Development of a Haptic Sensor System for Monitoring Human Skin Conditions

Human skin, which mainly consists of epidermis, dermis and hypodermis, is the largest organ of a human body. It has a lot of roles, for example, protection function, moisture maintenance function and sensory function. Moreover, it becomes a parameter for estimation of the health condition and beauty, because the skin is the outermost layer of a human body. At present, ocular inspection and palpation are generally used for detection of human skin condition such as surface appearance, and extensibility. Ocular inspection and palpation are important diagnosis procedures to examine patient's skin condition quickly. However, it is difficult to quantify an evaluation by these diagnosis procedures, because it is very subjective. A development of handy method in order to evaluate the skin condition objectively is craved to dermatologists, and cosmetic industries. So far, various methods of evaluating skin condition objectively have been developed. However, these methods are substitutions of ocular inspection, or only measure some specific physical parameters of skin such as elasticity. In this paper, the sensor that can measure various parts of human body in various conditions is developed. The polyvinylidene fluoride (PVDF) film, that is a kind of piezoelectric materials, is used as the sensory receptor in the sensor system. The functionality and signal processing of the sensor system are investigated by measurement of 15 kinds of artificial skin models, which are made of silicone rubber with different elasticity and roughness. Finally, the clinical test for human skin is conducted using the sensor system. Skin of medial forearm and base of thumb of 6 subjects are measured by the sensor. The obtained results show that two parameters calculated from the sensor output correspond to the subjective evaluations of extensibility and smoothness of the skin.