Development of tough and stretchable materials for wearable electronics

Gargi, Ghosh Sungkyunkwan University 2023 국내박사

New generations of wearable electronics are rapidly merging with bioelectronics offering a robust and emerging framework for invasive and on-skin electronics that are expected to be flexible, stretchable, conformable, lightweight, and long-lasting. These wearable devices can be worn comfortably on human skin (3-55% in elongation) without causing user discomfort, delamination, and device failure. Mostly, the advances that are made in the field of wearable soft electronics have been achieved on substrates. The prevalence of these synthetic polymers in wearable soft electronics can bring tremendous benefits to daily life due to their structural integrity. Consequently, this prevalent use of synthetic polymers in soft electronics has been a major cause for landfills and oceanfills with far-reaching consequences for the environment as well as humankind. Hence, it is highly essential for these materials to be seamlessly integrated with the environment and human health. In fact, their successful integration into our ecosystem depends on the creation of materials that are recyclable, environmentally relevant in terms of degradability, and interface with biological systems without causing harm. Moreover, the development of sustainable material with recyclability or transient nature and their incorporation into electronics is essential for the progression of new technologies, environmental protection, human health, and a sustainable future. However, creation of such materials has been hampered due to the challenges of balancing these properties. Here, we have utilized both intrinsic and extrinsic methods to develop materials with stretchability, toughness and sustainability (recyclability/ biodegradability/ bio-disintegrability). First, we developed an intrinsically stretchable thermoplastic copolymer with a random sequence of hard and soft domains in the polyimide backbone in which their superior traits are harnessed to enable the properties of the copolymer to be tunable and balanced. In addition, the polymer is recyclable and shows excellent processability. Furthermore, the utility of the copolymer was successfully demonstrated for a wearable temperature sensor on the stretchable copolymer and a copolymer-based fully stretchable sweat collection patch, suggesting that they have great potential in soft electronics. Secondly, we developed a biodegradable, biocompatible and stretchable composite microfiber of poly(glycerol sebacate) (PGS) and polyvinyl alcohol (PVA) for transient stretchable device applications. As an application, the stretchable microfiber-based strain sensor was fabricated by incorporation of Au nanoparticles (AuNPs) in the composite microfiber. Finally, we developed a bio-disintegrable substrate (NFR-WPU) embedded with biodegradable nanofibers which acts as a reinforcement to render a non-degradable substrate bio-disintegrable. An optimal loading amount of NFs into the NFR-WPU significantly enhanced the toughness by 19 times and also has a disintegration rate nine times greater than that of pristine non- degradable WPU. Finally, disintegrable and stretchable triboelectric and capacitive touch sensors on the NFR-WPU were fabricated and demonstrated for potential use in transient wearable electronics. In conclusion, the results of this study will open up new horizons of material designing for future electronics by addressing the currently existing limitations in harnessing a material with balanced properties. 새로운 세대의 웨어러블 전자 제품은 빠르게 바이오 전자 제품과 병합되어 침입 및 피부 위 전자 제품을 위한 강력하고 새로운 프레임워크를 제공하고 있다. 이러한 웨어러블 기기는 사용자 불편, 박리 및 기기 고장을 유발하지 않고 사람 피부에 편안하게 착용할 수 있다(신장 3-55%). 대부분 웨어러블 소프트 일렉트로닉스 분야의 발전은 기판에서 이루어졌다. 웨어러블 소프트 일렉트로닉스에서 이러한 합성 중합체의 보급은 구조적 무결성으로 인해 일상 생활에 엄청난 이점을 가져올 수 있다. 결과적으로, 소프트 일렉트로닉스에서 이러한 합성 중합체의 널리 사용은 환경과 인류에게 광범위한 결과를 초래하는 매립지와 해양 매립지의 주요 원인이 되었다. 따라서, 이러한 물질들이 환경 및 인간의 건강과 원활하게 통합되는 것은 매우 중요하다. 사실, 재활용 가능성 또는 일시적인 특성을 가진 지속 가능한 물질의 개발과 그것들의 전자공학으로의 통합은 신기술, 환경보호, 인간의 건강, 그리고 지속 가능한 미래의 발전을 위해 필수적이다. 그러나, 이러한 특성들의 균형을 맞추는 문제로 인해 이러한 재료들의 생성이 방해를 받고 있다. 여기서, 우리는 신축성, 강인성 및 지속 가능성(재활용성/생분해성/바이오 분해성)을 가진 재료를 개발하기 위해 내재적 및 외재적 방법을 모두 사용했다. 먼저, 우리는 폴리이미드 골격에서 하드 도메인과 소프트 도메인의 무작위 시퀀스를 가진 본질적으로 신축성이 있는 열가소성 공중합체를 개발했는데, 이는 공중합체의 특성이 조정 가능하고 균형을 이룰 수 있도록 우수한 특성을 이용한다. 또한, 신축성 공중합체 상의 웨어러블 온도 센서 및 공중합체 기반의 완전 신축성 땀 포집 패치에 대하여 공중합체의 유용성이 성공적으로 입증되어 소프트 일렉트로닉스 분야에서 큰 잠재력을 가지고 있음을 시사하였다. 둘째로, 우리는 일시적인 신축성 장치 애플리케이션을 위한 폴리(글리세롤 세바세이트)와 폴리비닐알코올(PVA)의 생분해성, 생체적합성 및 신축성 복합 마이크로파이버를 개발했다. 애플리케이션으로는, 복합 마이크로파이버에 Au 나노입자(AuNPs)를 혼입시켜 신축성 마이크로파이버 기반의 스트레인 센서를 제작하였다. 마지막으로, 우리는 생물 분해성 나노 섬유가 내장된 생물 분해성 기판(NFR-WPU)을 개발했는데, 이는 분해 불가능한 기판을 생물 분해성으로 만드는 강화제 역할을 한다. 마지막으로, NFR-WPU의 분해 가능하고 신축 가능한 트라이보 전기 및 용량성 터치 센서는 일시적인 웨어러블 전자 장치에서 잠재적으로 사용할 수 있도록 제작되고 시연되었다. 결론적으로, 본 연구의 결과는 균형잡힌 특성을 가진 재료를 활용하는 데 있어 현재 존재하는 한계를 해결함으로써 미래 전자공학에 대한 재료 설계의 새로운 지평을 열 것이다.

