MIRAI Technology Institute, Shiseido Co., Ltd., Yokohama, Japan.
Department of Computer Sciences, Tokyo Metropolitan University, Hino, Japan.
Int J Cosmet Sci. 2023 Dec;45(6):851-861. doi: 10.1111/ics.12892. Epub 2023 Aug 29.
The mechanical condition and tactile evaluation of skin are essential for the development of skin care products. Most of the existing commercial instruments and studies aim to evaluate the skin surface by pressing it for hardness or by using imaging sensors, but there have been few instrumental measurements employing rubbing motion. Here, we have developed a sensor specialized for tactile sensation and the contact phenomenon during skin rubbing.
The developed sensor has three features: It can measure body parts including cheeks and arms, automate the rubbing motion of the probe and measure vibration and friction simultaneously. It is hand-held, with metal probes that rub the skin surface while rotating under a motor drive; it has an accelerometer and a force sensor beneath the probe measuring vibration and friction forces. To evaluate the validity of the sensor's measurements, artificial skin models were measured using the developed sensor and commercially available sensors and the results were compared. The relationship between the sensor output, surface roughness measurement and sensory evaluation was also investigated. Additionally, we evaluated the inter-rater reliability when measuring actual skin.
The measurements of five artificial skin models with different surface shapes showed a high correlation (r = 0.99) between the vibration intensity values evaluated by the developed sensor and those measured by a tri-axial acceleration sensor attached to a fingernail. The correlation coefficient between the vibration intensity values and surface roughness was r = 0.91, and the correlation with the sensory evaluation score of roughness was r = 0.99. The friction coefficients measured by the developed sensor and the force plate had r = 0.93, based on measurements of five artificial skin models with different friction conditions. The inter-rater correlation coefficients between the three participants of the developed sensor were as high as 0.92 and 0.94 for the vibration and friction measurements respectively.
The vibration intensities and friction coefficients from the sensor were highly correlated with those of the conventional sensor. The inter-rater reliability was also high. The developed sensor can be useful for tactile evaluation in skin-care product development.
皮肤的机械状况和触觉评估对于护肤品的开发至关重要。现有的大多数商业仪器和研究旨在通过按压皮肤来评估其硬度，或使用成像传感器，但很少有仪器采用摩擦运动进行测量。在这里，我们开发了一种专门用于触觉和皮肤摩擦过程中接触现象的传感器。
所开发的传感器具有三个特点：它可以测量脸颊和手臂等身体部位；能够自动进行探头的摩擦运动；并且能够同时测量振动和摩擦力。它是手持式的，金属探头在电机驱动下旋转，摩擦皮肤表面；在探头下方有一个加速度计和一个力传感器，分别测量振动和摩擦力。为了评估传感器测量的有效性，使用所开发的传感器和市售传感器测量了人工皮肤模型，并对结果进行了比较。还研究了传感器输出、表面粗糙度测量和感官评估之间的关系。此外，我们评估了在测量实际皮肤时的评分者间信度。
对五种具有不同表面形状的人工皮肤模型的测量结果表明，所开发的传感器评估的振动强度值与附着在指甲上的三轴加速度传感器测量的振动强度值之间具有高度相关性（r=0.99）。振动强度值与表面粗糙度之间的相关系数为 r=0.91，与粗糙度感官评估得分的相关系数为 r=0.99。在所测量的五种具有不同摩擦条件的人工皮肤模型中，所开发的传感器测量的摩擦力系数与力板的摩擦力系数之间的相关系数为 r=0.93。三位评分者使用所开发的传感器进行振动和摩擦力测量的评分者间相关性系数分别高达 0.92 和 0.94。
传感器的振动强度和摩擦力系数与传统传感器高度相关。评分者间信度也很高。所开发的传感器可用于护肤品开发中的触觉评估。
