Teflon Capillary Research Articles

Hydrophilic Modification of Polytetrafluoroethylene (PTFE) Capillary Membranes with Chemical Resistance by Constructing Three-Dimensional Hydrophilic Networks.

Polytetrafluoroethylene (PTFE) capillary membranes, known for the great chemical resistance and thermal stability, are commonly used in membrane separation technologies. However, the strong hydrophobic property of PTFE limits its application in water filtration. This study introduces a method whereby acrylamide (AM), N, N-methylene bisacrylamide (MBA), and vinyltriethoxysilane (VTES) undergo free radical copolymerization, followed by the hydrolysis-condensation of silane bonds, resulting in the formation of hydrophilic three-dimensional networks physically intertwined with the PTFE capillary membranes. The modified PTFE capillary membranes prepared through this method exhibit excellent hydrophilic properties, whose water contact angles are decreased by 24.3-61.2%, and increasing pure water flux from 0 to 1732.7-2666.0 L/m2·h. The enhancement in hydrophilicity of the modified PTFE capillary membranes is attributed to the introduction of hydrophilic groups such as amide bonds and siloxane bonds, along with an increase in surface roughness. Moreover, the modified PTFE capillary membranes exhibit chemical resistance, maintaining the hydrophilicity even after immersion in strong acidic (3 wt% HCl), alkaline (3 wt% NaOH), and oxidative (3 wt% NaClO) solutions for 2 weeks. In conclusion, this promising method yields modified PTFE capillary membranes with great hydrophilicity and chemical resistance, presenting substantial potential for applications in the field of water filtration.

Guiding as a General Consequence of the Charged Particle Interaction with the Inner Surface of an Insulator Capillary—Guiding of 1 MeV Proton Microbeam through Polytetrafluoroethylene Macrocapillary

The transmission of energetic, 1 MeV proton microbeam through a single, cylindrical shaped, macrometer-sized polytetrafluoroethylene capillary was studied experimentally. The capillary axis was tilted with respect to the axis of the incident ion beam. The tilting, the aspect ratio of the capillary and the small beam divergence disabled the geometrical transmission of the beam through the target. The intensity, energy, deflection and charge state of the transmitted beam were investigated. We found that the pure guided transmission of a MeV/amu energy ion beam is observable. We clearly identified three completely different stages during the guiding process according to the measured energy distribution of transmitted particles. At the beginning the transmission intensity was low and only inelastic contributions with energy lower than 1 MeV were found in the spectrum. Later, in the second stage, the elastic peak appeared and became more and more significant. Finally, when the stable transmission evolved, only the elastic peak was present and the inelastic area was totally absent as a direct consequence of the ion guiding and as a result of the charged particle interaction with a charged inner surface of the insulator capillary.

A reusable optical fiber sensor for ethanol gas detection with a large concentration range

Ethanol is an important material in for chemical, pharmaceutical or food industry. But ethanol gas in the air induces health danger and explosion risk. Therefore, the concentration of ethanol gas must be monitored. In this paper, an optical fiber device for ethanol gas detection is demonstrated. Glycerol aqueous solution is taken as the ethanol absorbent, a Teflon capillary is used as the gas permeable cell and a surface plasmon resonance (SPR) fiber sensor is employed as the receiver. When ethanol gas permeates into the capillary and be absorbed by the absorbent, the refractive index of the absorbent is modulated and then detected by the SPR sensor. With this principle, sensing devices were fabricated and tested. Within the range of 0–7534 ppm, the limit of detection (LOD) is obtained as 38.31 ppm. In cycle test, the excellent reusability, repeatability and durability are testified. In addition, with the large detectable range and low cost, the proposed device may realize wide applications in industrial process.

A Microfluid Fiber Device for Trace Detection of Aggregation Induced Emission Molecules

An ultra-sensitive microfluid device for detecting aggregation of induced emission molecules is proposed and demonstrated. The minimum detectable concentration is greatly reduced by use of a micromachined fiber tip and a liquid core waveguide. The fiber tip is a tapered-microlens structure with optimized shape parameters. The liquid waveguide is formed with low refractive index Teflon capillary. The dependence of photoluminescence intensity on the concentration change is tested with the device. The limit of detection is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.316 \boldsymbol {\mu }\text{M}$ </tex-math></inline-formula> , the volume of the sample solution used is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.649 \boldsymbol {\mu }\text{L}$ </tex-math></inline-formula> and the minimum detectable concentration is down to 100 nM. It is a valuable result obtained with fiber spectrometer (a CCD-type machine), better than that obtained with traditional fluorospectro photometer (a photomultiplier tubes-type one). The reversibility and stability are also testified through experimental method. Together with the compact size, small sample volume and high sensitivity, the durable microfluidic sensing device has great potential for biosensing applications.

