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At least 19 records

Multivariate Analysis To Quantify Species in the Presence of Direct Interferents: Micro-Raman Analysis of HNO 3 in Microfluidic Devices

Microfluidic devices are a growing field with significant potential for application to small scale processing of solutions. Much like large scale processing, fast, reliable, and cost effective means of monitoring the streams during processing are needed. Here we apply a novel Micro-Raman probe to the on-line monitoring of streams within a microfluidic device. For either macro or micro scale process monitoring via spectroscopic response, there is the danger of interfering or confounded bands obfuscating results. By utilizing chemometric analysis, a form of multivariate analysis, species can be accurately quantified in solution despite the presence of overlapping or confounded spectroscopic bands. This is demonstrated on solutions of HNO 3 and NaNO 3 within micro-flow and microfluidic devices.

Lines, Amanda M.↗

Micro-Raman technology to interrogate two-phase extraction on a microfluidic device

Microfluidic devices provide ideal environments to study solvent extraction. When droplets form and generate plug flow down the microfluidic channel, the device acts as a microreactor in which the kinetics of chemical reactions and interfacial transfer can be examined. Among the many benefits of microreactors is the ability to maintain small sample volumes, which is especially important when studying solvent extraction in harsh environments, such as in separations related to the nuclear fuel cycle. In solvent extraction, the efficiency of the process depends on complex formation and rates of transfer in biphasic systems. Thus, it is important to understand the kinetic parameters in an extraction system to maintain a high efficiency and effectivity of the process. Here we present a methodology that combines chemometric analysis with on-line micro-Raman spectroscopy to monitor biphasic extractions within a microfluidic device. This monitoring provided concentration measurements in both organic and aquoeus plugs as they flowed through the microfluidic channel. The biphasic system studied was comprised of HNO3 as the aqueous phase and 30 % (v/v) tributyl phosphate in n-dodecane comprised the organic phase, which simulated the Plutonium Uranium Redox EXtraction (PUREX) process. Using pre-equilibrated solutions (post extraction) the validity of the technique and methodology is illustrated. Following this validation, solutions that were not equilibrated were examined and the kinetics of interfacial mass transfer within the biphasic system were established. Results were compared to kinetics already determined on a macro scale to prove the efficacy of the technique

extraction, interfacial transport, liquid:liquid e↗

A versatile and low-cost chip-to-world interface: enabling ICP-MS characterization of isotachophoretically separated lanthanides on a microfluidic device

Microfluidics offer novel and state-of-the-art pathways to process materials. Microfluidic systems drastically reduce timeframes and costs associated with traditional lab-scale efforts in the area of analytical sample preparations. The challenge arises in effectively connecting microfluidics to off-chip analysis tools to accurately characterize samples after treatment on-chip. Here, a fused silica microfluidic device (MFD) is connected to a fused-silica capillary in order to create a world-to-chip connection between the MFD and an inductively coupled plasma mass spectrometer (ICP-MS). Specifically, this is demonstrated by utilizing isotachophoresis (ITP) on a microfluidic chip to separate samples containing up to 14 lanthanides into elementally pure bands. The separated sample is successfully transferred across a 7 nL dead space at the microchip-capillary junction, such that separation resolution is maintained and even increased through the interface and into the ICP-MS, where the elemental composition of the separated sample is analysed. Lanthanide samples of varying composition are detected using ICP-MS, demonstrating this versatile and cost-effective approach that does not degrade the separation quality achieved on the MFD. This simple and inexpensive connection enables fast, low-cost sample preparation immediately prior to injection into an ICP-MS or other analytical instruments.

Lackey, Hope E.↗

Microfluidic device for drug delivery

A microfluidic device is provided for delivering a drug to an individual. The microfluidic device includes a body that defines a reservoir for receiving the drug therein. A valve interconnects the reservoir to an output needle that is insertable into the skin of an individual. A pressure source urges the drug from the reservoir toward the needle. The valve is movable between a closed position preventing the flow of the drug from the reservoir to the output needle and an open position allowing for the flow of the drug from the reservoir to the output needle in response to a predetermined condition in the physiological fluids of the individual.

