A Pumpless Acoustofluidic Platform for Size-Selective Concentration and Separation of Microparticles

Abstract

We have designed a pumpless acoustofluidic device for the concentration and separation of different sized particles inside a single-layered straight polydimethylsiloxane (PDMS) microfluidic channel. The proposed device comprises two parallel interdigitated transducers (IDTs) positioned underneath the PDMS microchannel. The IDTs produce high-frequency surface acoustic waves that generate semipermeable virtual acoustic radiation force field walls that selectively trap and concentrate larger particles at different locations inside the microchannel and allow the smaller particles to pass through the acoustic filter. The performance of the acoustofluidic device was first characterized by injecting into the microchannel a uniform flow of suspended 9.9 μm diameter particles with various initial concentrations (as low as 10 particles/mL) using a syringe pump. The particles were trapped with ∼100% efficiency by a single IDT actuated at 73 MHz. The acoustofluidic platform was used to demonstrate the pumpless separation of 12.0, 4.8, and 2.1 μm microparticles by trapping the 12 and 4.8 μm particles using the two IDTs actuated at 73 and 140 MHz, respectively. However, most of the 2.1 μm particles flowed over the IDTs unaffected. The acoustofluidic device was capable of rapidly processing a large volume of sample fluid pumped through the microchannel using an external syringe pump. A small volume of the sample fluid was processed through the device using a capillary flow and a hydrodynamic pressure difference that did not require an external pumping device.

Open source acoustofluidics

“…[1][2][3][4][5][6] Acoustofluidic technologies, which combine acoustics and microfluidics, have demonstrated promising potential for the design and integration of POC technologies. [7][8][9][10][11][12] Acoustofluidic technologies have the capability of interacting with fluidic environments in a contact-free and precise manner; 13,14 this capability has been leveraged to achieve many useful applications in biology and medicine including sample concentration, 15,16 sample mixing, [17][18][19] sample delivery, 20 and cell/particle separation. 7,21,22 While all of these factors make acoustofluidic devices excellent candidates for use at the POC, one of the major draw-backs associated with acoustofluidic devices is the additional equipment needed to operate effectively; commonly, acoustofluidic devices rely on bulky and expensive function generators for signal generation, amplifiers for increasing the signal power, syringe pumps for precise fluid manipulation, and microscopes for microscale imaging.…”

“…[7][8][9][10][11][12] Acoustofluidic technologies have the capability of interacting with fluidic environments in a contact-free and precise manner; 13,14 this capability has been leveraged to achieve many useful applications in biology and medicine including sample concentration, 15,16 sample mixing, [17][18][19] sample delivery, 20 and cell/particle separation. 7,21,22 While all of these factors make acoustofluidic devices excellent candidates for use at the POC, one of the major draw-backs associated with acoustofluidic devices is the additional equipment needed to operate effectively; commonly, acoustofluidic devices rely on bulky and expensive function generators for signal generation, amplifiers for increasing the signal power, syringe pumps for precise fluid manipulation, and microscopes for microscale imaging. 13,14,17,23,24 Although acoustofluidic devices are presented as simple solutions to complex problems, each of these external systems introduce operational constraints that hinder the use of acoustofluidic technology at the POC, making the technology less approachable to researchers and clinicians who could benefit from it.…”

“…The system is based on the readily available Arduino prototyping platform, and allows for the integration of the key components for acoustofluidic device operation. We use this open source acoustofluidic system to operate several flexural wave based devices, 7,21 achieving functions including rotation of cells and microorganisms, and operation of a device which has the potential to achieve viscous sample liquefaction, in a portable manner. Additionally, using an open source syringe pump design, we also achieved size-based portable particle separation, using low-frequency flexural waves.…”

Exploring contraction–expansion inertial microfluidic‐based particle separation devices integrated with curved channels

“…Generally, these methods can be divided into two main categories: active and passive. Using active methods, an external force field in electrical, magnetic, and acoustic forms is applied for separation. With passive methods, there is no external factor involved in the separation process .…”

A Handy Liquid Metal Based Non-Invasive Electrophoretic Particle Microtrap

“…Cole et al [ 12 ] demonstrated a kind of DEP microfluidics that combined the flexibility and programmability of microliter dispensing with the scalability and single-cell sensitivity of flowing droplet microfluidics. Acoustic and optical forces have also been utilized for particle [ 13 , 14 ] and droplet [ 15 , 16 , 17 ] manipulation. Optical tweezers [ 18 ] are a typical tool for single cell manipulation, which use a highly focused laser beam to provide an attractive or repulsive force.…”