Microfluidic Air-Liquid Cavity Acoustic Transducers for On-Chip Integration of Sample Preparation and Sample Detection

Abstract

A simple low-cost yet versatile microtechnology platform is demonstrated as capable of performing a variety of microfluidic actuation functions including on-chip pumping, mixing, cell/particle sorting, and sample extraction. This technology termed air-liquid cavity acoustic transducers (ALCATs) uses trapped air bubbles as the functional elements. When an external acoustic energy source is applied to the device, the trapped bubbles oscillate, generating acoustic streaming within the fluid. By controlling their relative position and angle with the liquid channel/chamber, the ALCAT can push away or pull in the surrounding liquid contents and its contained particulates. In this report, we provide a general introduction of the ALCAT microtechnology platform and its application to enhancing biomolecular assays.

Versatile hybrid acoustic micromixer with demonstration of circulating cell-free DNA extraction from sub-ml plasma samples

“…configuration, the system can provide efficient mixing from no flow rate (static flow reported earlier) up to a total flow rate of 200 μl min −1 (12 ml h −1 ), which is significantly higher than results from previous similar devices. 14,15,[20][21][22][23] The system geometrical configuration could be optimised to enable the homogenisation of higher flow rates.…”

“…Researchers have previously developed a variety of highly efficient bubble-based micromixers, [13][14][15][16][17][18][19][20][21][22][23][24] but most of them are fabricated using (SU-8 mould) soft-lithography, a highly manual and laborious technique that requires specialised equipment and is difficult to mass-manufacture. Furthermore, the total cost of microfluidic chips fabricated using this technique is usually underestimated and can be unaffordable for many research groups.…”

“…Furthermore, the total cost of microfluidic chips fabricated using this technique is usually underestimated and can be unaffordable for many research groups. 25 Other authors have investigated the use of thermoplastics and other fabrication techniques, such as CNC micro-milling, 17,18 laser cutting 21 and hot embossing, 22 however they share a common limitation along with the soft-lithography-based devices: the actuator (piezoelectric transducer) has to be glued using permanent adhesives to the bulk of the chip, impeding the individual control of more than one micromixer per chip and complicating the assembly process.…”

Microvalves and Micropumps for BioMEMS

“…However, this pump design utilized large channels (1.6 × 1.6 mm 2 ) and could only pump against a maximum backpressure of 0.13 Pa. Andrea Prosperetti's group has demonstrated the pumping of fluid through millimeter-scale tubes based on the growth and collapse of bubbles [98][99][100]. More recently, Abraham Lee's group applied similar concepts into a planar microfluidic format, creating a lateral cavity acoustic transducer (LCAT) [101][102][103]. The LCAT uses bubbles trapped in the lateral cavities of their device during fluid filling, which are then excited by the acoustic field generated by an external piezoelectric buzzer ( Figure 33).…”

LCAT pump optimization for an integrated microfluidic droplet generator

“…Based on this mechanism of microstreaming flow, we developed the lateral-cavity-acoustic-transducer (LCAT) technique (Tovar and Lee 2009), and exploited it to pump aqueous liquids (Tovar et al 2011), shorten the incubation period of protein assay (Lee et al 2010), extract plasma from whole blood (Doria et al 2011), switch particles (Patel et al 2012), and shear DNA (Okabe and Lee 2013) in simple microfluidic devices. Samples within the LCAT chip can be manipulated via the microstreaming flow induced by acoustic waves from piezoelectric transducers (PZTs) that are located beneath the chip and energized through a battery or USB powered circuit (Tovar et al 2011).…”