Name: pneumatically driven microfluidic platform for micro-particle concentration
Uploaded: 2022-02-01T14:15:00
Description: Watch this Scientific Journal Video about Pneumatically Driven Microfluidic Platform for Micro-Particle Concentration at JoVE.com

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(Ministry of Science and ICT). (No. NRF-2021R1A2C1011380).

1. Designing the microfluidic platform for particle concentration
<ol>
	<li>Design the pneumatic microfluidic platform consisting of one pneumatic valve for fluid flow in the 3D flow network and three pneumatic valves for sieve (Vs), fluid (Vf), and particle (Vp) valve operation (Figure 1). 
	NOTE: Vs blocks concentrate particles from the liquid, and Vf and Vp allow fluid and particle release after concentration. Three pneumatic ports provide compressed air from the f...

<ol>
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This platform provides a simple way to purify and concentrate particles of various sizes. Particles are accumulated and released through pneumatic valve control, and no clogging is observed because there is no passive structure. Using this device, the concentration of particles of three sizes is presented. However, the operating pressure, the time required for concentration, and the rate may vary depending on the device dimensions, particle size magnification, and the pressure at Vs18,<...

Due to the importance of biological analysis, microfluidic and biomedical microelectromechanical systems (BioMEMS) technologies1,2 are used to develop and study devices for the purification and collection of micromaterials2,3,4.&#160;Particle capture is categorized as active or passive. Active traps have been used for external dielectric5, magnetophoretic6, auditory7, visual8, or thermal9 forces acting on independent particles, enabling precise control of their movements. However, an interaction between the particle and external force is required; thus, the throughput is low. In microfluidic systems, controlling the flow rate is very important because the external forces are transmitted to the target particles.
In general, passive microfluidic devices have micropillars in microchannels10,11. Particles are filtered through interaction with a flowing fluid, and these devices are easy to design and inexpensive to manufacture. However, they cause particle clogging in micro-pillars, so more complex devices have been developed to prevent particle clogging12. Microfluidic devices with complex structures are generally suitable for managing a limited number of particles13,14,15,16,17,18.
This article describes a method to fabricate and operate a pneumatically driven microfluidic platform for large particle concentrations that overcomes the shortcomings18 as mentioned above. This platform can block and concentrate particles by deformation and actuation of the thin diaphragm layer of the sieve valve (Vs) plate that accumulates in curved microfluidic channels. Particles accumulate in curved microfluidic channels, and the concentrated particles can separate by discharging the working fluid via the actuation of two PDMS seals on/off valves18. This method makes it possible to process a limited number of particles or concentrate a large number of small particles. Operating conditions such as the magnitude of flow rate and compressed air pressure can prevent unwanted cell damage and increase cell trapping efficiency.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1.5 mm puncture</td>
			<td>Self procduction</td>
			<td>Self procduction</td>
			<td>This puncture was made by requesting a mold maker based on the Miltex&#174; Biopsy Punch with Plunger (15110-15) product.</td>
		</tr>
		<tr>
			<td>4 inch Silicon Wafer/SU-8 mold</td>
			<td>4science</td>
			<td>29-03573-01</td>
			<td>4 inch (100) Ptype silicon wafer/SU-8 mold</td>
		</tr>
		<tr>
			<td>Carboxyl Polystyrene Crosslinked Particle(24.9 &#956;m)</td>
			<td>Spherotech</td>
			<td>CPX-200-10</td>
			<td>Concentrated bead sample1</td>
		</tr>
		<tr>
			<td>Flow meter</td>
			<td>Sensirion</td>
			<td>SLI-1000</td>
			<td>Flow measurement</td>
		</tr>
		<tr>
			<td>High-speed camera</td>
			<td>Photron</td>
			<td>FASTCAM Mini</td>
			<td>Observation of concentration</td>
		</tr>
		<tr>
			<td>Hot plate</td>
			<td>As one</td>
			<td>HI-1000</td>
			<td>heating plate for curing of liquid PDMS</td>
		</tr>
		<tr>
			<td>KOVAX-SYRINGE 10 mL/Syringe</td>
			<td>Koreavaccine</td>
			<td>22G-10ML</td>
			<td>Fill the microfluidic channel with bubble-free demineralized water.</td>
		</tr>
		<tr>
			<td>Laboratory Conona treater/Atmospheric plasma</td>
			<td>Electro-Technic</td>
			<td>BD-20AC</td>
			<td>Chip bonding/atmospheric plasma</td>
		</tr>
		<tr>
			<td>Liquid polydimethylsiloxane, PDMS</td>
			<td>Dow Corning Inc.</td>
			<td>Sylgard 184</td>
			<td>Components of chip</td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Olympus</td>
			<td>IX-81</td>
			<td>Observation of concentration</td>
		</tr>
		<tr>
			<td>PEEK Tubes</td>
			<td>SAINT-GOBAIN PPL CORP.</td>
			<td>AAD04103</td>
			<td>Inject or collect particles</td>
		</tr>
		<tr>
			<td>Polystyrene Particle(4.16 &#956;m)</td>
			<td>Spherotech</td>
			<td>PP-40-10</td>
			<td>Concentrated bead sample3</td>
		</tr>
		<tr>
			<td>Polystyrene Particle(8.49 &#956;m)</td>
			<td>Spherotech</td>
			<td>PP-100-10</td>
			<td>Concentrated bead sample2</td>
		</tr>
		<tr>
			<td>Pressure controller/&#956;flucon</td>
			<td>AMED</td>
			<td>&#956;flucon</td>
			<td>Control of air pressure</td>
		</tr>
		<tr>
			<td>Spin coater</td>
			<td>iNexus</td>
			<td>ACE-200</td>
			<td>spread the liquid PDMS on SU-8 mold</td>
		</tr>
	</tbody>
</table>

