Direct laser writing is a powerful and flexible 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, heralding a variety of new applications - optically actuated micro-robotics. I will describe how these devices can be designed, fabricated and controlled. Once trapped, we are able to accurately measure the translational and rotational Brownian motion of the structures in real-time in 3D using high-speed video stereo-microscopy. This enables their motion to be controlled automatically using feedback - transforming these structures into quantitative tools. I will discuss a range of applications, including the imaging of surface topography inside a sealed micro-fluidic chamber, work towards the controlled rotation of cells about an arbitrary axis, and the development of a form of ultra-gentle hydrodynamic micro-manipulation.
