Reciprocating flow-based centrifugal microfluidics mixer

Abstract

Proper mixing of reagents is of paramount importance for an efficient chemical reaction. While on a large scale there are many good solutions for quantitative mixing of reagents, as of today, efficient and inexpensive fluid mixing in the nanoliter and microliter volume range is still a challenge. Complete, i.e., quantitative mixing is of special importance in any small-scale analytical application because the scarcity of analytes and the low volume of the reagents demand efficient utilization of all available reaction components. In this paper we demonstrate the design and fabrication of a novel centrifugal force-based unit for fast mixing of fluids in the nanoliter to microliter volume range. The device consists of a number of chambers (including two loading chambers, one pressure chamber, and one mixing chamber) that are connected through a network of microchannels, and is made by bonding a slab of polydimethylsiloxane (PDMS) to a glass slide. The PDMS slab was cast using a SU-8 master mold fabricated by a two-level photolithography process. This microfluidic mixer exploits centrifugal force and pneumatic pressure to reciprocate the flow of fluid samples in order to minimize the amount of sample and the time of mixing. The process of mixing was monitored by utilizing the planar laser induced fluorescence (PLIF) technique. A time series of high resolution images of the mixing chamber were analyzed for the spatial distribution of light intensities as the two fluids (suspension of red fluorescent particles and water) mixed. Histograms of the fluorescent emissions within the mixing chamber during different stages of the mixing process were created to quantify the level of mixing of the mixing fluids. The results suggest that quantitative mixing was achieved in less than 3 min. This device can be employed as a stand alone mixing unit or may be integrated into a disk-based microfluidic system where, in addition to mixing, several other sample preparation steps may be included.

Pneumatic pumping in centrifugal microfluidic platforms

“…Other applications of pneumatic pumping include its use in rapid mixing of fluids in microsystems (Kellogg and Carvalho 2003;Noroozi et al 2009). In Noorozi et al, the authors showed efficient mixing by oscillating fluids through a mixing chamber by repeated pneumatic pumping and centrifugation (Noroozi et al 2009).…”

“…In Noorozi et al, the authors showed efficient mixing by oscillating fluids through a mixing chamber by repeated pneumatic pumping and centrifugation (Noroozi et al 2009). Their system addresses a key issue in microfluidics as micromixing becomes difficult in the microdomain due to low Reynolds numbers and hence predominately laminar flow.…”

Phase-selective graphene oxide membranes for advanced microfluidic flow control

“…Centrifugal microfluidics offers the benefit that the force field can be accurately controlled over several orders of magnitude by a spindle motor 1 . Such 'Lab-on-aDisc' (LoaD) platforms have emerged as a highly useful tool in biomedical diagnostics because many of the necessary laboratory unit operations (LUOs) in bioanalysis, such as pumping 2 , plasma extraction 3 , mixing 4 , and metering 5 , can be fully automated and implemented. Liquid-handling steps can then be controlled by running a designated spin-frequency protocol to modulate interactions between on-disc liquids and microstructures 1 .…”

Euler force actuation mechanism for siphon valving in compact disk-like microfluidic chips

“…To avoid the surface treatment and external manipulation of plastics, several new actuation mechanisms have been proposed to optimize the use of real estate on a CD-like chip. These new mechanisms include pneumatic pumping, 6,7 suction-enhanced, 8 and supernatant decanting methods. 9 As pointed out in Ref.…”