Study reveals unexpected movement of drug-delivery swimming robots

Testing locomotion in non-Newtonian fluids

The team used two types of tiny swimmers, a sphere and a helix (modeled after the corkscrew shape of certain bacteria). They embedded a magnet within each, and tested them first in Newtonian fluid. (The viscosity of Newtonian fluids, such as water or alcohol, never changes, no matter how much the fluid is shaken or stirred.) They used millimeter-scale swimmers, but matched the physics of microswimming by increasing the viscosity of the test fluids.

At the same time, the way the swimmers pushed against the surrounding fluid near the wall also caused them to move sideways while moving forward, resulting in a diagonal trajectory. But when they placed the swimmers in a synthetic non-Newtonian fluid meant to simulate mucus or blood, the researchers observed an unexpected behavior: under the same magnetic actuation, the swimmers moved sideways in the opposite direction from what they did in a Newtonian fluid.

Implications for targeted drug-delivery systems

The next step for the research is to explore the effects of rheology on swimmers designed at the microscale-swimmers in this study were millimeter-sized-and with different shapes.

Although targeted drug delivery remains many years away, findings like this represent the incremental advances that will bring the concept from theory to practice.

Source:

Lehigh University

Journal reference: