Positive-tone micropatterning via a selective dissolution pathway for friction modification

Texturing is a convenient and versatile strategy to engineer the properties of a surface. In this study, the combination of photolithography with dynamic covalent bonds facilitates the fabrication of positive-tone surface patterns from a photopolymer. Selective photoactivation of a photolatent base catalyst in a 3D covalently crosslinked thiol-ene network allows for a spatially controlled solvent-assisted transesterification approach (alcoholysis). The photoactive resin is cured with visible light (450 nm), which makes it processable via vat photopolymerization. Furthermore, orthogonality between the curing and the activation reaction of the transesterification catalyst, which is activated using light with a different wavelength (405 nm), is ensured. Micropatterns that aim to affect or modify the friction properties are inscribed into the surface by selective light exposure using a photomask. The tribological behavior was evaluated in a ball-on-plate (BOP) measurement setup, where thiol-ene films with line or dimple surface patterns exhibit a significant increase in the coefficient of friction (COF) compared to the non-textured polymer films.