Cardiovascular disease is the leading cause of death and has dramatically increased in recent years. Continuous cardiac monitoring is particularly important for early diagnosis and prevention, and ...flexible and stretchable electronic devices have emerged as effective tools for this purpose. Their thin, soft, and deformable features allow intimate and long‐term integration with biotissues, which enables continuous, high‐fidelity, and sometimes large‐area cardiac monitoring on the skin and/or heart surface. In addition to monitoring, intimate contact is also crucial for high‐precision therapies. Combined with tissue engineering, soft bioelectronics have also demonstrated the capability to repair damaged cardiac tissues. This review highlights the recent advances in wearable and implantable devices based on flexible and stretchable electronics for cardiovascular monitoring and therapy. First, wearable/implantable soft bioelectronics for cardiovascular monitoring (e.g., the electrocardiogram, blood pressure, and oxygen saturation level) are reviewed. Then, advances in cardiovascular therapy based on soft bioelectronics (e.g., mesh pacing, ablation, robotic sleeves, and electronic stents) are discussed. Finally, device‐assisted tissue engineering therapy (e.g., functional electronic scaffolds and in vitro cardiac platforms) is discussed.
Over the past few decades, soft bioelectronics have been widely adopted in biomedical research fields to address limitations in each field. Here, wearable and implantable devices based on flexible and stretchable electronics for cardiovascular monitoring and therapy that overcome the problems with conventional treatments are reviewed. In addition, the emerging field of device‐assisted tissue engineering is highlighted.
The diverse vision systems found in nature can provide interesting design inspiration for imaging devices, ranging from optical subcomponents to digital cameras and visual prostheses, with more ...desirable optical characteristics compared to conventional imagers. The advantages of natural vision systems include high visual acuity, wide field of view, wavelength‐free imaging, improved aberration correction and depth of field, and high motion sensitivity. Recent advances in soft materials, ultrathin electronics, and deformable optoelectronics have facilitated the realization of novel processes and device designs that mimic biological vision systems. This review highlights recent progress and continued efforts in the research and development of bioinspired artificial eyes. At first, the configuration of two representative eyes found in nature: a single‐chambered eye and a compound eye, is explained. Then, advances in bioinspired optic components and image sensors are discussed in terms of materials, optical/mechanical designs, and integration schemes. Subsequently, novel visual prostheses as representative application examples of bioinspired artificial eyes are described.
Vision systems in nature are highly attractive in the field of imaging devices due to the applicability for optical subcomponents, digital cameras, and visual prostheses. The most recent advances in bioinspired imaging systems based on soft materials/device designs, ultrathin electronics, and deformable optoelectronics are reviewed. A representative application example of the bioinspired artificial eye, novel visual prostheses, is also discussed.
Flexible and stretchable electronics and optoelectronics configured in soft, water resistant formats uniquely address seminal challenges in biomedicine. Over the past decade, there has been enormous ...progress in the materials, designs, and manufacturing processes for flexible/stretchable system subcomponents, including transistors, amplifiers, bio‐sensors, actuators, light emitting diodes, photodetector arrays, photovoltaics, energy storage elements, and bare die integrated circuits. Nanomaterials prepared using top‐down processing approaches and synthesis‐based bottom‐up methods have helped resolve the intrinsic mechanical mismatch between rigid/planar devices and soft/curvilinear biological structures, thereby enabling a broad range of non‐invasive, minimally invasive, and implantable systems to address challenges in biomedicine. Integration of therapeutic functional nanomaterials with soft bioelectronics demonstrates therapeutics in combination with unconventional diagnostics capabilities. Recent advances in soft materials, devices, and integrated systems are reviewes, with representative examples that highlight the utility of soft bioelectronics for advanced medical diagnostics and therapies.
The technological advances in the field of flexible and stretchable electronics have burgeoned tremendously over the past decade, enabling multifunctional bio integrated electronics and optoelectronics systems. Recent progress in nanomaterials, device design, and system integration strategies for flexible and stretchable bioelectronics systems is reviewed in the context of wearable sensors/actuators, minimally invasive surgical tools, and soft implantable devices.
