Proving the concept, the team made a 3 x 3 matrix with nine 10 x 10mm vibrating units (touchels perhaps?).
Its mechanism involves a plastic bi-morph layer – the two-dimensional polymer equivalent of a bi-metallic strip.
In this case, the two polymers layers in the sheet are a 2μm coating of PEDOT-Tos on PET films tens of microns thick.
Back-illuminating the sheet with near-infra-red light from an LED array causes the flexible sheet to deform locally into a bump. In the research device, the LED array was on a rigid PCB, but a flexible LED structure was also demonstrated.
“The light-induced deformation is reversible, spatially localised and rapidly controllable. The proposed actuator can produce vibrotactile stimulation over 10 dB at arbitrary areas in the human-sensitive frequency range from 125 to 300Hz using an input power of ~2.6mW/mm2,” according to ‘A light-driven vibrotactile actuator with a polymer bimorph film for localised haptic rendering’, a paper published by the American Chemical Society (ACS).
However, deformation is not yet strong enough, under 10μm: “The research team is currently engaged in follow-up studies to create vibrations that are strong enough for users to feel the sensation by increasing the efficiency of light-to-vibration energy conversion and to reduce the consumption of electric energy,” according to ACS.
Although flexible, the lack of electrical connections within the moving structure bodes well for reliability – the technology is seen as a potential supplement to Braille, and plans are under way to commercialise it for vehicles and smartphones.
“The technology is expected to be used to support people who are vulnerable with information, such as the visually challenged, by practically applying the original technology designed to deliver information through tactile sensation,” said ETRI department head Shin Hyung-cheol.
‘A light-driven vibrotactile actuator with a polymer bimorph film for localised haptic rendering‘ can be found in ACS journal Applied Materials & Interfaces. The image is courtesy of ACS/ETRI.
PEDOT-Tos = p-toluenesulfonate-doped poly(3,4-ethylenedioxythiophene)
PET = polyethylene terephthalate