Scientists at the University of Sheffield have discovered that tiny spherical bead-like devices can be guided by physical structures while swimming inside fluids. The team believes its research (“Boundaries can steer active Janus spheres”), published in Nature Communications, could lead to using structures in the body to guide drug delivery, or cracks in rocks to direct environmental clean-up and exploration.

These devices, which are a similar size to cells and bacteria, i.e., around a hundredth of the average diameter of a strand of human hair, might find applications in the delivery of drugs to a specific location inside the body or outside of the body to diagnose diseases in blood samples. Examples include finding proteins indicating cardiac problems or looking for circulating tumor cells that can indicate the spread of cancer. Previous studies have focused on working with external magnetic fields to guide the devices, but this requires constant observation so that the device can be guided manually.

The research conducted at Sheffield relies on a new technique, giving the devices a catalytic coating on one side, which creates a chemical reaction when fuel molecules are added, causing the device to move automatically on a pre-determined route.

“When you're dealing with objects on such a small scale, we found that although our method of moving the devices using a coating and chemical reaction worked very effectively, it was difficult to control its direction, due to other molecules in the fluid jostling it,” explained Stephen Ebbens, Ph.D., department of chemical and biological engineering at Sheffield. “We've been working on ways to overcome this and control the movement of the devices [directed by natural structures] along a path.”

Dr. Ebbens said his team is now working on a number of applications for these devices in the body, in the shorter term as tools for medical diagnosis.

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