Motorised matchsticks keep on going
11 Oct 2013 by Evoluted New Media
Motorised microscopic matchsticks whose speed and direction of motion can be controlled have been developed by an interdisciplinary team of scientists at the University of Warwick.
By adding a small amount of catalyst to the head of microscopic rods, researchers found the rods were propelled towards a chemical fuel added to a matchstick/microsphere mixture, in a phenomenon is known as chemotaxis.
The team – which included chemists, physicists and computer scientists – placed silica-managanese oxide ‘heads’ on the matchstick material, and placed them in a mixture with ordinary polymer microspheres. They then introduced hydrogen peroxide as the chemical fuel in one particular place.
“We choose high aspect rod-like particles are they are a favourable geometry for chemotactic swimmers, as seen for example in nature in the shaped of certain motile organisms,” said research leader Dr Stefan Bon.
“We placed the ‘engine’ that drives the self-propulsion as a matchstick head on the rods because having the engine in the ‘head’ of the rod helps us align the rod along the direction of travel, would also show the asymmetry perpendicular to the direction of self-propulsion, and at the same time it maintains rotational symmetry parallel to the plane of motion.”
The matchsticks were rapidly propelled towards the hydrogen peroxide when added to the mixture, while the microspheres continued to move under Brownian motion or convection currents. The reaction was so strong that more than half of the matchstick particles did not reverse their orientation once over their 90 seconds of travel even though they were contending with other forces.
“Our approach is very versatile and should allow for future fabrication of micro-components of added complexity,” said Bon. “The ability to direct motion of these colloidal structures can form a platform for advances in supracolliodal science, the self-assembly of small objects. It may even provide some insight into how rod shapes were selected for self-propelled microscopic shapes in the natural world.”
This research is published in Materials Horizons. Previously, most research has focussed on the use of a magnetic field or application of light to influence the motion of the microscopic components.
Chemotaxis of catalytic silica-manganese oxide “matchstick” particles http://pubs.rsc.org/en/content/articlelanding/2014/mh/c3mh00003f#!divAbstract
