Stretchable hybrid electronics: combining rigid electronic devices with stretchable interconnects into high-performance on-skin electronics

이병문,Hyeon Cho,정수진,윤재영,장동주,이동건,김다현,정승준,Yongtaek Hong 한국정보디스플레이학회 2022 Journal of information display Vol.23 No.3

Stretchable hybrid electronics (SHE) that combine high-performance rigid electronic devices withstretchable interconnects offer a facile route for accessing and processing bio-signals and humaninteractions. Incorporated with sensors and wireless communications, SHE achieves novel applicationssuch as biomedical diagnosis, skin prosthetics, and robotic skin. The implementation of reliableSHE requires the comprehensive development of stretchable electrodes, bonding techniques, andstrain-engineered integration schemes. This review covers the recent development of enabling technologiesfor SHE in terms of materials, structures, and system engineering. We introduce variousstrategies for stretchable interconnects based on novel materials and structural designs. In particular,we classify SHE into three groups based on strain-relief configurations: thin-film devices onrigid islands, rigid devices with stretchable bridges, and flexible circuits with stretchable bridges. Appropriate methods for substrates, stretchable interconnects, and bonding between rigid and softcomponents and their pros and cons are extensively discussed. We also explore state-of-the-artSHE in advanced human-machine interfaces and discuss the challenges and prospects for futuredirections.

Three-dimensional out-of-plane geometric engineering of thin films for stretchable electronics: a brief review

Moon, Dong-Bin,Lee, Jaedeuk,Roh, Eun,Lee, Nae-Eung Elsevier 2019 THIN SOLID FILMS - Vol.688 No.-

<P><B>Abstract</B></P> <P>Recent progress in engineering approaches for stretchable electronics and electronic components, including strategies focused on materials science or structural engineering, offer high signal-to-noise detection of vital signs via systems that provide conformal, noninvasive contact to curvilinear skin and are unobtrusive during human activity, such as general motion, exercise, and respiration. Structural engineering strategies with flexible thin films, whose deformation can be categorized as two-dimensional (2D) in-plane or three-dimensional (3D) out-of-plane, provide a release of stress created by stretching, bending, or twisting. Beyond 2D in-plane structural engineering techniques, 3D out-of-plane structural engineering techniques effectively distribute nonlinear and multidirectional 3D strain. Here, we review recent advances in 3D out-of-plane engineering techniques, including wavy and wrinkled structures, pop-up structures, kirigami and origami structures, and nature-inspired structures, and describe the strain distribution mechanisms, fabrication processes, applications, and characteristics of these approaches. We conclude with perspectives on applications of stretchable electronic devices with multidirectional stretchability and the existing challenges for future research.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Strain minimization in layers under deformation is important for stretchable electronics. </LI> <LI> 3D out-of-plane structural engineering for stretchable electronics is reviewed. </LI> <LI> Future challenges for fully stretchable electronics are discussed. </LI> </UL> </P>

신축성 전자소자를 위한 신축성 전극 및 스트레인 센서 개발 동향

박진영,이원재,남현진,좌성훈 한국마이크로전자및패키징학회 2018 마이크로전자 및 패키징학회지 Vol.25 No.4

In this paper, we review the latest technical progress and commercialization of stretchable interconnectors, stretchable strain sensors, and stretchable substrates for stretchable electronics. The development of stretchable electronics can pave a way for new applications such as wearable devices, bio-integrated devices, healthcare and monitoring, and soft robotics. The essential components of stretchable electronic devices are stretchable interconnector and stretchable substrate. Stretchable interconnector should have high stretchability and high electrical conductivity as well as stability under severe mechanical deformation. Therefore several nanocomposite-based materials using CNT, graphene, nanowire, and metal flake have been developed. Geometric engineering such as wavy, serpentine, buckled and mesh structure has been well developed. Stretchable substrate should also pose high stretchability and compatibility with stretchable sensing or interconnecting material. We summarize the recent research results of new materials for stretchable interconnector and substrate as well as strain sensors. The Important challenges in development of the stretchable interconnector and substrate are also briefly discussed.

