Dead Volume Research Articles

Investigation of the effect of dead volume on the shape of breakthrough curve – New method designed to correct this effect

At laboratory scale, the reactor volume may be the same order of magnitude as the dead volume of the experimental set-up. The purpose of this study is to provide a new simple method to obtain a breakthrough curve on an inert porous media (without adsorption), corrected from the influence of the dead volume, to study only the effect of the axial dispersion. Indeed, our study parameters (pressure, low flow rate, fixed bed column filled with an inert porous media) did not allow us to use the classical and simple method, known as Point by Point (PBP). This new method (Elementary Surface Area ESA) is based on the substraction of elementary surfaces of dead volume and raw breakthrough curves, whereas the PBP method is built on a point by point substraction. Therefore, each elementary surface, defined by two points of the breakthrough curve, induces a smoothing of the fluctuations observed by the PBP method. So the ESA method could be considered as an inprovment of PBP one. Analysis of breakthrough curve requires calibration of the measurement devices for both flow rate and gas stream composition. Some calibration results are also presented in this paper.

Characterization of the Dynamic Flow Response in Microfluidic Devices.

The purpose of this study is to characterize the dynamic response of fluid flow in microchannels, which can show significant delay times before reaching steady flow conditions. Two main sources of these delays are numerically and experimentally investigated, the hydraulic compliance which originates from the flexibility of the system components (microchannel, tubing, syringe, etc.), and the compressibility of the liquid dead volume in the setup, also known as the "bottleneck effect". A fluid-structure interaction model is presented for the compliance of rectangular PDMS microchannels that is used to form a numerically based relation for the compliance as a function of the pressure and geometry. This relation is successfully able to predict the dynamics of the flow inside PDMS microchannels in stop-flow experiments. The time delays associated with the bottleneck effect is also shown when using different syringe volumes, microchannel resistances, and liquid types. In these tests, the bottleneck effect has a much larger effect compared to the compliance of the PDMS microchannels. This is true even when using softer PDMS by increasing the monomer-to-curing agent mixing ratio. The characterization that is presented here allows for a simple analysis of microfluidic networks using the hydraulic-circuit approach.

Device for automated aseptic sampling: Automated sampling solution for future cell and gene manufacturing.

Cell sampling is a key step performed regularly throughout the cell manufacturing process to gather cell samples for cell growth, progress, and characteristics analysis. While the current method of sampling by pipetting in a biosafety cabinet is commonly used, it is labour-intensive and susceptible to contamination risks. We have developed Device for Automated Aseptic Sampling (DAAS), to enable automated, small volume (0.02-1.00mL) aseptic sampling with minimal dead volume primarily for cell and gene therapy manufacturing. The aim of DAAS is to enable an accurate and consistent sampling process, with minimal contamination risks and interruption to the cells in culture. DAAS can potentially interface with other automated solutions to enable automated and streamlined cell manufacturing workflow and reduce overall manufacturing costs. DAAS has been verified as an aseptic sampling solution via repeated microbial ingression tests. It has also been tested for achieving comparable cell density and viability compared to manual pipetting, with negligible cross-sample carryover when used to sample Jurkat cells of different cell concentrations. The application of using DAAS to sample cell periodically and monitor cell growth and viability continuously for prolonged cell culture was successfully demonstrated with Jurkat cell culture in a static culture flask and donor T cell culture in an automated bioreactor system over a culture duration of 10days in a Biosafety Level-2 laboratory. Overall, DAAS presents great potential as an automated and aseptic sampling solution, offering cell and gene therapy manufacturers easier and more frequent access to cell samples with minimal interruptions to the cell culture. This enables close monitoring of cell culture and a more automated, connected and cost-effect cell and gene therapy manufacturing process.

