In vitro evaluation of skin adhesives during perspiration

To bridge the gap between current in vitro and in vivo testing, we present the use of a perspiration simulator to evaluate the performance of skin adhesives during sweating. The perspiration simulator mimics human skin in key aspects such as roughness, water contact angle, sweat pore size, sweat pore density, and can be operated at different perspiration rates. In contrast to in vivo testing, a well-defined experimental setup with minimal variation is therefore successfully achieved. To demonstrate the capabilities of the reported perspiration simulator, two model adhesives with different water absorption capabilities are assessed. The peel forces as a function of time are thereby measured during perspiration of a 0.154 M NaCl solution. The peel force decreases immediately when the perspiration rate exceeds the water uptake as determined by an immersion test. However, when the water absorption capabilities are sufficiently high, a delay in the decrease in peel force is observed. Through the use of a fluorescent dye, we can further correlate the loss of adhesion with a spreading of liquid at the skin-adhesive interface.