Sensitivity-enhanced temperature sensor based on encapsulated S-taper fiber Modal interferometer

We demonstrated a simple technique for a highly sensitive temperature sensor based on an “S”-shape fiber taper Mach-Zehnder interferometer (MZI) with no need of special fibers or micromachining technique using high power lasers. To enhance the sensitivity, an S-shape single mode fiber (SMF) taper was encapsulated in a capillary filled with high thermos-optic coefficient liquid. We experimentally investigated the tuning parameters for the sensor, such as the taper shape, the material of the capillary, and the role of the filling liquid. Our results show a maximum sensitivity of −15.66 nm/°C in a measurement range of 28–32 °C, and −11.88 nm/°C from 25.1 °C to 35 °C for isopropanol sealed in Teflon capillary. The multi-interference model simulation shows that a critical cladding mode is responsible for the high sensitivity. Simple configuration, ease of fabrication, robustness and low cost make it suitable for high sensitivity temperature sensing applications.

＞500 W passively-cooled fiber cladding light stripper

To realize of passive-cooling high power fiber cladding light stripper, it is important to optimize the thermal management of both the fiber and the package. By using Teflon capillaries to make segmental etching configuration on fiber, using copper as the package material, and optimizing the package structure through finite element thermal simulations, cladding light stripper capable of handling 500 W power was designed and fabricated. It was experimentally verified that the stripping efficiency reached 23.7 dB and the temperature increase rate on the bare fiber of cladding light stripper was as low as 0.007 ℃/W. In addition, at 540 W of power injection, cladding light stripper could work continuously if mounted on water-cooled cold plate, and could work for 50 s each time if mounted on cold plate filled with phase-change material, with the maximum temperature of package being 58.7 ℃ and 80 ℃ respectively. The researches and results could provide valuable information to the design and development of high power fiber lasers.

A durable and miniature microfluid device for detection of aggregation-induced emission molecules

An aggregation-induced emission (AIE) molecules detecting device was proposed. It was a microfluid sensor, fabricated with Teflon AF 2400 capillary and micromachining technique. The Teflon capillary played three roles in the detecting system simultaneously: the microfluid channel, the optical waveguide and the fluorescence collector. The microfluid channel was formed by a laser ablated micro hole and an open capillary end. The optical waveguide and the fluorescence collector were functionalized by the particular refractive index (RI) of the capillary, which was 1.29, lower than water (RI: 1.33). When filled with AIE solution, the Teflon capillary had a RI distribution of inner higher and outer lower which form an optical waveguide. Then the excited fluorescence was collected and transmitted within it. The length of capillary was optimized through an experimental method. With an optimized device, the fluorescence intensity depending on the concentration was tested. The experimental results were in accordance with the traditional micro plate spectrophotometer methods. The limit of detection (LOD) was obtained as 3.94 μM with only 1.946 μl volume solutions, better than previous works. The bending loss of the device was also examined. With the curvature of 10.3 m−1, only 13% transmission loss was detected which means the sensing device could be expected to apply in vivo. In addition with the advantages of small size and durable structure, the proposed device has bright future in many biosensing applications.

Plasma Flows of High-Current Discharge in a Capillary and Their Propagation Across a Magnetically Insulated Line

The characteristics of sources of plasma flows formed by high-current discharges in polyethylene, teflon, and ceramic capillaries are presented that allow high-velocity flows of high-density plasma to be obtained. The influence of the initial voltage on the capillary, rate of current growth, and current amplitude on the parameters of the formed plasma bunches and on the service life of the capillaries made of the examined dielectrics is shown. Experimental data on propagation of bunches in crossed electric and magnetic fields of a magnetically insulated transmission line are presented.

Properties and Reactivity of Hydroxides of Group 13 Elements In, Tl, and Nh from Molecular and Periodic DFT Calculations.

