하이드로젤 기반의 터치 센싱과 무선 전력 전송 이온-전자 혼성 장치에 관한 연구

학위논문(박사)--서울대학교 대학원 :공과대학 재료공학부,2020. 2. 오규환.As the rise of ubiquitous computing and the Internet of Thing facilitate the frequent interaction between human and machines, the importance of human machine interfaces (HMI) has been emphasized. Despite recent advances in HMI, current devices based on metals or semiconductors are still limited in use due to mechanical mismatches with humans having soft skins and tissues. In this respect, hydrogels are promising alternative for conventional conductive materials. The hydrogels are polymer networks swollen with the water. The polymer networks enable the hydrogel to maintain their shape like a solid and to withstand deformation. The water in the hydrogel dissolves the ions, making the hydrogel ionic conductive. Thus, hydrogels with ions can be served as stretchable ionic conductors to transmit electrical signals and power even in the stretched state. However, there are also issues that arise because of the use of ions as charge carriers. Herein, I demonstrate how to solve the issues when using hydrogels and how to take advantage of their characteristics. Two ionic devices were developed and explored; a hydrogel touchpad that can stretch more than 1000% and a gel receiver that can receive electrical power wirelessly. In first part, highly stretchable and transparent touch panel consisting of hydrogels was explored. Because human-computer interactions are increasingly important, touch panels may require stretchability and biocompatibility in order to allow integration with the human body. However, most touch panels have been developed based on stiff and brittle electrodes. We demonstrate an ionic touch panel based on a polyacrylamide hydrogel containing lithium chloride salts. The panel is soft and stretchable, so it can sustain a large deformation. The panel can freely transmit light information because the hydrogel is transparent, with 98% transmittance for visible light. A surface-capacitive touch system was adopted to sense a touched position. The panel can be operated under more than 1000% areal strain without sacrificing its functionalities. Epidermal touch panel use on skin was demonstrated by writing words, playing a piano, and playing games. In second part, we have explored a wireless power transfer system using an ionic conductor as a power receiving parts. A number of implantable biomedical devices that require electric power have been developed and wireless power transfer (WPT) systems are emerging as a way to provide power to these devices without requiring a hardwired connection. Most of WPT have been based on conventional conductive materials, such as metals, which tend to be less biocompatible and stiff. Herein, we describe a development of an ionic wireless power transfer (IWPT) system on the basis of ionic conductor. A power receiver of the IWPT consisting of polyacrylamide hydrogel with NaCl salts was delivered power through the ionic current induced by capacitive coupling. The hydrogel receiver, easy to fabricate, flexible, transparent, and biocompatible, received power at a distance of 5 cm from the transmitter, and even when inserted inside the mouse. Charge accumulation caused by the prevention of discharge on electrical double layers (CAPDE) induced electrochemical reactions in the IWPT. The mechanism of CAPDE was studied and the amount of products was controlled by tuning the circuit parameter.