Photoactive integrated microfluidic valves for on-chip fluid control

In microfluidics, on-chip fluid control is crucial for applications where programmable and automated fluid handling with low dead volume and limited auxiliary equipment is desired. This is, for instance, the case for point-of-care (POC) devices, especially in low resource settings. The integration of photoactive valves into a disposable microfluidic chip is one method of attaining low-power and non-contact fluid control in the blink of an LED. A liquid crystal network (LCN) based micro-valve was developed, which enables rapid fluid transfer on-chip by opening a venting channel upon illumination at 80 mW cm-2 with a 455 nm wavelength LED. We show in two proof-of-principle devices that multiple valves can be integrated into a 3D-printed microfluidic chip. Their individual actuation leads to directed sequential filling as well as draining of a reaction chamber, providing the prerequisite for intricate on-chip processes. Thus, our photoactive valves show the potential of facilitating programmable lab-on-a-chip experiments, for instance, for sample preparation such as for bind-wash-elute protocols, for immunoassay, or for amplification-based detection methods.

OpenPrep: Sensor Event-driven Open Column Chromatographic Sample Preparation System.

We propose a sensor event-driven, open-column chromatographic sample preparation system─OpenPrep. This system replaces the problematic flow selector valve with a noncontact built-in sensor, eliminating carryover and clogging issues, which are commonly encountered in pump-driven chromatographic systems. The innovative valveless column-flow design, combined with a compact gantry dispenser and motion stage-based fraction collector, reduces the sample flow path to a disposable component with a postcolumn dead volume of only 0.5 mL. This configuration is superior to conventional dynamic flow systems owing to its ability to minimize sample consumption, eluent loss, and cleaning waste generation. Thus, OpenPrep can be ideal for preventing cross-contamination. Owing to the rapid flow-transfer and stop approach, OpenPrep achieves higher reagent delivery accuracy and precision compared to ISO 8655-2 piston-operated pipettes, by minimizing liquid residue on the dispensing tip. Sensor-driven flow control ensures precise eluent collection and automatic regulation of the mobile-phase flow rate through an online calibration algorithm, meeting all the requirements for accurate and reproducible column flow control. OpenPrep features an open architecture for both hardware and software, offering high flexibility for analyzing samples with considerable variations in radioactivity and matrix compositions, such as radioactive waste. The proof-of-concept implementation of a multistage sequential separation strategy, using five resin columns to separate Re, Sr, Fe, and Ni from a single sample, demonstrates that OpenPrep provides enhanced flexibility and reconfigurability, improved operational efficiency, and cost-effective customization. Excellent chemical yields were obtained for Re, Sr, and Ni in the range of 83-97%, with less than 2.6% relative standard deviation at a flow rate three times faster than the gravity method. Additionally, improved recovery performance of Fe was achieved by applying a slower flow rate compared to gravity flow.

Comparison of experimental and simulated separation performance in capillary tube-in-manifold devices

A metal tube-in-manifold packed bed capillary column device, designed to overcome common limitations associated with capillary LC separations, is described. Experimental results of initial packing tests with sub-3 μm core-shell particles demonstrated efficiencies greater than 47,000 plates/m for a separation performed using the column device. Computational fluid dynamics (CFD) modeling of the multicomponent separation used for this work was validated against experimental LC results and the optimized model was able to effectively predict component peak retention times. However, the accuracy of predicted efficiencies requires further refinement. The tube-in-manifold design demonstrates that packed capillary columns with cylindrical cross-sectional channel geometry and ultrahigh pressure, low dead volume fluidic connections are achievable.

Effect of Pouring Techniques and Funnel Structures on Crucible Metallurgy: Physical and Numerical Simulations

In the planar flow casting process of amorphous strips, the flow behavior of molten metal and the inclusion content in the crucible are crucial to the morphology and magnetic properties of the material. This study conducts a comparative analysis of the effects of non-immersed and immersed funnels, as well as various funnel structures, on the fluid flow and inclusion removal efficiency in the crucible by integrating numerical and physical models. The findings reveal that for the same pouring flow rate, the diameter of the liquid column in non-immersed pouring conditions is smaller than that of the funnel outlet, leading to a faster injection flow velocity. As a result, the melt in the crucible is subjected to severe impacts, accompanied by an increased possibility of slag entrapment. Conversely, immersed pouring substantially reduces the velocity of the molten metal at the funnel outlet, thereby extending the residence time in the crucible and diminishing the volume of the dead zone. Additionally, the molten metal backflows due to the negative pressure formed in the inner chamber of the funnel. The design of a trumpet-shaped funnel increases the effective volume while reducing the height of the backflow fluid, consequently reducing the velocity of the molten metal at the funnel outlet and prolonging the residence time. Compared to the conventional pouring process with the non-immersed funnel, the outlet velocity is reduced from 1.1 m/s to 0.12 m/s by adopting the immersed funnel with an inverted trapezoidal trumpet structure. This reduction results in a stable flow state, a 9.69% reduction in the dead zone volume fraction, and a 22.96% increase in average inclusion removal efficiency. These improvements demonstrate that a crucible funnel with a well-designed structure and the implementation of an immersion process can significantly improve the metallurgical effects in the planar flow casting process.

