Soft Microbots for in vivo Transport

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The field of microrobotics seeks to develop very small machines capable of performing tasks that cannot currently be accomplished with traditional instruments. Often targeted for biomedical applications within the body, microrobots (microbots) could be used to deliver chemotherapeutic drugs to specific locations to treat cancer or to break up blockages within blood vessels as in the case of stroke or in heart diseases. Challenges remain however both in fabricating microbots and powering them, especially when biocompatible materials are desired. This award will study and test the use of soft liquid microbots, created with a magnetic shell that allows directed rolling with application of an external magnetic field. Fabricated using emulsion-based techniques, this approach allows for easy synthesis, ready control, enhanced biocompatibility, and efficient drug delivery. The motion of these soft microbots over surfaces is different from their rigid counterparts. This award will investigate the traction and movement of soft microbots over a variety of hard and soft surfaces under the applied magnetic fields to enhance and optimize their movement for targeted applications. Microbot locomotion is challenging because of the reversible nature of microscale fluid flow, a limitation that can be overcome by breaking flow-field symmetry with a nearby surface. When translating along an interface, rolling microbots travel faster than sliding ones because of their significantly smaller friction coefficient. This phenomenon has been utilized with rotating wheel-shaped microbots for targeting occlusive clots located in small arteries, delivering drugs, and inducing lysis via a combination of mechanical and biochemical action. Recent studies, however, have used rigid microbots that roll inefficiently with significant slip and difficulty navigating confined environments. Addressing these drawbacks, this award proposes the use of soft microbots based on superparamagnetic Pickering emulsions. They will provide enhanced biocompatibility and large drug encapsulation capacity and can alter their shape to enhance traction by accommodating interactions with viscoelastic in vivo environments. Soft Pickering emulsion microbots will be fabricated and the nature of their transport on various surfaces and in various environments will be investigated. The ability of these soft microbots to transport and deliver drugs within various biomimetic environments will also be explored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.