유비쿼터스 컴퓨팅과 사물인터넷의 등장으로 사람과 기계간의 상호작용이 빈번해짐에 따라 휴먼-머신 인터페이스의 중요성이 점점 강조되어왔다. 휴먼-머신 인터페이스 기술의 발전에도 불구하고 금속과 반도체를 기반으로 한 현재의 디바이스들은 부드러운 피부와 조직을 가지고 있는 사람과의 기계적 물성의 불일치로 인해 사용이 제약되고 있다. 이런 측면에서 하이드로젤은 기존의 전도성 물질들의 대안으로서 등장했다. 하이드로젤은 다량의 수분을 머금고 있는 고분자 네트워크이다. 고분자 네트워크는 하이드로젤이 형체를 유지하고 또 변형을 견딜 수 있게 해주며 하이드로젤 내부의 수분은 이온을 녹여 하이드로젤이 이온 전도성을 가질 수 있게 해준다. 따라서 하이드로젤은 늘어난 상태에서도 전기 신호와 전력을 전달할 수 있는 신축성이 있는 전도체로 사용될 수 있다. 하지만 이온을 전하전달체로 사용한다는 것은 새로운 문제들을 야기할 수 있다. 이 논문에서 하이드로젤을 어떻게 이온 전도체로 이용하는지 또 그로 인한 문제들을 어떻게 다뤄야 하는지 말하고자 한다. 두 가지의 이온성 장치를 제작하였고 그에 대한 논의를 할 것이다. 첫 번째 장에서는 하이드로젤로 이루어진 투명하고 늘어날 수 있는 터치패널에 대해 논의할 것이다. 인간과 컴퓨터의 상호작용이 중요해짐에 따라 인간과의 통합이 가능하도록 생체적합성을 가지면서도 늘어날 수 있는 터치패널에 대한 수요가 증가하였다. 우리는 LiCl 염을 포함한 폴리아크릴아마이드 (polyacrylamide) 하이드로젤로 터치패널을 만들었다. 하이드로젤 터치패드는 부드럽고 신축성이 있어서 높은 변형을 견딜 수 있었다. 또한 하이드로젤은 높은 투명성을 가진 재료이기 때문에 가시광선 영역에서 98 %의 투명도를 보였다. 하이드로젤 터치패드는 표면 정전용량 식 터치 감지 시스템을 기반으로 제작되었으며 1000%가 넘는 변형이 주어진 상황에서도 정상적으로 작동하였다. 하이드로젤 터치패드는 피부에 부착된 형태로도 사용이 가능하였으며 피부에 부착된 상태로 글을 쓰거나 피아노를 치거나 게임을 하는 등의 동작을 수행할 수 있었다. 두 번째 장에서는 이온 전도체를 이용해서 무선으로 전력을 전달 할 수 있는 시스템에 대해 논의할 것이다. 이식형 의료장비에 전력을 제공할 수 있는 방법들 중에서 무선 전력 전송 방식은 지속적으로 충분한 양의 전력을 공급할 수 있다는 면에서 주목받고 있다. 대부분의 무선 전력 전송 시스템은 효율을 높이기 위해 전도성이 높은 금속을 사용하지만 금속은 딱딱하고 생체적합성이 부족한 재료이다. 이 논문에서 우리는 이온성 무선 전력 전송 장치를 제작하였다. 이온성 무선 전력 전송 장치는 부드럽고 투명하고 생체적합성이 뛰어난 하이드로젤 수신부를 통해 전력을 전달받는다. 이온성 무선 전력 전송 시스템은 5 cm 떨어진 거리에서도 전력을 전달 할 수 있었고 심지어 쥐의 피하에 이식된 전력 수신장치에도 피부를 통과하여 전력을 전달 할 수 있었다. 또한 이온성 장치에서 문제로 여겨지는 전기화학반응을 의도적으로 발생시키는 회로를 구성하여 원하는 전기화학반응을 유도해 낼 수 있었다. 이온성 무선 전력 전송 시스템 내에서의 전기화학반응의 발생 기작을 확인하였고 회로 설계를 통해 전기화학반응으로 인한 생성물의 양을 조절할 수 있었다.Chapter 1. Introduction 1 1.1. Study Background 1 1.1.1 Ionic conduction 1 1.1.2 Stretchable ionics. 2 1.1.2.1 Issues on the stretchable ionic devices 2 1.1.2.2 Applications of stretchable ionic devices 4 1.2. Purpose of Research 12 Reference 13 Chapter 2. Highly stretchable, transparent ionic touch panel 16 2.1. Introduction 16 2.2. Experimental section 18 2.2.1 Materials 18 2.2.2 An ionic touch strip. 19 2.2.3 Transparent ionic touch panel. 20 2.2.4 Epidermal touch panel. 20 2.3. Results and Discussion 21 2.3.1 A working principle of an ionic touch strip. 21 2.3.2 Sensing mechanism for a 1-dimensional touch strip 27 2.3.3 Latency of the ionic touch panel 29 2.3.4 Parasitic capacitance and baseline current. 32 2.3.5 Accumulated currents induced by touches during the stretching of a gel strip. 34 2.3.6 Strain rate effects of a gel strip during a uniaxial stretching. 35 2.3.7 Resolution of the ionic touch panel. 38 2.3.8 Position-sensing in a 2D ionic touch panel. 40 2.3.9 A stretchable touch panel. 49 2.3.10 Operation of an ionic touch panel under an anisotropic deformation. 55 2.3.11 An epidermal touch panel that is soft and transparent. 57 2.3.12 The insulation of the epidermal touch panel. 58 2.4. Conclusion 63 Reference 64 Chapter 3. Ionic wireless power transfer 67 3.1. Introduction 67 3.2. Experimental section and backgrounds 70 3.2.1 Materials and synthesis 70 3.2.2 Experimental setup for IWPT 71 3.2.3 Power transfer in series resistorinductorcapacitor (RLC) circuits. 71 3.2.4 The structure of the coupling capacitor. 75 3.3. Results and Discussion 77 3.3.1 Basic princibles and operations of an Ionic wireless power transfer (IWPT) 77 3.3.2 Characteristics of IWPT 83 3.3.3 Implantation of an IWPT system. 89 3.3.4 CAPDE for NADPH regeneration 98 3.3.5 Analysis of the voltages generated in the CEDL 112 3.4. Conclusion 114 Reference 115 Chapter 4. Conclusion 119 Abstract in Korean 121 Biography 124Docto

