Biomedical micro- and nanofluidic systems combined with surface forces.

Abstract

Recent advances in micro- and nanofluidics offer new opportunities to develop novel analytical tools for biomedical applications by providing unprecedented capabilities to create structures, patterns, and fluid flows that enable precise sample handling and analysis on the length scale of individual cells or molecules. Development of successful micro- and nanofluidic bioanalytical systems, however, requires fundamental understanding and control of scaling effects introduced by the drastic reduction in the size of fluidic channels. The most important consequence of using micro- and nanofluidic devices is a tremendous increase in the surface-to-volume ratio, which makes surface forces such as surface tension, van der Waals forces, surface adhesion, and electrical forces play a dominant role in governing transport phenomena. The work described in this dissertation presents multidisciplinary efforts directed towards the development of several new types of micro- and nanofluidic systems whose operational mechanisms are enabled by or involve the use of surface forces to create and manipulate different kinds of fluid flows in polymeric micro- and nanofluidic channels for analysis of cells, biomolecules, and functional micro- and nanoparticles. Specifically, we demonstrate unique analytical capabilities provided by engineering of surface chemistry, geometry, and mechanics of elastomeric micro- and nanofabricated structures through five different types of biomedical analysis systems: (i) surface tension-driven microdevices based on air-liquid two-phase microfluidics for inexpensive and volume-efficient flow cytometric analysis of cells, (ii) dynamic and reversible fluidic switching of high-speed air-liquid two-phase flows using electrowetting-assisted flow pattern change for development of multiphase biochemical systems and cell/particle sorting, (iii) compartmentalized three-dimensional <italic>in vitro</italic> microfluidic airway systems for experimental investigation of acoustically-detectable mechanical injury of airway epithelial cells during airway reopening, (iv) reconfigurable elastomeric nanochannels for tunable nanofluidic manipulation of fluids, nanoparticles, DNA, and polymers, and (v) self-contained and simple microfluidic sorting devices with hydrodynamic separation amplification capable of gravity-driven and size-dependent sorting of particles and droplets for biomedical applications.