glycemic homeostasis.
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http://dx.doi.org/10.3390/ijms21113824DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311998PMC
May 2020

Soft Material-Enabled Electronics for Medicine, Healthcare, and Human-Machine Interfaces.

Materials (Basel) 2020 Jan 22;13(3). Epub 2020 Jan 22.

George W. Woodruff School of Mechanical Engineering, Institute for Electronics and Nanotechnology, Georgia Institute of Technology, Atlanta, GA 30332, USA.

Soft material-enabled electronics offer distinct advantages over conventional rigid and bulky devices for numerous wearable and implantable applications. Soft materials allow for seamless integration with skin and tissues due to the enhanced mechanical flexibility and stretchability. Wearable devices with multiple sensors offer continuous, real-time monitoring of biosignals and movements, which can be applied for rehabilitation and diagnostics, among other applications. Soft implantable electronics offer similar functionalities, but with improved compatibility with human tissues. Biodegradable soft implantable electronics are also being developed for transient monitoring, such as in the weeks following surgeries. New composite materials, integration strategies, and fabrication techniques are being developed to further advance soft electronics. This paper reviews recent progresses in these areas towards the development of soft material-enabled electronics for medicine, healthcare, and human-machine interfaces.
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http://dx.doi.org/10.3390/ma13030517DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7040651PMC
January 2020

Mechanically transformative electronics, sensors, and implantable devices.

Sci Adv 2019 11 1;5(11):eaay0418. Epub 2019 Nov 1.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.

Traditionally, electronics have been designed with static form factors to serve designated purposes. This approach has been an optimal direction for maintaining the overall device performance and reliability for targeted applications. However, electronics capable of changing their shape, flexibility, and stretchability will enable versatile and accommodating systems for more diverse applications. Here, we report design concepts, materials, physics, and manufacturing strategies that enable these reconfigurable electronic systems based on temperature-triggered tuning of mechanical characteristics of device platforms. We applied this technology to create personal electronics with variable stiffness and stretchability, a pressure sensor with tunable bandwidth and sensitivity, and a neural probe that softens upon integration with brain tissue. Together, these types of transformative electronics will substantially broaden the use of electronics for wearable and implantable applications.
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http://dx.doi.org/10.1126/sciadv.aay0418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824851PMC
November 2019

Wireless optofluidic brain probes for chronic neuropharmacology and photostimulation.

Nat Biomed Eng 2019 08 5;3(8):655-669. Epub 2019 Aug 5.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.

Both in vivo neuropharmacology and optogenetic stimulation can be used to decode neural circuitry, and can provide therapeutic strategies for brain disorders. However, current neuronal interfaces hinder long-term studies in awake and freely behaving animals, as they are limited in their ability to provide simultaneous and prolonged delivery of multiple drugs, are often bulky and lack multifunctionality, and employ custom control systems with insufficiently versatile selectivity for output mode, animal selection and target brain circuits. Here, we describe smartphone-controlled, minimally invasive, soft optofluidic probes with replaceable plug-like drug cartridges for chronic in vivo pharmacology and optogenetics with selective manipulation of brain circuits. We demonstrate the use of the probes for the control of the locomotor activity of mice for over four weeks via programmable wireless drug delivery and photostimulation. Owing to their ability to deliver both drugs and photopharmacology into the brain repeatedly over long time periods, the probes may contribute to uncovering the basis of neuropsychiatric diseases.
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http://dx.doi.org/10.1038/s41551-019-0432-1DOI Listing
August 2019

Advanced Soft Materials, Sensor Integrations, and Applications of Wearable Flexible Hybrid Electronics in Healthcare, Energy, and Environment.

Adv Mater 2020 Apr 8;32(15):e1901924. Epub 2019 Jul 8.

George W. Woodruff School of Mechanical Engineering, Wallace H. Coulter Department of Biomedical Engineering, Institute for Electronics and Nanotechnology, Parker H. Petit Institute for Bioengineering and Biosciences, Center for Flexible and Wearable Electronics Advanced Research, Neural Engineering Center, Institute for Materials, Institute for Robotics and Intelligent Machines, Georgia Institute of Technology, Atlanta, GA, 30332, USA.

Recent advances in soft materials and system integration technologies have provided a unique opportunity to design various types of wearable flexible hybrid electronics (WFHE) for advanced human healthcare and human-machine interfaces. The hybrid integration of soft and biocompatible materials with miniaturized wireless wearable systems is undoubtedly an attractive prospect in the sense that the successful device performance requires high degrees of mechanical flexibility, sensing capability, and user-friendly simplicity. Here, the most up-to-date materials, sensors, and system-packaging technologies to develop advanced WFHE are provided. Details of mechanical, electrical, physicochemical, and biocompatible properties are discussed with integrated sensor applications in healthcare, energy, and environment. In addition, limitations of the current materials are discussed, as well as key challenges and the future direction of WFHE. Collectively, an all-inclusive review of the newly developed WFHE along with a summary of imperative requirements of material properties, sensor capabilities, electronics performance, and skin integrations is provided.
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http://dx.doi.org/10.1002/adma.201901924DOI Listing
April 2020

Microscale Inorganic LED Based Wireless Neural Systems for Chronic Optogenetics.

Front Neurosci 2018 23;12:764. Epub 2018 Oct 23.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea.

Billions of neurons in the brain coordinate together to control trillions of highly convoluted synaptic pathways for neural signal processing. Optogenetics is an emerging technique that can dissect such complex neural circuitry with high spatiotemporal precision using light. However, conventional approaches relying on rigid and tethered optical probes cause significant tissue damage as well as disturbance with natural behavior of animals, thus preventing chronic optogenetics. A microscale inorganic LED (μ-ILED) is an enabling optical component that can solve these problems by facilitating direct discrete spatial targeting of neural tissue, integration with soft, ultrathin probes as well as low power wireless operation. Here we review recent state-of-the art μ-ILED integrated soft wireless optogenetic tools suitable for use in freely moving animals and discuss opportunities for future developments.
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http://dx.doi.org/10.3389/fnins.2018.00764DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6205995PMC
October 2018

Stretchable, Implantable, Nanostructured Flow-Diverter System for Quantification of Intra-aneurysmal Hemodynamics.

ACS Nano 2018 08 20;12(8):8706-8716. Epub 2018 Jul 20.

Department of Mechanical and Nuclear Engineering, Institute for Engineering and Medicine, Center for Rehabilitation Science and Engineering , Virginia Commonwealth University , Richmond , Virginia 23284 , United States.

Random weakening of an intracranial blood vessel results in abnormal blood flow into an aneurysmal sac. Recent advancements show that an implantable flow diverter, integrated with a medical stent, enables a highly effective treatment of cerebral aneurysms by guiding blood flow into the normal vessel path. None of such treatment systems, however, offers post-treatment monitoring to assess the progress of sac occlusion. Therefore, physicians rely heavily on either angiography or magnetic resonance imaging. Both methods require a dedicated facility with sophisticated equipment settings and time-consuming, cumbersome procedures. In this paper, we introduce an implantable, stretchable, nanostructured flow-sensor system for quantification of intra-aneurysmal hemodynamics. The open-mesh membrane device is capable of effective implantation in complex neurovascular vessels with extreme stretchability (500% radial stretching) and bendability (180° with 0.75 mm radius of curvature) for monitoring of the treatment progress. A collection of quantitative mechanics, fluid dynamics, and experimental studies establish the fundamental aspects of design criteria for a highly compliant, implantable device. Hemocompatibility study using fresh ovine blood captures the device feasibility for long-term insertion in a blood vessel, showing less platelet deposition compared to that in existing implantable materials. In vitro demonstrations of three types of flow sensors show quantification of intra-aneurysmal blood flow in a pig aorta and the capability of observation of aneurysm treatment with a great sensitivity (detection limit as small as 0.032 m/s). Overall, this work describes a mechanically soft flow-diverter system that offers an effective treatment of aneurysms with an active monitoring of intra-aneurysmal hemodynamics.
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http://dx.doi.org/10.1021/acsnano.8b04689DOI Listing
August 2018

Miniaturized, Battery-Free Optofluidic Systems with Potential for Wireless Pharmacology and Optogenetics.

Small 2018 01 7;14(4). Epub 2017 Dec 7.

