Strain-Sensitive and Strain-Insensitive Flexible Electronics for Healthcare Monitoring

Flexible electronics have emerged as an important technology in healthcare monitoring, enabling continuous assessment of physiological signals through conformable integration with human tissues. The mechanical deformation of human tissues during daily activities presents a unique challenge: some monitoring applications require high strain sensitivity for accurate motion detection, while others demand stable electrical performance regardless of mechanical deformation. This review systematically examines recent advances in flexible electronics for healthcare monitoring, classifying devices based on their fundamental design objective, whether to detect or to ignore mechanical strain. The fundamental mechanisms and material strategies for achieving controllable strain response in both strain-sensitive and strain-insensitive designs are first respectively analyzed. Subsequently, physiological monitoring requirements are mapped across anatomical systems from cavity organs to hard tissues, demonstrating how different strain environments necessitate specific device design strategies. It is further explored how these strain-engineered properties enable various monitoring functions, from motion tracking and rehabilitation assessment to continuous vital sign monitoring and chemical sensing. Finally, current challenges in stability and biocompatibility are addressed, while perspectives on future developments in material design and device integration are provided. Through this strain-magnitude-based systematic examination, this review aims to facilitate the rational design of flexible electronic devices for specific healthcare monitoring needs.