Network based micro-mobility architecture for 6LoWPAN

Bag, Gargi Ajou Univ. 2010 국내박사

thesis provides an in depth analysis of the existing mobility support protocols in terms of different aspects of mobility management such as location management, handover management, routing, route optimization and security. Also it discusses the goals and mobility requirements of 6LoWPAN. A network based micro-mobility management architecture is proposed for 6LoWPAN. The micro-mobility management architecture embodies three schemes. The first scheme is LoWMob, which is a network based mobility scheme aims to provide mobility support to mobile 6LoWPAN nodes at the adaptation layer of the 6LoWPAN. In order to achieve that, LoWMob proposes to utilize 6LoWPAN’s adaptation layer message format and 16 bit addressing scheme to carry mobility related signaling. A distributed version of LoWMob(DLoWMob) is proposed in order to distribute the traffic concentration at the gateway. Route Optimization of data packets of two mobile nodes located in the same PAN is also considered. A security scheme is also proposed in order to provide mutual authentication of the MN and a PAN and to secure MN’s data packets. The third scheme is LoWPMIPv6 which is a lightweight implementation of PMIPv6 (LoWPMIPv6) for 6LoWPAN. It provides mobility support at the network layer and proposes compression of mobility related messages in order to reduce the overhead on the PAN nodes. The three schemes (LoWMob, DLoWMob and LoWPMIPv6) is then compared in order determine their suitability for 6LoWPAN. The performance of our proposed schemes is evaluated in terms of mobility signaling costs, end-to-end delay, and packet success ratio both in Qulanet and analytically.

