Fluid Handling System Research Articles

Conceptual Design of a Fluid Handling System with Dosing and Mixing for PCR Applications

Typically, samples for PCR instruments are prepared manually by trained laboratory personnel, which in this case refers to the sample preparation, the dispensing of a master mix and a biological sample with subsequent mixing. To reduce the workload, there are approaches towards fully automated PCR systems, but in most cases only proprietary thermal cyclers can be used. Other approaches involve a similarly complex robotic solution. In this work, the spectrum was extended by a method that can be integrated into the workflow of existing PCR protocols. For this purpose, a user-friendly solution using a microfluidic chip was developed. For the sample preparation different mixing concepts were selected as well as a concept for aliquoting. Optimization and evaluation were assisted by utilization of simulations to study system behavior. The systems consisting of a mixer and a flow splitter were manufactured by milling. Subsequently, the mixing and aliquoting capability of the system could be investigated in the laboratory assembly. The testing of this prototype showed moderate results which are attributed to the accuracy of the laboratory assembly.

Optimizing the radiosynthesis of [68Ga]DOTA-MLN6907 peptide containing three disulfide cyclization bonds – a GCC specific chelate for clinical radiopharmaceuticals

In the present study, the effect of radiolabeling conditions on radiolabeling efficiency and achievable specific activity of a DOTA-conjugated highly-lipophilic peptide containing three disulfide cyclization bonds was examined. The peptide is designed to bind specifically (with high affinity) to cell-surface receptor guanylyl cyclase C (GCC), which is universally expressed by colorectal cancer cells. The effect of systematic variation of chemical parameters pH, mass of peptide, acetate buffer concentration (ionic strength), and inclusion of ethanol in the radiolabeling reaction vessel on achievable specific activity and labeling efficiency was examined. In addition, a unique approach to acetone-based elution of 68Ga from an initial cation-exchange pre-concentration column is introduced, which improved radiochemical yield and radiochemical purity. For the evaluation of the acetone-based method, two different post-radiolabeling reverse-phase (C18) approaches to purify the final radiolabeled peptide were tested. These results revealed the potential for peptide degradation via the cleavage of disulfide cyclization bonds to form free thiols when using one of these C18 cartridges. The final optimized procedure enabled radiolabeling efficiency of greater than 99% and specific activity greater than 35 MBq/nmole in less than 30 min. The optimized parameters were amenable to the use of an automated 68Ge/68Ga generator and fluid-handling system for clinical production of the GCC receptor-specific [68Ga]DOTA-MLN6907 peptide. The chemical characteristics of individual peptides govern the most appropriate radiolabeling conditions for the preparation of radiopharmaceuticals.

Effect of Oxygen Depletion to the Cathode on the Working of Solid Oxide Fuel Cells

During the recent years, SOFC research has mainly been aimed at reducing the capital cost to effectively compete with other power generation technologies. CMR Prototech, Norway is a provider of technical solutions, product designs and tools for various application areas. Currently, CMR Prototech is planning to develop 2 MW modular fuel cell systems for subsea operation. Each module consists of 200 stacks, each stack producing 10kW. In order to address the technical challenges faced during this development and to make SOFC technology feasible for offshore applications more research on fuel cells in marine environment is necessary. This research was aimed at determining the effects of a) reducing partial pressure of oxygen and b) NaCl contamination on the performance of the SOFC cathode of a single SOFC cell. This present paper focuses on the effect of oxygen partial pressure. Single cell tests were performed in a versatile test station, fully automated and controlled using LabVIEW programming. The fluid handling system with mass flow controllers and four-points measurement probes along with field-point connections were installed in the test station. A set of experiments were conducted, reducing the partial pressure of oxygen supplied to the cathode stopwise (at thre relevant temperatures, namely 800, 850 and 900oC). All the cells were characterized and analyzed by I-V curves. The grain structures of the cells were characterized by scanning electron microscopy (SEM) before and after the experiments.

