Miniaturization of mechanical actuators in skin-integrated electronics for haptic interfaces

Skin-integrated electronics, also known as electronic skin (e-skin), are rapidly developing and are gradually being adopted in biomedical fields as well as in our daily lives. E-skin capable of providing sensitive and high-resolution tactile sensations and haptic feedback to the human body would open a new e-skin paradigm for closed-loop human–machine interfaces. Here, we report a class of materials and mechanical designs for the miniaturization of mechanical actuators and strategies for their integration into thin, soft e-skin for haptic interfaces. The mechanical actuators exhibit small dimensions of 5 mm diameter and 1.45 mm thickness and work in an electromagnetically driven vibrotactile mode with resonance frequency overlapping the most sensitive frequency of human skin. Nine mini actuators can be integrated simultaneously in a small area of 2 cm × 2 cm to form a 3 × 3 haptic feedback array, which is small and compact enough to mount on a thumb tip. Furthermore, the thin, soft haptic interface exhibits good mechanical properties that work properly during stretching, bending, and twisting and therefore can conformally fit onto various parts of the human body to afford programmable tactile enhancement and Braille recognition with an accuracy rate over 85%.

Reciprocal Interference Between Audition and Touch in the Perception of Duration

Audition and touch interact with one another and share a number of similarities; however, little is known about their interplay in the perception of temporal duration. The present study intended to investigate whether the temporal duration of an irrelevant auditory or tactile stimulus could modulate the perceived duration of a target stimulus presented in the other modality (i.e., tactile or auditory) adopting both a between-participants (Experiment 1) and a within-participants (Experiment 2) experimental design. In a two-alternative forced-choice task, participants decided which of two events in a target modality was longer. The simultaneously distractor stimuli were presented with a duration that was either congruent or incongruent to the target’s. Results showed that both the auditory and tactile modalities affected duration judgments in the incongruent condition, decreasing performance in both experiments. Moreover, in Experiment 1, the tactile modality enhanced the perception of auditory stimuli in the congruent condition, but audition did not facilitate performance for the congruent condition in the tactile modality; this tactile enhancement of audition was not found in Experiment 2. To the best of our knowledge, this is the first study documenting audiotactile interactions in the perception of duration, and suggests that audition and touch might modulate one another in a more balanced manner, in contrast to audiovisual pairings. The findings support previous evidence as to the shared links and reciprocal influences when audition and touch interact with one another.