Allosteric effects of calcium and voltage on the gating of a calcium sensitive potassium channel

Talukder, Gargi Stanford University 2001 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The cloned potassium channel <italic>mSlo</italic> is sensitive to intracellular calcium as well as to changes in membrane voltage. In this dissertation, I have examined the effects of both calcium and voltage on the gating of single molecules of <italic>mSlo</italic> heterologously expressed in <italic>Xenopus laevis</italic> oocytes. Using the inside out voltage clamp recording technique, I have examined the single channel kinetics of <italic>mSlo</italic> to determine the complexity of its gating in the absence of any intracelluar calcium. I have found that the intrinsic voltage dependence of <italic>mSlo</italic> is quite complex, and that even in the absence of calcium the channel is able to occupy multiple closed and open conformational states. I extended this study of channel gating in zero calcium by examining gating behavior in single channels composed of subunits with non-identical voltage sensors. I was able to form these heteromeric channels by coexpressing wildtype <italic>mSlo</italic> channels with the R207Q point mutant. This point mutation neutralizes a residue in the S4 transmembrane region of the subunit, and its result on gating is to shift the equilibrium of voltage sensor activation toward negative voltages. By examining the behavior of channels composed of both wildtype and R207Q subunits, I was able to test the possibility of cooperative interactions between voltage sensors in this channel. My results indicate that the voltage sensors of <italic>mSlo</italic> do not show a strong evidence of cooperativity during channel gating. Similarly, I investigated the possibility of cooperative interactions between the calcium sensors of <italic>mSlo</italic> by studying the gating of single molecules of <italic>mSlo</italic> with non-identical calcium sensors. I formed these heteromers by coexpressing wildtype subunits with chimeric subunits. The chimeric subunits were formed from the core of <italic>mSlo1 </italic> and the C-terminus of <italic>mSlo3</italic>, a large conductance potassium channel that is voltage dependent but shows no sensitivity to changes in intracellular calcium. My results with these calcium sensor heteromultimers show that the calcium sensors of <italic>mSlo</italic> also act independently during channel gating.

Fundamentals of Nanopipette Probes and Applications with Electrospray and Electrochemical Microscopy (FEM Simulations) to Study Nanoscale Systems

Jagdale, Gargi Satishraj ProQuest Dissertations & Theses Indiana University 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Nanoscale measurements to study heterogeneity in chemical and biological systems are essential to identify and understand the underlying processes, which cannot be observed from ensemble measurements. Nanopipettes, glass capillaries pulled to nanoscale size tip openings, provide an interesting tool for studies of such heterogeneity at small length scales. Work presented here details fundamentals of electrospray (ES) mass spectrometry (MS) analysis through nanometer-sized emitters. Determination of ES flow rates during self-aspirated ES from nanopipettes and effect of emitter geometry and solution conductivity are described. The debate on whether native structures of protein and protein complexes are preserved during ES from nanometer emitters is addressed. With the understanding of the fundamental nature of ES, new methods for the study of local chemistry and single nanoparticles are developed. Simultaneous liquid extraction and chemical analysis nanopipette probe design is proposed for local chemical analysis. ES deposition from nanopipettes to obtain single, isolated particles for single entity electrochemistry (SEE) measurements is described. Fast detection of ES from nanopipettes with 70-100 nm orifice is developed to detect single particle (26 nm and 60 nm diameter) translocation through the emitter tip during ES. Furthermore, finite element method (FEM) simulation studies to inform experimental studies of nanoscale electrochemical systems where nanopipettes are used as probes are discussed. Studies of electrocatalysis of nanoparticles, heterogeneous surface charge at the mineral-air interface, and local electric field determinations were performed through simulations to support experimental results.