Omnidirectionally stretchable, high performance supercapacitors based on a graphene-carbon-nanotube layered structure

Nam, I.,Bae, S.,Park, S.,Yoo, Y.G.,Lee, J.M.,Han, J.W.,Yi, J. Elsevier 2015 Nano energy Vol.15 No.-

The development of stretchable energy storage systems for fully power-independent and stretchable devices for the next generation is increasing. Here, we report on a graphene-carbon-nanotube-layered structure for use as a stretchable electrode and its application in all-solid-state stretchable supercapacitors and various electronics. In this system, graphene serves as a floating track and carbon nanotubes convert external stress into the stretching motion of the electrode. The structure provides omnidirectional deformation without inhomogeneous interface stress and slip stress between active sites and the stretching passive components. The suggested system offers significant improvement over existing methodologies for fabricating stretchable energy storage systems and electronics in terms of density of capacitance, negligible passive volume, biaxial and twisted deformation, and durability. The integration of stretchable electrodes in various substrates and their application as all-solid-state, stretchable supercapacitors are demonstrated, and a high value of capacitance in the deformed state of 329Fg<SUP>-1</SUP> was achieved (based on mass of the graphene). The physical characteristics of the system are also revealed by first-principle calculations and three-dimensional finite-element methods.

Highly Stretchable and Highly Conductive PEDOT:PSS/Ionic Liquid Composite Transparent Electrodes for Solution-Processed Stretchable Electronics

Teo, Mei Ying,Kim, Nara,Kee, Seyoung,Kim, Bong Seong,Kim, Geunjin,Hong, Soonil,Jung, Suhyun,Lee, Kwanghee American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.1

<P>Stretchable conductive materials have received great attention owing to their potential for realizing next generation stretchable electronics. However, the simultaneous achievement of excellent mechanical stretchability and high electrical conductivity as well as cost-effective fabrication has been a significant challenge. Here, we report a highly stretchable and highly conducting polymer that was obtained by incorporating an ionic liquid. When 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM TCB) was added to an aqueous conducting polymer Solution of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), it was found that EMIM:TCB acts not only as a secondary dopant but also as a plasticizer for PEDOT:PSS, resulting in a high conductivity of >1000 S cm with stable performance at tensile strains up to 50% and even up to 180% in combination with the prestrained substrate technique. Consequently, by exploiting the additional benefits of high transparency and solution-processability of PEDOT:PSS, we were able to fabricate a highly stretchable, semitransparent, and wholly solution processed alternating current electroluminescent device with unimpaired performance at 50% strain by using PEDOT:PSS/EMIM TCB composite films as both bottom and top electrodes.</P>

카본나노튜브/Ecoflex 복합체로 제작된 고신축성 및 고감도 신축성 스트레인 센서

황보유환,남현진,좌성훈 대한금속·재료학회 2023 대한금속·재료학회지 Vol.61 No.7

Wearable strain sensors with high and broad sensitivity, high stretchability and excellentmechanical endurance will be widely useful in smart wearable electronics. In this work, we developed astretchable strain sensor fabricated with a simple stencil printing technique. The stretchable strain sensorwas fabricated using a multi-walled carbon nanotubes (MWCNTs)-Ecoflex composite paste on an Ecoflexsubstrate. In particular, using IPA solvent, CNT particles were uniformly dispersed in the Ecoflex binder. Theeffect of the amount of Ecoflex resin on the stretchability and sensitivity of the sensor were also investigated. It was found that as the amount of Ecoflex resin increased, the stretchability of the sensor increased. Thefabricated stretchable strain sensor showed a maximum stretchability of 1,000% with a wide sensitivity rangefrom 3 to 12,287. The hysteresis tests indicated that the hysteresis of the fabricated stretchable strain sensorwas very small, the electrical resistances of the sensors quickly returned to original value after tests. Thestrain sensor showed excellent mechanical durability during cyclic repeated tensile tests of 400,000 cycles. Theresults of the cross-cut adhesion tests indicated that the adhesion strength between the sensor composite layerand Ecoflex substrate was excellent. We also demonstrated the potential application of the stretchable sensorin wearable electronics by bending tests on a human finger and wrist.

Stretchable Electronics using Liquid Metals

박성준 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

The gallium-based liquid metals are extremely soft and retains electrical conductivity under large strains due to fluidic nature. The metallic conductivity of these electrodes could be utilized for multiple purposes, such as embedded stretchable antennas, shape memory ability and interconnects. Liquid metals can also be patterned within soft materials in unique ways, such as injection into microchannels, vacuum filling into capillary networks, and 3D printing. Thus, the use of liquid metals has exciting implications for ultra-stretchable and soft devices that can take advantage of the high deformability and stretchable conductivity. This presentation describes recent efforts to control the shape and function of liquid metals for applications in soft and stretchable electronics.

