Abstract
We demonstrate an acoustic platform for micro-vortexing in disposable polymer microfluidic chips with small-volume (20 μl) reaction chambers. The described method is demonstrated for a variety of standard vortexing functions, including mixing of fluids, re-suspension of a pellet of magnetic beads collected by a magnet placed on the chip, and lysis of cells for DNA extraction. The device is based on a modified Langevin-type ultrasonic transducer with an exponential horn for efficient coupling into the microfluidic chip, which is actuated by a low-cost fixed-frequency electronic driver board. The transducer is optimized by numerical modelling, and different demonstrated vortexing functions are realized by actuating the transducer for varying times; from fractions of a second for fluid mixing, to half a minute for cell lysis and DNA extraction. The platform can be operated during 1 min below physiological temperatures with the help of a PC fan, a Peltier element and an aluminum heat sink acting as the chip holder. As a proof of principle for sample preparation applications, we demonstrate on-chip cell lysis and DNA extraction within 25 s. The method is of interest for automating and chip-integrating sample preparation procedures in various biological assays.
Highlights
Vortexing is a standard method for manual sample preparation in biotechnology research and clinical laboratories, e.g. when re-suspending a pellet of centrifuged micro-beads suspended in a test tube
We demonstrate an ultrasound-based multi-purpose micro-vortexing platform designed for sample preparation in disposable polymer microfluidic chips with simple channel geometries
In the last set of experiments, we investigate whether our acoustic micro-vortexing method can be used for cell lysis as well as integrated DNA extraction
Summary
Vortexing is a standard method for manual sample preparation in biotechnology research and clinical laboratories, e.g. when re-suspending a pellet of centrifuged micro-beads suspended in a test tube. Cell lysis has previously been performed in miniature chambers by various techniques (Nan et al 2014) including acoustic methods, e.g., lysis of bacterial spores by either sonication at 40 kHz in a cartridge combined with a filter (Taylor et al 2001), or by sonication at 1.4 MHz with a dual-transducer system submerged in a water tank (Warner et al 2009). Both these systems have rather complex physical structure that makes them difficult to integrate in microfluidics. Chip-integrated acoustic methods for cell lysis have been demonstrated by, e.g., bulk acoustic waves in a
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