Microscale sampling of the coral gastrovascular cavity reveals a gut-like microbial community

Animal guts contain numerous microbes, which are critical for nutrient assimilation and pathogen defence. While corals and other Cnidaria lack a true differentiated gut, they possess semi-enclosed gastrovascular cavities (GVCs), where vital processes such as digestion, reproduction and symbiotic exchanges take place. The microbiome harboured in GVCs is therefore likely key to holobiont fitness, but remains severely understudied due to challenges of working in these small compartments. Here, we developed minimally invasive methodologies to sample the GVC of coral polyps and characterise the microbial communities harboured within. We used glass capillaries, low dead volume microneedles, or nylon microswabs to sample the gastrovascular microbiome of individual polyps from six species of corals, then applied low-input DNA extraction to characterise the microbial communities from these microliter volume samples. Microsensor measurements of GVCs revealed anoxic or hypoxic micro-niches, which persist even under prolonged illumination with saturating irradiance. These niches harboured microbial communities enriched in putatively microaerophilic or facultatively anaerobic taxa, such as Epsilonproteobacteria. Some core taxa found in the GVC of Lobophyllia hemprichii from the Great Barrier Reef were also detected in conspecific colonies held in aquaria, indicating that these associations are unlikely to be transient. Our findings suggest that the coral GVC is chemically and microbiologically similar to the gut of higher Metazoa. Given the importance of gut microbiomes in mediating animal health, harnessing the coral “gut microbiome” may foster novel active interventions aimed at increasing the resilience of coral reefs to the climate crisis.

Interpretation of possible biogas production capacity by investigating the effects of anaerobic digester tank geometry and angular velocity on flow characteristics.

Mixing performance in reactors producing biogas through anaerobic digestion is one of the parameters that directly affect biogas yield. The most commonly used mixing model for bioreactors in biogas-production processes is mechanical mixing. In the present study, we focus on the geometry of the tank, where the mechanical mixing actually takes place. In this context, by using the six-blade standard Rushton impeller in two different types of tank, flow patterns involving velocity, dead zone volume, turbulent kinetic energy, and turbulent eddy dissipation rate in the angular velocity range of 25-100rpm were observed, and the possible effects of the results on biogas production were interpreted. A new impeller design was proposed that maximizes the interface between the fluid inside the reactor tank and the impeller, which has the potential to reduce the dead zone volume to significantly lower levels. Our results showed that the lowest dead zone volume was achieved for a 60° slope reactor tank compared to the conventional 90° slope reactor tank at an angular velocity of 100rpm. The dead zone volume decreased to 0.000094 m3 at 100rpm in the 60° slope reactor tank with a total volume of 0.0305 m3, which by comparison was 0.000374 m3 in the 90° slope reactor tank. The magnitudes of both maximum turbulent kinetic energy and maximum turbulent eddy dissipation were higher in the 60° slope reactor tank at all angular velocities examined, which would be expected to enhance mixing performance. It is hoped that the reader will benefit from the results of this study; however, further studies should be conducted on the use of actual biowaste as the working fluid instead of water.

