UNC-CH Physics and Astronomy Prelim

Jake Brooks

“Actuating Surface Attached Post (ASAP) Arrays as Pumps and Swimmers in Low Reynolds Number Environments”

Cilia are slender organelles protruding from the surface of many biological cells. These structures are present throughout the body and serve to drive fluid flow over the tissue surface. These cilia have inspired research in micro-actuators to study fluid transport and mixing phenomena in a low Reynolds number environment. We have developed a process for mold-and-release fabrication of actuating surface-attached post (ASAP) arrays with cross-sectional areas of less than 1 square micron at aspect ratios as high as 23:1. We also have control over the cross-section shape of individual posts and lattice parameters of their lateral organization. Our protocol includes centrifugal deposition of magnetic material into the molds, which yields micropillars with paramagnetic tips. The ASAP can then be actuated with a dynamic magnetic that allows us to have predictable control over the actuation pattern of a given ASAP geometry. This high level of design control gives us freedom to tailor ASAP arrays to study fluid pumping, fluid mixing, and particle capture applications. We are also working on ASAP-driven synthetic micro-swimmers. Fluid pumping experiments will guide ASAP micro-swimmer design, as the swimming problem can be thought of as a different reference frame of the pumping problem. We are expanding the applications of the ASAP platform to include dynamic topography-independent cell motility substrates by immersing ASAP with lower modulus compliant gel. These substrates have well-defined changes in stiffness directly from the ASAP geometry. By actuating ASAP within this soft material, we create localized stresses to individual cells to induce a cell response.

A public version of this event will be held via Zoom: https://unc.zoom.us/j/93985408948?from=addon