Parametric Foam-Like Capacitive Sensors for 3-D Printing of Deformable Parts With Sensing Capabilities

Additive manufacturing (AM) paves the way for augmenting parts with sensors fabricated in situ, i.e., directly within the part, using functional materials deposited at the same time as the structural materials. However, achieving this goal at low cost remains challenging. This article investigates the design of parametric capacitive sensors that can be embedded in complex designs. The sensors can be manufactured on multimaterial extrusion 3-D printers using commercially available nonconductive and conductive thermoplastic polyurethane. The proposed sensor consists of a parameterized foam-like structure sandwiched between two conductive plates. This allows the designer to tune both the mechanical and capacitive responses of the sensor. The effect of changing the parameters of the foam-like structure on the sensor behavior is investigated. The parametric sensors are embedded in complex parts, creating a pressure-sensitive push button, a gamepad, and an analog joystick. Conductive traces and shields are directly integrated within the components, alongside all the structural elements that form the designs. The devices are fully functional immediately after fabrication, requiring no additional processing or assembly.