pneumatically driven microfluidic platform for micro-particle concentration

The present article introduces a method for fabricating and operating a pneumatic valve to control particle concentration using a microfluidic platform. This platform has a three-dimensional (3D) network with curved fluid channels and three pneumatic valves, which create networks, channels, and spaces through duplex replication with polydimethylsiloxane (PDMS). The device operates based on the transient response of a fluid flow rate controlled by a pneumatic valve in the following order: (1) sample loading, (2) sample blocking, (3) sample concentration, and (4) sample release. The particles are blocked by thin diaphragm layer deformation of the sieve valve (Vs) plate and accumulate in the curved microfluidic channel. The working fluid is discharged by the actuation of two on/off valves. As a result of the operation, all particles of various magnifications were successfully intercepted and disengaged. When this technology is applied, the operating pressure, the time required for concentration, and the concentration rate may vary depending on the device dimensions and particle size magnification.

Figure 8 shows the flow rate of the fluid rates for a four-stage platform operation, as mentioned in Table 2. The first stage is the loading state (a state). The platform was supplied with fluid with all valves open, and the working fluid (Qf) and particles (Qp) are almost identical as the microfluidic channel network exhibits structural symmetry. In the second stage (b state), compressed air was transported to Vs to block the particles, and as the Vs diaphragm deformed, the...

Watch this Scientific Journal Video about Pneumatically Driven Microfluidic Platform for Micro-Particle Concentration at JoVE.com

Pneumatically Driven Microfluidic Platform for Micro-Particle Concentration

The present protocol describes a pneumatic microfluidic platform that can be used for efficient microparticle concentration.

The present article introduces a method for fabricating and operating a pneumatic valve to control particle concentration using a microfluidic platform. ...

