Active pneumatic control of centrifugal microfluidic flows for lab-on-a-chip applications

Abstract

This paper reports a novel method of controlling liquid motion on a centrifugal microfluidic platform based on the integration of a regulated pressure pump and a programmable electromechanical valving system. We demonstrate accurate control over the displacement of liquids within the system by pressurizing simultaneously multiple ports of the microfluidic device while the platform is rotating at high speed. Compared to classical centrifugal microfluidic platforms where liquids are solely driven by centrifugal and capillary forces, the method presented herein adds a new degree of freedom for fluidic manipulation, which represents a paradigm change in centrifugal microfluidics. We first demonstrate how various core microfluidic functions such as valving, switching, and reverse pumping (i.e., against the centrifugal field) can be easily achieved by programming the pressures applied at dedicated access ports of the microfluidic device. We then show, for the first time, that the combination of centrifugal force and active pneumatic pumping offers the possibility of mixing fluids rapidly (~0.1 s) and efficiently based on the creation of air bubbles at the bottom of a microfluidic reservoir. Finally, the suitability of the developed platform for performing complex bioanalytical assays in an automated fashion is demonstrated in a DNA harvesting experiment where recovery rates of about 70% were systematically achieved. The proposed concept offers the interesting prospect to decouple basic microfluidic functions from specific material properties, channel dimensions and fabrication tolerances, surface treatments, or on-chip active components, thus promoting integration of complex assays on simple and low-cost microfluidic cartridges.

Siphon-Induced Droplet Break-Off for Enhanced Mixing on a Centrifugal Platform

“…Can require specific chemical reagents stored on disc. [73,76,77] Wall deformation Mixing is enhanced by deforming chamber walls to induce liquid movement.…”

“…Examples for passive mixing principles are bas/relief structures incorporated in the channel walls to induce advection in a liquid flow [63] and multi-lamination of flow [64], e.g., through split-and-recombine strategies [65,66].Mixing principles using the specific effects on centrifugal lab-on-a-disc platforms [67] include Coriolis-force induced split-and-recombine [68], advection [69], reciprocating flow induced by centrifugo-pneumatic pumping [52,70], mixing enhanced by the Euler force through periodically changing angular acceleration [71,72] and/or magnetic beads [51], mixing by use of chemically generated bubbles [73], and mixing enhanced by deformation of soft chamber walls [74,75]. Mixing can also be enhanced through external pumping such as provision of external air sources [76,77]. These technologies are critically appraised in Table 1.In this paper we present and characterize a passive, batch-mode, siphon-based mixer on a centrifugal microfluidic lab-on-a-disc platform.…”

Lumped-Element Modeling for Rapid Design and Simulation of Digital Centrifugal Microfluidic Systems

“…To switch a valve, these "lab-frame" elements interact with the disc cartridge, either at rest or during spinning. The actuation can be powered by pneumatic pressure sources [8][9], heating of phase-change materials [10][11][12][13], or even varying the chip orientation with respect to the radial direction [14][15][16]. While these may provide enhanced and more flexible control, these active valving mechanisms typically involve additional instrumentation, maintenance, cost, and susceptibility to failure.…”

Flow Control Based on Constant Pressure Microfluidic Pump System

“…The core technique of microfluidic driving device is its injection mode and the corresponding driving mode. Using different theories people have invented various kinds of microfluidic driving and control technology that taking advantage of pressure, electricity, heat, surface tension, centrifugal force and so on [4][5][6].…”