Skin Properties in Microscale on Live Human Skin Properties in Microscale on Live Human

Authors: Miguel Coto

Advisor: Dr. Mojtaba Azadi

Obtaining the mechanical properties of the skin stratum corneum and epidermis in-vivo will provide medical professionals with a way to obtain and record quantitative values on their reports. The stratum corneum and epidermis are 20 and 130 µm thick, respectively. Many of the tools are generally much larger than this length scale, which consequently may result in the mechanical properties of undesirable layers below the skin. Atomic Force Microscopy (AFM), an instrument capable of capturing mechanical properties of stationary soft materials at microscale is used in this study. In comparison to other methods, using the AFM is theoretically and fundamentally superior in terms of collecting accurate data from small and stationary samples. However, using AFM on live human subjects in microscale imposes experimental challenges. In this study, a stabilizing fixture was developed that minimize the subject’s hand motion and results in reliable data collection from the AFM. In this study, a 5µm radius spherical probe with maximum indentation depth of 2µm is used to detect the skin elastic modulus of samples in various parts of the human arm, as well as fixed/dried skin samples in-vitro. Furthermore, the Force Curves obtained from indentation of the AFM were analyzed in accordance with the Hertz Model. The value obtained is compared with the data found in the literature. An elastic modulus of 36 ± 19.42 MPa (mean, SD) was obtained for in-vivo testing on the forearm. Furthermore, when testing 2 in-vitro samples of skin taken from different sites of the arm, a Young’s Modulus of 10.04 ± 1.891 MPa (mean, SD) and 3.810 ± 0.53 MPa (mean, SD) were recorded. In the future work, more human subjects with different skin characteristics (i.e. dryness, sensitivity, tone.) as well as different skin conditions (i.e. infections, allergies, cancer) will be hired. Higher sample numbers will allow us to evaluate the feasibility of a developing this technique to a reliable and quantitative practical method for clinical diagnosis of skin conditions.