Fabrication of a Pneumatic Microparticle Concentrator

Abstract

We developed a microfluidic platform employing (normally open) pneumatic valves for particle concentration. The device features a three-dimensional network with a curved fluidic channel and three pneumatic valves (a sieve valve (Vs) that concentrates particles and two ON/OFF rubber-seal pneumatic valves that block the working fluid). Double-sided replication employing polydimethylsiloxane (PDMS) was used to fabricate the network, channel, and chamber. Particles were blocked by deformation of the Vs diaphragm, and then accumulated in the curved microfluidic channel. The working fluid was discharged via operation of the two ON/OFF valves. After concentration, particles were released to an outlet port. The Vs pressure required to block solid particles varying in diameter was determined based on the height of the curved microchannel and a finite element method (FEM) simulation of Vs diaphragm displacement. Our method was verified according to the temporal response of the fluid flow rate controlled by the pneumatic valves. Furthermore, all particles with various diameters were successfully blocked, accumulated, and released. The operating pressure, time required for concentration, and concentration ratio were dependent on the particle diameter. The estimated concentration percentage of 24.9 µm diameter polystyrene particles was about 3.82% for 20 min of operation.Micromachines 2020, 11, 40 2 of 12 are lifted, and then the trapped cells are released. A microfiltration mechanism of particles using structural deformation of the thin membrane was developed [25]. The beads or cells are trapped at voids formed in the two corners of a microfluidic channel by the structural difference between the pneumatically inflated thin diaphragm and the microfluidic channel with a rectangular cross section. A pneumatic filtration system was also developed for the size-based separation of particles [26]. It consists of the pneumatic micropump for automatic liquid transport and normally closed valves for the separation of the particles. The filtration mechanism is based on adjustable deformation of the flexible membrane, defining the gap between the microchannel and the floating block structure, which determines the maximum diameter of the bead/cell that can pass through the filter structure. An integrated microfluidic device for dynamic trapping and high-throughput patterning of cells using pneumatic microstructures [27] was investigated. There are two kinds of membrane structures, that is, an array of active U-shaped microstructures for dynamic localization of cells and an umbrella structure for protecting trapped cells in the process of rinsing.In general, these methods are suitable for handling a limited number of particles when considering the operating methods and structures of the microfluidic platform. The operation conditions such as the flow rate and the magnitude of the compressed air pressure are carefully controlled to prevent unwanted damage to the cells. Further, additional microstructures are also needed to increase cell tr...

Pneumatically Driven Microfluidic Platform and Fully Automated Particle Concentration System for the Capture and Enrichment of Pathogens

“…Figure b illustrates the structure and operational method of the sieve valve for particle concentration. The curved chamber structure was fabricated using the thermal transfer process of an inflated PDMS diaphragm and bonded to the valve diaphragm. , The valve structure comprises a valve diaphragm, a curved channel and chamber, and an interconnection channel. The antibody-modified microbeads in the working fluid (Qin_a) are blocked by the deformed diaphragm of the sieve valve (V_s) and accumulate in the curved fluid channel.…”

“…Each layer is fabricated using soft lithography, and their surfaces are modified by corona discharge treatment and sequentially bonded . As shown in Figure b, curved structures in the 3D fluid network layer are successfully fabricated using the double-sided replication process of PDMS . The diameter and height of the fluid chamber are 1584 and 188 μm, respectively.…”

“…In addition, it is very hard to collect all beads trapped in the microchannel due to the sticking problem − on the surface of PDMS. Therefore, based on the experimental experience, beads of the size of 10 μm were properly selected and used for the concentration of bacteria and OMVs.…”

“…The valve diaphragm and bottom layer are prepared using the spin-coating and the curing process of liquid PDMS. As a core structure of the microfluidic platform, the double-sided replication process with two SU-8 molds is employed to fabricate the 3D fluidic network with the curved pneumatic valve chambers and microfluidic channels at the front and interconnection channels at the back . The prepared PDMS layers are sequentially bonded using corona discharge treatment.…”

“…A pressure of 100 kPa is applied to the microvalves (V_a, V_p, V_b, V_t, and V_w) to block fluid flow. According to a previous work, 44 all particles with three different diameters (4.16, 8.49, and 24.9 μm) were successfully blocked, accumulated, and released. The operating pressure, time required for concentration, and the concentration ratio were dependent on the particle diameter.…”