Rubbery electronics and sensors from intrinsically stretchable elastomeric composites of semiconductors and conductors

A general strategy to impart mechanical stretchability to stretchable electronics involves engineering materials into special architectures to accommodate or eliminate the mechanical strain in nonstretchable electronic materials while stretched. We introduce an all solution-processed type of electronics and sensors that are rubbery and intrinsically stretchable as an outcome from all the elastomeric materials in percolated composite formats with P3HT-NFs [poly(3-hexylthiophene-2,5-diyl) nanofibrils] and AuNP-AgNW (Au nanoparticles with conformally coated silver nanowires) in PDMS (polydimethylsiloxane). The fabricated thin-film transistors retain their electrical performances by more than 55% upon 50% stretching and exhibit one of the highest P3HT-based field-effect mobilities of 1.4 cm2/V.s, owing to crystallinity improvement. Rubbery sensors, which include strain, pressure, and temperature sensors, show reliable sensing capabilities and are exploited as smart skins that enable gesture translation for sign language alphabet and haptic sensing for robotics to illustrate one of the applications of the sensors

Highly Sensitive Soft Foam Sensors for Wearable Applications

Due to people’s increasing desire for body health monitoring, the needs of knowing humans’ body parameters and transferring them to analyzable and understandable signals become increasingly attractive and significant. The present body-sign measurement devices are still bulky medical devices used in settings such as clinics or hospitals, which are accurate, but expensive and cannot achieve the personalization of usage targets and the monitoring of real-time body parameters. Many commercial wearable devices can provide some of the body indexes, such as the smartwatch providing the pulse/heartbeat information, but cannot give accurate and reliable data, and the data could be influenced by the user’s movement and the loose wearing habit, either. In this way, developing next-generation wearable devices combining good wearable experience and accuracy is gathering increasing attention. The aim of this study is to develop a high-performance pressure/strain sensor with the requirements of comfortable to wear, and having great electromechanical behaviour to convert the physiological signal to an analyzable signal

A Design-Led, Materials Based Approach to Human Centered Applications Using Modified Dielectric Electroactive Polymer Sensors

