Molecular motors use light, store energy

Written by: Graham Pitcher | Published:

A team at CNRS' Institut Charles Sadron led by Prof Nicolas Giuseppone from the Université de Strasbourg, has made a polymer gel that can contract through the action of artificial molecular motors. When activated by light, these nanoscale motors twist the polymer chains in the gel, which contracts by several centimetres. The new material can also store the light energy absorbed.

In biology, molecular motors are highly complex protein assemblies that operate over distances in the region of 1nm. However, when millions of them join up, they can work in a coordinated way, with effects at the macroscale.

Chemists, say the researchers, have sought to produce this type of motion using artificial motors. To achieve this, the team replaced a gel's reticulation points – which cross link the polymer chains – with rotating molecular motors made up of two parts that turn relative to each other when provided with energy. They succeeded in getting the motors to work in a coordinated and continuous manner, right up to the macroscale: when the motors are activated by light, they twist the polymer chains in the gel, which makes it contract.

Light energy is turned into mechanical energy through the twisting of the polymer chains and stored in the gel. If the material is exposed to light for a long time, the amount of energy contained in the contraction of the polymer chains can trigger a sudden rupture of the gel. The researchers are now working on ways to take advantage of this way of storing light energy and reusing it.

The left image shows a schematic representation of a polymer gel whose chains are cross linked using rotating molecular motors (the red and blue parts of the motor turn relative to each other when provided with energy). When exposed to light, right, the motors start to rotate, twisting the polymer chains and contracting the gel by as much as 80%.

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