Molecular machines are found everywhere in nature and are made up of complicated assemblies of proteins. As their name suggests, they work on the nanoscale and are responsible for a host of processes in living organisms, such as ion transport, ATP synthesis and cell division. Indeed, our muscles are controlled by the movement of thousands of millions of these tiny machines, which when coordinated together act over macroscopic distances – that is, centimetres across.

Although artificial nanomachines have advanced in leaps and bounds over the last decade, it is still difficult to synchronize the movement of assemblies of these nanodevices so that they behave more like their natural counterparts. A team of researchers led by Nicolas Giuseppone of the University of Strasbourg has been actively working in this field and has now made a motor based on a gel made from the polymer polyethylene glycol (PEG) that contracts when exposed to UV light.

Motors act over longer distances

Giuseppone and colleagues made their devices by replacing the reticulating points in the gel (which join the polymer chains together) with molecular motors composed of two components that rotate in one direction with respect to each other when supplied with energy. When activated by light, they roll up chains of the polymer gel onto themselves, which causes the gel to contract by up to 80% its original volume. The researchers succeeded in making millions of these motors rotate in a coordinated way for the first time and have so extended the distance over which they work – "up to the human-sized scale," Giuseppone tells nanotechweb.org.

The motors can also store part of the light energy absorbed as mechanical energy, something that might make them useful for applications in artificial muscles, nano- and micro-robots, and advanced mechanical motors that work using nanomachines. Indeed, if the motors are exposed to light for prolonged periods, the amount of energy contained in the contracting polymer chains can then become too great and the gel can rupture violently, says Giuseppone. “We are thus looking for a way to better exploit this energy and harness it in a controlled way.”

The work is published in Nature Nanotechnology doi:10.1038/nnano.2014.315.