| Description |
Maintaining healthy skin is vital for protection, sensation, and water conservation in the human body. Skin health is usually judged subjectively through sight and touch, and skin haptic properties are often described using arbitrary terms such as ‘softness', ‘smoothness', or ‘dryness'. Although qualitative haptic characterization is often sufficient for general comparison between skin states, a quantitative approach is needed to characterize minute changes in skin condition. This thesis details the use of a precision magnetic levitation haptic device to characterize the haptic properties of human skin in vivo before, during, and after treatment with each of eight commercially available shower gels. Although prior research has sought to characterize the haptic properties of human skin in vitro and in vivo, very few studies have compared the haptic effects of commercial skin products having relatively similar formulations. Additionally, related studies have typically utilized simple, low-precision devices and fixtures. Various metrics were used to characterize the haptic properties of human skin, including friction, dynamic skin stretch, and viscous damping. A hybrid force-position control algorithm was developed to control a precision 6-DOF magnetic levitation robotic device with silicone tactor to touch, stroke, or stretch human skin in vivo. Data were collected from 32 human subjects and analyzed primarily to investigate the effects of shower gel type on each of the chosen test metrics. Other factors investigated include skin test location, order, and subject age and gender. Results showed significant differences between the effects of various shower gels, especially after accounting for variance between subjects. Most notably, Olay and Soft Soap Nutri-Serums gels yielded the highest skin coefficients of friction 20 minutes after treatment, indicating higher levels of skin hydration than other gel treatments. Conversely, Sweet Pea gel treatment yielded the lowest skin coefficient of friction. Additionally, when applied to the skin as un-lathered gels, Soft Soap Nutri-Serums and Soft Soap Shea Butter yielded viscous damping constants twice that of other gels, while Dove Go Fresh yielded the lowest. When lathered into foam on skin, Sweet Pea gel yielded the highest viscous damping constant, while Dove Go Fresh again yielded the lowest. |
