Toward all flexible sensing systems for next-generation wearables

Recent advances in science and technology have enabled a promising future for wearable devices with the ability to seamlessly interact with their users. The next generation of wearable systems should be fully flexible, conformable, multifunctional, and energy autonomous. Over the past decade or two, significant progress has been made in wearable soft sensors, whereas the development of flexible integrated circuits (ICs) for sensing front-end and data processing is just starting to gain momentum. This review article comprehensively examines the state of the art in flexible ICs for wearable applications. It discusses the progress and challenges in various dimensions, including materials, devices, and circuits. The paper further discusses essential algorithms for processing sensor data and provides insights into their hardware implementations. A co-design strategy is emphasized to holistically address the realization of wearable systems at different levels. By shedding light on the ongoing progress and challenges in the field, this paper provides a forward-looking perspective for future efforts in advancing flexible sensing systems for the next generation of wearables and aims to attract a wider readership in relevant fields. • This paper reviews the latest developments in analog front-end realized on the flexible substrate for wearable applications. • This paper reviews the processing needed for wearables, both from software and hardware viewpoint. • This paper complements many other reviews in wearables by summarizing the advances in circuit and system level.