Adsorption energies, Eads, of gaseous hydroxides of In, Tl, and the superheavy element Nh on surfaces of Teflon and gold are predicted using molecular and periodic relativistic DFT calculations. The ambition of the work is to assist related "one atom at a time" gas-phase chromatography experiments on the volatility of NhOH. The obtained low values of Eads(MOH), where M = In, Tl, Nh, on Teflon should guarantee easy transportation of the molecules through the Teflon capillaries from the accelerator to the chemistry setup. Straightforward band-structure DFT calculations using the revPBE-D3(BJ) functional have given an Eads(MOH) value of 161.4 kJ/mol on the Au(111) surface, being indicative of significant molecule-surface interaction. The MOH-gold surface binding is shown to take place via the oxygen atom of the hydroxide, with the oxygen-gold charge density transfer increasing from InOH to NhOH. The trend in Eads(MOH) is shown to be InOH < TlOH < NhOH, caused by increasing molecular dipole moments and decreasing stability of the hydroxides in this row. A trend in Eads of the atoms of these elements on gold is, however, opposite, In > Tl > Nh, caused by the increasing relativistic contraction and stabilization of the np1/2 AO with Z. These opposite trends in Eads(MOH) and Eads(M) in group 13 lead to almost equal Eads(Nh) and Eads(NhOH) values, making identification of Nh, as a type of species, difficult by measuring its adsorption enthalpy on gold.

Protein separation through preliminary experiments concerning pH and salt concentration by tube radial distribution chromatography based on phase separation multiphase flow using a polytetrafluoroethylene capillary tube

Protein mixtures were separated using tube radial distribution chromatography (TRDC) in a polytetrafluoroethylene (PTFE) capillary (internal diameter=100µm) separation tube. Separation by TRDC is based on the annular flow in phase separation multiphase flow and features an open-tube capillary without the use of specific packing agents or application of high voltages. Preliminary experiments were conducted to examine the effects of pH and salt concentration on the phase diagram of the ternary mixed solvent solution of water–acetonitrile–ethyl acetate (8:2:1 volume ratio) and on the TRDC system using the ternary mixed solvent solution. A model protein mixture containing peroxidase, lysozyme, and bovine serum albumin was analyzed via TRDC with the ternary mixed solvent solution at various pH values, i.e., buffer–acetonitrile–ethyl acetate (8:2:1 volume ratio). Protein was separated on the chromatograms by the TRDC system, where the elution order was determined by the relation between the isoelectric points of protein and the pH values of the solvent solution.

Non-tapered PTFE capillary as robust and stable nanoelectrospray emitter for electrospray ionization mass spectrometry.

The successful implementation of electrospray ionization mass spectrometry (ESI-MS) largely relies on the physical and chemical properties of electrospray emitters. Current ESI emitters based on pulled glass or fused-silica capillaries suffer from complicated fabrication procedures and short lifetime because of clogging and breakage problems. ESI emitters with high robustness, easy operation, and low cost are in great demand. We proposed to directly use non-pulled and non-tapered polytetrafluoroethylene (PTFE) capillaries as nanoelectrospray emitters. We evaluated and studied the performance of PTFE emitters under different flow rates and ESI voltages. Their applications in direct infusion and liquid chromatography (LC)-MS analysis were achieved. High stable electrospray (relative standard deviation of total ion current intensity <5%) can be obtained at flow rates from 100nL/min to 1500nL/min and at ESI voltages from 1.8kV to 2.9kV using non-tapered PTFE emitters. Different types of samples including small-molecule drugs, peptides, and proteins can be detected with high sensitivity. LC-MS analysis of two model peptides was successfully demonstrated. We have demonstrated that a non-tapered PTFE capillary can be a promising ESI emitter for both direct infusion and LC-MS analysis. We envision it could find broad applications in high-throughput MS analysis fields, such as drug screening and proteomics, where robust and reproducible operations are essentially required. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis of metal and semiconductor nanoparticles in a flow of immiscible liquids

Nanoparticles of silver and cadmium selenide are obtained by the method of synthesis in a flow of immiscible liquids (water/toluene, water/dodecane); these nanoparticles manifest, respectively, the effects of plasmon resonance and the spatial confinement of charge carriers. The reactor used is a polytetrafluoroethylene capillary with temperature-controlled sections for particle nucleation and growth with the supply of precursors using micropumps. The diameters of the particles are determined from absorbance spectra and are found to be 40 nm for Ag nanoparticles and 1–2 nm for CdSe nanoparticles (depending on the growth duration).

