Ya Chang

Flexible skin electronics are increasingly sought after for their potential in sensing and drug delivery within wearable human–machine interfaces. However, developing multifunctional applications that maintain biocompatibility and stable electrical performance under various mechanical deformations remains a challenge. Here, we introduce tattoo paper-based graphene–gold conductors that are approximately 0.04 mm thick and feature a dual conductive pathway within the graphene–gold film. By integrating a folding structure with this dual conductive pathway, we can mitigate the strain effects on the electrical resistance of film-based conductors, resulting in wider areas of stable resistance. In addition, we have designed film conductors with a kirigami structure, which achieves a high initial conductivity of 1.5 × 10³ S cm⁻¹ and exhibits negligible resistance changes across a broad strain range of 0 to 130%. We utilize these conductors to develop waterproof on-skin patches that incorporate electrically and optically active heaters for body heating and drug delivery. Furthermore, we have created an on-skin dialing interface using these conductors, which enables users to make telephone calls based on triboelectric nanogenerators.

Wearable electronics have received extensive attention in human–machine interactions, robotics, and health monitoring. The use of multifunctional sensors that are capable of measuring a variety of mechanical or environmental stimuli can provide new functionalities for wearable electronics. Advancements in material science and system integration technologies have contributed to the development of high-performance flexible multifunctional sensors. This review presents the main approaches, based on functional materials and device structures, to improve sensing parameters, including linearity, detection range, and sensitivity to various stimuli. The details of electrical, biocompatible, and mechanical properties of self-powered sensors and wearable wireless systems are systematically elaborated. Finally, the current challenges and future developmental directions are discussed to offer a guide to fabricate advanced multifunctional sensors.