Automated cassette-based production of high specific activity [203/212Pb]peptide-based theranostic radiopharmaceuticals for image-guided radionuclide therapy for cancer

A method for preparation of Pb-212 and Pb-203 labeled chelator-modified peptide-based radiopharmaceuticals for cancer imaging and radionuclide therapy has been developed and adapted for automated clinical production. Pre-concentration and isolation of radioactive Pb2+ from interfering metals in dilute hydrochloric acid was optimized using a commercially-available Pb-specific chromatography resin packed in disposable plastic columns. The pre-concentrated radioactive Pb2+ is eluted in NaOAc buffer directly to the reaction vessel containing chelator-modified peptides. Radiolabeling was found to proceed efficiently at 85°C (45min; pH 5.5). The specific activity of radiolabeled conjugates was optimized by separation of radiolabeled conjugates from unlabeled peptide via HPLC. Preservation of bioactivity was confirmed by in vivo biodistribution of Pb-203 and Pb-212 labeled peptides in melanoma-tumor-bearing mice. The approach has been found to be robustly adaptable to automation and a cassette-based fluid-handling system (Modular Lab Pharm Tracer) has been customized for clinical radiopharmaceutical production. Our findings demonstrate that the Pb-203/Pb-212 combination is a promising elementally-matched radionuclide pair for image-guided radionuclide therapy for melanoma, neuroendocrine tumors, and potentially other cancers.

A Practical Method of Predicting Calcium Carbonate Scale Formation in Well Completions

Summary Scale formation in downhole tubular-flow passages can cause partial to complete plugging that will affect production or injection rates adversely. In an intelligent-well completion in which the interval-control-valve (ICV) opening must be changed to control flow rate, the completion will become ineffective if plugging of clearances prevents valve actuation. To mitigate these problems, a method to predict the potential rate of scale formation under realistic conditions has been developed. This empirical method allows prediction of tool performance under scale-forming conditions for downhole applications, and uses chemical data and flow fields generated by computational-fluid-dynamics (CFD) models for downhole tools. Chemical data are obtained from laboratory tests on coupons by use of brines matching the chemistry of connate fluids. Tests were conducted in a high-pressure, corrosion-resistant vessel over a range of high pressures (100 to 10,000 psi) and high temperatures (75 to 150 °C) to simulate downhole well conditions. Two test sets were conducted, each with fluid at rest and with an impeller generating low velocity in the reaction vessel, ranging from 4 hours to 4 days, with scaling rates determined from coupon-weight gain. Concentrations in the range of 50 to 125% of the typical connate-fluid concentration were used. The weight-gain data obtained from the coupon tests and from a tube-plugging test were used to develop an empirical model for scale-growth rate at a given point on a solid surface with pressure, pressure gradient, temperature, fluid velocity, and brine concentration as independent variables. Artificial-intelligence methodology was used to develop this model, which can be used to predict the scale-growth rate for any arbitrary geometry. By use of the internal geometry of any tool to be modeled, a CFD model is prepared and the pressure, fluid velocity, and pressure-gradient data are generated for the entire internal solid surface of the tool for a given flow rate through the tool. These data are fed into the empirical model to calculate the scale-growth rate, which is integrated to obtain scale thickness at each point of the internal solid boundary. To verify accuracy, scale formation in a 4.5-in. ICV was predicted at high-pressure, high-temperature conditions at a low flow rate. Laboratory tests on the valve matched the model predictions well enough, which enabled Petrobras to design a better completion and fluid-handling system for a presalt well.

Monitoring of Sequentially Loaded Reagents to a Detection Area in a Microfluidic Chip

This paper presents a new scheme for monitoring the sequential loading of reagents to a detection site to conduct biological assays. The automation of the sequential loading of biological reagents to a detection site is monitored by a lens-less charged couple device (CCD). The fluid handling system employs a custom edge detection algorithm to determine the location of the channel edges. This custom edge detection method outperformed the built in Matlab edge detection functions. A parametric study was performed to determine the effects wavelength, height above a detection site, and voltage of a light emitting diode (LED), would have on the systems performance. A white light emitting diode, a voltage of 2.6V and a height of at least 20mm above the detection produced the best results. The fluid handling system was also able to work with channels that had different geometric designs and with different types of fluid. This research focuses for the first time on the monitoring of sequentially loading reagents to a detection site using a CCD imager that is also used for detection. Keywords: Active fluid control, CCD, fluid handling, lab-on-chip, microfluidics, sequential loading.

A digital microfluidic device with integrated nanostructured microelectrodes for electrochemical immunoassays.

Nanostructured microelectrodes (NMEs) are three-dimensional electrodes that have superb sensitivity for electroanalysis. Here we report the integration of NMEs with the versatile fluid-handling system digital microfluidics (DMF), for eventual application to distributed diagnostics outside of the laboratory. In the new methods reported here, indium tin oxide DMF top plates were modified to include Au NMEs as well as counter and pseudoreference electrodes. The new system was observed to outperform planar sensing electrodes of the type that are typically integrated with DMF. A rubella virus (RV) IgG immunoassay was developed to evaluate the diagnostic potential for the new system, relying on magnetic microparticles coated with RV particles and analysis by differential pulse voltammetry. The limit of detection of the assay (0.07 IU mL(-1)) was >100× below the World Health Organization defined cut-off for rubella immunity. The sensitivity of the integrated device and its small size suggest future utility for distributed diagnostics.

Comparison of model-based flow rate estimation methods in frequency-converter-driven pumps and fans

Fluid handling systems such as pump and fan systems are found to have a significant potential for energy efficiency improvements. To determine the energy-saving potential, there is a need for easily implementable methods to monitor the system output. This essential information provides an opportunity to identify inefficient operation of the fluid handling system and to control the output of the pumping system according to process needs. Model-based pump or fan monitoring methods implemented in variable-speed drives have proven to be able to give information on the system output without additional metering; however, the present model-based methods may not be usable or sufficiently accurate in the whole operation range of the fluid handling device. To apply model-based system monitoring in a wider selection of systems and to improve the accuracy of the monitoring, this paper proposes a new method for pump and fan output monitoring with variable-speed drives. The method uses a combination of already known operating point estimation methods. Laboratory measurements are used to verify the benefits and applicability of the improved estimation method, and the new method is compared with five previously introduced model-based estimation methods. According to the laboratory measurements, the new estimation method is the most accurate and reliable of the model-based estimation methods.

A fluid handling system with finger-tightened connectors for biological studies at kiloatmosphere pressures

We present a high-pressure fluid handling system based around a simple-to-construct seal for applications in the biologically relevant kiloatmosphere range. Connectors are compact and finger tightened, as compared to the wrench tightening required of cone-type seals commonly used. The seal relies on an O-ring compression, and the system has been tested up to 2000 atm. While the system was designed for biological studies, it should be versatile enough for a wide range of applications, thus contributing finger-tightened convenience to the kiloatmosphere range.

A real-time PCR analyzer compatible with high-throughput automated processing of 2-/spl mu/L reactions in glass capillaries

This paper describes the development of a real-time polymerase chain reaction testbed for the analysis of up to 48 1- to 2-/spl mu/L reactions in glass capillaries. It is suitable for high-throughput experimentation when used as a downstream module for ACAPELLA-5K, an automated, high-precision, fluid-handling system developed in our laboratory over the past five years. The testbed features a laser-induced fluorescence scanner with high-sensitivity photomultiplier tubes for the detection of three spectral wavelengths. The scanner has a detection threshold of 1-nM fluorescein in a 1-/spl mu/L detection volume. Peltier-effect thermoelectric elements are used to control thermal cycles with a slew rate of 3/spl deg/C/s, and a set point tracking accuracy of /spl plusmn/0.5/spl deg/C. Analyzer design and performance are presented. Experimental results show a successful detection of 3 copies//spl mu/L of the albumin gene in serial dilutions of human genomic deoxyribonucleic-acid. Detection levels down to 4 copies//spl mu/L of the t(14;18) translocation associated with the cancer follicular lymphoma, was demonstrated in RL-7 cells. Note to Practitioners-Real-time polymerase chain reaction is a thermally driven in-vitro replication of specific segments of DNA, with simultaneous monitoring or reaction product by means of fluorescence detection. This process is important in biochemical analysis for the detection and/or estimation of gene concentration in DNA samples. By increasing the concentration of an initially undetectable gene and monitoring the kinetic history of the reaction, an estimate of the initial concentration can be computed. Although there exists a plethora of commercial real-time PCR instruments, none of these instruments are suitable for low-volume (single-digit microliters) reagents and high-throughput processing while preserving a high degree of fidelity to obtain reliable, repeatable results, and versatility (support for different fluorogenic probes, different operating modes, etc.). The A5K-automated fluid handling and sample preparation system addresses the high-throughput reaction preparation in small-volume glass capillaries. The testbed presented here is a downstream processing module for A5K. To address the challenges posed by the use of low-volume, elongated reaction vessels, we employ a scanning optical system with a novel inline illumination method to address up to 48 capillaries. We empirically demonstrate that the system's performance is comparable to that of existing commercial real-time PCR platforms, and verify its repeatability and versatility. Future work will address the development of a more compact instrument that can be directly integrated with A5K.

