Fabrication of Flexible Wearable Mechanosensors Utilizing Piezoelectric Hydrogels Mechanically Enhanced by Dipole–Dipole Interactions

Conductive hydrogels have been increasingly employed to construct wearable mechanosensors due to their excellent mechanical flexibility close to that of soft tissues. In this work, piezoelectric hydrogels are prepared through free radical copolymerization of acrylamide (AM) and acrylonitrile (AN) and further utilized in assembling flexible wearable mechanosensors. Introduction of the polyacrylonitrile (PAN) component in the copolymers endows the hydrogels with excellent piezoelectric properties. Meanwhile, significant enhancement of mechanical properties has been accessed by forming dipole-dipole interactions, which results in a tensile strength of 0.51 MPa. Flexible wearable mechanosensors are fabricated by utilizing piezoelectric hydrogels as key signal converting materials. Self-powered piezoelectric pressure sensors are assembled with a sensitivity (S) of 0.2 V kPa^-1. Additionally, resistive strain sensors (gauge factor (GF): 0.84, strain range: 0-250%) and capacitive pressure sensors (S: 0.23 kPa^-1, pressure range: 0-8 kPa) are fabricated by utilizing such hydrogels. These flexible wearable mechanosensors can monitor diverse body movements such as joint bending, walking, running, and stair climbing. This work is anticipated to offer promising soft materials for efficient mechanical-to-electrical signal conversion and provides new insights into the development of various wearable mechanosensors.