Developing ultrasound tactile sensitivity testing device with optical detector for measuring surface strain

There are various receptor types or free nerve endings underneath skin. Human tactile sensation is a combination of these receptors, and each receptors have own characteristics for mechanical, vibrational stimulation on skin surface. Recently, focused ultrasound have been reported as a new tool for evoking tactile sensation in skin. Other studies performed by subjective test with human subjects, but the underlying mechanism of focused ultrasound stimulation in skin tissue remains unknown yet. The main reason of unknown mechanism is lack of reliability in experiment result since these studies have to explain focused ultrasound stimulation induced tactile sensations based on subjective explanation of human subjects. In this study, therefore, we aim to develop tactile sensitivity testing device with observing deformation of interfacing layer by optical vibrometer, and evaluate performance of custom-made device based on subject's experience and displacement of surface. The result shows mechanical properties and tactile threshold evaluation of developed device is enough to verifying tactile sensitivity in human subject with objective observation.