B-031 A new Ready to use Bio-Rad Quality Control to Streamline Daily Workflow

Abstract Background A comprehensive Quality Management System starts with performing a daily Quality Control (Q.C.) process. The daily Q.C. process monitors the Instrument’s optimal performance and detects shifts and trends. However, the existing traditional daily Q.C. process is not only prone to manual errors, but also time consuming, costly and labor intensive. We evaluated a Bio-Rad InteliQTM Load and go Quality Control that comes in a barcoded tube ready to be loaded. We monitored the workflow efficiency gained in comparison to the traditional quality control material that comes in glass vials. Methods We evaluated the new quality control material ready to load on the instrument. This new Q.C. (Bio-Rad InteliQ Assayed Multiqual Control - 3 levels) were processed in parallel with our routine Q.C. (Bio-Rad Assayed Chemistry Lyphocheck vials - 2 levels). We performed the evaluation on Abbott Architect c8000 Chemistry analyzers in our central Laboratory (NGHA-Jeddah). The Q.C. was stored frozen. Before testing it was thawed at room temperature as per the insert instruction. Over a 5 days period, in parallel with our routine quality control, we run the new Q.C. Two times per day for 33 analytes. We monitored the processing time difference between the new and current approaches. We monitored the stability of all the analytes in the tube after Two days and again after Five days. We also monitored the cost effectiveness, labor intensiveness, probability of operator error and the overall improvement in workflow and Turn Around Time. Results Over the evaluation period, we observed the following: - Saving 40 minutes in average per week only for chemistry Q.C (time spent in reconstituting, mixing and aliquoting old Q.C) - 100% reduction in waste of plastic consumables such as pipette and plastic tubes. - Save an average of 1.0 ml dead volume in every 5.0 ml old Q.C. vial (20% of the volume, hence saving 20% of the total Q.C. cost). The dead volume wasted due to aliquoting step using the old Q.C. - 100% Eliminated delays caused by operator error such as wrong reconstitution, inadequate mixing and wrong Q.C. aliquoting. Not needed for the InteliQ. - High score of staff satisfaction. - Stability of the 32 analytes was excellent except that of Co2, which deteriorated by 14% after Two days as indicated in the insert package. Co2 day five result deteriorated by 34%. Conclusions Bio-Rad InteliQ is easy to use. It saves time and cost. When combined with Unity Q.C. data management solution it can streamline Q.C. workflow, eliminate operator errors, reduce T.A.T. and increase the overall laboratory performance. It may also work optimally with Instruments that have on-board fridge for Q.C.

Continuous Casting Tundish Dead Volume Study by Physical Modeling and Computational Investigation

Flow efficiency in a two‐strand continuous casting tundish is studied by analyzing the residential time distribution (RTD) curves in a small‐scale tundish water model using a conductive NaCl solution tracer. The velocity fields in the tundish water model are measured by particle image velocimetry, which is used to validate the results of the mathematical model in the article. It is found that the tracer concentration has a significant impact on the predicted dead volume fraction in the RTD analysis. Validated mathematical modeling of the computational fluid dynamics (CFD) technology is performed to explore the root cause of the defective results in the RTD analysis. It is found that the flow inside the tundish is sensitive to density variations caused by the injected tracer. A denser tracer will stay lower in the tundish by gravity and flow out of the tundish more quickly. A proper tracer concentration in the water model experiments is discussed to visualize the dead volume and improve tundish furniture design efficiently for future work, a new method using CFD modeling is proposed in this article, which can directly demonstrate the dead volume's location.

Development of a superheated water chromatography method for the sustainable determination of preservatives in foods and cosmetics

The present research focused on the use of high temperatures to achieve fast separations in Liquid Chromatography (LC) and minimize the consumption of organic solvents. Particularly, superheated water was employed, by exploiting the decrease in dielectric constant of water when increasing the temperature. To realize this kind of application, the availability of LC columns resistant at high temperature is mandatory. Recently, porous graphitic carbon (PGC) columns have been proposed as stationary phases resistant up to 250 °C. Hardware modifications were also necessary to guarantee the efficient heating of the mobile phase prior of entering the column, as well as its rapid cooling before detection by photodiode array (PDA). Specifically, an LC system was interfaced to a GC oven, which hosted the LC column; to achieve a fast and efficient heating of the eluent coming from the autosampler prior to enter into the column, a pre-heating tube was interposed between the autosampler outlet and the column inlet. Instead, a cooling loop was connected between the column outlet and the PDA cell. A mixture of 1-nitroalkanes was used to evaluate the performance of the system in terms of dead volumes, band broadening and peak shape, as well as chromatographic efficiency and resolution. The use of higher temperatures allowed to perform analyses at higher flow rates in reduced analysis time and was also in terms of peak bandwidth resulting to increased efficiency for the most retained compound. Moreover, van't Hoff plots were obtained at different temperature, confirming that the most retained analyte greatly benefited of the temperature increase.The system was applied to the analysis of parabens in cosmetic and food products. The method combined eco-sustainable sample preparation with high-temperature LC separation on a PGC column and was fully validated in terms of linearity, precision, accuracy and detection and quantification limits. The developed method was critically evaluated by comparing the output of different metric tools implemented in the last decade for the quantitative assessment of the greenness.

