Scientists in the US have developed nanomotors that are propelled through liquids using an electric field. 

Nanomotors are nano-sized machines that convert energy into motion and have a number of potential biomedical applications, including drug delivery and microsurgery. Catalytic nanowires, constructed with ends made from different metals, are one of the most studied varieties of synthetic nanomotor but they require a chemical fuel such as hydrogen peroxide to power them. Now Joseph Wang at the University of California, San Diego, has developed nanowire motors that don't require additional chemicals. 

The polypyrrole-cadmium nanowires contain a diode, which allows an electric current to flow in only one direction. When an alternating current electric field is applied to the nanowires, the electrical energy is converted into movement, propelling them a distance equivalent to seven times their body length in one second. 

Fuel-free nanomotors are preferable for biomedical applications as they do not require additional chemicals, explains Wang, which inspired his team to look for a new propulsion method. 'We have been working on synthetic nanomotors over the past three years, exploring new designs with enhanced speed and force and alternate propulsion principles that will enhance their performance,' he says. 

José Pingarrón, an expert on nanomotors from the Complutense University of Madrid, Spain, views the work as 'an important contribution to the field of nanomachines', saying that it shows nicely the possibility of controlling nanowire propulsion using an electrical field. 

Wang and colleagues are now turning their attention to testing their diode nanomotors in a biomedical environment. 

Hilary Burch