A tactile sensor for detection of physical properties of human skin<i>in vivo</i>

TLDR

The change in frequency of a vibrating sensor under fixed contact pressure reflects acoustic impedance, which is related to soft tissue stiffness. The study evaluates a spring‑loaded tactile sensor with displacement sensing for non‑invasive assessment of human skin stiffness and elasticity in vivo. The sensor uses a 61‑kHz piezoelectric vibrator and a displacement sensor to measure frequency shifts caused by spring compression when contacting an object. The sensor successfully detected variations in skin stiffness and elasticity across age, daily changes, and cosmetic use, proving easy to handle and suitable for field work.

Abstract

A spring loaded tactile sensor with displacement sensing has been evaluated for non-invasive assessment of physical properties, stiffness and elasticity, of human skin in vivo. The tactile sensor consists of a piezoelectric vibrator (61 kHz) with a vibration pickup, electronics and PC with software for measurement of the change in frequency when the sensor is attached to an object. Integrated with the tactile sensor is a displacement sensor that shows the compression of the spring that loads the sensor element against the object during measurement. Under certain conditions (e.g. fixed contact pressure) this change in frequency monitors the acoustic impedance of the object and is related to the stiffness of soft tissue. The experimental results on silicone gum and on healthy Japanese and Swedish women indicated that the instrument was able to detect changes in stiffness and elastic related properties of human skin, related to age, day-to-day variations and application of cosmetics. The instrument was concluded to be easy to handle and suitable for field work.