Soft ionic liquid multi-point touch sensor

The development of electronic skin (e-skin) and soft tactile sensing has recently attracted great interest. Here we report for the first time on a novel ionic liquid (IL) based soft pressure sensor with multi-point touch detection capability using 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]⁺[BF₄]^-) as a highly conductive sensing medium. The sensing mechanism is attributed to the repopulation of charge cations and anions in aqueous solution under pressure. The sensor can detect two dimensional touching positions with a sensitivity of -0.28% kPa^-1. Our sensor showed good stability and temperature independence thanks to the incompressibility of IL in the range of touch pressure and the appropriate signal measurement configuration. We successfully demonstrated the sensor's capability to detect multi-point human touch with different pressure levels. Our simple design with smart structures and ease of fabrication processes enable the development of a soft and low-cost sensor with multiple-point sensing capabilities on a single chip.