Precise Nanoliter Fluid Handling System with Integrated High-Speed Flow Sensor

A system for accurate low-volume delivery of liquids in the micro- to nanoliter range makes use of an integrated miniature flow sensor as part of an intelligent feedback control loop driving a micro-solenoid valve. The flow sensor is hydraulically connected with the pressurized system liquid in the dispensing channel and located downstream from the pressure source, above the solenoid valve. The sensor operates in a differential mode and responds in real-time to the internal flow-pulse resulting from the brief opening interval of the solenoid valve leading to a rapid ejection of a fluid droplet. The integral of the flow-pulse delivered by the sensor is directly proportional to the volume of the ejected droplet from the nozzle. The quantitative information is utilized to provide active control of the effectively dispensed or aspirated volume by adjusting the solenoid valve accordingly. This process significantly enhances the precision of the fluid delivery. The system furthermore compensates automatically for any changes in the viscosity of the dispensed liquid. The data delivered by the flow sensor can be saved and backtracked in order to confirm and validate the aspiration and dispensing process in its entirety. The collected dispense information can be used for quality control assessments and automatically be made part of an electronic record.

Automated electrochemical CV profiling of LED structures on wafer scale

A newly developed equipment is presented to perform (photo-)electrochemical (PEC) CV profiling in semiconductor structures. The equipment is fully automated to handle sample sizes from some mm2 up to 6″ wafers. Fully automated loading of the electrochemical cell, fluid handling system, automatic unloading of the fluid, and drying of the sample at the end of the measurement are incorporated into the setup. Furthermore, together with a wafer stepper it is possible to perform wafer topography measurements. The hardware makes use of a recently, especially for group III-nitrides developed etch procedure named “cyclic oxidation”: featuring high etch rates in the range of 3 μm/h for n- and p-type (Al,In)GaN layers together with mirror-like etched surface morphology. Using this new equipment, LED structures have been characterized by CV profiling. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Pulsed electric field processing of high acid liquid foods: A review

Publisher Summary Pulsed electric field (PEF) is a nonthermal food preservation method using high voltage electric field to kill spoilage microorganisms in foods. PEF treatment maintains flavor, color, taste and nutritional value of foods while destroying microorganisms. PEF is useful in processing liquid foods where the food can flow between two electrodes. The generation of PEF processing requires a pulsed power supply, a series of treatment chambers and a temperature regulating system. Therefore, a PEF system usually consists of a high voltage pulse generator, a treatment chamber and a fluid handling system. To process a product using PEF in a continuous system, the product flows through a series of PEF treatment chambers where it is exposed to the desired electric field strength for a desired amount of time. The pulse generator is capable of converting low voltage electricity into high voltage energy to be stored in capacitors until discharged. Three different shapes of high voltage waveforms can be generated and applied to foods. The three waveforms are square wave, exponential decay and under-damped RCL (resistive capacitive and inductive discharge circuit). High voltage electricity is transferred into the food product in the treatment chambers, which may be designed for either static (batch) or continuous processing.

Covalent bound sensing layers on surface acoustic wave (SAW) biosensors

This paper reports on the development of immunosensors based on commercially available surface acoustic wave (SAW) devices working at 380 MHz. Approaches for coating the sensor surface with a sensing layer of receptive biomolecules are presented and discussed. It was found that the sensitivity strongly relates to the immobilization method. Additionally, the sensitivity can be influenced by the density of accessible biomolecules on the active sensing area. Usually, by most of the standard immobilization procedures, two-dimensional layers of receptive biomolecules are obtained. We present a three-dimensional layer, which provides a higher absolute amount of recognition molecules. A dextran layer is photoimmobilized to the sensor surface and the recognition molecules are covalently embedded into the dextran matrix. The feasibility of specific immunosensing is investigated using SAW sensors connected to a fluid handling system.

Development of immunosensors based on commercially available surface acoustic wave (SAW) devices

In the present paper we report about the development of immunosensors based on commercially available surface acoustic wave (SAW) devices. The SAW devices applied were originally developed for use in modern telecommunications and are thus available as series products at low costs. For biosensing applications the devices must be coated with a shielding layer to prevent corrosion of the aluminum structures in aqueous media. Thin films of polyimide and parylene, respectively, show good shielding properties and were used as a basis for immobilization of receptor molecules. Various approaches to coating the shielded surfaces with receptive biomolecules are presented briefly and discussed. Finally, covalent binding of dextran as an intermediate layer on SAW devices is described. Dextran bonding is achieved by a photoimmobilization process. The aryldiazirine-functionalized bovine serum albumin (T-BSA) serves as a multifunctional light-activated linking agent (photolinker polymer). Dextran and the photolinker are mixed and photobonded to the sensor surface. Essential parameters of the coating procedure are optimized. Immobilization of proteins to the dextran layer via carbodiimide chemistry is demonstrated. The feasibility of specific immunosensing is investigated using SAW sensors connected to a fluid handling system.

