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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B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+tunable+micro+filter+modulated+by+pneumatic+pressure+for+cell+separation.">A tunable micro filter modulated by pneumatic pressure for cell separation.</a> Sensors and Actuators B: Chemical. 142 (1), 389-399 (2009).</li><li>Chang, Y. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+tunable+microfluidic-based+filter+modulated+by+pneumatic+pressure+for+separation+of+blood+cells.">A tunable microfluidic-based filter modulated by pneumatic pressure for separation of blood cells.</a> Microfluidics and Nanofluidics. 12 (1-4), 85-94 (2012).</li><li>Oh, C. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+pneumatic+valves+with+spherical+dome-shape+fluid+chambers.">Fabrication of pneumatic valves with spherical dome-shape fluid chambers.</a> Microfluidics and Nanofluidics. 19 (5), 1091-1099 (2015).</li><li>Liu, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+trapping+and+high-throughput+patterning+of+cells+using+pneumatic+microstructures+in+an+integrated+microfluidic+device.">Dynamic trapping and high-throughput patterning of cells using pneumatic microstructures in an integrated microfluidic device.</a> Lab on a Chip. 12 (9), 1702-1709 (2012).</li><li>Jang, J. H., Jeong, O. 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C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Poly(dimethylsiloxane)+as+a+material+for+fabricating+microfluidic+device.">Poly(dimethylsiloxane) as a material for fabricating microfluidic device.</a> Accounts of Chemical Research. 35 (7), 491-499 (2002).</li><li>Brivio, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+MALDI-chip+integrated+system+with+a+monitoring+window.">A MALDI-chip integrated system with a monitoring window.</a> Lab on a Chip. 5 (4), 378-381 (2005).</li><li>Jeong, O. 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M., Voldman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+scalable+addressable+positive+dielectrophoretic+cell-sorting+array.">A scalable addressable positive dielectrophoretic cell-sorting array.</a> Analytical Chemistry. 77 (24), 7976-7983 (2005).</li><li>Pamme, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On-chip+free-flow+magnetophoresis:+Separation+and+detection+of+mixtures+of+magnetic+particles+in+continuous+flow.">On-chip free-flow magnetophoresis: Separation and detection of mixtures of magnetic particles in continuous flow.</a> Journal of Magnetism and Magnetic Materials. 307 (2), 237-244 (2006).</li><li>Harris, N. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+of+a+micro-engineered+ultrasonic+particle+manipulator.">Performance of a micro-engineered ultrasonic particle manipulator.</a> Sensors and Actuators B: Chemical. 111, 481-486 (2005).</li><li>Yoon, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clogging-free+microfluidics+for+continuous+size-based+separation+of+microparticles.">Clogging-free microfluidics for continuous size-based separation of microparticles.</a> Scientific Reports. 6 (1), 1-18 (2016).</li><li>Beattie, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clog-free+cell+filtration+using+resettable+cell+traps.">Clog-free cell filtration using resettable cell traps.</a> Lab on a Chip. 14 (15), 2657-2665 (2014).</li><li>Cheng, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+bubble-+and+clogging-free+microfluidic+particle+separation+platform+with+multi-filtration.">A bubble- and clogging-free microfluidic particle separation platform with multi-filtration.</a> Lab on a Chip. 16 (23), 4517-4526 (2016).</li></ol>

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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Engineering