Department of Electrical, Computer, and Energy Engineering, University of Colorado Boulder, Boulder, CO, 80309, USA.

Combination of optogenetics and pharmacology represents a unique approach to dissect neural circuitry with high specificity and versatility. However, conventional tools available to perform these experiments, such as optical fibers and metal cannula, are limited due to their tethered operation and lack of biomechanical compatibility. To address these issues, a miniaturized, battery-free, soft optofluidic system that can provide wireless drug delivery and optical stimulation for spatiotemporal control of the targeted neural circuit in freely behaving animals is reported. The device integrates microscale inorganic light-emitting diodes and microfluidic drug delivery systems with a tiny stretchable multichannel radiofrequency antenna, which not only eliminates the need for bulky batteries but also offers fully wireless, independent control of light and fluid delivery. This design enables a miniature (125 mm ), lightweight (220 mg), soft, and flexible platform, thus facilitating seamless implantation and operation in the body without causing disturbance of naturalistic behavior. The proof-of-principle experiments and analytical studies validate the feasibility and reliability of the fully implantable optofluidic systems for use in freely moving animals, demonstrating its potential for wireless in vivo pharmacology and optogenetics.
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http://dx.doi.org/10.1002/smll.201702479DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5912318PMC
January 2018

Minimally invasive probes for programmed microfluidic delivery of molecules in vivo.

Curr Opin Pharmacol 2017 10 9;36:78-85. Epub 2017 Sep 9.

Department of Electrical, Computer, and Energy Engineering, University of Colorado Boulder, CO 80309, USA; Materials Science and Engineering Program, University of Colorado Boulder, CO 80309, USA. Electronic address:

Site-specific drug delivery carries many advantages of systemic administration, but is rarely used in the clinic. One limiting factor is the relative invasiveness of the technology to locally deliver compounds. Recent advances in materials science and electrical engineering allow for the development of ultraminiaturized microfluidic channels based on soft materials to create flexible probes capable of deep tissue targeting. A diverse set of mechanics, including micro-pumps and functional materials, used to deliver the drugs can be paired with wireless electronics for self-contained and programmable operation. These first iterations of minimally invasive fluid delivery devices foreshadow important advances needed for clinical translation.
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http://dx.doi.org/10.1016/j.coph.2017.08.010DOI Listing
October 2017

Self-assembled three dimensional network designs for soft electronics.

Nat Commun 2017 06 21;8:15894. Epub 2017 Jun 21.

Departments of Materials Science and Engineering, Biomedical Engineering, Chemistry, Mechanical Engineering, Electrical Engineering and Computer Science, Neurological Surgery, Center for Bio-Integrated Electronics, Simpson Querrey Institute for BioNanotechnology, McCormick School of Engineering and Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60208, USA.

Low modulus, compliant systems of sensors, circuits and radios designed to intimately interface with the soft tissues of the human body are of growing interest, due to their emerging applications in continuous, clinical-quality health monitors and advanced, bioelectronic therapeutics. Although recent research establishes various materials and mechanics concepts for such technologies, all existing approaches involve simple, two-dimensional (2D) layouts in the constituent micro-components and interconnects. Here we introduce concepts in three-dimensional (3D) architectures that bypass important engineering constraints and performance limitations set by traditional, 2D designs. Specifically, open-mesh, 3D interconnect networks of helical microcoils formed by deterministic compressive buckling establish the basis for systems that can offer exceptional low modulus, elastic mechanics, in compact geometries, with active components and sophisticated levels of functionality. Coupled mechanical and electrical design approaches enable layout optimization, assembly processes and encapsulation schemes to yield 3D configurations that satisfy requirements in demanding, complex systems, such as wireless, skin-compatible electronic sensors.
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http://dx.doi.org/10.1038/ncomms15894DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5482057PMC
June 2017

Ferromagnetic, folded electrode composite as a soft interface to the skin for long-term electrophysiological recording.

Adv Funct Mater 2016 Oct 9;26(40):7281-7290. Epub 2016 Sep 9.

