Flexible tactile actuator for wearable haptics

February 09, 2018 // By Julien Happich
In cooperation with the Electronics and Telecommunications Research Institute (ETRI), researchers from the Korea Advanced Institute of Science and Technology (KAIST) have designed a flexible tactile actuator less than 1mm thick, yet capable of a 100 to 200Hz perceivable mechanical output even under the typical pressures of human touch.

The very simple and cost-effective elastomer-based device is made up of a layer of microstructured dielectric elastomer (polydimethylsiloxane or PDMS) sandwiched between two PET films each sporting an indium tin oxide (ITO) electrode. The microstructures consist of pyramidal shapes obtained from casting the uncured elastomer solution into an inverted pyramid silicon mold (fabricated via an anisotropic wet etching technique).

Operating principle of the microstructured DEA
generating vibration in the normal direction due to the
interaction between an elastic reaction force (Fk)
and an electrostatic attraction force (Fe).

Applying a biased positive sinusoidal voltage across the ITO electrodes compresses the microstructures, subject to the coulomb forces and electrostatic attraction. As the amplitude of the biased sinusoidal voltage decreases, the microstructures return to their original shape (through elastic force) and generate a perceivable reaction force in the thickness direction.

In a paper titled "High-pressure endurable flexible tactile actuator based on microstructured dielectric elastomer" published in Applied Physics Letters, the researchers explain that for a given pyramid height, the compressibility of the actuator can be tuned, as well as its resonance frequency by changing the interspacing between the micro-pyramids.