Interaction of proton microbeam with the inner surface of a polytetrafluoroethylene macrocapillary

The transmission of 1MeV proton microbeam through a single, cylindrically shaped, micrometre-sized polytetrafluoroethylene capillary was studied. The capillary axis was tilted with respect to the axis of the incident ion beam. The tilting, the aspect ratio of the capillary and the small beam divergence disabled the geometrical transmission of the beam through the target. The time dependence of the intensity, the charge-state and the deflection of the transmitted beam were investigated. We found that pure guided transmission of a MeV/amu energy ion beam is possible through an insulator capillary.

Microscale extraction and phase separation using a porous capillary.

We report the use of a porous polytetrafluoroethylene capillary for the inline separation of liquid-liquid segmented flows, based on the selective wetting and permeation of the porous capillary walls by one of the liquids. Insertion of a narrow flow restriction at the capillary outlet allows the back pressure to be tuned for multiple liquid-liquid combinations and flow conditions. In this way, efficient separation of aqueous-organic, aqueous-fluorous and organic-fluorous segmented flows can be readily achieved over a wide range of flow rates. The porous-capillary-separator enables the straightforward regeneration of a continuous flow from a segmented flow, and may be applied to various applications, including inline analysis, biphasic reactions, and purification. As a demonstration of the latter, we performed a simple inline aqueous-organic extraction of the pH indicator 2,6-dichloroindophenol. An aqueous solution of the conjugate base was mixed with hydrochloric acid in continuous flow to protonate the indicator and render it organic-soluble. The indicator was then extracted from the aqueous feed into chloroform using a segmented flow. The two liquids were finally separated inline using a porous PTFE capillary, with the aqueous phase emerging as a continuous stream from the separator outlet. UV-visible absorption spectroscopy showed the concentration of indicator in the outflowing aqueous phase to be less than one percent of its original value, confirming the efficacy of the extraction and separation process.

Transient Calcium Carbonate Hexahydrate (Ikaite) Nucleated and Stabilized in Confined Nano- and Picovolumes

Calcium carbonate precipitation at different values of the nominal ionic activity product (IAP) is studied in nanoliter and picoliter droplets at (20 ± 2 °C). Experiments are carried out through direct mixing of equimolar reactant solutions using two different setups: first, droplet-based microfluidics using Teflon capillaries (nanoliter experiments) and second, the microinjection technique under oil (picoliter droplets). Instantaneous precipitation of a metastable CaCO3 phase is initially observed. This phase is stabilized in time by reducing the initial volume of the experiments from the nano- to picoliters range and when the CaCl2/Na2CO3 ratio approaches 1. Further analysis by X-ray diffraction, transmission electron microscopy, and selected area electron diffraction confirms the first nucleated phase is CaCO3·6H2O (ikaite) and in few droplets ikaite plus CaCO3·H2O (monohydrocalcite). No evidence of amorphous calcium carbonate (ACC) is found even in conditions where the IAP exceeds the solubility product of this phase. The in vitro finding of ikaite formation and stabilization due to volume confinement is an unexpected result since it is the first time that this hydrous phase is stabilized at room temperature (it is normally found at near 0 °C) in the absence of additives. This result can be of interest for those biomineralization processes occurring in the confined volumes of intracellular vesicles and for biomimetic materials science in general.

Detection of Mycobacterium tuberculosis Using a Capillary-Array Microsystem with Integrated DNA Extraction, Loop-Mediated Isothermal Amplification, and Fluorescence Detection

This article reports for the first time a high-throughput microfluidic system with fully integrated loop-mediated isothermal amplification (LAMP) analysis. With the developed system, parallel Mycobacterium tuberculosis detections were implemented in polytetrafluoroethylene capillaries through the utilization of droplet technology coupled with magnetic beads. During the analysis, liquid plugs containing different types of sample or reagents are sequentially introduced into the capillaries and made to form droplets therein. The whole analytical process, including DNA extraction, LAMP, and detection of the amplified products were conducted in such droplets. The developed microsystem is able to process 10 samples in parallel. The entire diagnostic procedure, from sample-in to answer-out, can be automatically completed within 50 min with a limit of detection (LOD) of 10 bacteria. This microsystem was evaluated by analyzing clinical samples, and a clinical sensitivity (positive detection rate) of 96.8% and specificity (negative detection rate) of 100% were achieved. The presented capillary LAMP assay features high-throughput and low-cost and thus is a promising tool for rapid tuberculosis diagnosis.