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

This paper introduces a class of ferromagnetic, folded, soft composite material for skin-interfaced electrodes with releasable interfaces to stretchable, wireless electronic measurement systems. These electrodes establish intimate, adhesive contacts to the skin, in dimensionally stable formats compatible with multiple days of continuous operation, with several key advantages over conventional hydrogel based alternatives. The reported studies focus on aspects ranging from ferromagnetic and mechanical behavior of the materials systems, to electrical properties associated with their skin interface, to system-level integration for advanced electrophysiological monitoring applications. The work combines experimental measurement and theoretical modeling to establish the key design considerations. These concepts have potential uses across a diverse set of skin-integrated electronic technologies.
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http://dx.doi.org/10.1002/adfm.201603146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390688PMC
October 2016

Microfluidic neural probes: in vivo tools for advancing neuroscience.

Lab Chip 2017 04;17(8):1406-1435

Electronics and Telecommunications Research Institute, Bio-Medical IT Convergence Research Department, Daejeon, 34129, Republic of Korea.

Microfluidic neural probes hold immense potential as in vivo tools for dissecting neural circuit function in complex nervous systems. Miniaturization, integration, and automation of drug delivery tools open up new opportunities for minimally invasive implants. These developments provide unprecedented spatiotemporal resolution in fluid delivery as well as multifunctional interrogation of neural activity using combined electrical and optical modalities. Capitalizing on these unique features, microfluidic technology will greatly advance in vivo pharmacology, electrophysiology, optogenetics, and optopharmacology. In this review, we discuss recent advances in microfluidic neural probe systems. In particular, we will highlight the materials and manufacturing processes of microfluidic probes, device configurations, peripheral devices for fluid handling and packaging, and wireless technologies that can be integrated for the control of these microfluidic probe systems. This article summarizes various microfluidic implants and discusses grand challenges and future directions for further developments.
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http://dx.doi.org/10.1039/c7lc00103gDOI Listing
April 2017

Epidermal mechano-acoustic sensing electronics for cardiovascular diagnostics and human-machine interfaces.

Sci Adv 2016 Nov 16;2(11):e1601185. Epub 2016 Nov 16.

Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

Physiological mechano-acoustic signals, often with frequencies and intensities that are beyond those associated with the audible range, provide information of great clinical utility. Stethoscopes and digital accelerometers in conventional packages can capture some relevant data, but neither is suitable for use in a continuous, wearable mode, and both have shortcomings associated with mechanical transduction of signals through the skin. We report a soft, conformal class of device configured specifically for mechano-acoustic recording from the skin, capable of being used on nearly any part of the body, in forms that maximize detectable signals and allow for multimodal operation, such as electrophysiological recording. Experimental and computational studies highlight the key roles of low effective modulus and low areal mass density for effective operation in this type of measurement mode on the skin. Demonstrations involving seismocardiography and heart murmur detection in a series of cardiac patients illustrate utility in advanced clinical diagnostics. Monitoring of pump thrombosis in ventricular assist devices provides an example in characterization of mechanical implants. Speech recognition and human-machine interfaces represent additional demonstrated applications. These and other possibilities suggest broad-ranging uses for soft, skin-integrated digital technologies that can capture human body acoustics.
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http://dx.doi.org/10.1126/sciadv.1601185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5262452PMC
November 2016

Preparation and implementation of optofluidic neural probes for in vivo wireless pharmacology and optogenetics.

Nat Protoc 2017 Feb 5;12(2):219-237. Epub 2017 Jan 5.

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.

This Protocol Extension describes the fabrication and technical procedures for implementing ultrathin, flexible optofluidic neural probe systems that provide targeted, wireless delivery of fluids and light into the brains of awake, freely behaving animals. As a Protocol Extension article, this article describes an adaptation of an existing Protocol that offers additional applications. This protocol serves as an extension of an existing Nature Protocol describing optoelectronic devices for studying intact neural systems. Here, we describe additional features of fabricating self-contained platforms that involve flexible microfluidic probes, pumping systems, microscale inorganic LEDs, wireless-control electronics, and power supplies. These small, flexible probes minimize tissue damage and inflammation, making long-term implantation possible. The capabilities include wireless pharmacological and optical intervention for dissecting neural circuitry during behavior. The fabrication can be completed in 1-2 weeks, and the devices can be used for 1-2 weeks of in vivo rodent experiments. To successfully carry out the protocol, researchers should have basic skill sets in photolithography and soft lithography, as well as experience with stereotaxic surgery and behavioral neuroscience practices. These fabrication processes and implementation protocols will increase access to wireless optofluidic neural probes for advanced in vivo pharmacology and optogenetics in freely moving rodents.This protocol is an extension to: Nat. Protoc. 8, 2413-2428 (2013); doi:10.1038/nprot.2013.158; published online 07 November 2013.
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http://dx.doi.org/10.1038/nprot.2016.155DOI Listing
February 2017

Epidermal electronics for electromyography: An application to swallowing therapy.