Beebe, David J.↗

Aerosol jet printing of surface acoustic wave microfluidic devices

Abstract The addition of surface acoustic wave (SAW) technologies to microfluidics has greatly advanced lab-on-a-chip applications due to their unique and powerful attributes, including high-precision manipulation, versatility, integrability, biocompatibility, contactless nature, and rapid actuation. However, the development of SAW microfluidic devices is limited by complex and time-consuming micro/nanofabrication techniques and access to cleanroom facilities for multistep photolithography and vacuum-based processing. To simplify the fabrication of SAW microfluidic devices with customizable dimensions and functions, we utilized the additive manufacturing technique of aerosol jet printing. We successfully fabricated customized SAW microfluidic devices of varying materials, including silver nanowires, graphene, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). To characterize and compare the acoustic actuation performance of these aerosol jet printed SAW microfluidic devices with their cleanroom-fabricated counterparts, the wave displacements and resonant frequencies of the different fabricated devices were directly measured through scanning laser Doppler vibrometry. Finally, to exhibit the capability of the aerosol jet printed devices for lab-on-a-chip applications, we successfully conducted acoustic streaming and particle concentration experiments. Overall, we demonstrated a novel solution-based, direct-write, single-step, cleanroom-free additive manufacturing technique to rapidly develop SAW microfluidic devices that shows viability for applications in the fields of biology, chemistry, engineering, and medicine.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Automated control of microfluidic devices based on machine learning

A system is provided to automatically monitor and control the operation of a microfluidic device using machine learning technology. The system receives images of a channel of a microfluidic device collected by a camera during operation of the microfluidic device. Upon receiving an image, the system applies a classifier to the image to classify the operation of the microfluidic device as normal, in which no adjustment to the operation is needed, or as abnormal, in which an adjustment to the operation is needed. When an image is classified as normal, the system may make no adjustment to the microfluidic device. If, however, an image is classified as abnormal, the system may output an indication that the operation is abnormal, output an indication of a needed adjustment, or control the microfluidic device to make the needed adjustment.

42 ENGINEERING↗

Automated control of microfluidic devices based on machine learning

A system is provided to automatically monitor and control the operation of a microfluidic device using machine learning technology. The system receives images of a channel of a microfluidic device collected by a camera during operation of the microfluidic device. Upon receiving an image, the system applies a classifier to the image to classify the operation of the microfluidic device as normal, in which no adjustment to the operation is needed, or as abnormal, in which an adjustment to the operation is needed. When an image is classified as normal, the system may make no adjustment to the microfluidic device. If, however, an image is classified as abnormal, the system may output an indication that the operation is abnormal, output an indication of a needed adjustment, or control the microfluidic device to make the needed adjustment.

Giera, Brian↗

Simple Check Valves for Microfluidic Devices

A simple design concept for check valves has been adopted for microfluidic devices that consist mostly of (1) deformable fluorocarbon polymer membranes sandwiched between (2) borosilicate float glass wafers into which channels, valve seats, and holes have been etched. The first microfluidic devices in which these check valves are intended to be used are micro-capillary electrophoresis (microCE) devices undergoing development for use on Mars in detecting compounds indicative of life. In this application, it will be necessary to store some liquid samples in reservoirs in the devices for subsequent laboratory analysis, and check valves are needed to prevent cross-contamination of the samples. The simple check-valve design concept is also applicable to other microfluidic devices and to fluidic devices in general. These check valves are simplified microscopic versions of conventional rubber- flap check valves that are parts of numerous industrial and consumer products. These check valves are fabricated, not as separate components, but as integral parts of microfluidic devices. A check valve according to this concept consists of suitably shaped portions of a deformable membrane and the two glass wafers between which the membrane is sandwiched (see figure). The valve flap is formed by making an approximately semicircular cut in the membrane. The flap is centered over a hole in the lower glass wafer, through which hole the liquid in question is intended to flow upward into a wider hole, channel, or reservoir in the upper glass wafer. The radius of the cut exceeds the radius of the hole by an amount large enough to prevent settling of the flap into the hole. As in a conventional rubber-flap check valve, back pressure in the liquid pushes the flap against the valve seat (in this case, the valve seat is the adjacent surface of the lower glass wafer), thereby forming a seal that prevents backflow.