This paper describes a design-led exploratory scoping study into the potential use of an industry standard dielectric electroactive polymer (DEAP) sensor for applications in assistive healthcare. The focus of this activity was to explore the physical format and integration of soft materials and sensor combinations with properties that afford an opportunity for accurate and unobtrusive real time body mapping and monitoring. The work involved a series of practical investigations into the capacitance changes in the sensor brought on by deformation through different ways of stretching. The dielectric sensors were selected as a direct mapping tool against the body based on the similarity of the stretch qualities of both the sensor and human skin and muscle resulting in a prototype vest for real time breathing monitoring through sensing thoracic movement. This involved modification of the standard sensors and handcrafting bespoke sensors to map critically relevant areas of the thorax

Tactile and Touchless Sensors Printed on Flexible Textile Substrates for Gesture Recognition

Tesis por compendio[EN] The main objective of this thesis is the development of new sensors and actuators using Printed Electronics technology. For this, conductive, semiconductor and dielectric polymeric materials are used on flexible and/or elastic substrates. By means of suitable designs and application processes, it is possible to manufacture sensors capable of interacting with the environment. In this way, specific sensing functionalities can be incorporated into the substrates, such as textile fabrics. Additionally, it is necessary to include electronic systems capable of processing the data obtained, as well as its registration. In the development of these sensors and actuators, the physical properties of the different materials are precisely combined. For this, multilayer structures are designed where the properties of some materials interact with those of others. The result is a sensor capable of capturing physical variations of the environment, and convert them into signals that can be processed, and finally transformed into data. On the one hand, a tactile sensor printed on textile substrate for 2D gesture recognition was developed. This sensor consists of a matrix composed of small capacitive sensors based on a capacitor type structure. These sensors were designed in such a way that, if a finger or other object with capacitive properties, gets close enough, its behaviour varies, and it can be measured. The small sensors are arranged in this matrix as in a grid. Each sensor has a position that is determined by a row and a column. The capacity of each small sensor is periodically measured in order to assess whether significant variations have been produced. For this, it is necessary to convert the sensor capacity into a value that is subsequently digitally processed. On the other hand, to improve the effectiveness in the use of the developed 2D touch sensors, the way of incorporating an actuator system was studied. Thereby, the user receives feedback that the order or action was recognized. To achieve this, the capacitive sensor grid was complemented with an electroluminescent screen printed as well. The final prototype offers a solution that combines a 2D tactile sensor with an electroluminescent actuator on a printed textile substrate. Next, the development of a 3D gesture sensor was carried out using a combination of sensors also printed on textile substrate. In this type of 3D sensor, a signal is sent generating an electric field on the sensors. This is done using a transmission electrode located very close to them. The generated field is received by the reception sensors and converted to electrical signals. For this, the sensors are based on electrodes that act as receivers. If a person places their hands within the emission area, a disturbance of the electric field lines is created. This is due to the deviation of the lines to ground using the intrinsic conductivity of the human body. This disturbance affects the signals received by the electrodes. Variations captured by all electrodes are processed together and can determine the position and movement of the hand on the sensor surface. Finally, the development of an improved 3D gesture sensor was carried out. As in the previous development, the sensor allows contactless gesture detection, but increasing the detection range. In addition to printed electronic technology, two other textile manufacturing technologies were evaluated.[ES] La presente tesis doctoral tiene como objetivo fundamental el desarrollo de nuevos sensores y actuadores empleando la tecnología electrónica impresa, también conocida como Printed Electronics. Para ello, se emplean materiales poliméricos conductores, semiconductores y dieléctricos sobre sustratos flexibles y/o elásticos. Por medio de diseños y procesos de aplicación adecuados, es posible fabricar sensores capaces de interactuar con el entorno. De este modo, se pueden incorporar a los sustratos, como puedan ser tejidos textiles, funcionalidades específicas de medición del entorno y de respuesta ante cambios de este. Adicionalmente, es necesario incluir sistemas electrónicos, capaces de realizar el procesado de los datos obtenidos, así como de su registro. En el desarrollo de estos sensores y actuadores se combinan las propiedades físicas de los diferentes materiales de forma precisa. Para ello, se diseñan estructuras multicapa donde las propiedades de unos materiales interaccionan con las de los demás. El resultado es un sensor capaz de captar variaciones físicas del entorno, y convertirlas en señales que pueden ser procesadas y transformadas finalmente en datos. Por una parte, se ha desarrollado un sensor táctil impreso sobre sustrato textil para reconocimiento de gestos en 2D. Este sensor se compone de una matriz formada por pequeños sensores capacitivos basados en estructura de tipo condensador. Estos se han diseñado de forma que, si un dedo u otro objeto con propiedades capacitivas se aproxima suficientemente, su comportamiento varía, pudiendo ser medido. Los pequeños sensores están ordenados en dicha matriz como