Electro-active polymers (EAPs) are polymers that respond to an electrical stimulus (voltage or current) by changing their size or shape. They have applications in fields ranging from soft robotics and artificial muscles to electrically tunable lenses and haptic feedback devices; owing to their simple fabrication and relatively low material costs associated with them. Dielectric elastomer actuators (DEAs), which belong to the family of EAPs, are known to produce high actuation strains, and are made by sandwiching an EAP layer between two compliant electrodes. They work on the principle of Maxwell stresses, which is induction of stress due to electric field pressure from the free charges on the surface of insulating material; and the actuation performance of DEAs depend on external stimulus like applied electric fields, thickness and area of the sandwiched region; and intrinsic material properties like relative permittivity and elastic modulus. Compliancy of electrodes is also extremely critical for the performance of DEAs.
The subject of tactile perception has enjoyed widespread attention; driven by an ensemble of factors like evolution of sense of touch in robotics, tactile perception in virtual and augmented reality, and enhancing the quality of human-machine interaction for touch sensitive consumer products. DEAs have been investigated for applications in tactile and vibrotactile feedback devices via different approaches. Since the deformation produced in the active DEA layer can be small, appropriate coupling is required for out-of-plane deformation; and various approaches like hydrostatic and rigid mechanical couplings have been tried out previously. We have demonstrated a transparent device to provide unobstructed topographic texture change. We use an all transparent system based on thickness mode actuation of DEA; with the elastomeric layer, compliant electrodes and the soft passive layer as all transparent materials. Thickness mode actuation makes use of different strains produced in the active and nonactive regions of the device to produce out of plane deformations on a smooth surface; and is fabricated by coupling a soft elastomeric layer with DEA device. The device has a high actuation performance with vertical deformation of 0.155 mm and good cyclability. The overall transparency of the device is high in the visible region, with an optical transmittance of 76 percent at 550 nm. To the best of our knowledge, this is first of its kind device architecture, as well, which enables integration of DEAs onto a wide variety of substrates to enable tactile feedback.