Ann Arbor Times

Microrobots made from magnetic droplets may improve targeted drug delivery, according to a new study published in Science Advances. The research was conducted through simulations at the University of Michigan and experiments at the University of Oxford.

The study highlights that current intravenous drug delivery methods send less than 1% of medicine to the intended tissue. The team developed two-sided microrobots composed of a gel for carrying drugs and embedded magnets for control. In experiments simulating treatment for inflammatory bowel disease, the microrobots were delivered by catheter into a pig intestine and guided to specific sites using a magnetic field. After reaching their target, the gel dissolved to release a dye, confirming successful delivery. Some gels were designed for delayed release, dissolving over longer periods.

After dispensing their cargo, the magnetic particles were retrieved via catheter. Researchers say this approach could allow different drugs to be delivered to multiple inflammation sites along the intestine, potentially improving treatment options for conditions like inflammatory bowel disease.

The team also demonstrated another use case with a human knee model. Microrobots released at an accessible area were maneuvered to hard-to-reach locations to deliver dye before being extracted.

“With this work, we’re moving closer towards very advanced therapeutic delivery. Our advanced fabrication techniques enable the creation of soft robotic systems with remarkable features and motion capabilities,” said Molly Stevens, the John Black Professor of Bionanoscience at the University of Oxford Institute of Biomedical Engineering and co-senior author of the study.

The fabrication process involves pushing gel containing magnetic particles through a narrow channel intersected by oil, creating evenly sized droplets where magnetic particles settle at one end and empty gel remains on top. These permanent magnetic droplet-derived microrobots (PMDMs) are about 0.2 millimeters wide.

“Traditional microrobot fabrication has very low throughput. Using microfluidics, we can generate hundreds of microrobots within minutes. It significantly increases efficiency and decreases fabrication cost,” said Yuanxiong Cao, doctoral student in the Stevens Group at Oxford and co-lead author.

Simulations helped predict how these microrobots move in response to different magnetic field frequencies and tested their navigation through complex environments using simulated obstacle courses.

In practice, an electromagnet controlled by commercial software creates fields that move chains of microrobots in walking, crawling or swinging motions; these chains can assemble or disassemble as needed to traverse obstacles.

“I was amazed to see how much control we have over the different particles, especially for the assembly and disassembly cycles, based on the magnetic field frequency,” said Philipp Schönhöfer, co-lead author and research investigator in chemical engineering at U-M in Sharon Glotzer’s group.

Researchers plan next steps including designing new microrobots capable of navigating more intricate environments and studying larger swarms under varying conditions.

“With our computational platform, we have now also developed a playground to explore an even wider design space, which has already triggered ideas for more complex microrobot architectures inspired by the PMDM concept,” Schönhöfer said.

Imperial College London researchers contributed as well. Funding came from several organizations including universities in Oxford and Michigan as well as national science agencies from China, Britain and the United States. Computational support included resources from Purdue University’s Anvil system and Advanced Research Computing at University of Michigan.