Light-driven micro-tool equipped with a syringe function

Leveraging developments in microfabrication open new possibilities for optical manipulation. With the structural design freedom from three-dimensional printing capabilities of two-photon polymerization, we are starting to see the emergence of cleverly shaped ‘light robots’ or optically actuated micro-tools that closely resemble their macroscopic counterparts in function and sometimes even in form. In this work, we have fabricated a new type of light robot that is capable of loading and unloading cargo using photothermally induced convection currents within the body of the tool. We have demonstrated this using silica and polystyrene beads as cargo. The flow speeds of the cargo during loading and unloading are significantly larger than when using optical forces alone. This new type of light robot presents a mode of material transport that may have a significant impact on targeted drug delivery and nanofluidics injection. Light-driven microtools that pick up and drop off cargo through light-induced convection currents have been made by a team in Denmark. The tools, which resemble racing cars in shape, are fabricated, positioned and used to manipulate cargo by light. Jesper Glückstad at the Technical University of Denmark and colleagues used two-photon polymerization to produce the ‘chassis’ and ‘wheels’ of the tools and then deposited metal layers in their interiors using electron-beam physical vapour deposition. The car is maneuvered by illuminating its wheels with four trapping beams. When the metal layers are illuminated by light, they heat up and generate convection currents that can be used to suck up and spew out cargo—silica and polystyrene beads in this case. The researchers anticipate that such tools could be used for drug delivery.