Review and Thermal Calculation of a Shell and Tube Heat Exchanger with Baffles in Cross - Counter Flow Arrangement

In one pass shell and tube heat exchanger with baffles one fluid flows inside of parallel tubes and other fluid flows outside of tubes in perpendicular to tube axis changing alternately its direction. Passing the window of the baffles the shell side fluid deviates its flow direction rapidly. This creates just behind the window of each baffle a so-called “dead volume” which renders a stagnation of flow. This dead volume assumed to be triangular in shape causing the flow behind the window to be conical.In this thermal model the “dead volume” taken into account and change of temperature of the shell side fluid during its flow from tube to tube is considered. The thermal analysis of the cross- counter flow arrangement for any number of tube in bundle with progressive changes in tube length has been carried out. The numerical computations with different tube and baffle numbers are performed. It is found that at the beginning the effectiveness of the heat exchanger increases distinctly with increasing tube number and baffle number. But after certain number of tube and baffles the increasing rate weakens and it becomes very small. Due to the presence of “dead volume” there is reduction in the thermally active heat transfer surface area which leads to a smaller value of Number of Transfer Units (NTU). Hence, the results of computation obtained in this paper with the consideration of the “dead volume” will provide lower value of the effectiveness than that of without the consideration of it.

NanoRidge filters: Fabrication strategies and performance optimization for nano-scale microfluidic particle filtration.

Filters with high throughput, minimal dead volume, and greater sensitivity to particle size are needed, which traditional benchtop filtration cannot provide. Leveraging microfabrication techniques developed by the electronics and optics industries, the filters presented here feature a unique serpentine "NanoRidge" structure, offering a continuous filtration gap spanning over three meters on a compact 4 × 14.5 mm2 footprint. This design provides more precise size filtration cut-offs and consistent flow paths compared to traditional membrane filtration systems. Despite challenges associated with glass substrate deformation impacting uniform filter gap sizes, the study provides valuable insights into the development of NanoRidge filters (NRFs) for enhancing filtration efficiency in preparatory techniques and sample analysis. This study describes the fabrication and testing of these new filter types and directly compares the performance to traditional membrane filters using the metrics of particle size cut-off (the smallest difference in particle size which can be filtered vs passed) and particle loss. The NanoRidge filters were characterized using imaging (during fabrication, post-fabrication and use, fluorescent particles captured and small molecule dye), pressure and flow measurements, and a series of particle sizes "filter or pass" studies. Particle capacity (100-250 nm) ranged from 5 × 108 to 7 × 109 in 1 ml samples at a flow rate of 100 μl/min with backpressure in the range of 1-3 Bar. The optimized fabrication procedure for the 150 nm NRF yielded a small particle recovery of 95% while also achieving a large particle filtration of 73%. High filtration efficiency was also proven in the final 60 and 80 nm NRF fabrication procedures at 96% and 91%, respectively.