Recent technological advances in nanomaterials have driven the development of high‐performance light‐emitting devices with flexible and stretchable form factors. Deformability in such devices is ...mainly achieved by replacing the rigid materials in the device components with flexible nanomaterials and their assemblies (e.g., carbon nanotubes, silver nanowires, graphene, and quantum dots) or with intrinsically soft materials and their composites (e.g., polymers and elastomers). Downscaling the dimensions of the functional materials to the nanometer range dramatically decreases their flexural rigidity, and production of polymer/elastomer composites with functional nanomaterials provides light‐emitting devices with flexibility and stretchability. Furthermore, monolithic integration of these light‐emitting devices with deformable sensors furnishes the resulting display with various smart functions such as force/capacitive touch‐based data input, personalized health monitoring, and interactive human–machine interfacing. These ultrathin, lightweight, and deformable smart optoelectronic devices have attracted widespread interest from materials scientists and device engineers. Here, a comprehensive review of recent progress concerning these flexible and stretchable smart displays is presented with a focus on materials development, fabrication techniques, and device designs. Brief overviews of an integrated system of advanced smart displays and cutting‐edge wearable sensors are also presented, and, to conclude, a discussion of the future research outlook is given.
The recent research developments and progress regarding flexible and stretchable smart displays are reviewed comprehensively. Important advancements concerning materials development, fabrication techniques, and device designs are summarized, compared, and discussed, with a detailed description of smart display applications. In addition, the outlook for future research in this field is discussed.
Stretchable electronics are mechanically compatible with a variety of objects, especially with the soft curvilinear contours of the human body, enabling human‐friendly electronics applications that ...could not be achieved with conventional rigid electronics. Therefore, extensive research effort has been devoted to the development of stretchable electronics, from research on materials and unit device, to fully integrated systems. In particular, material‐processing technologies that encompass the synthesis, assembly, and patterning of intrinsically stretchable electronic materials have been actively investigated and have provided many notable breakthroughs for the advancement of stretchable electronics. Here, the latest studies of such material‐based approaches are reviewed, mainly focusing on intrinsically stretchable electronic nanocomposites that generally consist of conducting/semiconducting filler materials inside or on elastomer backbone matrices. Various approaches for fabricating these intrinsically stretchable electronic materials are presented, including the blending of electronic fillers into elastomer matrices, the formation of bi‐layered heterogeneous electronic‐layer and elastomer support‐layer structures, and modifications to polymeric molecular structures in order to impart stretchability. Detailed descriptions of the various conducting/semiconducting composites prepared by each method are provided, along with their electrical/mechanical properties and examples of device applications. To conclude, a brief future outlook is presented.
The latest research developments and progress regarding material‐based approaches for the fabrication of stretchable electronics are comprehensively reviewed. Detailed descriptions of various stretchable conducting/semiconducting composites are given, along with their electrical/mechanical properties, material processing strategies, and examples of device applications. In addition, the outlook for future research in this field is discussed.
Highly conductive and intrinsically stretchable electrodes are vital components of soft electronics such as stretchable transistors and circuits, sensors and actuators, light-emitting diode arrays, ...and energy harvesting devices. Many kinds of conducting nanomaterials with outstanding electrical and mechanical properties have been integrated with elastomers to produce stretchable conductive nanocomposites. Understanding the characteristics of these nanocomposites and assessing the feasibility of their fabrication are therefore critical for the development of high-performance stretchable conductors and electronic devices. We herein summarise the recent advances in stretchable conductors based on the percolation networks of nanoscale conductive fillers in elastomeric media. After discussing the material-, dimension-, and size-dependent properties of conductive fillers and their implications, we highlight various techniques that are used to reduce the contact resistance between the conductive filler materials. Furthermore, we categorize elastomer matrices with different stretchabilities and mechanical properties based on their polymeric chain structures. Then, we discuss the fabrication techniques of stretchable conductive nanocomposites toward their use in soft electronics. Finally, we provide representative examples of stretchable device applications and conclude the review with a brief outlook for future research.
