Development and Characterization of Skin Phantoms for Validation of Wearable Hydration and Bioimpedance Sensors - PROJECT SUMMARY Advances in wearable health-monitoring devices demand reliable dry electrodes, yet validation remains largely empirical. Current methods depend on human or animal testing with little physiological control, introducing variability that complicates interpretation and slows translation. To overcome these barriers, we developed a first-of-its-kind skin phantom that replicates human low-frequency impedance (1 Hz–1 kHz) with precise hydration control. Building on this work, we will create a multiparametric phantom spanning 0.1 Hz–5 MHz and incorporating controlled motion, perspiration, and evaporation to capture realistic skin behavior. Tunable porosity in the outer stratum corneum will model hydration states, while deeper layers with tailored conductive and dielectric fillers will reproduce tissue resistive and capacitive properties. Our central hypothesis is that systematic variation of pore size, spacing, and number, combined with layered dielectric design, will accurately match in-vivo skin impedance and hydration dynamics. Our plan integrates three aims. Aim 1: Fully characterize the phantom’s ability to mimic hydration, perspiration, and evaporation by adjusting porosity and environment, including humidity control and saline release, and produce a predictive impedance look-up table for reproducible electrode testing. Aim 2: Develop layered structures that replicate deep-tissue impedance, guided by finite-element modeling, and tune conductive and dielectric content until impedance matches human cadaver data within ±5 %. Aim 3: Validate the completed phantom against in-vivo human skin from thirty adults aged 18–85, with hydration standardized by corneometer; success is phantom impedance within ±10 % of averaged human data under static and motion conditions, including 10 % cyclic strain at 0.5 Hz. These aims directly address the limits of current methods. Approaches such as humidity chambers, saline- soaked cloths, or porcine skin cannot maintain reproducible hydration or capture dynamic perspiration and evaporation. Our controllable, layered design enables standardized comparisons across laboratories, reduces reliance on human or animal subjects, lowers cost, and provides mechanistic insight into skin– electrode contact impedance, advancing both scientific understanding and sensor development. Expected outcomes include a validated open-source phantom and a public database of skin impedance and hydration states that establish a reproducible platform for designing and evaluating wearable hydration and bioimpedance sensors. These resources will speed clinical and commercial adoption of next- generation biosensing technologies, support future R01 and R35 proposals focused on disease-specific hydration monitoring and advanced multilayer tissue modeling.
