Development of a sensor for monitoring hair conditions

In this paper, a haptic sensor system for evaluation of human hair under dry and wet conditions is developed. The polyvinylidene fluoride (PVDF) film, which is a kind of piezoelectric material, is used as the sensory receptor. The sensor consists of an acrylic base, a silicone rubber, a PVDF film. A surface projection is put on the PVDF film as the contacting part. The sensor output is obtained by contacting and scanning objects. Evaluation for human hairs has problems due to randomicity and difficulty of putting them uniformly without overlapping. Therefore, panels imitating the physical and chemical properties of human hair surface are fabricated and used as measuring objects for stable measurement. First, these panels with dry and wet conditions are measured by two sensors with different contacting parts. The measurement results are compared with human sensory evaluation, and the suitable sensor is investigated. Next, panels cleaned down with several kinds of treatment are measured by the sensor. By comparison between the sensor output and human sensory evaluation, it is confirmed that the sensor system can discriminate the treatment effects in dry conditions. Finally, the surface projection on the PVDF film and the sensor structure are improved in order to measure under wet conditions as well as under dry conditions. The sensor outputs have a good correlation with human sensory evaluation. It is found that the improved sensor system is available for monitoring hair conditions in both dry and wet conditions.