en una cuadrícula. Cada sensor tiene una posición que viene determinada por una fila y por una columna. Periódicamente se mide la capacidad de cada pequeño sensor con el fin de evaluar si ha sufrido variaciones significativas. Para ello es necesario convertir la capacidad del sensor en un valor que posteriormente es procesado digitalmente. Por otro lado, con el fin de mejorar la efectividad en el uso de los sensores táctiles 2D desarrollados, se ha estudiado el modo de incorporar un sistema actuador. De esta forma, el usuario recibe una retroalimentación indicando que la orden o acción ha sido reconocida. Para ello, se ha complementado la matriz de sensores capacitivos con una pantalla electroluminiscente también impresa. El resultado final ofrece una solución que combina un sensor táctil 2D con un actuador electroluminiscente realizado mediante impresión electrónica sobre sustrato textil. Posteriormente, se ha llevado a cabo el desarrollo de un sensor de gestos 3D empleando una combinación de sensores impresos también sobre sustrato textil. En este tipo de sensor 3D, se envía una señal que genera un campo eléctrico sobre los sensores impresos. Esto se lleva a cabo mediante un electrodo de transmisión situado muy cerca de ellos. El campo generado es recibido por los sensores y convertido a señales eléctricas. Para ello, los sensores se basan en electrodos que actúan de receptores. Si una persona coloca su mano dentro del área de emisión, se crea una perturbación de las líneas de los campos eléctricos. Esto es debido a la desviación de las líneas de campo a tierra utilizando la conductividad intrínseca del cuerpo humano. Esta perturbación cambia/afecta a las señales recibidas por los electrodos. Las variaciones captadas por todos los electrodos son procesadas de forma conjunta pudiendo determinar la posición y el movimiento de la mano sobre la superficie del sensor. Finalmente, se ha llevado a cabo el desarrollo de un sensor de gestos 3D mejorado. Al igual que el desarrollo anterior, permite la detección de gestos sin necesidad de contacto, pero incrementando la distancia de alcance. Además de la tecnología de impresión electrónica, se ha evaluado el empleo de otras dos tecnologías de fabricación textil.[CA] La present tesi doctoral té com a objectiu fonamental el desenvolupament de nous sensors i actuadors fent servir la tecnologia de electrònica impresa, també coneguda com Printed Electronics. Es va fer us de materials polimèrics conductors, semiconductors i dielèctrics sobre substrats flexibles i/o elàstics. Per mitjà de dissenys i processos d'aplicació adequats, és possible fabricar sensors capaços d'interactuar amb l'entorn. D'aquesta manera, es poden incorporar als substrats, com ara teixits tèxtils, funcionalitats específiques de mesurament de l'entorn i de resposta davant canvis d'aquest. Addicionalment, és necessari incloure sistemes electrònics, capaços de realitzar el processament de les dades obtingudes, així com del seu registre. En el desenvolupament d'aquests sensors i actuadors es combinen les propietats físiques dels diferents materials de forma precisa. Cal dissenyar estructures multicapa on les propietats d'uns materials interaccionen amb les de la resta. manera El resultat es un sensor capaç de captar variacions físiques de l'entorn, i convertirles en senyals que poden ser processades i convertides en dades. D'una banda, s'ha desenvolupat un sensor tàctil imprès sobre substrat tèxtil per a reconeixement de gestos en 2D. Aquest sensor es compon d'una matriu formada amb petits sensors capacitius basats en una estructura de tipus condensador. Aquests s'han dissenyat de manera que, si un dit o un altre objecte amb propietats capacitives s'aproxima prou, el seu comportament varia, podent ser mesurat. Els petits sensors estan ordenats en aquesta matriu com en una quadrícula. Cada sensor té una posició que ve determinada per una fila i per una columna. Periòdicament es mesura la capacitat de cada petit sensor per tal d'avaluar si ha sofert variacions significatives. Per a això cal convertir la capacitat del sensor a un valor que posteriorment és processat digitalment. D'altra banda, per tal de millorar l'efectivitat en l'ús dels sensors tàctils 2D desenvolupats, s'ha estudiat la manera d'incorporar un sistema actuador. D'aquesta forma, l'usuari rep una retroalimentació indicant que l'ordre o acció ha estat reconeguda. Per a això, s'ha complementat la matriu de sensors capacitius amb una pantalla electroluminescent també impresa. El resultat final ofereix una solució que combina un sensor tàctil 2D amb un actuador electroluminescent realitzat mitjançant impressió electrònica sobre substrat tèxtil. Posteriorment, s'ha dut a terme el desenvolupament d'un sensor de gestos 3D emprant una combinació d'un mínim de sensors impresos també sobre substrat tèxtil. En aquest tipus de sensor 3D, s'envia un senyal que genera un camp elèctric sobre els sensors impresos. Això es porta a terme mitjançant un elèctrode de transmissió situat molt a proper a ells. El camp generat és rebut pels sensors i convertit a senyals elèctrics. Per això, els sensors es basen en elèctrodes que actuen de receptors. Si una persona col·loca la seva mà dins de l'àrea d'emissió, es crea una pertorbació de les línies dels camps elèctrics. Això és a causa de la desviació de les línies de camp a terra utilitzant la conductivitat intrínseca de el cos humà. Aquesta pertorbació afecta als senyals rebudes pels elèctrodes. Les variacions captades per tots els elèctrodes són processades de manera conjunta per determinar la posició i el moviment de la mà sobre la superfície del sensor. Finalment, s'ha dut a terme el desenvolupament d'un sensor de gestos 3D millorat. A l'igual que el desenvolupament anterior, permet la detecció de gestos sense necessitat de contacte, però incrementant la distància d'abast. A més a més de la tecnologia d'impressió electrònica, s'ha avaluat emprar altres dues tecnologies de fabricació tèxtil.Ferri Pascual, J. (2020). Tactile and Touchless Sensors Printed on Flexible Textile Substrates for Gesture Recognition [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153075TESISCompendi