Med Eng Phys 2016 08 30;38(8):807-12. Epub 2016 May 30.

Institute for Reconstructive Sciences in Medicine (iRSM), Misericordia Community Hospital, Edmonton, Alberta, Canada; Department of Communication Sciences and Disorders, Faculty of Rehabilitation Medicine, University of Alberta, 8205 114St 2-70 Corbett Hall, Edmonton, Alberta, Canada.

Head and neck cancer treatment alters the anatomy and physiology of patients. Resulting swallowing difficulties can lead to serious health concerns. Surface electromyography (sEMG) is used as an adjuvant to swallowing therapy exercises. sEMG signal collected from the area under the chin provides visual biofeedback from muscle contractions and is used to help patients perform exercises correctly. However, conventional sEMG adhesive pads are relatively thick and difficult to effectively adhere to a patient's altered chin anatomy, potentially leading to poor signal acquisition in this population. Here, the emerging technology of epidermal electronics is introduced, where ultra-thin geometry allows for close contouring of the chin. The two objectives of this study were to (1) assess the potential of epidermal electronics technology for use with swallowing therapy and (2) assess the significance of the reference electrode placement. This study showed comparative signals between the new epidermal sEMG patch and the conventional adhesive patches used by clinicians. Furthermore, an integrated reference yielded optimal signal for clinical use; this configuration was more robust to head movements than when an external reference was used. Improvements for future iterations of epidermal sEMG patches specific to day-to-day clinical use are suggested.
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http://dx.doi.org/10.1016/j.medengphy.2016.04.023DOI Listing
August 2016

Wireless Optofluidic Systems for Programmable In Vivo Pharmacology and Optogenetics.

Cell 2015 Jul 16;162(3):662-74. Epub 2015 Jul 16.

Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA; Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA; Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA. Electronic address:

In vivo pharmacology and optogenetics hold tremendous promise for dissection of neural circuits, cellular signaling, and manipulating neurophysiological systems in awake, behaving animals. Existing neural interface technologies, such as metal cannulas connected to external drug supplies for pharmacological infusions and tethered fiber optics for optogenetics, are not ideal for minimally invasive, untethered studies on freely behaving animals. Here, we introduce wireless optofluidic neural probes that combine ultrathin, soft microfluidic drug delivery with cellular-scale inorganic light-emitting diode (μ-ILED) arrays. These probes are orders of magnitude smaller than cannulas and allow wireless, programmed spatiotemporal control of fluid delivery and photostimulation. We demonstrate these devices in freely moving animals to modify gene expression, deliver peptide ligands, and provide concurrent photostimulation with antagonist drug delivery to manipulate mesoaccumbens reward-related behavior. The minimally invasive operation of these probes forecasts utility in other organ systems and species, with potential for broad application in biomedical science, engineering, and medicine.
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http://dx.doi.org/10.1016/j.cell.2015.06.058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4525768PMC
July 2015

Soft materials in neuroengineering for hard problems in neuroscience.

Neuron 2015 Apr;86(1):175-86

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Department of Electrical and Computer Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. Electronic address:

We describe recent advances in soft electronic interface technologies for neuroscience research. Here, low modulus materials and/or compliant mechanical structures enable modes of soft, conformal integration and minimally invasive operation that would be difficult or impossible to achieve using conventional approaches. We begin by summarizing progress in electrodes and associated electronics for signal amplification and multiplexed readout. Examples in large-area, surface conformal electrode arrays and flexible, multifunctional depth-penetrating probes illustrate the power of these concepts. A concluding section highlights areas of opportunity in the further development and application of these technologies.
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http://dx.doi.org/10.1016/j.neuron.2014.12.035DOI Listing
April 2015

Soft, curved electrode systems capable of integration on the auricle as a persistent brain-computer interface.

