A Three – tier bio-implantable sensor monitoring and communications platform

One major hindrance to the advent of novel bio-implantable sensor technologies is the need for a reliable power source and data communications platform capable of continuously, remotely, and wirelessly monitoring deeply implantable biomedical devices. This research proposes the feasibility and potential of combining well established, ‘human-friendly' inductive and ultrasonic technologies to produce a proof-of-concept, generic, multi-tier power transfer and data communication platform suitable for low-power, periodically-activated implantable analogue bio-sensors. In the inductive sub-system presented, 5 W of power is transferred across a 10 mm gap between a single pair of 39 mm (primary) and 33 mm (secondary) circular printed spiral coils (PSCs). These are printed using an 8000 dpi resolution photoplotter and fabricated on PCB by wet-etching, to the maximum permissible density. Our ultrasonic sub-system, consisting of a single pair of Pz21 (transmitter) and Pz26 (receiver) piezoelectric PZT ceramic discs driven by low-frequency, radial/planar excitation (-31 mode), without acoustic matching layers, is also reported here for the first time. The discs are characterised by propagation tank test and directly driven by the inductively coupled power to deliver 29 μW to a receiver (implant) employing a low voltage start-up IC positioned 70 mm deep within a homogeneous liquid phantom. No batteries are used. The deep implant is thus intermittently powered every 800 ms to charge a capacitor which enables its microcontroller, operating with a 500 kHz clock, to transmit a single nibble (4 bits) of digitized sensed data over a period of ~18 ms from deep within the phantom, to the outside world. A power transfer efficiency of 83% using our prototype CMOS logic-gate IC driver is reported for the inductively coupled part of the system. Overall prototype system power consumption is 2.3 W with a total power transfer efficiency of 1% achieved across the tiers