This article reviews the cascade strategy of stretchable conductive nanocomposites where various filler materials are processed for stretchable electronic applications.
Colloidal nanocrystals have been intensively studied over the past three decades due to their unique properties that originate, in large part, from their nanometer‐scale sizes. For applications in ...electronic and optoelectronic devices, colloidal nanoparticles are generally employed as assembled nanocrystal solids, rather than as individual particles. Consequently, tailoring 2D patterns as well as 3D architectures of assembled nanocrystals is critical for their various applications to micro‐ and nanoscale devices. Here, recent advances in the designed assembly, film fabrication, and printing/integration methods for colloidal nanocrystals are presented. The advantages and drawbacks of these methods are compared, and various device applications of assembled/integrated colloidal nanocrystal solids are discussed.
The preparation, formatting, and applications of colloidal nanoparticle solids have burgeoned tremendously over the last thirty years due to the remarkable crossover of ideas from many materials science fields. Here, general information on the preparation of colloidal nanocrystalline solids via thin‐film formation and various printing techniques is presented. In addition, their integration into a number of advanced electronic applications is discussed.
Wearable bioelectronic technologies have made significant progresses in personalized health management through non‐invasive monitoring of health indicators. However, current wearable systems cannot ...measure biochemical information and physiological signals simultaneously, which limits integrated data analysis and their widespread clinical applications. Here, an integrated multifunctional wearable health management system composed of a disposable sweat‐based glucose sensing strip and a wearable smart band is reported. The integrated system with control software electrochemically analyzes sweat glucose levels and continuously monitors vital signs (i.e., heart rate, blood oxygen saturation level, and physical activity). Different sweat collecting sites and sweat generation methods are tested in short‐ and long‐term studies with multiple human subjects by using the developed wearable system, leading to optimized protocols for health monitoring. By combining sweat glucose data and physiological monitoring data, pre‐ and post‐exercise blood glucose levels and blood glucose changes resulting from physical activities are reliably estimated, providing key information for preventing hypoglycemic shock during intense exercise. The integrated wearable system offers a novel comprehensive personalized health management strategy through combined analysis of key metabolic and physiological health indicators.
An integrated multifunctional wearable health monitoring system that consists of a disposable sweat‐based glucose sensing strip and a wearable smart band is developed for pre‐/post‐exercise glucose‐level estimation and comprehensive personalized health management. Multiple short‐term human studies under various conditions are performed, and optimized protocols for the integrated system to perform accurate and user‐friendly sweat‐based metabolic data analysis are reported.
Carbon nanotubes (CNTs) are a promising material for use as a flexible electrode in wearable energy devices due to their electrical conductivity, soft mechanical properties, electrochemical activity, ...and large surface area. However, their electrical resistance is higher than that of metals, and deformations such as stretching can lead to deterioration of electrical performances. To address these issues, here a novel stretchable electrode based on laterally combed CNT networks is presented. The increased percolation between combed CNTs provides a high electrical conductivity even under mechanical deformations. Additional nickel electroplating and serpentine electrode designs increase conductivity and deformability further. The resulting stretchable electrode exhibits an excellent sheet resistance, which is comparable to conventional metal film electrodes. The resistance change is minimal even when stretched by ≈100%. Such high conductivity and deformability in addition to intrinsic electrochemically active property of CNTs enable high performance stretchable energy harvesting (wireless charging coil and triboelectric generator) and storage (lithium ion battery and supercapacitor) devices. Monolithic integration of these devices forms a wearable energy supply system, successfully demonstrating its potential as a novel soft power supply module for wearable electronics.
Stretchable electrodes using a laterally combed carbon nanotube (CNT) network are fabricated by restructuring of vertically aligned CNTs through a lateral‐combing process. Subsequent Ni‐electroplating further enhances the conductivity of the laterally combed CNT network. This novel nanostructure is used as electrically and electrochemically high performance electrodes in wearable energy harvesting (wireless charger and triboelectric generator) and storage (lithium ion battery and supercapacitor) devices.