Willis, Peter A.↗

In Situ Chemical Monitoring and Imaging of Contents within Microfluidic Devices Having a Porous Membrane Wall Using Liquid Microjunction Surface Sampling Probe Mass Spectrometry

The ability to observe dynamic chemical processes (e.g., signaling, transport, etc.) in vivo or in situ using nondestructive chemical imaging opens a new door to understanding the complex dynamics of developing biological systems. With the advent of “biology-on-a-chip” devices has come the ability to monitor dynamic chemical processes in a controlled environment, using these engineered habitats to capture key features of natural systems while allowing visual observation of system development. Having the capability to spatially and temporally map the chemical signals within these devices may yield new insights into the forces that drive biosystem development. Here, a porous membrane sealed microfluidic device was designed to allow normal microfluidic operation while enabling continuous, location specific sampling and chemical characterization by liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS). LMJ-SSP was used to extract fluids with nL-to-μL/min flow rates directly from selected areas of the microfluidic device without negatively impacting the device function. These extracts were subsequently characterized using MS. This technique was used to acquire MS images of the entirety of several multi-input microfluidic devices having different degrees of fluid mixing. LMJ-SSP MS imaging visualized the spatial distribution of chemical components within the microfluidic channels and could visualize chemical reactions occurring in the device. These microfluidic devices with a porous membrane wall are wholly compatible with the construction of biology-on-a-chip devices. This ultimately would enable correlation of biosystem physical structure with an evolving chemical environment

47 OTHER INSTRUMENTATION↗

Particle-Based Microfluidic Device for Providing High Magnetic Field Gradients

A microfluidic device for manipulating particles in a fluid has a device body that defines a main channel therein, in which the main channel has an inlet and an outlet. The device body further defines a particulate diverting channel therein, the particulate diverting channel being in fluid connection with the main channel between the inlet and the outlet of the main channel and having a particulate outlet. The microfluidic device also has a plurality of microparticles arranged proximate or in the main channel between the inlet of the main channel and the fluid connection of the particulate diverting channel to the main channel. The plurality of microparticles each comprises a material in a composition thereof having a magnetic susceptibility suitable to cause concentration of magnetic field lines of an applied magnetic field while in operation. A microfluidic particle-manipulation system has a microfluidic particle-manipulation device and a magnet disposed proximate the microfluidic particle-manipulation device.

Lin, Adam Y.↗

Microfabrication of plastic-PDMS microfluidic devices using polyimide release layer and selective adhesive bonding

In this study, we present an improved method to bond poly(dimethylsiloxane) (PDMS) with polyimide (PI) to develop flexible substrate microfluidic devices. The PI film was separately fabricated on a silicon wafer by spin coating followed by thermal treatment to avoid surface unevenness of the flexible substrate. In this way, we could also integrate flexible substrate into standard micro-electromechanical systems (MEMS) fabrication. Meanwhile, the adhesive epoxy was selectively transferred to the PDMS microfluidic device by a stamp-and-stick method to avoid epoxy clogging the microfluidic channels. To spread out the epoxy evenly on the transferring substrate, we used superhydrophilic vanadium oxide film coated glass as the transferring substrate. After the bonding process, the flexible substrate could easily be peeled off from the rigid substrate. Contact angle measurement was used to characterize the hydrophicity of the vanadium oxide film. X-ray photoelectron spectroscopy analysis was conducted to study the surface of the epoxy. We further evaluated the bonding quality by peeling tests, which showed a maximum bonding strength of 100 kPa. By injecting with black ink, the plastic microfluidic device was confirmed to be well bonded with no leakage for a day under 1 atm. Finally, this proposed versatile method could bond the microfluidic device and plastic substrate together and be applied in the fabrication of some biosensors and lab-on-a-chip systems.

42 ENGINEERING↗

Rapid Protein Separations in Microfluidic Devices

This paper describes fabrication of glass and plastic microfluidic devices for protein separations. Although the long-term goal is to develop a microfluidic device for two-dimensional gel electrophoresis, this paper focuses on the first dimension-isoelectric focusing (IEF). A laser-induced fluorescence (LIF) imaging system has been built for imaging an entire channel in an IEF device. The whole-channel imaging eliminates the need to migrate focused protein bands, which is required if a single-point detector is used. Using the devices and the imaging system, we are able to perform IEF separations of proteins within minutes rather than hours in traditional bench-top instruments.

