Dip-dip-dry: solvent-induced tuning of polylactic acid surface properties

The dip-dip-dry method is a novel surface treatment that can tune the wetting properties of polylactic acid (PLA). This fast, solvent-induced method yields water contact angles up to 150°, resulting from hierarchical microstructure growth at the surface. This ˜100% increase in static contact angle is achieved by successively dipping the solid PLA samples in solvent and coagulant baths, the choice of which allows us to tune the surface properties, producing wetting states approaching « lotus » or « petal » effects. SEM imaging, XRD and contact angle measurements have been deployed to characterize treated substrates, demonstrating stable properties, with only a gradual loss of the residual solvent to evidence the passage of time. Polymer crystallinity largely influenced the extent of surface modification - unless surface texturation (sanding) was applied, solvents only had a minor effect on wettability on crystalized substrates.