3D printed stretchable coaxial fiber grid for dual-mode multifunctional tactile sensor array

Tactile sensors play a critical role in the Internet of Things (IoT) and wearable devices. However, although current tactile sensors can precisely measure pressure, the simple fabrication of stretchable high-performance tactile sensors with a broad measuring range and multifunctions is still challenging. Herein, an ink-direct writing 3D printing method is developed to fabricate novel stretchable dual-mode tactile sensors with coaxial fiber structure. The 3D printed coaxial fibers have an outer skin composed of silicone rubber and polytetrafluoroethylene micropowders thixotropic agent and an inner core of an ionic conductive solution composed of polyvinyl alcohol and sodium chloride. The coaxial fibers exhibit excellent electrical conductivity (0.54 S cm−1) and outstanding stretchability, as high as 390 %. The intersection of the two fibers constitutes a dual-mode tactile sensor which can operate in triboelectric or capacitive modes with complementary measurement ranges from 0.0003 to 0.4517 N. Besides, by combining the signals from the two modes, the sensor can identify the material that comes into contact with the sensor. A 3D printed network of tactile sensor arrays made of warp-weft interwoven coaxial fibers is able to accurately detect the locations of multi-point contact with the array. This dual-mode multifunctional tactile sensor can be widely used in various applications such as the IoT and wearable devices.