Soft Micropneumatic Touchpad

Soft tactile sensors outputting fluidic signals have many potential applications in soft microfluidic devices and soft robots. However, existing systems have been limited to a single or a few sensors in parallel, so they are not comparable to the state-of-the-art electrical resistive and capacitive touchpads, which can detect rich tactile information, including touch location, pressure, area, and even multiple touches simultaneously. This work reports a soft micropneumatic touchpad. The touchpad consists of 32 pneumatic channels inside soft elastomer, with 16 channels aligned row-wise and 16 column-wise. The flow resistance of each channel is measured using a pressure divider. When the pad is touched, the cross-sectional area of the channels close to the contact location deforms, which changes the flow resistance of those channels. With 32 sensing channels, the location, depth, area of the contact, and even two simultaneous touches can be detected. Letters hand-written on the touchpad can be reconstructed from the measured data. With the assumption of sparsity, a tactile pressure map, with a value at each 16 × 16 grid point, can also be reconstructed. This work opens a path to replace electronic tactile sensors in soft devices with all-fluidic alternatives.