Covalent photolinker-mediated immobilization of an intermediate dextran layer to polymer-coated surfaces for biosensing applications

A new method is presented for the covalent binding of dextran as an intermediate layer on surface acoustic wave (SAW) devices. For biosensing applications in aqueous media commercially available SAW devices require surface passivation to prevent corrosion of the aluminum device structures in electrolytes. Thin films of polyimide and parylene revealed exceptional passivation properties. They were used as a base for dextran immobilization. Covalent binding of dextran to polymer-coated surfaces was achieved by photoimmobilization. Aryldiazirine-functionalized bovine serum albumin served as the multifunctional light-activable linking agent (photolinker polymer). Dextran and photolinker polymer were mixed and photobonded to sensor surfaces. Essential photoimmobilization parameters were optimized. The binding of proteins to dextran applying carbodiimide chemistries was exemplified with anti-urease antibodies and the feasibility of specific immunosensing was investigated on SAW sensors connected to a fluid handling system.

AN INTEGRATED PEF PILOT PLANT FOR CONTINUOUS NONTHERMAL PASTEURIZATION OF FRESH ORANGE JUICE

A pilot plant scale pulsed electric field (PEF) continuous processing system was integrated with an asepticpackaging machine to demonstrate the efficacy of PEF technology as a nonthermal pasteurization method for freshorange juice. Major system components include a 40,000 V/17 MWp high voltage pulse generator, a set of multiple stageco-field flow PEF treatment chambers, a fluid handling system for flow control and a Benco Aspack/2 aseptic thermalform packaging machine. Orange juice was processed at a 75 ~ 125 L/h flow rate and packed aseptically into 200 mLplastic cup containers. Microbially enhanced orange juice (MEOJ) tests validated the microbial inactivation effect of thisintegrated PEF system. The PEF treated and aseptically packaged fresh orange juice demonstrated the feasibility of PEFtechnology to extend the product shelf life with very little loss of flavor, vitamin C, and color.

A fluid handling system for a chemical microanalyzer

In this paper we present the design and fabrication of the two fundamental components of a fluid handling system intended to be the core of a chemical microanalyzer for measuring heavy metals in ground water. The first fluidic component is a micropump with built-in passive valves. The pump body is fabricated by thermoplastic moulding, whereas the passive valves are obtained by reaction injection moulding. The second fluidic component is an active valve, also fabricated by thermoplastic moulding. Both devices are driven by miniaturized electromagnetic actuators. Experiments demonstrate that the head pressure produced by the pump is and the maximum flow rate is . The active valve is designed to be normally closed till an external pressure of .

Electrical characterization of a charged workpiece grounded-sprayer electrostatic painting system

In situations where paint resistivity is low, as it is with waterborne paints, it is not possible to use conventional electrostatic painting systems without isolating the sprayer, the fluid handling system, and the paint containers. An alternative technique is to apply high voltage to the workpiece and ground the sprayer. The electrical characteristics of such a system are evaluated and compared with those of the conventional electrostatic spraying system using computer simulations. It is shown that a charged workpiece grounded-sprayer system can achieve a transfer efficiency that is comparable to that of a conventional electrostatic system. The results also predict an enhancement in the film build along curved surfaces and strong wraparound. These predictions have been confirmed experimentally. Furthermore, the analysis indicates that there is no improvement in the paint deposition for recessed surfaces. >

An infrared sensitive stopped-flow apparatus (for studying fast chemical reactions)

A Perkin-Elmer 237 infrared spectrophotometer has been modified to enable stopped-flow kinetic measurements to be made. The machine has a single-beam system, with the radiation chopped at 2 kHz; the detector is a liquid nitrogen cooled InSb photoconductive device; a new form of sampling circuit associated with this detector is described. A new form of 'diaphragm syringe' has been developed for the fluid handling system. The machine is sensitive from 4000 cm-1to 1800 cm-1with a signal to noise level less than 0.3%; kinetics of reactions may be studied with half lives ranging from ca. 10 ms to 10 s; it is purged of CO2and H2O and may be thermostated between 10 degrees C and 40 degrees C. The apparatus is being applied to the study of the reactions of various organometallic and transition metal complexes containing ligands with infrared absorptions in the region of 2000 cm-1.