Creation of various skin sensations using pulsed focused ultrasound: Evidence for functional neuromodulation

Ultrasound application to neural tissues modifies their activity, and it is increasingly considered as a new mode of functional neuromodulation in both central and peripheral nervous system. We investigate that ultrasound focused to skin surface can induce differential peripheral sensations by modulating the activity of sensory receptors. Pulsed focused ultrasound was applied to the last digit of human hands for 10 s using combinations of acoustic frequencies (350 and 650 kHz), tone-burst-durations (0.1 and 1.0 ms), pulse repetition frequencies (10 and 100 Hz) with 1% duty cycle, and acoustic intensities (3-100 mW/cm²), divided into two ambient temperatures (20 and 40C). On insonification, volunteers reported cooling, warming, vibrotactile sensations, and mild nociception, while there was no actual increase to the skin temperature. Continuous insonification, in contrast to pulsed insonification, failed to elicit these sensations. Our results suggest that pulsed ultrasound temporarily modifies the activity of the sensory receptors on the skin, and casts future utility in dermatological applications as well as in the field of haptic device interfaces.