Rapid prototyping and parametric optimization of plastic acoustofluidic devices for blood–bacteria separation

Abstract

Acoustic manipulation has emerged as a versatile method for microfluidic separation and concentration of particles and cells. Most recent demonstrations of the technology use piezoelectric actuators to excite resonant modes in silicon or glass microchannels. Here, we focus on acoustic manipulation in disposable, plastic microchannels in order to enable a low-cost processing tool for point-of-care diagnostics. Unfortunately, the performance of resonant acoustofluidic devices in plastic is hampered by a lack of a predictive model. In this paper, we build and test a plastic blood-bacteria separation device informed by a design of experiments approach, parametric rapid prototyping, and screening by image-processing. We demonstrate that the new device geometry can separate bacteria from blood while operating at 275% greater flow rate as well as reduce the power requirement by 82%, while maintaining equivalent separation performance and resolution when compared to the previously published plastic acoustofluidic separation device.

Whole-System Ultrasound Resonances as the Basis for Acoustophoresis in All-Polymer Microfluidic Devices

“…However, partly due to the lack of good theoretical understanding, it has proven difficult to make good all-polymer BAW-devices for acoustofluidics. But a few results for such devices have been published, including focusing of polymer beads [32][33][34][35], lipids [32], and red blood cells [33,36], as well as blood-bacteria separation [37] and purification of lymphocytes [38].…”

Microparticle Acoustophoresis in Aluminum-Based Acoustofluidic Devices with PDMS Covers

“…Following the results of Ref. [17], we investigate numerically, if better acoustophoresis, quantified by the focusing figure of merit F defined in Equation (15), is obtained by exciting the half-wave resonance mode (which is anti-symmetric around the nodal plane at y = 0). This is achieved by splitting the top electrode and applying an anti-symmetric ac voltage, as sketched in Figure 4 for a device with a split-gap of size 50 µm × 40 µm cut into the top surface of the Pz26 transducer.…”

“…Figure 4, as a function of the actuation frequency f and the thickness H pd of the PDMS cover. The area of the points is proportional to the focusing figure of merit F defined in Equation (15). The "A " marks the resonance mode for H pd = 1.5 mm as in mode "S" of Figure 3.…”

“…Simple mass-produced glass capillary tubes have been used for trapping of microparticles [2][3][4][5][6][7] and even nanoparticles [8,9]. The first attempts of using polymer-based devices have been published showing applications such as focusing of polymer beads [10][11][12][13], lipids [10], and red blood cells [11,14], as well as blood-bacteria separation [15] and purification of lymphocytes [16]. Although a cheaper material, polymers are difficult to use in acoustofluidics due to their low acoustic contrast relative to water, but recently it was shown how to circumvent this problem by use of the whole-system-resonance principle [17].…”

“…we show one example of plotting the focusing figure of merit F of Equation(15) as a function of frequency f , here for the specific case of H top = H bot = 110 µm. The strongest resonance is found at f = 2.302 MHz and is marked "B".…”