“Feeling Small: Exploring the Tactile Perception Limits”, 2013-09-12 ():
The human finger is exquisitely sensitive in perceiving different materials, but the question remains as to what length scales are capable of being distinguished in active touch.
We combine material science with psychophysics to manufacture and haptically explore a series of topographically patterned surfaces of controlled wavelength, but identical chemistry. Strain-induced surface wrinkling and subsequent templating produced 16 surfaces with wrinkle wavelengths ranging from 300 nm to 90 μm and amplitudes between 7 nm and 4.5 μm. Perceived similarities of these surfaces (and 2 blanks) were pairwise scaled by participants and interdistances among all stimuli were determined by individual differences scaling (INDSCAL).
The tactile space thus generated and its 2 perceptual dimensions were directly linked to surface physical properties—the finger friction coefficient and the wrinkle wavelength. Finally, the lowest amplitude of the wrinkles so distinguished was ~10 nm, demonstrating that human tactile discrimination extends to the nanoscale.
[Keywords: physics, psychology, soft materials, surface chemistry]