Tuned-in flow control

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Original Entry by Che-Hang Yu, AP225 Fall 2009

Overview

Title: Microfluidics: Tuned-in flow control

Author: Howard A. Stone

Journal: Nature Physics 5, 178 - 179 (2009)

Subject Categories: Fluid dynamics; Electronics, photonics and device physics


Summary

In order to eliminate the bulky external pump to control the flow of liquids in a microfluidic channel, designing microfluidic circuits to selectively control the flow of multiple different fluids based on the analogical idea to the electrical circuit by Lesile et al. is presented in this paper. This approach can help reduce the amount of equipments to operate a microfluidic systems, and therefore improve their portability and widen their applicability.

Taking the advantage of the elastic response of certain soft materials, Lesile et al. successfully introduce multiple elememts in series to build the frequency-dependent microfluidic circuit. This approach is inspired by the electrical circuit theoty. For example, when a resistance, R, is jointed with a capacitance, C, their combined response is frequency-dependent, and their characteristic frequency is 1/(RC). Besides, a analogical concept from a diode is used to provide a d.c. component to a.c. forcing. The microfluidic analogue of resistance comes from the viscus resistanece of the flow channel and also from the viscosity of fluid. The fluid equivalnent of capacitance results from the expansion and constraction of the elastic reservoirs, like a water balloon to hold varying amounts of liquid. Lesile et al. also introduce the pressure-sensitive valve as a microfluidic equivalent of diode to provide a net flow.