Multi-length scale hierarchical architecture overcoming pressure sensing range-speed tradeoff for skin electronics†
Pressure sensing electronics have gained significant attention in human–machine interface, soft robotics, and wearable biomedical applications. However, the existing sensor architectures are inadequate in overcoming the classical tradeoff among sensing range, sensitivity, and speed. Herein, a contact architecture combining a unique microstructure and hierarchical scheme is presented to overcome the pressure sensing range-speed tradeoff in flexible pressure sensors. A sensitive piezoresistive pressure sensor capable of simultaneously achieving a wide three orders-of-magnitude sensing range and tens of milliseconds fast response is demonstrated. This sensor consists of 3D porous laser-induced graphene (LIG) electrodes contacted with a rough layer of silver microflowers (AgMFs), where silver nanoflakes (AgNFs) were grown on polystyrene (PS) spheres. Sensing is hierarchically performed via various mechanisms across different length scales, i.e., on the nanoscale by the contact change among AgNFs and that between AgNFs and LIG and on the microscale by the deformation-induced resistance change in the AgMFs and 3D porous LIG. The multi-length scale contact architecture featuring a combination of the unique AgMF microstructure and the hierarchical scheme opens a new avenue for advanced flexible pressure sensors requiring a wide range operation without compromising their sensitivity and speed.