Complex micromachines produced and driven by light

Summary form only given. We describe a method which we think is most promising for the building of complex micromechanical devices, where mechanical, optical and electrical components can be readily integrated. The method is based on the photopolymerisation of light curing resins. If polymerisation is performed by a focused laser beam and the reaction is initiated by two-photon excitation, the volume in which the polymerisation reaction proceeds can be very small, i.e. high spatial resolution can be achieved. By moving the focus along a predetermined trajectory, objects of arbitrary shape can be built. The force exerted by focused laser light of the order of 10 mW intensity upon micrometer-size objects has also the right magnitude to move them, i.e. the mechanical systems can be activated by light.