Coextrusion of Multifunctional Smart Sensors

Three‐dimensional (3D) printing of a piezoelectric sensor conventionally involves a minimum of three steps: fabrication of the sensor structure, electrode deposition to collect the generated charges, and electrical poling. Here, the authors report a novel approach to fabricate a working piezoelectric sensor with its electrodes in a single step. The authors optimize the rheological characteristics of a piezoelectric nanocomposite ink, formulated and processed to work without the need for poling, and a metallic conductive paint for coextrusion. The authors then employ solvent evaporation‐assisted 3D printing to coextrude ready‐to‐use sensors. The process fabricates conformal sensors, 3D self‐supported cat whiskers with aspect ratios over 15, and filaments spanning over 2 cm. The authors present potential applications in the form of aero‐elastic sensors and smart active thread for wearable electronics. The authors print sensors directly on fused deposition modeling printed miniature wings to monitor aero‐elastic stability. In another application, the authors use the coextruded filament in the form of a piezoelectric thread for wearable sensors for knee‐joint and respiration monitoring. The self‐powered piezoelectric sensing elements are an attractive alternative for customized, multi‐material applications where each watt and each gram counts such as wearables, and micro‐drones. The process is adaptable to other multi‐material and multi‐component printing needs beyond piezoelectric materials.