Have you ever wondered how small mammals such as beavers and sea otters keep warm underwater, without a thick layer of blubber? A group of researchers at Massachusetts Institute of Technology has drawn inspiration from these animals to create a material where the wetsuits of the future could be made off.

The fur of beavers and otters consists of two layers. The outer, coarse guard hair repels water and forms a protective layer for the underfur. This layer consists of short, densely packed hairs that trap air as the animal dives into the water, keeping it warm.

The research was inspired by a visit to a Taiwan wetsuit manufacturer, Sheico Group, that asked if there was a bioinspired solution for wetsuits. After all, wetsuits are designed to keep the person wearing it warm in cold water, but to obtain that quality, they are made of thick rubber, constraining the movements of the wearer.

To imitate the underfur, the scientists made different moulds by cutting thousands of tiny holes in small acrylic blocks. With a software programme, the size and spacing of the individual hairs was altered, so that the researchers could test what would give best result once the samples were made. The moulds were then filled with soft casting rubber called PDMS (polydimethylsiloxane).

The material was tested by submerging the surfaces vertically into a vat of silicone oil at various speeds. This kind of liquid makes it easier to observe the formation of air pockets. In testing various surfaces, they found that the denser the fur and the quicker the material was submerged, the more air was trapped between the hairs. More air means more warmth which lasts longer. From this observation, a mathematical model could be made to calculate the amount of trapped air.

The material is particularly interesting for surfers, as the constantly move in and out of the water. It could provide a thinner, warmer, but much hairier wetsuit in the future.