Water-activated material may find applications in robotics

Most soft robotics systems rely on synthetic polymers which respond to external stimuli to produce their movement. However, such polymers tend to be slow to respond, cannot generate high power or force, and fail on contact with water. The Columbia team, based in the laboratory of Ozgur Sahin, an associate professor of biological sciences of physics, has an outer material which is not only completely resistant to water but actually responds to its presence by delivering force and motion.

In a paper in Advanced Materials Technologies, the Columbia team describes their material as a composite made from spores – it is produced by bacteria that are often used as food supplements – and ultraviolet-curable adhesives.

The composite is formed in sheets which are stacked together to form a structure that expands or contracts in response to humidity or moisture as the spores swell or shrink. Depending on the design of the pattern of the assembly of composite sheets, the assembly can bend, fold, or unfold.