Assemblies of Microfluidic Channels and Micropillars Facilitate Sensitive and Compliant Tactile Sensing

Recent advances in soft electronics are enabling new devices that can stretch and conform to curved, soft, or dynamic surfaces, whether in engineering systems or the human body. However, the close coupling of mechanical and electronic behavior in these devices can limit performance and introduce artifacts. In order to mitigate negative effects, and to facilitate greater control over mechanical and electronic performance, we present a method for designing soft tactile sensors based on multi-layer heterogeneous 3D structures that combine active layers, containing embedded liquid metal electrodes, with passive and mechanically tunable layers, containing air cavities and micropillar array geometric supports. The assembled devices consist of thin membranes that integrate arrays of tactile sensors with 2-mm spatial resolution. They are produced using a soft lithography fabrication method based on the casting, alignment, and fusion of multiple functional layers in a soft polymer substrate. We have optimized the electronic and mechanical performance of these devices using numerical simulations. The results accurately predicted measured performance, making it possible to tailor both electronic and mechanical properties. These methods enable the design of tactile sensing arrays that are highly conformable and robust, and that possess a number of desirable attributes, including high sensitivity, monotonic output, good linearity, low cross-talk, low rate dependence, and low hysteresis. This may enable new applications in wearable electronics, healthcare, and robotics.