소형동물의 뇌신경 자극을 위한 완전 이식형 신경자극기

학위논문(박사)--서울대학교 대학원 :공과대학 전기·정보공학부,2020. 2. 김성준.In this study, a fully implantable neural stimulator that is designed to stimulate the brain in the small animal is described. Electrical stimulation of the small animal is applicable to pre-clinical study, and behavior study for neuroscience research, etc. Especially, behavior study of the freely moving animal is useful to observe the modulation of sensory and motor functions by the stimulation. It involves conditioning animal's movement response through directional neural stimulation on the region of interest. The main technique that enables such applications is the development of an implantable neural stimulator. Implantable neural stimulator is used to modulate the behavior of the animal, while it ensures the free movement of the animals. Therefore, stable operation in vivo and device size are important issues in the design of implantable neural stimulators. Conventional neural stimulators for brain stimulation of small animal are comprised of electrodes implanted in the brain and a pulse generation circuit mounted on the back of the animal. The electrical stimulation generated from the circuit is conveyed to the target region by the electrodes wire-connected with the circuit. The devices are powered by a large battery, and controlled by a microcontroller unit. While it represents a simple approach, it is subject to various potential risks including short operation time, infection at the wound, mechanical failure of the device, and animals being hindered to move naturally, etc. A neural stimulator that is miniaturized, fully implantable, low-powered, and capable of wireless communication is required. In this dissertation, a fully implantable stimulator with remote controllability, compact size, and minimal power consumption is suggested for freely moving animal application. The stimulator consists of modular units of surface-type and depth-type arrays for accessing target brain area, package for accommodating the stimulating electronics all of which are assembled after independent fabrication and implantation using customized flat cables and connectors. The electronics in the package contains ZigBee telemetry for low-power wireless communication, inductive link for recharging lithium battery, and an ASIC that generates biphasic pulse for neural stimulation. A dual-mode power-saving scheme with a duty cycling was applied to minimize the power consumption. All modules were packaged using liquid crystal polymer (LCP) to avoid any chemical reaction after implantation. To evaluate the fabricated stimulator, wireless operation test was conducted. Signal-to-Noise Ratio (SNR) of the ZigBee telemetry were measured, and its communication range and data streaming capacity were tested. The amount of power delivered during the charging session depending on the coil distance was measured. After the evaluation of the device functionality, the stimulator was implanted into rats to train the animals to turn to the left (or right) following a directional cue applied to the barrel cortex. Functionality of the device was also demonstrated in a three-dimensional maze structure, by guiding the rats to navigate better in the maze. Finally, several aspects of the fabricated device were discussed further.본 연구에서는 소형 동물의 두뇌를 자극하기 위한 완전 이식형 신경자극기가 개발되었다. 소형 동물의 전기자극은 전임상 연구, 신경과학 연구를 위한 행동연구 등에 활용된다. 특히, 자유롭게 움직이는 동물을 대상으로 한 행동 연구는 자극에 의한 감각 및 운동 기능의 조절을 관찰하는 데 유용하게 활용된다. 행동 연구는 두뇌의 특정 관심 영역을 직접적으로 자극하여 동물의 행동반응을 조건화하는 방식으로 수행된다. 이러한 적용을 가능케 하는 핵심기술은 이식형 신경자극기의 개발이다. 이식형 신경자극기는 동물의 움직임을 방해하지 않으면서도 그 행동을 조절하기 위해 사용된다. 따라서 동물 내에서의 안정적인 동작과 장치의 크기가 이식형 신경자극기를 설계함에 있어 중요한 문제이다. 기존의 신경자극기는 두뇌에 이식되는 전극 부분과, 동물의 등 부분에 위치한 회로부분으로 구성된다. 회로에서 생산된 전기자극은 회로와 전선으로 연결된 전극을 통해 목표 지점으로 전달된다. 장치는 배터리에 의해 구동되며, 내장된 마이크로 컨트롤러에 의해 제어된다. 이는 쉽고 간단한 접근방식이지만, 짧은 동작시간, 이식부위의 감염이나 장치의 기계적 결함, 그리고 동물의 자연스러운 움직임 방해 등 여러 문제점을 야기할 수 있다. 이러한 문제의 개선을 위해 무선통신이 가능하고, 저전력, 소형화된 완전 이식형 신경자극기의 설계가 필요하다. 본 연구에서는 자유롭게 움직이는 동물에 적용하기 위하여 원격 제어가 가능하며, 크기가 작고, 소모전력이 최소화된 완전이식형 자극기를 제시한다. 설계된 신경자극기는 목표로 하는 두뇌 영역에 접근할 수 있는 표면형 전극과 탐침형 전극, 그리고 자극 펄스 생성 회로를 포함하는 패키지 등의 모듈들로 구성되며, 각각의 모듈은 독립적으로 제작되어 동물에 이식된 뒤 케이블과 커넥터로 연결된다. 패키지 내부의 회로는 저전력 무선통신을 위한 지그비 트랜시버, 리튬 배터리의 재충전을 위한 인덕티브 링크, 그리고 신경자극을 위한 이상성 자극파형을 생성하는 ASIC으로 구성된다. 전력 절감을 위해 두 개의 모드를 통해 사용률을 조절하는 방식이 장치에 적용된다. 모든 모듈들은 이식 후의 생물학적, 화학적 안정성을 위해 액정 폴리머로 패키징되었다. 제작된 신경자극기를 평가하기 위해 무선 동작 테스트가 수행되었다. 지그비 통신의 신호 대 잡음비가 측정되었으며, 해당 통신의 동작거리 및 데이터 스트리밍 성능이 검사되었고, 장치의 충전이 수행될 때 코일간의 거리에 따라 전송되는 전력의 크기가 측정되었다. 장치의 평가 이후, 신경자극기는 쥐에 이식되었으며, 해당 동물은 이식된 장치를 이용해 방향 신호에 따라 좌우로 이동하도록 훈련되었다. 또한, 3차원 미로 구조에서 쥐의 이동방향을 유도하는 실험을 통하여 장치의 기능성을 추가적으로 검증하였다. 마지막으로, 제작된 장치의 특징이 여러 측면에서 심층적으로 논의되었다.Chapter 1 : Introduction 1 1.1. Neural Interface 2 1.1.1. Concept 2 1.1.2. Major Approaches 3 1.2. Neural Stimulator for Animal Brain Stimulation 5 1.2.1. Concept 5 1.2.2. Neural Stimulator for Freely Moving Small Animal 7 1.3. Suggested Approaches 8 1.3.1. Wireless Communication 8 1.3.2. Power Management 9 1.3.2.1. Wireless Power Transmission 10 1.3.2.2. Energy Harvesting 11 1.3.3. Full implantation 14 1.3.3.1. Polymer Packaging 14 1.3.3.2. Modular Configuration 16 1.4. Objectives of This Dissertation 16 Chapter 2 : Methods 18 2.1. Overview 19 2.1.1. Circuit Description 20 2.1.1.1. Pulse Generator ASIC 21 2.1.1.2. ZigBee Transceiver 23 2.1.1.3. Inductive Link 24 2.1.1.4. Energy Harvester 25 2.1.1.5. Surrounding Circuitries 26 2.1.2. Software Description 27 2.2. Antenna Design 29 2.2.1. RF Antenna 30 2.2.1.1. Design of Monopole Antenna 31 2.2.1.2. FEM Simulation 31 2.2.2. Inductive Link 36 2.2.2.1. Design of Coil Antenna 36 2.2.2.2. FEM Simulation 38 2.3. Device Fabrication 41 2.3.1. Circuit Assembly 41 2.3.2. Packaging 42 2.3.3. Electrode, Feedthrough, Cable, and Connector 43 2.4. Evaluations 45 2.4.1. Wireless Operation Test 46 2.4.1.1. Signal-to-Noise Ratio (SNR) Measurement 46 2.4.1.2. Communication Range Test 47 2.4.1.3. Device Operation Monitoring Test 48 2.4.2. Wireless Power Transmission 49 2.4.3. Electrochemical Measurements In Vitro 50 2.4.4. Animal Testing In Vivo 52 Chapter 3 : Results 57 3.1. Fabricated System 58 3.2. Wireless Operation Test 59 3.2.1. Signal-to-Noise Ratio Measurement 59 3.2.2. Communication Range Test 61 3.2.3. Device Operation Monitoring Test 62 3.3. Wireless Power Transmission 64 3.4. Electrochemical Measurements In Vitro 65 3.5. Animal Testing In Vivo 67 Chapter 4 : Discussion 73 4.1. Comparison with Conventional Devices 74 4.2. Safety of Device Operation 76 4.2.1. Safe Electrical Stimulation 76 4.2.2. Safe Wireless Power Transmission 80 4.3. Potential Applications 84 4.4. Opportunities for Further Improvements 86 4.4.1. Weight and Size 86 4.4.2. Long-Term Reliability 93 Chapter 5 : Conclusion 96 Reference 98 Appendix - Liquid Crystal Polymer (LCP) -Based Spinal Cord Stimulator 107 국문 초록 138 감사의 글 140Docto

