Manufacturing of integrated wearable systems for human-centric healthcare

Abstract

Human-centric healthcare is revolutionizing traditional medical practices by enabling individuals to monitor their health status more conveniently and in real-time, even remotely obtaining diagnostic advice. Achieving this vision relies heavily on the development of wearable systems, which are critical in providing continuous health monitoring and personalized care. These systems require interdisciplinary knowledge, encompassing materials science, device engineering, microelectronics, and backend data processing. Unlike traditional bulky lab-used medical equipment, wearable systems demand compact, flexible, and highly reliable sensors that can operate in complex environments, offering higher signal-to-noise ratio (SNR) (50 times higher than the traditional sensor), better interference resistance (3 orders better than the traditional sensor), and low-power consumption (lower than 20nW). Among various bioelectronics, organic electrochemical transistors (OECTs) stand outs as flagship devices for wearable sensing and computing. However, their use in wearable systems requires them to possess flexibility, softness, and stretchability, all while maintaining the high electrical performance. This necessitates the development of fabrication methods that are compatible with these new demands, which are often incompatible with traditional microfabrication processes. In this work, we explore how OECTs can be produced using facile low-temperature printing techniques. This makes them not only cost-effective but also scalable for large-scale production, offering a competitive advantage over conventional fabrication approaches. We first demonstrate the potential of OECTs in wearable health monitoring systems by developing a coin-sized, fully integrated, and minimally invasive continuous glucose monitoring system (CGMs). This system utilizes OECTs to amplify electrochemical signals for accurate glucose detection, with the OECT channel material poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) patterned using printing techniques. Through the combination of flexible printed circuit board (fPCB) technology and inkjet printing, we fabricate a flexible OECT glucose sensor, demonstrating its application in wearable glucose monitoring. To further improve the performance of soft OECTs for wearables, we developed a customized printing platform to fabricate fully printed and soft OECT arrays. With the customized printing platform, we optimize the selection and modification of different functional layer materials, which allows for the manufacturing of soft and stretchable OECT arrays. Additionally, we explore the use of these fully printed OECT arrays in wearable in-sensor computing systems. The integration of high-performance sensing with in-sensor computing enables real-time data processing within the wearable system. Finally, we discuss the future potential of tissue-like OECTs, which combine stretchable and self-healing properties with high electrical performance, holding the potential for hybrid bio-transistor circuits and soft integrated circuits in fully integrated wearable systems for healthcare. The manufacturing techniques and integration strategies investigated in this thesis advance the field of bioelectronics, paving the way for the next generation of personalized wearable electronics. By combining various printing technologies, we enable the mass production of highly functional, integrated systems for wearable sensing, computing, and tissue engineering, ultimately contributing to the advancement of wearable health technologies and biological research tools.