A soft and transparent visuo-haptic interface pursuing wearable devices

We report an integrated soft and transparent visuo-haptic interface which is compatible with flexible devices and wearable gadgets. The visuo-haptic interface is composed of a touch-sensitive visual display based on polymer waveguides and a dielectric elastomer microactuators (DEMA) array. The touch-sensitive visual display, formed via continuative multi-step photo-lithography, is a multi-layered structure with a tactile-sensing layer stacked onto a visual-imaging layer. The dual-functional layer is thin (total thickness: < 200 μm) and transparent (transmittance: as high as 90%). The DEMA forming a unit cell of the array is designed as multiple three-dimensional structures with silver-nanowires (AgNWs) compliant electrode. When an electric voltage is applied across compliant electrodes formed on the sides, individual micro-actuators expand directly in an upward direction. Thanks to the verticallydeformable design, the DEMA produces programmable large normal forces up to about 30 times of thresholds at a localized area. An output force response of the DEMA is reversible, fast (< 1 ms delay), durable (output force degradation: < 8 % during a million cycles) and large enough to be used in human tactile interfaces. Due to the synergetic benefits from the functional layers, the visuohaptic interface allows demonstration of programmable tactile response with visual information while being intimately attached on human skin.