Implantable Microsystem Technologies For Nanoliter-Resolution Inner Ear Drug Delivery

Advances in protective and restorative biotherapies have created new opportunities to use site-directed, programmable drug delivery systems to treat auditory and vestibular disorders. Successful therapy development that leverages the transgenic, knock-in, and knock-out variants of mouse models of human disease requires advanced microsystems specifically designed to function with nanoliter precision and with system volumes suitable for implantation. The present work demonstrates a novel biocompatible, implantable, and scalable microsystem consisted of a thermal phase-change peristaltic micropump with wireless control and a refillable reservoir. The micropump is fabricated around a catheter microtubing (250 μm OD, 125 μm ID) that provided a biocompatible leak-free flow path while avoiding complicated microfluidic interconnects. Direct-write micro-scale printing technology was used to build the mechanical components of the pump around the microtubing directly on the back of a printed circuit board assembly. In vitro characterization results indicated nanoliter resolution control over the desired flow rates of 10–100 nL/min by changing the actuation frequency, with negligible deviations in presence of up to 10× greater than physiological backpressures and ±3°C ambient temperature variation. A biocompatibility study was performed to evaluate material suitability for chronic subcutaneous implantation and clinical translational development. A stand-alone, refillable, in-plane, scalable, and fully implantable microreservoir platform was designed and fabricated to be integrated with the micropump. The microreservoir consists two main components: a cavity for storing the drug and a septum for refilling. The cavity membrane is fabricated with thin Parylene-C layers, using a polyethylene glycol (PEG) sacrificial layer. The septum thickness is minimized by pre-compression down to 1 mm. The results of in vitro characterization indicated negligible restoring force for the optimized cavity membrane and thousands of punctures through the septum without leakage. The micropump and microreservoir were integrated into microsystems which were implanted in mice. The microtubing was implanted into the round window membrane niche for infusion of a known ototoxic compound (sodium salicylate) at 50 nL/min for 20 min. Real-time shifts in distortion product otoacoustic emission thresholds and amplitudes were measured during the infusion. The results match with syringe pump gold standard. For the first time a miniature and yet scalable microsystem for inner ear drug delivery was developed, enabling drug discovery opportunities and translation to human

