Materials able to regenerate after damage have been the object of investigation since the ancient times. For instance, self-healing concretes, able to resist earthquakes, aging, weather, and seawater have been known since the times of ancient Rome and are still the object of research. During the last decade, there has been an increasing interest in self-healing electronic materials, for applications in electronic skin (E-skin) for health monitoring, wearable and stretchable sensors, actuators, transistors, energy harvesting, and storage devices. Self-healing materials based on conducting polymers are particularly attractive due to their tunable high conductivity, good stability, intrinsic flexibility, excellent processability and biocompatibility. Here recent developments are reviewed in the field of self-healing electronic materials based on conducting polymers, such as poly 3,4-ethylenedioxythiophene (PEDOT), polypyrrole (PPy), and polyaniline (PANI). The different types of healing, the strategies adopted to optimize electrical and mechanical properties, and the various possible healing mechanisms are introduced. Finally, the main challenges and perspectives in the field are discussed. 

Recent Progress on Self‐Healable Conducting Polymers

Recent Status and Future Perspectives of 2D MXene for Micro-supercapacitors and Micro-batteries

This review is written to introduce infrared photon detectors based on solution-processable semiconductors. A new generation of solution-processable photon detectors have been reported in the past few decades based on colloidal quantum dots, two-dimensional materials, organics semiconductors, and perovskites. These materials offer sensitivity within the infrared spectral regions and the advantages of ease of fabrication at low temperature, tunable materials properties, mechanical flexibility, scalability to large areas, and compatibility with monolithic integration, rendering them as promising alternatives for infrared sensing when compared to vacuum-processed counterparts that require rigorous lattice matching during integration. This work focuses on infrared detection using disordered semiconductors so as to articulate how the inherent device physics and behaviors are different from conventional crystalline semiconductors. The performance of each material family is summarized in tables, and device designs unique to solution-processed materials, including narrowband photodetectors and pixel-less up-conversion imagers, are highlighted in application prototypes distinct from conventional infrared cameras. We share our perspectives in examining open challenges for the development of solution-processable infrared detectors and comment on recent research directions in our community to leverage the advantages of solution-processable materials and advance their implementation in next-generation infrared sensing and imaging applications.

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Solution-processable infrared photodetectors: Materials, device physics and applications

Electronics worn on the body have the potential to improve human health and the quality of life by monitoring vital signs and movements, displaying information, providing self-illumination for safety, and even providing new routes for personal expression through fashion. Textiles are a part of daily life in clothing, making them an ideal platform for wearable electronics. The acceptance of wearable e-textiles hinges on maintaining the properties of textiles that make them compatible with the human body. Beneficial properties such as softness, stretchability, drapability, and breathability come from the 3D fibrous structures of knitted and woven textiles. However, these structures also present considerable challenges for the fabrication of wearable e-textiles. Fabrication methods used for modern electronic devices are designed for 2D planar substrates and are mostly unsuitable for the complex 3D structures of textiles. There is thus an urgent need to develop fabrication methods specifically for e-textiles to advance wearable electronics. Solution-based fabrication methods are a promising approach to fabricating wearable e-textiles, especially considering that textiles have been successfully modified using pigmented dyes in dyebaths and printing inks for thousands of years. In this Account, we discuss our research on the solution-based electroless metallization of textiles to fabricate conductive e-textiles that are building blocks for e-textile devices. Electroless metallization solutions fully permeate textile structures to deposit metallic coatings on the surfaces of individual textile fibers, maintaining the inherent textile structures and wearability. The resulting e-textiles are highly conductive, soft, and stretchable. We furthermore discuss ways to turn the challenges related to textile structures into new opportunities by strategically using the structural features of textiles for e-textile device design. We demonstrate this textile-centric approach to designing e-textile devices using two examples. We discuss how the structure of an ultrasheer knitted textile forms a useful framework for new e-textile transparent conductive electrodes and describe the implementation of these electrodes to form highly stretchable light-emitting e-textiles. We also show how the structural features of velour fabrics form the basis for an innovative "island-bridge" strain-engineering structure that enables the integration of brittle electroactive materials and protects them from strain-induced damage, leading to the fabrication of stretchable textile-based lithium-ion battery electrodes. With the vast variety of textile structures available, we highlight the opportunities associated with this textile-centric design approach to advance textile-based wearable electronics. Such advances depend on a deep understanding of the relationship between the textile structure and the device requirements, which may potentially lead to the development of new textile structures customized to support specific devices. We conclude with a discussion of the challenges that remain for the future of e-textiles, including durability, sustainability, and the development of performance standards.

Wearable E-Textiles Using a Textile-Centric Design Approach.

Printed electronics (PEs), as a fast-growing advanced manufacturing technology in recent years, plays an essential role in development of wearable electronic sensors, flexible displays, human-machine interaction, and thin electronics owing to its low cost, high throughput, and the possibility to be fabricated on diverse thin substrates with good flexibility and stretchability. Various PEs have been developed, such as physical sensing devices, electrochemical sensors, wearable supercapacitors and energy harvesters, stretchable electrodes, thin-film transistors (TFTs), and printed transceiving circuits. In this work, recent progress on physical sensing devices and their interface circuits developed by the printing process are reviewed in terms of their functions, printing methods, materials, and performance. The printed physical sensors used for monitoring the basic biometric parameters through physical sensing mechanisms, such as temperature sensors for skin temperature, pressure sensors for human pulse wave, strain sensors for human motions, biopotential electrodes for electrocardiogram signals, and multiple-function physical sensing platforms, have been studied and highlighted with their good designs and advanced materials. The state-of-the-art printed interface circuits for the wearable sensors such as interconnects, TFTs, digital circuits, amplifiers, oscillators, and antennas have been reviewed in terms of their structures and functions from basic to advanced levels. The challenge and suggestions of the printed wearable devices for future developments are discussed and end with a conclusion.

Recent Progress in Printed Physical Sensing Electronics for Wearable Health-Monitoring Devices: A Review

Author(s): Bonnassieux, Y; Brabec, CJ; Cao, Y; Carmichael, TB; Chabinyc, ML; Cheng, KT; Cho, G; Chung, A; Cobb, CL; Distler, A; Egelhaaf, HJ; Grau, G; Guo, X; Haghiashtiani, G; Huang, TC; Hussain, MM; Iniguez, B; Lee, TM; Li, L; Ma, Y; Ma, D; McAlpine, MC; Ng, TN; Osterbacka, R; Patel, SN; Peng, J; Peng, H; Rivnay, J; Shao, L; Steingart, D; Street, RA; Subramanian, V; Torsi, L; Wu, Y | Abstract: This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.

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Anjung Chung

Papers

The 2021 flexible and printed electronics roadmap