From materials to structures: a holistic examination of achieving linearity in flexible pressure sensors

As a pivotal category in the realm of electronics skins, flexible pressure sensors have become a focal point due to their diverse applications such as robotics, aerospace industries, and wearable devices. With the growing demands for measurement accuracy, data reliability, and electrical system compatibility, enhancing sensor's linearity has become increasingly critical. Analysis shows that the nonlinearity of flexible sensors primarily originates from mechanical nonlinearity due to the nolinear deformation of polymers and electrical nonlinearity caused by changes in parameters such as resistance. These nonlinearities can be mitigated through geometric design, material design or combination of both. This work reviews linear design strategies for sensors from the perspectives of structure and materials, covering the following main points: (a) an overview of the fundamental working mechanisms for various sensors; (b) a comprehensive explanation of different linear design strategies and the underlying reasons; (c) a detailed review of existing work employing these strategies and the achieved effects. Additionally, this work delves into diverse applications of linear flexible pressure sensors, spanning robotics, safety, electronic skin, and health monitoring. Finally, existing constraints and future research prospects are outlined to pave the way for the further development of high-performance flexible pressure sensors.