Carbon Nanotube-Modified Fabric for Wearable Smart Electronic-skin with Exclusive Normal-Tangential Force Sensing Ability

It reports a fabric-based flexible electronic skin (e-skin) that differentiates normal pressure from tangential force with opposite resistance response. The e-skin, which is based on multiwall carbon nanotubes (MWNTs) anchored on the fabric surface, is synthesized using a roll-to-roll method by dipping wrinkled fabric into a diluted MWNT/Polydimethylsiloxane dispersion. Normal pressing causes a decrease in resistance (gauge factor of-1.4 KPa-1 at 30-610 Pa), while tangential force leads to an increase in resistance (gauge factor of 1.13 N-1 under a pressure loading of 1 KPa), with good durability observed at over 5000 times of cyclic pressing and tangential force loading. The e-skin is especially insensitive to both bending (<100 degrees) and elongation deformation (<10%) due to the wrinkled surficial structure. For potential applications, the e-skin can not only monitor wrist pulse, sense slight brush friction, but it can also work in a non-contacting mode to detect human breath. Furthermore, because the e-skin can produce opposite resistive responses to both pressure and friction, it can be applied to capture the complete force loading details during the process of picking up an object, which enables potential application for gentle grasping and manipulation of objects on artificial fingertips.