Millirobots Image
The team successfully converted cotton thread, origami, polydimethylsiloxane (PDMS) film and plastic pipe into soft reptile robot, multi-foot robot, walking robot and rolling robot respectively. (Photo source: City University of Hong Kong)

Researchers have developed an easy way to make millirobots by coating objects with a glue-like magnetic spray. Driven by the magnetic field, the coated objects can crawl, walk, or roll on different surfaces. As the magnetic coating is biocompatible and can be disintegrated into powders when needed, this technology demonstrates the potential for biomedical applications, including catheter navigation and drug delivery.

Composed of polyvinyl alcohol (PVA), gluten and iron particles, M-spray can adhere to the rough and smooth surfaces of one (1D), two (2D) or three-dimensional (3D) objects instantly, stably and firmly. The film it formed on the surface is just about 0.1–0.25 mm thick, which is thin enough to preserve the original size, form, and structure of the objects.

by wetting the solidified M-spray coating fully to make it adhesive like glue and then by applying a strong magnetic field, the distribution and alignment direction of the magnetic particles (easy magnetization axis) of the M-spray coating can be changed.