Passive, Self-Healable, Dielectric Elastomers for Structural Health Monitoring

NASA maintains the ability to track a large majority of objects in Earth’s orbit, however lack the ability to track objects smaller than five centimeters in diameter. These untrackable objects represent a significant danger to inflatable structures. This work seeks to synthesize and fabricate a self-healable, passive, dielectric elastomer impact sensor for structural health monitoring on inflatable space structures subject to impact by micrometeoroids and orbital debris. In a setting in which impact repairs can be extremely costly, the implementation of such a technology would not only alert personnel of such an event but would also serve to decrease the cost and time of repairs. This investigation synthesizes an intrinsically self-healing poly(dimethylsiloxane) via a supra-molecular network of multi-strength hydrogen bonds. The modified poly(dimethylsiloxane) network must be effective in harsh environments, particularly extremely low temperatures, as well as retain the dielectric properties of poly(dimethylsiloxane). Self-healing efficiency, stretchability and flexibility are also desirable properties to attain. Integration of the manufactured sensor arrays around a layer of woven ceramic fiber with conductive fabric electrodes, hypervelocity impact testing, and self-healing efficiency tests are performed and confirm the sensors capabilities. The performed tests demonstrate a measurable change in capacitance associated with impact damage and location. Success is represented by passive operation and the penetrated sensors’ ability to self-repair without compromising the sensors impact detection capabilities

