Elastomeric Foam-Based Soft Capacitive Pressure Sensors Using Direct Ink Writing

Abstract

Conformable and flexible tactile/pressure sensors are of interest in applications such as robotics, wearable, and interactive systems to measure the contact forces. These applications require a large number of robust sensors, for which simple manufacturing routes such as additive manufacturing can be useful. Herein, we present the fully 3-D printed capacitive touch sensors comprising of elastomeric foam-based soft dielectric layers (blends of polydimethylsiloxane (PDMS) and BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and silver nanowires (Ag NWs) composite-based electrodes. The devices were encapsulated with 3-D printed PDMS and tested under dynamic and static stimuli. The sensor with 1 wt.% of BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> exhibited the best performance with a sensitivity of 0.571% <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> kPa <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-1}$ </tex-math></inline-formula> and excellent linearity (99.32%). The observed capacitive behavior of the sensor is significantly higher than a similar sensor with bulk PDMS as the dielectric. The fabrication approach employed in this work has the untapped potential to develop soft and flexible electronic skin (e-skin) for wearables, health monitoring, and rehabilitation.