This protocol describe our method to fabricate and operate on pneumatically-driven microfluidic platform for multi-particle concentrations that overcomes shortcomings such as particle clogging and complex structures. This methods makes it possible to process an unlimited number of particles, concentrate on a large number of small particles, and prevent unwanted cell damage, and increases entropy efficiency. Due to the importance of biological analysis, microfluidic and biomedical microelectro mechanical systems technologies are used to develop and study devices for the purification and collection of micro-materials.To begin, use a pre-prepared pneumatic valve channel SU8 mold to replicate the PDMS layer for pneumatically controlling the valve. Pour 10 milliliters of liquid PDMS and one milliliter of curing agent into a prepared pneumatic valve channel mold, and heat activate at 90 degrees Celsius for 30 minutes. After the PDMS structures are cured, separate the SU8 mold.Punch three 1.5 millimeter pneumatic ports into the pneumatic valve channel using a 1.5 millimeter puncture. Pour 10 milliliters of liquid PDMS and one milliliter of curing agent into a clean SU8 mold. Spin coat for 15 seconds at 1500 revolutions per minute using a spin coater, then heat activate at 90 degrees Celsius for 30 minutes.Separate the SU8 mold after the PDMS structures are cured. Treat the PDMS structure with atmospheric plasma for 20 seconds. Using a microscope, align the plasma treated PDMS structures according to the channel structure.Bond the aligned PDMS structures by heating them at 90 degrees Celsius for 30 minutes. Using a 1.5 millimeter puncture, make a 1.5 millimeter diameter hole in the fluid channel inlet and outlets within the pneumatic channel part bonded to the thin diaphragm layer. Replicate both sides of the PDMS layer using two SU8 molds to make a microfluidic channel.Use a curved and rectangular microfluidic channel mold on the front, and a microfluidic interconnection channel mold on the rear. Pour 10 milliliters of liquid PDMS and one milliliter of curing agent into the curved and rectangular microfluidic channel mold, and spin coat it at 1200 revolutions per minute for 15 seconds, then create molds for the curved fluid chamber and fluid channels by heat activation at 90 degrees Celsius for 30 minutes. Separate the PDMS layer on which the microfluidic channel is formed.Then treat it with atmospheric plasma for 20 seconds to make a heat-activated mold covering the sealed vent wall by bonding to the glass wafer. Pour three milliliters of liquid PDMS into the interconnection channel of the SU8 mold. Arrange the structure, fabricated with the interconnection channel mold, in liquid PDMS on the microfluidic interconnect channel mold.Then dry the superimposed structure at 130 degrees Celsius for 30 minutes. After curing, remove the front SU8 mold from the microfluidic channel network layer and carefully peel off the rear PDMS mold. Pour 10 milliliters of liquid PDMS and one milliliter of curing agent into a clean SU8 mold and heat activate it at 90 degrees Celsius for 30 minutes.Separate the SU8 mold after the PDMS structures are cured. Treat the PDMS microfluidic interconnection channel molds with atmospheric plasma for 20 seconds. Using a microscope, align the plasma-treated PDMS structures according to the channel structure.Bond the aligned PDMS structures by heating at 90 degrees Celsius for 30 minutes. Align the PDMS structures prepared during this process according to the channel structure and bond them by treating with atmospheric plasma for 20 seconds. Using a 10 milliliter syringe, fill the microfluidic channel with bubble-free, demineralized water.To control the pressure of working fluid and the three pneumatic valves that control the microbead flow, insert a precision pressure controller with four or more outlet channels for the working fluid into the microfluidic platform. Prepare carboxyl polystyrene test particles of various sizes in distilled water. To control the flow rate of the working fluid, fill half of a glass bottle with the water and connect the glass bottle cap to the controller output channel and microvalve.Using an inverted microscope, observe all the platform operations and measure the operating flow rate over time at the outlet by a liquid flow meter. Inject the particle or fluid mixture under pressure at the inlet with the particle valve. Apply pressure to the CIV valve at 15 kilopascals, and particle valve at 18 kilopascals to actuate the valve.When the particles are concentrated, apply pressure only to the fluid valve. The flow rate of the fluids was divided into a four-stage platform operation. The first stage was the loading state.The working fluid and particles were almost identical as the microfluidic channel network exhibited structural symmetry. The second stage was the blocking state. The flow path narrowed, and the flow rate measured at the outlet port was reduced by hydraulic resistance.The third stage was the concentration state. The measured QP was close to zero, and the QF was about 1.42 times that of the blocking state. The final stage was the release state.The resulting flow and concentration rates proved that the sequential actuation programmed with the pneumatic valve work well due to flow changes. Particles were concentrated and accumulated in the collection area when the CIV valve and particle valve were closed, and all collected, concentrated particles were released within four seconds when only the fluid valve was closed. An essential part of this procedure is curing the rear structure where the PDMS layer is implanted by the some more pressure of the air layer.And the deformed film layer is suddenly activated. This platform can be used for auto-pretreatment of very concentrated and straight and suspended bioparticles, as the operation is not affected by the properties of the physical particles.

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