Assistant Professor of Chemical Engineering Bhuvnesh Bharti’s article, Directed Propulsion of Spherical Particles Along Three-Dimensional Helical Trajectories, seeks to answer the question of how to program the propulsion of artificial synthetic objects on a microscale.

The article, which has been recently published in Nature Communications, a peer-reviewed, open-access scientific journal, provides a new physical principle of designing next-generation microbots.

“Inspiration for this work comes from the lack of ability to control motion of objects that are 1/100 the diameter of a human hair,” says Bharti.

“The physics at this scale are very complex, and particles swimming in water at this microscale are equivalent to a human swimming in honey. Currently, we lack a facile tool to engineer surface forces on such particles that allow us to control the motion of micromachines at a microscale.”

This article was co-authored by LSU Chemical Engineering Professor William Shelton, LSU Chemical Engineering Graduate Student Jin Gyun Lee, Pennsylvania State University Chemical Engineering Graduate Student Allan Brooks, and Columbia University Associate Professor of Chemical Engineering Kyle Bishop.

Their study is a step toward designing new autonomous microscale vehicles, which can perform complex functions necessary for advanced biomedical procedures, including non-invasive surgery.

“My Roomba vacuum cleaner has an onboard computer that instructs how it should move in response to environmental cues. For colloidal microrobots we don’t have the luxury of powerful computers and general-purpose software. Instead we have to encode these rather primitive ‘programs’ more directly into the particle itself,” says Bishop.

“We add a metal patch to the spherical particle to instruct it how to move in the electric field. We use the shape of the metal patch as a primitive encoding medium - different patch shapes encode different motions in the field. This paper shows that the geometry of the metal patch can be a useful encoding medium for programming different types of complex motions in self-propelled colloids.”

One of the key aspects of the group’s research is the demonstration of the principle that a helically moving microsphere is more effective in navigating complex environments that contain several objects floating in their vicinity.

“A good analogy of this principle is,” explains Bharti, “suppose you’d like to cross a crowded street. If you try and run in a straight line, then you may not get very far. However, if you’re moving in a zigzag or curvilinear path, then you may get much farther away, and may even be able to cross the street.”

Their work has received support from the U.S. Department of Energy (DOE), with additional support from the Louisiana Board of Regents and the Alexandria, VA-based National Science Foundation (NSF).