Terahertz Microfluidic Sensing Using a Parallel-plate Waveguide Sensor

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic samples with a wide range of possible sensor designs such as interferometers and resonators 1,2. Most of the existing RI sensing applications focus on biological materials in aqueous solutions in visible and IR frequencies, such as DNA hybridization and genome sequencing. At terahertz frequencies, applications include quality control, monitoring of industrial processes and sensing and detection applications involving nonpolar materials.
Several potential designs for refractive index sensors in the terahertz regime exist, including photonic crystal waveguides 3, asymmetric split-ring resonators 4, and photonic band gap structures integrated into parallel-plate waveguides 5. Many of these designs are based on optical resonators such as rings or cavities. The resonant frequencies of these structures are dependent on the refractive index of the material in or around the resonator. By monitoring the shifts in resonant frequency the refractive index of a sample can be accurately measured and this in turn can be used to identify a material, monitor contamination or dilution, etc.
The sensor design we use here is based on a simple parallel-plate waveguide 6,7. A rectangular groove machined into one face acts as a resonant cavity (Figures 1 and 2). When terahertz radiation is coupled into the waveguide and propagates in the lowest-order transverse-electric (TE1) mode, the result is a single strong resonant feature with a tunable resonant frequency that is dependent on the geometry of the groove 6,8. This groove can be filled with nonpolar liquid microfluidic samples which cause a shift in the observed resonant frequency that depends on the amount of liquid in the groove and its refractive index 9.
Our technique has an advantage over other terahertz techniques in its simplicity, both in fabrication and implementation, since the procedure can be accomplished with standard laboratory equipment without the need for a clean room or any special fabrication or experimental techniques. It can also be easily expanded to multichannel operation by the incorporation of multiple grooves 10. In this video we will describe our complete experimental procedure, from the design of the sensor to the data analysis and determination of the sample refractive index.

The procedure for implementing a refractive index sensor for terahertz frequencies based on a grooved parallel-plate waveguide geometry is described here. The method yields a measurement of the refractive index of a small volume of liquid through monitoring of the shift in the resonant frequency of the waveguide structure

Refractive index (RI) sensing is a powerful noninvasive and label-free sensing technique for the identification, detection and monitoring of microfluidic ...

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

Picoinjection of Microfluidic Drops Without Metal Electrodes

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of these electrodes adds cumbersome and error-prone steps to the device fabrication process. We have developed a technique that obviates the needs for metal electrodes during picoinjection. Instead, it uses the injection fluid itself as an electrode, since most biological reagents contain dissolved electrolytes and are conductive. By eliminating the electrodes, we reduce device fabrication time and complexity, and make the devices more robust. In addition, with our approach, the injection volume depends on the voltage applied to the picoinjection solution; this allows us to rapidly adjust the volume injected by modulating the applied voltage. We demonstrate that our technique is compatible with reagents incorporating common biological compounds, including buffers, enzymes, and nucleic acids.

We have developed a technique for picoinjecting microfluidic drops that does not require metal electrodes. As such, devices incorporating our technique are simpler to fabricate and to use.

Existing methods for picoinjecting reagents into microfluidic drops require metal electrodes integrated into the microfluidic chip. The integration of ...

Time Multiplexing Super Resolving Technique for Imaging from a Moving Platform

We propose a method for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving imaging system, such as an airborne platform or satellite. The resolution improvement is obtained in a two-step process. First, three low resolution differently defocused images are being captured and the optical phase is retrieved using an improved iterative Gerchberg-Saxton based algorithm. The phase retrieval allows to numerically back propagate the field to the aperture plane. Second, the imaging system is shifted and the first step is repeated. The obtained optical fields at the aperture plane are combined and a synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution. The method resembles a well-known approach from the microwave regime called the Synthetic Aperture Radar (SAR) in which the antenna size is synthetically increased along the platform propagation direction. The proposed method is demonstrated through laboratory experiment.

A method for overcoming the optical diffraction limit is presented. The method includes a two-step process: optical phase retrieval using iterative Gerchberg-Saxton algorithm, and imaging system shifting followed by repetition of the first step. A synthetically increased lens aperture is generated along the direction of movement, yielding higher imaging resolution.

We propose a method for increasing the resolution of an object and overcoming the diffraction limit of an optical system installed on top of a moving ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Thermal Measurement Techniques in Analytical Microfluidic Devices

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. Micromachining techniques allow reduction of the thermal mass of fabricated structures and introduce the possibility to perform high sensitivity thermal measurements in the micro-scale and nano-scale devices. Combining thermal measurement techniques with microfluidic devices allows performing different analytical measurements with low sample consumption and reduced measurement time by integrating the miniaturized system on a single chip. The procedures of thermal measurement techniques for particle detection, material characterization, and chemical detection are introduced in this paper.

Here, we present three protocols for thermal measurements in microfluidic devices.

Thermal measurement techniques have been used for many applications such as thermal characterization of materials and chemical reaction detection. ...