Highly Conductive, Stretchable, and Transparent PEDOT:PSS Electrodes Fabricated with Triblock Copolymer Additives and Acid Treatment

Lee, Jin Ho,Jeong, Yu Ra,Lee, Geumbee,Jin, Sang Woo,Lee, Yong Hui,Hong, Soo Yeong,Park, Heun,Kim, Jung Wook,Lee, Sang-Soo,Ha, Jeong Sook American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.33

<P>Here, we report on a highly conductive, stretchable, and transparent electrode of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fabricated via modification with triblock copolymer, poly(ethylene glycol)-<I>block</I>-poly(propylene glycol)-<I>block</I>-poly(ethylene glycol) (PEO<SUB>20</SUB>-PPO<SUB>70</SUB>-PEO<SUB>20</SUB>, Pluronic P123), and post-treatment with sulfuric acid. The fabricated electrode exhibits high transparency (89%), high electrical conductivity (∼1700 S/cm), and minimal change in resistance (∼4%) under repetitive stretch-release cycles at 40% tensile strain after stabilization. P123 acts as a secondary dopant and plasticizer, resulting in enhanced electrical conductivity and stretchability of PEDOT:PSS. Furthermore, after sulfuric acid post-treatment, P123 helps the electrode to maintain its stretchability. A successful demonstration of the stretchable interconnection was shown by stretching the P123-modified PEDOT:PSS electrodes, which were connected with light-emitting diodes (LEDs) in series. Finally, a stretchable and transparent touch sensor consisting of our fabricated electrodes and an LED array and stretchable semitransparent supercapacitor were presented, suggesting a great potential of our electrodes in the application to various deformable devices.</P> [FIG OMISSION]</BR>

Stretchable, Bifacial Si-Organic Hybrid Solar Cells by Vertical Array of Si Micropillars Embedded into Elastomeric Substrates

Yoon, Sung-Soo,Khang, Dahl-Young American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.3

<P>Stretchable electronics has enabled many unforeseen applications in a variety of fields. Mechanical design concepts to achieve the stretchability without affecting the device functionality, however, are limited to few known practices, such as mechanical buckling, serpentine shape, or simple elastomeric composites. In this paper, we propose another mechanics design principle for high stretchability (>100%) based on the composite of vertical array of Si micropillars embedded into elastomer poly(dimethylsiloxane). The orthogonalization of active functional elements to applied strain direction enables highly stretchable electronic devices, where the applied strain is mostly absorbed into elastomer on interpillar space. On the other hand, the vertical pillars do not experience any noticeable strain at all. As a proof-of-concept demonstration, we fabricate stretchable Si-organic hybrid solar cells using such a design and the cell shows reasonable level of cell efficiency compared with planar counterparts. The cell can be stretched reversibly without any noticeable performance degradation. Furthermore, the cell can be operated in a bifacial mode by employing stretchable, transparent Ag nanowire-based electrodes. The mechanical design for stretchability demonstrated here would provide new opportunities for stretchable electronics.</P> [FIG OMISSION]</BR>

신축성 투명전극을 이용한, 플렉서블 일렉트로닉스

박장웅 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Transparent electrodes that can remain electrically conductive and stable under large mechanical deformations are highly desirable for applications in flexible and wearable electronics. Although indium tin oxide (ITO) shows up excellent electrical (low sheet resistance ~30 Ohm/sq) and optical (high transparency ~90%) properties, its brittleness limits many potential applications in flexible and wearable electronics. Thus, there is a clear and urgent need for new transparent conductive materials with superb mechanical properties. As alternatives to ITO, several materials like carbon nanotubes, metal nanowires, metal grids, graphene, and others have been studied for this purpose. Here, we present simple methods to fabricate reliably stretchable, transparent electrodes using one-dimensional and two-dimensional nanomaterials. We believe our approaches using one-dimensional and two-dimensional nanomaterials presents a promising strategy toward flexible, wearable electronics and implantable biosensor devices, and indicates the substantial promise of future electronics.