MICROFLUIDICS↗

Microfluidic Devices for Studying Biomolecular Interactions

Microfluidic devices for monitoring biomolecular interactions have been invented. These devices are basically highly miniaturized liquid-chromatography columns. They are intended to be prototypes of miniature analytical devices of the laboratory on a chip type that could be fabricated rapidly and inexpensively and that, because of their small sizes, would yield analytical results from very small amounts of expensive analytes (typically, proteins). Other advantages to be gained by this scaling down of liquid-chromatography columns may include increases in resolution and speed, decreases in the consumption of reagents, and the possibility of performing multiple simultaneous and highly integrated analyses by use of multiple devices of this type, each possibly containing multiple parallel analytical microchannels. The principle of operation is the same as that of a macroscopic liquid-chromatography column: The column is a channel packed with particles, upon which are immobilized molecules of the protein of interest (or one of the proteins of interest if there are more than one). Starting at a known time, a solution or suspension containing molecules of the protein or other substance of interest is pumped into the channel at its inlet. The liquid emerging from the outlet of the channel is monitored to detect the molecules of the dissolved or suspended substance(s). The time that it takes these molecules to flow from the inlet to the outlet is a measure of the degree of interaction between the immobilized and the dissolved or suspended molecules. Depending on the precise natures of the molecules, this measure can be used for diverse purposes: examples include screening for solution conditions that favor crystallization of proteins, screening for interactions between drugs and proteins, and determining the functions of biomolecules.

Wilson, Wilbur W.↗

Non-contact temperature control system for microfluidic devices

The present invention relates to a temperature control system for a microfluidic device. The system allows for non-contact heating by employing an infrared emitter. In some instances, the system can be used in conjunction with a centrifugal microfluidic device. Optionally, a mask can be implemented to provide selective heating of desired assay areas of the device.

Phaneuf, Christopher↗

Microfluidic Devices for Chemical and Biochemical Analysis in Microgravity

One often touted benefit of "Lab-on-a-Chip" devices is their potential for use in remote environments. The ultimate remote environment is outer space, and NASA has multiple needs in the area of analytical sensing capability in such an environment. In particular, we are interested in integrating microfluidic devices with NASA bioreactor systems. In such an integrated system, the microfluidic device will serve as a biosensor and be used for both feedback control and for detecting various bioproducts produced by cells cultured in the NASA bioreactors. As a first step in demonstrating the ability of microfluidic devices to operate under the extreme environmental conditions found in outer space, we constructed a portable, battery operated platform for testing under reduced gravity conditions on a NASA KC-135 reduced gravity research aircraft, (AKA "the vomit comet"). The test platform consisted of a microchip, two 0-8kV high voltage power supplies, a high voltage switch, a solid-state diode-pumped green laser, a channel photomultiplier, and an inertial mass measurement unit, all under the control of a laptop computer and powered by 10 D-cell alkaline batteries. Over the course of 4 KC-135 flights, 1817 fast electrophoretic separations of 4 amino acids and/or proteins were performed in a variety of gravitational environments including zero-G, Martian-G, lunar-G, and 2-G. Results from these experiments will be presented and discussed.

Roman, Gregory T.↗

Protein and nucleic acid detection for microfluidic devices

The present invention relates to methods for detecting targets by employing a temperature control system with a microfluidic device. The system allows for non-contact heating by employing an infrared emitter. In some instances, the system can be used in conjunction with a centrifugal microfluidic device. Optionally, a mask can be implemented to provide selective heating of desired assay areas of the device.

Koh, Chung-Yan↗

Detection of active and latent infections with microfluidic devices and systems thereof

The present invention relates to methods of detecting one or more targets of interest in a sample. In one instance, the target can be correlated to an active infection (e.g., by a virus and/or a bacterium). Methods can include treating the sample with a dissociation agent, thereby releasing the target of interest for more accurate detection (e.g., by use of a sedimentation-based centrifugal microfluidic devices). Also described herein are microfluidic devices and systems for use with a dissociation agent.

59 BASIC BIOLOGICAL SCIENCES↗