US and German scientists have used laser light to guide micro-particles through a solution towards a target. The technique could be applied to transport the particles to specific locations inside living cells, they say. These so-called ‘micro-swimmers’ consist of a polystyrene sphere with one hemisphere coated with a thin layer of gold.
The team used ‘photon nudging’, in which a weak laser light is used to intermittently illuminate the swimmers, to cause body-centred propulsion by photophoresis. The technique also allows adaptive control: the system continuously monitors the 3D orientation of the particle as it randomly rotates through the solution, so the operator can choose to only turn on the swimmer’s ‘engine’ when it is pointing towards the desired target.
B Qian et al, Chem. Sci., 2013.