Geometric Patterning: Controlling Small-Scale Flows with Repeated Microstructures
Brian Kirby, Cornell University, Ithaca, USA
Microfluidic devices offer many opportunities to study fluid transport and the physics of small-scale objects, including biological cells, microparticles, and nanomaterials. The ability to control the microstructure of microdevices, in particular, enables facile control of forces and flows in these systems. We present two example projects in which engineered microstructures enable novel analysis of biological systems. In the first, we demonstrate that devices with patterned ridges can combine two fields - one, a flow field that carries particles, and two, a dielectrophoretic field that causes particles to follow the ridge pattern when certain thresholds are satisfied. With this framework, we present a dielectric spectrometer that characterizes cells based on their dielectric response, which has been used to characterize membrane properties in Mycobacterium, the causative agent of tuberculosis and leprosy. In the second project, we demonstrate that devices with controlled obstacle arrays combine a flow field with an infinitely undersampled "sampling function" associated with collisions with obstacles, leading to collision modes and collision rates that can be predicted with undersampling theories from signal processing. These theories allow for simple prediction of performance, and allow rare cells (e.g., circulating tumor cells) to be captured from patient blood. I will present results obtained with the GEDI (geometrically enhanced diferential immunocapture) microdevice and show how rare cell capture enables genetic and functional analysis of patient cancer cells to monitor chemotherapeutic response and cancer evolution in real time.