Skin-Integrated wearable systems and implantable biosensors: a comprehensive review

Biosensors devices have attracted the attention of many researchers across the world. They have the capability to solve a large number of analytical problems and challenges. They are future ubiquitous devices for disease diagnosis, monitoring, treatment and health management. This review presents an overview of the biosensors field, highlighting the current research and development of bio-integrated and implanted biosensors. These devices are micro- and nano-fabricated, according to numerous techniques that are adapted in order to offer a suitable mechanical match of the biosensor to the surrounding tissue, and therefore decrease the body’s biological response. For this, most of the skin-integrated and implanted biosensors use a polymer layer as a versatile and flexible structural support, combined with a functional/active material, to generate, transmit and process the obtained signal. A few challenging issues of implantable biosensor devices, as well as strategies to overcome them, are also discussed in this review, including biological response, power supply, and data communication.This research was funded by FCT- FUNDAÇÃO PARA A CIÊNCIA E TECNOLOGIA, grant numbers: PTDC/EMD-EMD/31590/2017 and PTDC/BTM-ORG/28168/2017

Improving the mechanistic study of neuromuscular diseases through the development of a fully wireless and implantable recording device

Neuromuscular diseases manifest by a handful of known phenotypes affecting the peripheral nerves, skeletal muscle fibers, and neuromuscular junction. Common signs of these diseases include demyelination, myasthenia, atrophy, and aberrant muscle activity—all of which may be tracked over time using one or more electrophysiological markers. Mice, which are the predominant mammalian model for most human diseases, have been used to study congenital neuromuscular diseases for decades. However, our understanding of the mechanisms underlying these pathologies is still incomplete. This is in part due to the lack of instrumentation available to easily collect longitudinal, in vivo electrophysiological activity from mice. There remains a need for a fully wireless, batteryless, and implantable recording system that can be adapted for a variety of electrophysiological measurements and also enable long-term, continuous data collection in very small animals. To meet this need a miniature, chronically implantable device has been developed that is capable of wirelessly coupling energy from electromagnetic fields while implanted within a body. This device can both record and trigger bioelectric events and may be chronically implanted in rodents as small as mice. This grants investigators the ability to continuously observe electrophysiological changes corresponding to disease progression in a single, freely behaving, untethered animal. The fully wireless closed-loop system is an adaptable solution for a range of long-term mechanistic and diagnostic studies in rodent disease models. Its high level of functionality, adjustable parameters, accessible building blocks, reprogrammable firmware, and modular electrode interface offer flexibility that is distinctive among fully implantable recording or stimulating devices. The key significance of this work is that it has generated novel instrumentation in the form of a fully implantable bioelectric recording device having a much higher level of functionality than any other fully wireless system available for mouse work. This has incidentally led to contributions in the areas of wireless power transfer and neural interfaces for upper-limb prosthesis control. Herein the solution space for wireless power transfer is examined including a close inspection of far-field power transfer to implanted bioelectric sensors. Methods of design and characterization for the iterative development of the device are detailed. Furthermore, its performance and utility in remote bioelectric sensing applications is demonstrated with humans, rats, healthy mice, and mouse models for degenerative neuromuscular and motoneuron diseases

Beyond Tissue replacement: The Emerging role of smart implants in healthcare

Smart implants are increasingly used to treat various diseases, track patient status, and restore tissue and organ function. These devices support internal organs, actively stimulate nerves, and monitor essential functions. With continuous monitoring or stimulation, patient observation quality and subsequent treatment can be improved. Additionally, using biodegradable and entirely excreted implant materials eliminates the need for surgical removal, providing a patient-friendly solution. In this review, we classify smart implants and discuss the latest prototypes, materials, and technologies employed in their creation. Our focus lies in exploring medical devices beyond replacing an organ or tissue and incorporating new functionality through sensors and electronic circuits. We also examine the advantages, opportunities, and challenges of creating implantable devices that preserve all critical functions. By presenting an in-depth overview of the current state-of-the-art smart implants, we shed light on persistent issues and limitations while discussing potential avenues for future advancements in materials used for these devices

