Lateral air cavities for microfluidic pumping with the use of acoustic energy

Abstract

An acoustically activated micropump is fabricated and demonstrated using a single step lithography process and an off-chip acoustic energy source. Using angled lateral cavities with trapped air bubbles, acoustic energy is used to oscillate the liquid-air interface to create a fluidic driving force. The angled lateral cavity design allows for fluid rectification from the first-order pulsatile flow of the oscillating bubbles. The fluid rectification is achieved through the asymmetrical flow produced by the oscillating interface generating fluid flow away from the lateral cavity interface. Simulation and experimental results are used to develop a pumping mechanism that is capable of driving fluid at pressures of 350 Pa. This pumping system is then integrated into a stand-alone battery operated system to drive fluid from one chip to another.

Particle migration and sorting in microbubble streaming flows

“…Such microbubbles have been used in a number of microfluidics applications including transport and trapping, 12,13 micro-mixing, 14,15 and cell deformation and lysis. 16 While the bubbles are actively driven to oscillation, the particles in the bubble streaming flows experience size-dependent effects due to flow forces only, allowing us to trap and sort them passively, without the use of any external forces or small-scale geometric features.…”

Theory and experiment on resonant frequencies of liquid-air interfaces trapped in microfluidic devices

“…In recent years, researchers have expanded the functionalities of bubble-based microfluidic systems by trapping bubbles over solid structures. [4][5][6][7][8][9][10] These trapped-bubbles can have prescribed sizes, locations, and shapes and thus offer superior performance. For example, microfluidic devices using bubbles trapped across horseshoe-shaped structures (HSS) have effectively demonstrated several distinct functionalities (such as mixing, gradient generation, and enzymatic reaction).…”

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).…”

“…As long as the surface tension forces on the bubble remain greater than the maximum resonance amplitude, the bubbles stay trapped in place for the duration of pump operation. A maximum pumping pressure of 350 Pa was demonstrated in a device using 80 sets of 15° angled cavity pairs and a square-wave driving signal of 35 kHz and 25 V pp [103]. …”