P43 Noninvasive, mechanical characterization of skin and the effects of ageing; comparing automated and manually actuated indenters

Abstract Introduction and aims Skin is subject to structural and mechanical remodelling because of intrinsic and extrinsic ageing. Invasive skin biopsies, while informative of composition and architecture at a single timepoint, do not provide insights into longitudinal changes and are subject to clinical risks. Noninvasive mechanical characterization of skin is commonly undertaken with devices that cannot measure formal biomechanical properties. Comparing an automated indenter with a novel portable, manual indenter, this study aimed to noninvasively characterize the effects of ageing on biomechanical properties. Methods Twelve healthy White participants were recruited: young (n = 7; 24.1 ± 1.0 years) and aged (n = 5; 68.2 ± 5.2 years). Testing was performed within 30 × 30 mm regions of interest on the volar and dorsal forearm. Viscoelastic indentation was performed using a CETR UMT (Universal Mechanics Testing) machine and a bespoke manual indenter, both with the same 5-mm spherical probe. During indentation, the probe was lowered into the skin until a load of 0.3 N was reached, where it was held before being retracted. This generated load vs. indentation curves from which the skin’s stiffness (E) and viscoelastic recovery from mechanical load (W) were found. Results Both the indenters showed a reduction in with respect to age: EUMT decreased by 36.0% in volar and 24.6% dorsal; EManual decreased by 55.0% and 48.4%, respectively. Conversely, W increased with respect to age: WUMT increased by 53.3% in the volar forearm and 35.0% the dorsal forearm; WManual increased by 121.2% and 140.9%, respectively. Conclusions Both the automated and manual indenter were able to differentiate between age cohorts. While the manual indenter showed greater variability, its values remained comparable to the UMT, giving confidence in the ability to measure biomechanical properties on location. Future work will include further investigations involving other ethnicities and running a study with noninvasive and invasive measurements on the same cohort and finding predictive links between them.