Applied Mathematics Seminar | Henry Shum, Harnessing Chemical Reactions for Novel Functionality in Microfluidic Systems

Tuesday, January 17, 2017 2:30 pm - 2:30 pm EST (GMT -05:00)

MC 6460


Dr. Henry Shum 
Department of Chemical &  Petroleum Engineering | University of Pittsburgh


Harnessing Chemical Reactions for Novel Functionality in Microfluidic Systems


Chemical reactions are essential for biological processes, from the directed transport of molecules within a cell to the carefully orchestrated growth and morphological development of an organism. As we expand our experimental capabilities in nanofabrication and synthetic biology, it is becoming possible to construct artificial microscale systems that incorporate biological components or function on the same principles as their living analogues. Here, we examine two potential applications of chemical reactions in synthetic systems, namely, to generate tunable fluid flow fields in an enclosed microfluidic device and to design "artificial cells" that communicate with each other. Recent experiments demonstrated that an immobilised patch of enzyme could function as a pump, generating persistent flows in a small, fluid-filled chamber. Experimental evidence suggested that the fluid motion was due to buoyancy effects. We develop a mathematical model to describe the changes in fluid density in the chamber due to a generic chemical reaction. Unexpectedly, we find that non-trivial, time-dependent fluid flows can be generated even under the assumption that the reaction rate is constant. This raises the intriguing possibility of a new paradigm for achieving complex flow and particle transport in microfluidic devices. A network of enzymatic pumps could autonomously and dynamically regulate flow to transport cargo "intelligently". Before we can design such systems, however, we must understand the more general and fundamental problem of chemical reaction networks in spatially extended systems. Building on studies of gene regulatory network dynamics based on ordinary differential equations, we model the behaviour of colonies of artificial cells that act as localised sources of chemicals. We show that imposing an oscillatory reaction network known as the repressilator to regulate chemical production in the cells endows them with the capability to collectively gauge the population size and density of the colony, a common ability in microorganisms referred to as quorum sensing. Thus, simple physical and chemical processes can be harnessed to attain life-like, biomimetic functionality in synthetic systems.