Friction and vibration generated during sliding over bare skin correlate with perceived smoothness and moistness

Tactile perception of the skin is a key factor for consumers when evaluating skincare products, yet conventional sensory assessments are subjective, costly and often lack clear physical interpretations. This study aims to bridge this gap by developing a tactile sensor that quantifies physical parameters relevant to skin feel and combines these measurements with sensory evaluation.

A tactile sensor with a stainless-steel probe replicating a human fingerprint was developed to measure physical parameters-specifically, vibration and friction-during controlled rubbing on the cheek. Simultaneously, blinded sensory evaluations were performed by assessors rating six attributes: smooth-rough, moisturized-dry, soft-hard (surface), soft-hard (base), elastic-not elastic and oily-not oily. Multiple regression analyses were conducted using vibration features and friction coefficients as independent variables and sensory evaluation scores as dependent variables.

Regression analysis revealed that perceived smoothness (smooth-rough) was predicted by amplitudes of high-frequency vibration (R² = 0.708; adjusted R² = 0.676). Moistness (moisturized-dry) was best predicted by a combination of high-frequency vibration amplitude and friction coefficients (R² = 0.584; adjusted R² = 0.538). No significant regression models were obtained for the other sensory attributes.

These findings highlight the potential of objective, instrument-based tactile measurements to elucidate the physical basis of sensory evaluation terms in skincare. This approach may enhance the training of sensory evaluation panels and improve the consistency and reliability of product assessment, ultimately supporting more effective product development.