Earthworm inspires self-lubricating material

Researchers in Germany have taken inspiration from the earthworm to develop a material with a surface structure that self-lubricates whenever pressure is applied.

Self-lubricating material [Iris Maurer]
Because the lubricated material reduces friction and prevents the growth of microbes, scientists at the Leibniz-Institute for New Materials (INM) foresee numerous applications in industry and biomedicine. The team recently published their results in Advanced Materials.

The material is made of soft plastic, with droplets of silicone oil as a lubricant at the inside of it.

“When we put pressure on the material, the droplets change shape and migrate to the surface. The silicone oil then spreads evenly on the surface to a water and dirt-repellent sliding layer,” said Jiaxi Cui, head of the Switchable Microfluidics research group at INM.

The droplets then reform as the pressure decreases. In addition, the sliding layer can also be removed and formed repeatedly when pressure is reapplied to the material. “So it reacts dynamically to pressure – like a” breathing “system,” said Cui.

The surface structure of the new material also plays an important role. Cui said the skin surface of the earthworm is rough, which was replicated in the new material to ensure the uniform formation and adherence of the lubricant.

“The surface structure is also important for the longevity of the lubricating effect,” said Cui. “We compared the sliding film on our “earthworm structures” with a sliding film on a smooth surface: our structures survive 10,000 cycles of friction, whereas sliding films on smooth structures have only 300 friction cycles.”

There are already some structures that reduce friction, including those that are modelled on the functioning of animal skins, but they only work in a fluid environment.

“For the first time, we’re introducing an application that reduces friction in a solid environment, and we’ve been inspired by the earthworm because it also glides through a solid environment, Earth” Cui said.