Infiltrated electroless deposition of gold nanoparticles on porous Prussian blue-Fe2O3 hetero-microstructures for environmental remediation applications: A novel infiltration strategy to form 3-D nano-catalytic networks

Metal and metal oxide nanocomposites are promising candidates for heterogeneous catalytic applications. In this regard, most of the metal oxide inner core volume remains as a dead volume, not participating in the catalysis, only the metal/metal oxide hetero-junctions available at the surfaces are involved in the catalysis. Herein, we report a novel strategy for the infiltration of gold nanoparticles into the inner core of 3D-porous Prussian blue/Fe2O3 hetero-microstructures (PBFHM-Au) beyond its outer surface to form an advanced heterogeneous catalyst for the environmental remediation applications. The porosity of the Prussian blue microstructures is thermally tuned for the infiltration of gold ion precursor into the inner core volume of Prussian blue/Fe2O3 hetero-microstructures to facilitate the galvanic displacement reaction between Fe and Au to enlarge the lattice shell and form Au nanoparticle 3D networks throughout the PBFHM. Notably, the resulting PBFHM-Au2 shows enhanced structural stability electron transfer kinetics and catalytic activity in comparison with the only surface-attached Au/Fe2O3 composite. The obtained PBFHM-Au2 catalyst demonstrates remarkable catalytic activity for Rhodamine-B dye degradation with rate constant (k = 3.47 × 10−2 s−1) and p-nitrophenol reduction reactions with rate constant (k = 1.199 × 10−1 s−1).

Relative profile measurements in 1.5T MR-linacs: investigation of central axis deviations

Objective. In 1.5 T MR-linacs, the absorbed dose central axis (CAX) deviates from the beam's CAX due to inherent profile asymmetry. In addition, a measured CAX deviation may be biased due to potential lateral (to the beam) effective point of measurement (EPOML) shifts of the detector employed. By investigating CAX deviations, the scope of this study is to determine a set ofEPOMLshifts for profile measurements in 1.5 T MR-linacs.Approach. The Semiflex 3D ion chamber and microDiamond detector (PTW, Germany) were considered in the experimental study while three more detectors were included in the Monte Carlo (MC) study. CAX deviations in the crossline and inline profiles were calculated based on inflection points of the 10×10 cm2field, at five centers. In MC simulations, the experimental setup was reproduced. A small water voxel was simulated to calculate CAX deviation without the impact of the detector-specificEPOMLshift.Main results. All measurements were consistent among the five centers. MC-based and experimental measurements were in agreement within uncertainties. Placing the microDiamond in the vertical orientation does not appear to affect the detector'sEPOML, which is on its central longitudinal axis. For the Semiflex 3D in the crossline direction, the CAX deviation was 2.3 mm, i.e. 1 mm larger than the ones measured using the microDiamond and simulated considering the ideal water detector. Thus, anEPOMLshift of 1 mm is recommended for crossline profile measurements under both Semiflex 3D orientations. For the inline profile, anEPOMLshift of -0.5 mm was determined only for the parallel configuration. In the MC study, CAX deviations were found detector- and orientation-dependent. The dead volume is responsible for theEPOMLshift only in the inline profile and under the parallel orientation.Significance. This work contributes to data availability on the correction or mitigation of the magnetic field-induced changes in the detectors' response.

Influence of operating parameters on the flow of the molten bath during the swirl-type oxygen lance blowing process

ABSTRACT In top-blowing steelmaking, the flow behaviour of molten steel during supersonic jet impact into the molten bath is crucial for the refining process. In this study, the effects of lance height and operation pressure on velocity distribution and the flow characteristics of the molten bath during the swirl-type oxygen lance blowing process in a 260t converter were explored. The results demonstrate that compared to the traditional oxygen lance, the stirring efficiency of a molten bath with the swirl-type oxygen lance is improved due to the tangential momentum of the jet and the increase in cavity diameter. As the lance height increases, the flow is improved at the bottom and surroundings of the molten bath, and the dead zone volume of the molten bath decreases first and then increases. The best stirring efficiency is achieved at H = 40de. As the operation pressure increases, the impact strength of the jet increases, the flow at the upper zone of the bath is significantly improved, and the dead zone volume decreases.

