Medical microrobots have potential in surgery, therapy, imaging, and diagnostics

Abstract

Trypanosoma brucei , the pathogen that causes sleeping sickness, has a clever and insidious trick to help it navigate its hosts’ innards: It changes shape depending on its surroundings. In bodily fluids, the bacterium assumes a long and narrow shape to propel itself forward, whipping its tail-like flagellum and spinning like a corkscrew. In other settings and life stages, when it doesn't need motility, it shortens into a stumpy blob. In 2014, researchers at ETH Zurich devised microrobots that propel themselves by twisting, something like an artificial flagellum. Researchers direct the microrobots with external magnetic fields. Reproduced with permission from ref. 12. To Bradley Nelson, an engineer at ETH Zurich, the T. brucei ’s potentially deadly shape-shifting ability was both revelation and inspiration. “Parasites have evolved these interesting strategies to survive and move,” he says. “As an engineer, I’m not sure I’d ever have sat down and described something like that from scratch.” His laboratory focuses on developing microrobots that can navigate the human body to perform tasks, such as delivering drugs to a tumor or mechanically clearing blocked blood vessels. In July 2016, Nelson and his team introduced a T. brucei -inspired “origami robot,” a self-folding micromachine, made from a hydrogel, that optimizes its shape according to the viscosity and temperature of its environment (1). It propels itself forward—in experiments, through a viscous sugar solution—by whipping a flagellum-like tail. Scientists steer it by manipulating external magnetic fields. Nelson is among a cadre of scientists who are designing ever-smaller robots that have the potential to improve the precision of medicine. Broadly, the field of “medical microrobots” includes small devices from a millimeter down to a few microns. All aim to safely invade the body and improve health—by diagnosing or monitoring a disease, such as Alzheimer’s, in real time, measuring …