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Material surfaces can be switched to a structure designed to repel gas bubbles

What do rising bollards and biomaterial science have in common?

Materials that can repel gas bubbles on-demand

This material is programmed so that tiny cylinders rise from its surface and repel approaching air-bubbles, like the bollards that rise from the road and repel cars! Source: Left: Cropped from photo by Nigel Tadyanehondo on Unsplash. Right: Adapted from Materials & Design, Volume 163, Yi Jiang, Ulrich Mansfeld, Liang Fang, Karl Kratz, Andreas Lendlein, Temperature-induced evolution of microstructures on poly[ethylene-co-(vinyl acetate)] substrates switches their underwater wettability, 107530, Copyright (2019), with permission from Elsevier.

Have you ever come across cylindrical bollards, which are programmed to rise up from the road’s surface, preventing cars from approaching? Researchers at the Institute of Biomaterial Science have created a type of plastic that works in a similar way. The bollards are much smaller – around a 10th the width of a human hair - and repel air bubbles instead of cars.

To create this function, the researchers first moulded a polymer so that it had tiny cylinders (see image above), then the cylinders were compressed into the surface whilst the polymer was heated. This process creates the so-called “shape-memory effect”, meaning that the material is programmed to stay in this temporary shape until it is switched back to its original shape. When this flat polymer is submerged in a liquid, air bubbles are able to approach and stick to its surface. However, when the material is heated to the programmed temperature, the cylinders rise up from the surface and prevent air bubbles from attaching.

Designing polymeric surfaces with well-defined functions that are based exclusively on their geometrical structure is a major strategy in advanced functional materials. This ability to precisely control the tendency of gas bubbles to stick to a surface is of great interest in many modern applications, e.g. medical devices, gas storage and transport, electrodes, and membranes. This surface design is particularly noteworthy, as it is reprogrammable, and maintains its waterproof properties over a wide temperature range. This makes it particularly interesting for creating multifunctional devices.

Link to article in Materials and Design