Dynamic droplet behavior for analyte localization on phase change liquid infused surfaces

Phase-change liquid infused surfaces (PC-LIS) can enable responsive and adaptable interfacial control due to their tunable physical properties, including wetting behavior. These materials leverage the phase transition of oils/waxes infused within a micro- or nano-texture to dynamically alter their interfacial properties. Using thermal control, PC-LIS are able to dynamically switch between solid states in which droplet contact lines are more easily pinned and liquid states where droplet contact lines are mobile. This enables them to harness the slippery, anti-fouling behavior of LIS while also improving material durability to variable conditions such as abrasion or shearing flows, which can deplete lubricant from traditional, static LIS. Here, we demonstrate how the surface morphology and phase state of PC-LIS can be used to control dynamics of drops evaporating on the surfaces as well as the associated microparticle deposition outcomes. We report on how phase-switching controls contact angle hysteresis, sliding angle, and evaporation mode of drops to enable precise control over droplet mobility and deposition footprint. By using these materials to substantially reduce deposit footprint, we can enable new, simple methods for analyte localization for environmental sensing. This is especially important for dilute physical contaminants such as micro- and nano-plastic fragments. Using model plastic microparticles as well as real microplastics from plastic bottled drinking water, we demonstrate that PC-LIS can successfully concentrate analytes into a small, localized region for analysis by evaporating drops on surfaces in the liquid configuration. Following analyte localization, the materials can be reverted back to the solid configuration for detection using other techniques.