Proc Natl Acad Sci U S A 2015 Mar 16;112(13):3920-5. Epub 2015 Mar 16.

Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801;

Recent advances in electrodes for noninvasive recording of electroencephalograms expand opportunities collecting such data for diagnosis of neurological disorders and brain-computer interfaces. Existing technologies, however, cannot be used effectively in continuous, uninterrupted modes for more than a few days due to irritation and irreversible degradation in the electrical and mechanical properties of the skin interface. Here we introduce a soft, foldable collection of electrodes in open, fractal mesh geometries that can mount directly and chronically on the complex surface topology of the auricle and the mastoid, to provide high-fidelity and long-term capture of electroencephalograms in ways that avoid any significant thermal, electrical, or mechanical loading of the skin. Experimental and computational studies establish the fundamental aspects of the bending and stretching mechanics that enable this type of intimate integration on the highly irregular and textured surfaces of the auricle. Cell level tests and thermal imaging studies establish the biocompatibility and wearability of such systems, with examples of high-quality measurements over periods of 2 wk with devices that remain mounted throughout daily activities including vigorous exercise, swimming, sleeping, and bathing. Demonstrations include a text speller with a steady-state visually evoked potential-based brain-computer interface and elicitation of an event-related potential (P300 wave).
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http://dx.doi.org/10.1073/pnas.1424875112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4386388PMC
March 2015

Biodegradable elastomers and silicon nanomembranes/nanoribbons for stretchable, transient electronics, and biosensors.

Nano Lett 2015 May 24;15(5):2801-8. Epub 2015 Apr 24.

‡Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.

Transient electronics represents an emerging class of technology that exploits materials and/or device constructs that are capable of physically disappearing or disintegrating in a controlled manner at programmed rates or times. Inorganic semiconductor nanomaterials such as silicon nanomembranes/nanoribbons provide attractive choices for active elements in transistors, diodes and other essential components of overall systems that dissolve completely by hydrolysis in biofluids or groundwater. We describe here materials, mechanics, and design layouts to achieve this type of technology in stretchable configurations with biodegradable elastomers for substrate/encapsulation layers. Experimental and theoretical results illuminate the mechanical properties under large strain deformation. Circuit characterization of complementary metal-oxide-semiconductor inverters and individual transistors under various levels of applied loads validates the design strategies. Examples of biosensors demonstrate possibilities for stretchable, transient devices in biomedical applications.
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http://dx.doi.org/10.1021/nl503997mDOI Listing
May 2015

Rugged and breathable forms of stretchable electronics with adherent composite substrates for transcutaneous monitoring.

Nat Commun 2014 Sep 3;5:4779. Epub 2014 Sep 3.

Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

Research in stretchable electronics involves fundamental scientific topics relevant to applications with importance in human healthcare. Despite significant progress in active components, routes to mechanically robust construction are lacking. Here, we introduce materials and composite designs for thin, breathable, soft electronics that can adhere strongly to the skin, with the ability to be applied and removed hundreds of times without damaging the devices or the skin, even in regions with substantial topography and coverage of hair. The approach combines thin, ultralow modulus, cellular silicone materials with elastic, strain-limiting fabrics, to yield a compliant but rugged platform for stretchable electronics. Theoretical and experimental studies highlight the mechanics of adhesion and elastic deformation. Demonstrations include cutaneous optical, electrical and radio frequency sensors for measuring hydration state, electrophysiological activity, pulse and cerebral oximetry. Multipoint monitoring of a subject in an advanced driving simulator provides a practical example.
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http://dx.doi.org/10.1038/ncomms5779DOI Listing
September 2014

Multifunctional skin-like electronics for quantitative, clinical monitoring of cutaneous wound healing.

Adv Healthc Mater 2014 Oct 26;3(10):1597-607. Epub 2014 Mar 26.

Department of Materials Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.

