UNC-CH Physics and Astronomy Master’s Talk

Jacob Brooks

“Actuating Surface Attached Post (ASAP) Arrays: The Next Generation”

Biological cilia are slender organelles protruding from the surface of several different kinds of cells. These structures are fairly ubiquitous throughout the body and in most cases serve to drive fluid flow over the cell surface. These cilia have inspired research in micro-actuators that serve as an invaluable tool for studying fluid transport and mixing phenomena in a low Reynolds number environment. A current challenge in the field is the development of artificial cilia platforms (referred to here as actuating surface-attached post, or ASAP, arrays) with low small cross-section while maintaining a high aspect ratio. We have developed a process for mold-and-release fabrication of ASAP arrays with cross-sectional areas as small as 1 square micron at aspect ratios of 10:1 and greater. We have shown control over the cross-section shape of individual posts and the number density of posts in a given area. Another challenge we are continuing to address is homogeneous dispersion of magnetic nanoparticles in silicone polymer that can be cross-linked to form a hard, magnetically-responsive silicone rubber. Molding ASAP from such a material will provide control over magnetic loading of individual posts. Our protocol allows for the fabrication of magnetically-actuatable ASAP arrays with highly controllable design parameters. This freedom enables us to tailor ASAP arrays to study fluid pumping, fluid mixing, and particle capture applications.