Fully Integrated Biochip Platforms for Advanced Healthcare

Recent advances in microelectronics and biosensors are enabling developments of innovative biochips for advanced healthcare by providing fully integrated platforms for continuous monitoring of a large set of human disease biomarkers. Continuous monitoring of several human metabolites can be addressed by using fully integrated and minimally invasive devices located in the sub-cutis, typically in the peritoneal region. This extends the techniques of continuous monitoring of glucose currently being pursued with diabetic patients. However, several issues have to be considered in order to succeed in developing fully integrated and minimally invasive implantable devices. These innovative devices require a high-degree of integration, minimal invasive surgery, long-term biocompatibility, security and privacy in data transmission, high reliability, high reproducibility, high specificity, low detection limit and high sensitivity. Recent advances in the field have already proposed possible solutions for several of these issues. The aim of the present paper is to present a broad spectrum of recent results and to propose future directions of development in order to obtain fully implantable systems for the continuous monitoring of the human metabolism in advanced healthcare applications

Integrated Microsystems for Wireless Sensing Applications

Personal health monitoring is being considered the future of a sustainable health care system. Biosensing platforms are a very important component of this system. Real-time and accurate sensing is essential for the success of personal health care model. Currently, there are many efforts going on to make these sensors practical and more useful for such measurements. Implantable sensors are considered the most widely applicable and most reliable sensors for such accurate health monitoring applications. However, macroscopic (cm scale) size has proved to be a limiting factor for successful use of these systems for long time and in large numbers. This work is focused to resolve the issues related with miniaturizing these devices to a microscopic (mm scale) size scale which can minimize many practical difficulties associated with their larger counterparts currently. To accomplish this goal of miniaturization while retaining or even improving on the necessary capabilities for such sensing platforms, an integrated approach is presented which focuses on system-level miniaturization using standard fabrication procedures. First, it is shown that a completely integrated and wireless system is the best solution to achieve desired miniaturization without sacrificing the functionality of the system. Hence, design and implementation of the different components comprising the complete system needs to be done according to the requirements of the overall integrated system. This leads to the need of on-chip functional sensors, integrated wireless power supply, integrated wireless communication and integrated control system for realization of such system. In this work, different options for implementation of each of these subsystems are compared and an optimal solution is presented for each subsystem. For such complex systems, it is imperative to use a standard fabrication process which can provide the required functionality for all subsystems at smallest possible size scale. Complementary Metal Oxide Semiconductor (CMOS) process is the most appropriate of the technologies in this regard and has enabled incredible miniaturization of the computing industry. It also provides options for designing different subsystems on the same platform in a monolithic process with very high yield. This choice then leads to actual designs of subsystems in the CMOS technology using different possible methods. Careful comparison of these subsystems provides insights into different design adjustments that are made until the desired functions are achieved at the desired size scale. Integration of all these compatible subsystems in the same platform is shown to provide the smallest possible sensing platform to date. The completely wireless system can measure a host of different important analyte and can transmit the data to an external device which can use it for appropriate purpose. Results on measurements in phosphate buffer solution, blood serum and whole blood along with wireless communication in real biological tissues are provided. Specific examples of glucose and DNA sensors are presented and the use for many other relevant applications is also proposed. Finally, insights into animal model studies and future directions of the research are discussed. </p

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

Stepper microactuators driven by ultrasonic power transfer

Advances in miniature devices for biomedical applications are creating ever-increasing requirements for their continuous, long lasting, and reliable energy supply, particularly for implanted devices. As an alternative to bulky and cost inefficient batteries that require occasional recharging and replacement, energy harvesting and wireless power delivery are receiving increased attention. While the former is generally only suited for low-power diagnostic microdevices, the latter has greater potential to extend the functionality to include more energy demanding therapeutic actuation such as drug release, implant mechanical adjustment or microsurgery. This thesis presents a novel approach to delivering wireless power to remote medical microdevices with the aim of satisfying higher energy budgets required for therapeutic functions. The method is based on ultrasonic power delivery, the novelty being that actuation is powered by ultrasound directly rather than via piezoelectric conversion. The thesis describes a coupled mechanical system remotely excited by ultrasound and providing conversion of acoustic energy into motion of a MEMS mechanism using a receiving membrane coupled to a discrete oscillator. This motion is then converted into useful stepwise actuation through oblique mechanical impact. The problem of acoustic and mechanical impedance mismatch is addressed. Several analytical and numerical models of ultrasonic power delivery into the human body are developed. Major design challenges that have to be solved in order to obtain acceptable performance under specified operating conditions and with minimum wave reflections are discussed. A novel microfabrication process is described, and the resulting proof-of-concept devices are successfully characterized.Open Acces