Development of a Controlled Humidity Differential Electrochemical Gas Monitoring System

Lithium-air batteries (LABs) represent a promising future battery technology due to their high energy density, although several challenges hinder them from achieving their theoretical performance. These challenges include clogging of the porous air cathode by insoluble discharge products and high overpotentials during cycling [1, 2]. A recent proposal to address these issues involves the reversible formation and oxidation of LiOH in nonaqueous LABs. Of course, LiOH-based LABs require a proton source to form LiOH from the electrochemical reaction of oxygen and lithium ions [3]; humidity in air is an obvious choice for the proton source, making the relative humidity of LAB feed gas an important parameter to control and monitor during LAB electrochemical analysis.For LABs, galvanostatic charge/discharge coupled with quantitative gas evolution/consumption measurement is essential to understand the electrochemical processes during battery operation. Here, we report an advanced operando pressure measurement system that allows the control and monitoring of humidity in the cell headspace while also tracing overall gas consumption and evolution. Our gas handling system generates humid air using a water-containing chamber with a temperature control vessel to generate water vapor. A mass flow controller mixes dry air with humid air to generate specific relative humidity and send it to the cell. Using various low-volume in-line sensors, our system can track headspace humidity, temperature, and pressure within a custom-modified Swagelok-type cell. The total headspace volume must be small (~mL) since gas consumption occurs on a μmol scale in our lab-scale cells. To minimize headspace and dead volume within the Swagelok-type cell, a digital humidity and temperature sensor with exceptional accuracy was integrated into a customized printed circuit board (PCB). This PCB is attached to the small dead-volume Tee connection. To control the humidity inside the cell and achieve sensor data simultaneously, all sensors in the monitoring system are controlled by a LabVIEW program (National Instruments). To show the utility of this new system, we will present analyses of nonaqueous and solid-state LAB cells that operate at various humidities and current rates, while employing various known 2 e- and 4 e- oxygen reduction catalysts.

Fabrication of organic thin films using slit nozzle with a wide viscosity spectrum

A slit nozzle with a broad viscosity spectrum is highly demanded for slit coating of various materials with different viscosities without a compromise on the film quality. To this end, we have fabricated a multi-cavity slit nozzle with the inlet and vent holes for each cavity. Compared with a slit nozzle with a high-volume single cavity, such a multi-cavity slit nozzle further reduces the dead volume and thus material waste. As a design parameter in computational fluid dynamics (CFD) simulations for the multi-cavity slit nozzles, we have calculated the coefficient of variation in the internal pressure (Pcv) of the cavity and investigated the correlation between the simulated Pcv value and the measured thickness uniformity of low-viscosity (tens of cPs) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), medium-viscosity (5000 cPs) polydimethylsiloxane (PDMS), and high-viscosity (18,000 cPs) hard-PDMS films. It is addressed that the Pcv value that can ensure the thickness non-uniformity of less than 5 % is of the order of 1 %, and the internal pressure of the nozzle should not exceed a specific upper limit to protect a coating system against overload. Based on the design guideline provided, we have found that the upper limit of the viscosity spectrum of the triple-cavity slit nozzle with the 800-μm-thick shim is 79,000 cPs when the flow rate is 50 ml/min. Using the multi-cavity slit nozzle, we have fabricated a highly uniform PDMS film exhibiting the tensile strain as high as 180 %, which can be used as a substrate for stretchable displays. Furthermore, we have successfully fabricated flexible OLED stripes on the slit-coated conductive PEDOT:PSS stripes, showing the average luminance of 72.8 cd/m2 at 5 V and inter-stripe luminance non-uniformity as low as 8.2 %.

Integrated interferometers as a new platform for low cost gas chromatography detection

Gas chromatography is a reference method for gas analysis. As part of efforts to miniaturize gas chromatography systems, the miniaturization of detectors is essential. In this work, we report a new integrated photonic platform for gas chromatography analyte detection. The fabricated silicon die integrates Mach-Zehnder interferometers into low dead volume microfluidic channels, with coherent cost-effective detection scheme with a fixed 850 nm wavelength laser. A proof of concept is demonstrated with the separation and detection of three volatile organic compounds: heptane, octane, and toluene. Peaks’ widths at half height range from 1 to 5 s. Peaks are very well resolved by our system, which acquires more than 100 points per second. From a heptane dilution range, we evaluate the limit of detection of our system to be the headspace of a 0.26 % heptane concentration solution. To our knowledge, these are the first integrated Mach-Zehnder interferometers reported for gas chromatography detection. This work could open new strategies for fast low cost and low limit of detection specific gas chromatography silicon micro-detectors.