Microscale separation of immiscible liquids using a porous capillary

We describe a simple method for the direct inline separation of two immiscible liquids based on the selective wetting and permeation of a porous polytetrafluoroethylene capillary by one of the liquids. Using water dispersed in fluorous carrier fluid as a test system, quantitative recovery of the water from the carrier fluid is achieved over a wide range of flow conditions, with no contamination by the fluorous component even when present in large (ten-fold) excess. The exiting water stream may be readily redispersed by injecting additional carrier fluid downstream, allowing for repeated switching between the segmented and continuous flow regimes – a critical requirement for multistep chemical processing. The separator is shown to simplify in-line sample analysis by allowing measurements to be carried out quasi-statically without the need for fast instrumentation synchronised to the segmented water flow.

Selectivity of two types of sulfadimidine‐imprinted monolithic polymer‐based fibers

Molecularly imprinted polymeric monolithic fiber is a new technique of solid-phase microextraction that focuses on selectivity. However, the inner mechanism of increasing the selectivity is not well understood. Here, a new approach to improve the selectivity is shown through controlling the surface of a molecular imprinted polymeric monolithic fiber. Sulfadimidine-imprinted polymeric monolithic fibers were fabricated using two kinds of molds, the polytetrafluoroethylene capillary and the silica capillary. A mixture of sulfadimidine, sulfamerazine, sulfadiazine, and sulfametoxypirydazine was used to test the selectivity of the fibers to sulfadimidine. This paper demonstrates that the extraction ratio for sulfadimidine in mixture is increased to more than 150% in sulfadimidine-imprinted polymeric monolithic fiber compared to nonimprinted polymeric monolithic fiber. The extraction ratio is increased to about 30% in sulfadimidine-imprinted polymeric monolithic fiber fabricated from silica capillary than in the counterpart from nonimprinted polymeric monolithic fiber. The sulfadimidine-imprinted polymeric monolithic fibers were also applied to extract standard mixtures spiked into Pearl River water and milk. The results indicated that polytetrafluoroethylene-sulfadimidine imprinted polymeric monolithic fiber showed highest selectivity to sulfadimidine in complex samples.

Rapid Amplification and Detection of Foodborne Pathogenic Rotavirus by Continuous-flow Reverse Transcription-Polymerase Chain Reaction Integrated with Online Fluorescence Analysis

Abstract A continuous-flow polymerase chain reaction (PCR) microfluidic system integrated with reverse transcription (RT) of RNA and online fluorescence analysis was fabricated in this work and successfully applied for the fast amplification and identification of foodborne pathogenic rotaviruses. In this continuous-flow RT-PCR device, isothermal copper blocks provided the required temperatures for RT-PCR, and a polytetrafluoroethylene capillary was used as the RT-PCR reaction channel. By using circulating water to cool the annealing zone, annealing temperatures as low as 31 °C could be obtained for the herein-presented device, and good temperature control and stability was also achieved. Therefore, this device could be used for different PCR protocols. Online fluorescence analysis of the PCR products, which was integrated into this device, was subsequently carried out. When the flow rate was 7.5 mm s −1 , amplification of the cDNA reverse transcribed from rotavirus RNA and the subsequent online fluorescence analysis of the amplification products could be completed in about 12 min (about 10 min for amplification and about 2 min for analysis). By using this microfluidic device, the RT-PCR of rotavirus RNA and the online fluorescence analysis of its products could be accomplished within approximately 1 hour, with an RNA detection limit of 6.4 × 10 4 copies μL −1 . This study provides a new biochemical method for the rapid diagnosis of RNA-based viruses.

Droplet-based Extraction of Hepatitis B Virus DNA in a Capillary

A novel capillary droplet-based DNA-extraction method was developed, using the principle of water-in-oil droplet formation in a highly hydrophobic polytetrafluoroethylene capillary. By sequentially introducing droplets containing a sample or reagents, all the steps related to Hepatitis B virus DNA extraction from blood, including sample injection, DNA binding, magnetic bead rinsing, and DNA elution were continuously implemented in the capillary. Experimental results showed that Proteinase K lysis and elevated elution temperature facilitated higher extraction efficiency. Under optimized conditions, an extraction was completed within 25 min with microliter level consumption of the sample or reagent. The droplet-based method achieved an extraction efficiency of about 60%, which was comparable to that of conventional methods, with the relative standard deviation of extraction efficiency for the droplet-based method being relatively higher. In summary, the herein-developed droplet-based DNA-extraction method is simple, fast, and economic, thus having the potential to be integrated into a micro-total analysis system for nucleic acids.