The term "micro-rocket" might imply weaponry on a small scale. Not so the 3D inkjet-printed devices engineered at University of Sheffield. Measuring 300 microns in length and 100 microns in diameter, these devices are designed to deliver drugs or locate cancer cells within the human body.

The research was funded by grants from the Engineering and Physical Sciences Research Council.The micro-rockets are composed of a solution of dissolved silk mixed with an enzyme, rendering the devices biocompatible and relatively inexpensive compared with carbon nanotubes, metals and other materials used to manufacture drug delivery agents.

Methanol printed on top of the printed solution triggers a reaction to form a rigid rocket shape. This traps the enzyme within a silk lattice structure. The enzyme acts as a catalyst, reacting with fuel molecules to produce bubbles that propel the rocket forward (see video).

“By using a natural enzyme like catalase and silk which are fully biodegradable, our devices are far more biocompatible than earlier swimming devices,” says Dr Xiubo Zhao, from the department of Chemical and Biological Engineering. “The inkjet printing technique also allows us to digitally define the shape of a rocket before it’s produced. This makes it a lot easier to optimise the shape in order to control the way the device swims.”

The research was funded by grants from the Engineering and Physical Sciences Research Council.