Fig. 3: Experimental result of tactile perception test with pressure control.

a Schematic illustrations of the operating mechanism for pressure sensing and electrotactile stimulation applied on the finger at low pressure(left), and at high pressure (right). b, c, d Color maps recording the electrotactile sensation responses of 10 subjects when the current density and frequency are varied under four pressure control conditions. b The four pressure conditions were: uncontrolled pressure, low pressure (<40 kPa), medium pressure (~100 kPa), and high pressure (>170 kPa). c Electrotactile intensity for each finger pressure when the current density was changed from 0 to 0.075 A mm⁻². d Electrotactile texture for each finger pressure when the frequency is changed from 0 to 200 Hz. Perception response to the stimulation composed of six levels of current amplitude and confusion matrix (inset) with uncontrolled pressure (e) and with 100 kPa of controlled pressure (f). Data are presented as mean ± SEM. Distribution of responses at 3 of stimulation levels with uncontrolled pressure (g), and with a controlled pressure of 100 kPa (h).