Microfluidic Separation and Enrichment of Escherichia coli by Size Using Viscoelastic Flows

Bacteria that attach to surfaces aggregate in a hydrated polymeric matrix of their own synthesis to form biofilms. Formation of these sessile communities and their inherent resistance to antimicrobial agents are at the root of many persistent and chronic bacterial infections. Studies of biofilms have revealed differentiated, structured groups of cells with community properties. Recent advances in our understanding of the genetic and molecular basis of bacterial community behavior point to therapeutic targets that may provide a means for the control of biofilm infections.

The manipulation of fluids in channels with dimensions of tens of micrometres--microfluidics--has emerged as a distinct new field. Microfluidics has the potential to influence subject areas from chemical synthesis and biological analysis to optics and information technology. But the field is still at an early stage of development. Even as the basic science and technological demonstrations develop, other problems must be addressed: choosing and focusing on initial applications, and developing strategies to complete the cycle of development, including commercialization. The solutions to these problems will require imagination and ingenuity.

Despite the common wisdom that inertia does not contribute to microfluidic phenomena, recent work has shown a variety of useful effects that depend on fluid inertia for applications in enhanced mixing, particle separation, and bioparticle focusing. Due to the robust, fault-tolerant physical effects employed and high rates of operation, inertial microfluidic systems are poised to have a critical impact on high-throughput separation applications in environmental cleanup and physiological fluids processing, as well as bioparticle focusing applications in clinical diagnostics. In this review I will discuss the recent accelerated progress in developing prototype inertial microfluidic systems for a variety of applications and attempt to clarify the fundamental fluid dynamic effects that are being exploited. Finally, since this a nascent area of research, I will suggest some future promising directions exploiting fluid inertia on the microscale.