Non-invasive, biomedical devices have the potential to provide important, quantitative data for the assessment of skin diseases and wound healing. Traditional methods either rely on qualitative visual and tactile judgments of a professional and/or data obtained using instrumentation with forms that do not readily allow intimate integration with sensitive skin near a wound site. Here, an electronic sensor platform that can softly and reversibly laminate perilesionally at wounds to provide highly accurate, quantitative data of relevance to the management of surgical wound healing is reported. Clinical studies on patients using thermal sensors and actuators in fractal layouts provide precise time-dependent mapping of temperature and thermal conductivity of the skin near the wounds. Analytical and simulation results establish the fundamentals of the sensing modalities, the mechanics of the system, and strategies for optimized design. The use of this type of "epidermal" electronics system in a realistic clinical setting with human subjects establishes a set of practical procedures in disinfection, reuse, and protocols for quantitative measurement. The results have the potential to address important unmet needs in chronic wound management.
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http://dx.doi.org/10.1002/adhm.201400073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4177017PMC
October 2014

3D multifunctional integumentary membranes for spatiotemporal cardiac measurements and stimulation across the entire epicardium.

Nat Commun 2014 Feb 25;5:3329. Epub 2014 Feb 25.

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.

Means for high-density multiparametric physiological mapping and stimulation are critically important in both basic and clinical cardiology. Current conformal electronic systems are essentially 2D sheets, which cannot cover the full epicardial surface or maintain reliable contact for chronic use without sutures or adhesives. Here we create 3D elastic membranes shaped precisely to match the epicardium of the heart via the use of 3D printing, as a platform for deformable arrays of multifunctional sensors, electronic and optoelectronic components. Such integumentary devices completely envelop the heart, in a form-fitting manner, and possess inherent elasticity, providing a mechanically stable biotic/abiotic interface during normal cardiac cycles. Component examples range from actuators for electrical, thermal and optical stimulation, to sensors for pH, temperature and mechanical strain. The semiconductor materials include silicon, gallium arsenide and gallium nitride, co-integrated with metals, metal oxides and polymers, to provide these and other operational capabilities. Ex vivo physiological experiments demonstrate various functions and methodological possibilities for cardiac research and therapy.
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http://dx.doi.org/10.1038/ncomms4329DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4521772PMC
February 2014

Materials and optimized designs for human-machine interfaces via epidermal electronics.

Adv Mater 2013 Dec 25;25(47):6839-46. Epub 2013 Sep 25.

Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign Urbana, Illinois, 61801, USA.

Thin, soft, and elastic electronics with physical properties well matched to the epidermis can be conformally and robustly integrated with the skin. Materials and optimized designs for such devices are presented for surface electromyography (sEMG). The findings enable sEMG from wide ranging areas of the body. The measurements have quality sufficient for advanced forms of human-machine interface.
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http://dx.doi.org/10.1002/adma.201301921DOI Listing
December 2013

Capacitive epidermal electronics for electrically safe, long-term electrophysiological measurements.

Adv Healthc Mater 2014 May 16;3(5):642-8. Epub 2013 Oct 16.

Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.

Integration of capacitive sensing capabilities to epidermal electronic systems (EES) can enhance the robustness in operation for electrophysiological signal measurement. Capacitive EES designs are reusable, electrically safe, and minimally sensitive to motion artifacts. Experiments on human subjects illustrate levels of fidelity in ECG, EMG, and EOG recordings comparable to those of standard gel electrodes and of direct contact EES electrodes.
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http://dx.doi.org/10.1002/adhm.201300334DOI Listing
May 2014

Two-axis MEMS scanner with transfer-printed high-reflectivity, broadband monolithic silicon photonic crystal mirrors.

Opt Express 2013 Jun;21(11):13800-9

E L Ginzton Laboratory, Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA.

We present a two-axis electrostatic MEMS scanner with high-reflectivity monolithic single-crystal-silicon photonic crystal (PC) mirrors suitable for applications in harsh environments. The reflective surfaces of the MEMS scanner are transfer-printed PC mirrors with low polarization dependence, low angular dependence, and reflectivity over 85% in the wavelength range of 1490nm~1505nm and above 90% over the wavelength band of 1550~1570nm. In static mode, the scanner has total scan range of 10.2° on one rotation axis and 7.8° on the other. Dynamic operation on resonance increase the scan range to 21° at 608Hz around the outer rotation axis and 9.5° at 1.73kHz about the inner rotation axis.
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http://dx.doi.org/10.1364/OE.21.013800DOI Listing
June 2013
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