Fabricating microscopic tools: towards optically actuated micro-robotics

Abstract

Direct laser writing is a powerful and exible tool with which to create 3D micro-scale structures with nanoscale features. These structures can then be dispersed in aqueous media and dynamically actuated in three dimensions using optical tweezers. The ability to build, actuate and precisely measure the motion of complex microscopic structures heralds a variety of new applications - optically actuated micro-robotics. In this article we describe how these devices are designed, fabricated and controlled. Once trapped, we are able to accurately measure the translational and rotational Brownian motion of the structures in real-time (at up to a few kHz) in three dimensions using high-speed video stereo-microscopy. This enables their motion to be controlled automatically using feedback, transforming the structures into quantitative tools. We discuss a range of applications, including the imaging of surface topography inside a sealed micro- uidic chamber, and work towards the controlled rotation of cells about an arbitrary axis.