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Pneumatic programmable superrepellent surfaces

Morphological transformation of pneumatic PDMS surface allows tuning of its wettability

Tailoring the wettability of surfaces is a highly relevant technological challenge in the fields of liquid-repelling, anti-icing or energy harvesting, amongst others. Most current efforts focus on the development of novel, smart responsive materials with tunable properties when exposed to external stimuli such as thermal, magnetic, chemical or electric. However, as nature demonstrates on plant leaves or butterfly wings, structural modifications can be as, if not more efficient. As such, Songtao Chu, Xiaobao Cao, members of the deMello group and collaborators at the universities of Shanghai Jiao Tong, City of Hong Kong and Imperial College London, highlight in this study the potential of in-situ morphological transformation for tailoring wettability of pre-existing surfaces.

The developed programmable, superrepellent surface is constituted of separated polydimethylsiloxane (PDMS) chambers, connected to a microfluidic system and bonded onto a rigid substrate. Each compartment can be independently inflated or deflated at will, the convex curvature of the created dome being adjusted by changing the input medium pressure (water or air). Depending on the topography of the surface, water droplets will either roll or bounce, in direction controlled by the convex curvature, around the basic idea that evacuating the droplet from the surface decreases its wettability. To demonstrate the capacity of the platform, the surface was notably pneumatically programmed to generate a river-valley-like two-dimensional pathway allowing the controlled displacement of a droplet from one corner to the other.

Taking advantage of nature-inspired symmetry breaking and oscillator coupling mechanisms, this work wonderfully displays how in-situ morphological transformations of pre-existing surfaces can improve liquid repellency by reducing liquid-surface contact time.

Written by Thomas Moragues

Read the accepted manuscript here

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