Surface-enabled Manufacturing of Nanowheels for Metamaterial and Nanomotor Applications

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Colloidal assembly is envisioned as an effective method for the bottom-up fabrication of nanostructures for a broad range of applications from sensors to photonics to biomedical devices. This award investigates the application of rotating magnetic fields to paramagnetic nanoparticle colloids to form wheel-like clusters well suited for assembly into metamaterials and nanomotors. The process involves manipulating interparticle interactions and thus controlling colloidal structure formation. This project shows a microfluidic pathway to fabricating complex three-dimensional nanowheels. Potential applications of the nanowheels are in building optical metamaterials and disrupting bacterial biofilms. One potential near-term benefit of nanowheels and nanomotors is their use in medicine. Colloidal nanowheels can ablate blood clots using a physiochemical mechanism that results in dissolution rates significantly higher than clot dissolving drugs. Thus, the project outcomes potentially impact national health and well-being. The research on nanowheel manufacturing and translation is integrated with education and outreach programs to inspire young students in the field of colloid and interfacial science. Research results are incorporated into undergraduate and graduate courses. Plans are to enhance diversity in research programs by involving undergraduate students and recruiting talented underrepresented high school students and mentor them toward university study in science and engineering.Many desired colloidal nanostructures are inaccessible because of thermodynamic and kinetic constraints on their assembly and separation from the mixture. This project overcomes these limitations and shows a microfluidic pathway to fabricating complex three-dimensional nanowheels of different size, shape and composition. The research work takes advantage of the nanowheels' unique rolling behavior on topographically patterned surfaces to fractionate them into purified streams based on size and shape. The project's experimental framework, inspired by rotation of nanowheels and their interaction with properly designed roads, provides a transformative route to assemble and fractionate colloidal clusters efficiently. The underlying nanowheel rotation mechanism that exists at the interplay of fluid mechanics, field directed assembly, and tribology represents a significant advancement in the field of colloidal assembly. The outcome of these studies is a new assembly approach that accelerates translation of colloidal assembly into practical applications.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.