Capillary-based Centrifugal Microfluidic Device for Size-controllable Formation of Monodisperse Microdroplets

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal microfluidic device. W/O microdroplets have recently been used in powerful methods that enable miniaturized chemical experiments. Therefore, developing a versatile method to yield monodisperse W/O microdroplets is needed. We have developed a method for generating monodisperse W/O microdroplets based on a capillary-based centrifugal axisymmetric co-flowing microfluidic device. We succeeded in controlling the size of microdroplets by adjusting the capillary orifice. Our method requires equipment that is easier-to-use than with other microfluidic techniques, requires only a small volume (0.1-1 &#181;l) of sample solution for encapsulation, and enables the production of hundreds of thousands number of W/O microdroplets per second. We expect this method will assist biological studies that require precious biological samples by conserving the volume of the samples for rapid quantitative analysis biochemical and biological studies.

Here, we demonstrate a simple production method for size-controllable, monodisperse, water-in-oil (W/O) microdroplets using a capillary-based centrifugal microfluidic device. This method requires only a small sample volume and enables high-yield production. We expect this method will be useful for rapid biochemical and cellular analyses.

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal ...

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

Solvent Bonding for Fabrication of PMMA and COP Microfluidic Devices

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each thermoplastic of interest. Solvent bonding is a simple and versatile method that can be used to fabricate devices from a variety of plastics. An appropriate solvent is added between two device layers to be bonded, and heat and pressure are applied to the device to facilitate the bonding. By using an appropriate combination of solvent, plastic, heat, and pressure, the device can be sealed with a high quality bond, characterized as having high bond coverage, bond strength, optical clarity, durability over time, and low deformation or damage to microfeature geometry. We describe the procedure for bonding devices made from two popular thermoplastics, poly(methyl-methacrylate) (PMMA), and cyclo-olefin polymer (COP), as well as a variety of methods to characterize the quality of the resulting bonds, and strategies to troubleshoot low quality bonds. These methods can be used to develop new solvent bonding protocols for other plastic-solvent systems.

Solvent bonding is a simple and versatile method for fabricating thermoplastic microfluidic devices with high quality bonds. We describe a protocol to achieve strong, optically clear bonds in PMMA and COP microfluidic devices that preserve microfeature details, by a judicious combination of pressure, temperature, an appropriate solvent, and device geometry.

Thermoplastic microfluidic devices offer many advantages over those made from silicone elastomers, but bonding procedures must be developed for each ...

A Modular Microfluidic Technology for Systematic Studies of Colloidal Semiconductor Nanocrystals

Colloidal semiconductor nanocrystals, known as quantum dots (QDs), are a rapidly growing class of materials in commercial electronics, such as light emitting diodes (LEDs) and photovoltaics (PVs). Among this material group, inorganic/organic perovskites have demonstrated significant improvement and potential towards high-efficiency, low-cost PV fabrication due to their high charge carrier mobilities and lifetimes. Despite the opportunities for perovskite QDs in large-scale PV and LED applications, the lack of fundamental and comprehensive understanding of their growth pathways has inhibited their adaptation within continuous nanomanufacturing strategies. Traditional flask-based screening approaches are generally expensive, labor-intensive, and imprecise for effectively characterizing the broad parameter space and synthesis variety relevant to colloidal QD reactions. In this work, a fully autonomous microfluidic platform is developed to systematically study the large parameter space associated with the colloidal synthesis of nanocrystals in a continuous flow format. Through the application of a novel translating three-port flow cell and modular reactor extension units, the system may rapidly collect fluorescence and absorption spectra across reactor lengths ranging 3 - 196 cm. The adjustable reactor length not only decouples the residence time from the velocity-dependent mass transfer, it also substantially improves the sampling rates and chemical consumption due to the characterization of 40 unique spectra within a single equilibrated system. Sample rates may reach up to 30,000 unique spectra per day, and the conditions cover 4 orders of magnitude in residence times ranging 100 ms - 17 min. Further applications of this system would substantially improve the rate and precision of the material discovery and screening in future studies. Detailed within this report are the system materials and assembly protocols with a general description of the automated sampling software and offline data processing.

Detailed herein are the operation and assembly protocols of a modular microfluidic screening platform for the systematic characterization of colloidal semiconductor nanocrystal syntheses. Through fully adjustable system arrangements, highly efficient spectra collection may be carried out across 4 orders of magnitude reaction time scales within a mass transfer-controlled sampling space.

Colloidal semiconductor nanocrystals, known as quantum dots (QDs), are a rapidly growing class of materials in commercial electronics, such as light ...