Refreshable Tactile Display Based on a Bistable Electroactive Polymer and a Stretchable Serpentine Joule Heating Electrode

The demand for tactile interactive devices has been growing exponentially as the sense of touch enriches the human-machine interaction experience. However, the tactile devices reported so far cannot offer high-quality performance, compact form factor, and relatively simple system architecture for low-cost production. We report the fabrication of a 4 × 4 pneumatic tactile display with Braille standard resolution using a bistable electroactive polymer (BSEP) thin film and a serpentine-patterned carbon nanotube electrode. The BSEP is a variable stiffness material that exhibits a stiffness change of 3000-fold within the narrow temperature range of 43 ± 3 °C. The carbon nanotube electrode was patterned on the polymer film via a P3R process, Prestretch-Pattern-Protect-Release, which leads to a serpentine-patterned composite electrode that is highly stretchable, retains its high electrical conductivity up to an ∼200% area strain, and provides a fast Joule heating rate of 31 °C/s. The tactile pixels are diaphragm actuators that can be individually controlled to produce 0.7 mm out of plain deformation and greater than 50 g of blocking force by application of local heating and pneumatic pressure. The device can operate under low voltage supply (30 V) and has a lifetime of over 100 000 cycles without much performance degradation. This work could open a path to building compact, user-friendly, and cost-effective tactile devices for a variety of important applications.