Improvement of rectification effects in diffuser/nozzle structures with viscoelastic fluids

Abstract

This paper reports the improvement of rectification effects in diffuser/nozzle structures with viscoelastic fluids. Since rectification in a diffuser/nozzle structure with Newtonian fluids is caused by inertial effects, micropumps based on this concept require a relatively high Reynolds numbers and high pumping frequencies. In applications with relatively low Reynolds numbers, anisotropic behavior can be achieved with viscoelastic effects. In our investigations, a solution of dilute polyethylene oxide was used as the viscoelastic fluid. A microfluidic device was fabricated in silicon using deep reactive ion etching. The microfluidic device consists of access ports for pressure measurement, and a series of ten diffuser/nozzle structures. Measurements were carried out for diffuser/nozzle structures with opening angles ranging from 15°to 60°. Flow visualization, pressure drop and diodicity of de-ionized water and the viscoelastic fluid were compared and discussed. The improvement of diodicity promises a simple pumping concept at low Reynolds numbers for lab-on-a-chip applications.

Relaxation time of dilute polymer solutions: A microfluidic approach

“…Moreover, the elastic instability was found to depend on the rheological parameters of the polymer solution. Dilute polymer solutions were also investigated in various extensional microfluidic devices with cross-slot and expansioncontraction geometries [14][15][16][17][18][19][20].…”

Is microrheometry affected by channel deformation?

“…9 When dealing with PEO dilute solutions, however, the fluid can recirculate within the device inlet giving rise to vortex formation. 29 Nevertheless, due to the relatively small designed angle at the inlet a ¼ 20 , and in the range of Deborah number investigated, we can safely assume that no recirculation phenomena are present. In addition, we did not observe an anomalous particle distribution at the channel entrance.…”

Behavior of microdroplets in diffuser/nozzle structures

“…Nguyen and Huang (2001) used this concept to design and fabricate a micropump based on printed circuit board (PCB) technology. Recently, Groisman and Quake (2004) and Nguyen et al (2008) reported that the rectification effect is even stronger if a viscoelastic fluid is employed instead of a Newtonian fluid. To the best knowledge of the authors, none of the previous works investigated multiphase flow in a serial diffuser/nozzle structure.…”