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In materials science, the surface wettability of a biomaterial can be measured using the surface water contact angle as an important characterization of its hydrophilicity or hydrophobicity. The technique has attracted remarkable attention in recent years for materials development in the areas of energy, healthcare and environmental science. Bioinspired surfaces have been engineered with a variety of functionalities and special properties of wettability to mimic nature.
Among these, slippery liquid-infused porous surfaces (SLIPSs) outperformed their natural counterparts to provide state-of-the-art surfaces with stable and defect-free repellence for a variety of simple and complex liquids. To broaden the application of SLIPSs with tunable wettability, adaptive surfaces were made of liquid film supported by a nanoporous elastic substrate. Although contact-based regulation underwent many such improvements to enable the existing slippery surfaces, their space-time control via non-contact remain unrealized. In addition, slippery surfaces with programmable wettability that can spatiotemporally manipulate droplets for a breakthrough impact in microfluidics technology remain to be developed.
Science - Advances - Wang - Al - Novel
Now writing in Science Advances, Wang et al. present a novel, paraffin-infused porous graphene film (PIPGF) consisting of a porous graphene sponge material infused with paraffin. The process allowed paraffin to reversibly transition between solid and liquid phases with the photothermal effect of graphene under near-infrared (NIR) light. When the paraffin surface was heated to melting, water droplets could slide down along the graphene film, and when the paraffin was cooled, droplets pinned to the film surface. The surface wettability and state of matter of PIPGF could be remotely controlled with high stability and fast reversibility using NIR light. The authors integrated NIR masks so that paraffin could melt at corresponding patterns on the PIPGF to form programmable pathways for the slipping droplets. The PIPGF facilitated programmable wettability pathways to simplify liquid handling in microplates, droplet microarrays and in distinct microfluidic microreactors with...
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