Soft Tactile Sensors for Mechanical Imaging

Tactile sensing aims to electronically capture physical attributes of an object via mechanical contact. It proves indispensable to many engineering tasks and systems, in areas ranging from manufacturing to medicine and autonomous robotics. Biological skin, which is highly compliant, is able to perform sensing under challenging and highly variable conditions with levels of performance that far exceed what is possible with conventional tactile sensors, which are normally fabricated with non-conforming materials. The development of stretchable, skin-like tactile sensors has, as a result, remained a longstanding goal of engineering. However, to date, artificial tactile sensors that might mimic both the mechanical and multimodal tactile sensory capabilities of biological skin remain far from realization, due to the challenges of fabricating spatially dense, mechanically robust, and compliant sensors in elastic media. Inspired by these demands, this dissertation addresses many aspects of the challenging problem of engineering skin-like electronic sensors. In the first part of the thesis, new methods for the design and fabrication of thin, highly deformable, high resolution tactile sensors are presented. The approach is based on a novel configuration of arrays of microfluidic channels embedded in thin elastomer membranes. To form electrodes, these channels are filled with a metal alloy, eutectic Gallium Indium, that remains liquid at room temperature. Using capacitance sensing techniques, this approach achieves sensing resolutions of 1 mm$^{-1}$. To fabricate these devices, an efficient and robust soft lithography method is introduced, based on a single step cast. An analytical model for the performance of these devices is derived from electrostatic theory and continuum mechanics, and is demonstrated to yield excellent agreement with measured performance. This part of the investigation identified fundamental limitations, in the form of nonmonotonic behavior at low strains, that is demonstrated to generically affect solid cast soft capacitive sensors. The next part of the thesis is an investigation of new methods for designing soft tactile sensors based on multi-layer heterogeneous 3D structures that combine active layers, containing embedded liquid metal electrodes, with passive and mechanically tunable layers, containing air cavities and micropillar geometric supports. In tandem with analytical and computational modeling, these methods are demonstrated to facilitate greater control over mechanical and electronic performance. A new soft lithography fabrication method is also presented, based on the casting, alignment, and fusion of multiple functional layers in a soft polymer substrate. Measurements indicate that the resulting devices achieve excellent performance specifications, and avoid the limiting nonmonotonic behavior identified in the first part of the thesis. In order to demonstrate the practical utility of the devices, we used them to perform dynamic two-dimensional tactile imaging under distributed indentation loads. The results reflect the excellent static and dynamic performance of these devices. The final part of the thesis investigates the utility of the tactile sensing methods pursued here for imaging lumps embedded in simulated tissue. In order to facilitate real-time sensing, an electronic system for fast, array based measurement of small, sub-picofarad (pF) capacitance levels was developed. Using this system, we demonstrated that it is possible to accurately capture strain images depicting small lumps embedded in simulated tissue with either an electronic imaging system or a sensor worn on the finger, supporting the viability of wearable sensors for tactile imaging in medicine. In conclusion, this dissertation confronts many of the most vexing problems arising in the pursuit of skin-like electronic sensors, including fundamental operating principles, structural and functional electronic design, mechanical and electronic modeling, fabrication, and applications to biomedical imaging. The thesis also contributes knowledge needed to enable applications of tactile sensing in medicine, an area that has served as a key source of motivation for this work, and aims to facilitate other applications in areas such as manufacturing, robotics, and consumer electronics.Ph.D., Electrical Engineering -- Drexel University, 201