Flexible and wearable electronics are attracting wide attention due to their potential applications in wearable human health monitoring and care systems. Carbon materials have combined superiorities such as good electrical conductivity, intrinsic and structural flexibility, light weight, high chemical and thermal stability, ease of chemical functionalization, as well as potential mass production, enabling them to be promising candidate materials for flexible and wearable electronics. Consequently, great efforts are devoted to the controlled fabrication of carbon materials with rationally designed structures for applications in next‐generation electronics. Herein, the latest advances in the rational design and controlled fabrication of carbon materials toward applications in flexible and wearable electronics are reviewed. Various carbon materials (carbon nanotubes, graphene, natural‐biomaterial‐derived carbon, etc.) with controlled micro/nanostructures and designed macroscopic morphologies for high‐performance flexible electronics are introduced. The fabrication strategies, working mechanism, performance, and applications of carbon‐based flexible devices are reviewed and discussed, including strain/pressure sensors, temperature/humidity sensors, electrochemical sensors, flexible conductive electrodes/wires, and flexible power devices. Furthermore, the integration of multiple devices toward multifunctional wearable systems is briefly reviewed. Finally, the existing challenges and future opportunities in this field are summarized.

A carbonized plain-weave silk fabric is fabricated into wearable and robust strain sensors, which can be stretched up to 500% and show high sensitivity in a wide strain range. This sensor can be assembled into wearable devices for detection of both large and subtle human activities, showing great potential for monitoring human motions and personal health.

The rational design of high‐performance flexible pressure sensors attracts attention because of the potential applications in wearable electronics and human–machine interfacing. For practical applications, pressure sensors with high sensitivity and low detection limit are desired. Here, ta simple process to fabricate high‐performance pressure sensors based on biomimetic hierarchical structures and highly conductive active membranes is presented. Aligned carbon nanotubes/graphene (ACNT/G) is used as the active material and microstructured polydimethylsiloxane (m‐PDMS) molded from natural leaves is used as the flexible matrix. The highly conductive ACNT/G films with unique coalescent structures, which are directly grown using chemical vapor deposition, can be conformably coated on the m‐PDMS films with hierarchical protuberances. Flexible ACNT/G pressure sensors are then constructed by putting two ACNT/G/PDMS films face to face with the orientation of the ACNTs in the two films perpendicular to each other. Due to the unique hierarchical structures of both the ACNT/G and m‐PDMS films, the obtained pressure sensors demonstrate high sensitivity (19.8 kPa−1, <0.3 kPa), low detection limit (0.6 Pa), fast response time (<16.7 ms), low operating voltage (0.03 V), and excellent stability for more than 35 000 loading–unloading cycles, thus promising potential applications in wearable electronics.

Conspectus Soft bioelectronics that could be integrated with soft and curvilinear biological tissues/organs have attracted multidisciplinary research interest from material scientists, electronic engineers, and biomedical scientists. Because of their potential human health-related applications, soft bioelectronics require stringent demands for biocompatible components. Silk, as a kind of well-known ancient natural biopolymer, shows unique combined merits such as good biocompatibility, programmable biodegradability, processability into various material formats, and large-scale sustainable production. Such unique merits have made silk popular for intensive design and study in soft bioelectronics over the past decade. Due to the development of fabrication techniques in material processing and progress in research, silk has been engineered into a variety of advanced materials including silk fibers/textiles, nanofibers, films, hydrogels, and aerogels. Natural and regenerated silk materials can also be transformed into intrinsically nitrogen-doped and electrically conductive carbon materials, due to their unique molecular structure and high nitrogen content. The rich morphologies and varied processing options for silk materials can furnish transformed carbon materials with well-designed structures and properties. The favorable and unique material merits of silk materials and silk-derived carbon materials offer potential applications in soft electronics. Based on commercial silk fibers/textiles and the availability of re-engineered silk materials with versatile technological formats, functional soft electronics have been explored with silk as flexible biosupports/biomatrixes or active components. These soft systems include bioresorbable electronics, ultraconformal bioelectronics, transient electronics, epidermal electronics, textile electronics, conformal biosensors, flexible transistors, and resistive switching memory devices. Silk-derived carbon materials with rationally designed morphologies and structures have also been developed as active components for wearable sensors, electronic skins, and flexible energy devices, which provide novel concepts and opportunities for soft electronics. In this Account, we highlight the unique hierarchical and chemical structure of natural silk fibers, the fabrication strategies for processing silk into materials with versatile morphologies and into electrically conductive carbon materials, as well as recent progress in the development of silk-based advanced materials (silk materials and silk-derived carbon materials) for soft bioelectronics. The design and functionality of soft electronics developed with commercial silk fibers/textiles, re-engineered silk materials, and silk-derived carbon materials as biosubstrate/matrix and active components is introduced in detail. We further discuss future challenges and prospects for developing silk-based soft bioelectronics for wearable healthcare systems. By leveraging the unique advantages of silk-based advanced materials, the design and con...

Flexible skin-mimicking electronics are highly desired for development of smart human-machine interfaces and wearable human-health monitors. Human skins are able to simultaneously detect different information, such as touch, friction, temperature, and humidity. However, due to the mutual interferences of sensors with different functions, it is still a big challenge to fabricate multifunctional electronic skins (E-skins). Herein, a combo temperature-pressure E-skin is reported through assembling a temperature sensor and a strain sensor in both of which flexible and transparent silk-nanofiber-derived carbon fiber membranes (SilkCFM) are used as the active material. The temperature sensor presents high temperature sensitivity of 0.81% per centigrade. The strain sensor shows an extremely high sensitivity with a gauge factor of ∼8350 at 50% strain, enabling the detection of subtle pressure stimuli that induce local strain. Importantly, the structure of the SilkCFM in each sensor is designed to be passive to other stimuli, enabling the integrated E-skin to precisely detect temperature and pressure at the same time. It is demonstrated that the E-skin can detect and distinguish exhaling, finger pressing, and spatial distribution of temperature and pressure, which cannot be realized using single mode sensors. The remarkable performance of the silk-based combo temperature-pressure sensor, together with its green and large-scalable fabrication process, promising its applications in human-machine interfaces and soft electronics.