A multilayer PVA-C skin phantom mimicking optical-thermal-mechanical properties for laser medicine

A multi-layer polyvinyl alcohol cryogel (PVA-C) skin phantom that comprises stratum corneum, viable epidermis, and dermis is prepared by freezing-thawing cycles combined with layered casting to achieve optical, thermal, and mechanical mimicry of human skin. The properties of PVA-C hydrogel phantoms are predominantly governed by their PVA network structure, whose cross-link can be enhanced by both increasing PVA concentration and freezing-thawing cycles. These two structural reinforcement methods can also effectively enhance the scattering coefficient of the phantom synchronously, and the optical absorption properties of skin tissue can be adjusted by incorporating varying content of melanin. The ideal number of freezing-thawing cycles should be ≥ 7, allowing a stable PVA structure. The optimal parameters for the most skin-like phantom is determined to be 20% (w/w) PVA and 3.5/8/15:1000 (w/w, lightly/medium/highly pigmented epidermis) melanin. Visualization results from schlieren method showed that the proposed three-layer skin phantom closely resembles the in vivo hyperpigmented dermatoses model during Q-switched laser thermotherapy.