Glass Capillary Research Articles

Flexible disk ultramicroelectrode: Facile preparation and high-resolution scanning electrochemical microscopy imaging

BackgroundScanning electrochemical microscopy (SECM) is a kind of scanning probe technology that enables the obtainment of surface morphology and electrochemical information by recording changes in Faraday current triggered by the movement of probe. ResultsIn this work, flexible disk ultramicroelectrode (UME) with highly repeatable geometry are fabricated through a simple and universal strategy that involves vacuum pulling the glass capillaries inserted with platinum wire (gold wire, carbon fiber, etc.), followed by a rapidly heated sealing and polishing process. Based on the optical and electrochemical characterization, the as-prepared UMEs possess favorable geometric shape with a small RG value from 1.7 to 2. Consequently, when applied as probe components for SECM imaging on interdigital electrodes, it can achieve excellent spatial resolution and high sensitivity at short working distances. Moreover, due to the outstanding flexibility, the as-prepared UMEs can be minimally damaged arising from tip-sample collision and produce invisible trace on apple peel after the contact scanning, which is far superior to the traditional UME and suggests the application potential in bio-related fields. SignificanceOur work will inspire the application of flexible UMEs as probe components in SECM, and consequently promote the widespread use of SECM with reduced collision threshold and low operational difficulty.

Highly sensitive fiber vector magnetic field sensor based on an open-cavity Mach-Zehnder interferometer filled with magnetic fluid

In this paper, we proposed and demonstrated a highly sensitive fiber vector magnetic field sensor utilizing an open-cavity Mach-Zehnder interferometer (MZI) filled with magnetic fluid. The MZI sensor was fabricated using large-offset splicing technique to form an open cavity, facilitating the easy introduction of magnetic fluid samples into the open cavity. The MZI sensor was then encapsulated in a glass capillary containing diluted magnetic fluid. As the applied magnetic field varies, the refractive index of the magnetic fluid undergoes a corresponding change, subsequently inducing a shift in the transmission spectrum of the MZI. By monitoring the wavelength shift of the transmission spectrum, we can accurately detect the intensity of the magnetic field. The proposed sensor can achieve vector magnetic field measurement because of the axially asymmetric open-cavity MZI. The maximum sensitivity to magnetic field direction is 0.260 nm/°. Notably, the proposed sensor achieves an ultrahigh sensitivity, reaching an value of −17.306 nm/mT within the range of 4 mT to 7 mT. In addition, a temperature sensitivity of 2.236 nm/℃ is obtained within the temperature range of 30 ℃ to 65 ℃. Given its advantages, including high sensitivity, compact size and low cost, our MZI sensor holds immense potential for diverse applications in magnetic field measurement.

Acoustotaxis‑based pump-less separation of highly motile human sperm by a SAW-in-capillary acoustofluidic platform

In artificial reproductive technologies mirroring in vivo fertilization, there is a correlation between sperm motility and fertilization outcomes. Here, we present a technology for separating sperm based on motility, which uses a biocompatible, pump-less, and simple acoustofluidic approach. Our developed and fabricated sperm separation configuration is an acoustofluidic platform consisting of a circular glass capillary tube mounted on top of a ZnO-based surface acoustic wave (SAW) device. It can separate highly motile sperm from small volumes of normal raw human semen samples. This configuration allows the generated traveling SAW to couple into the capillary, causing highly motile sperm cells to swim against the propagation direction of the traveling SAW along the capillary tube. We term this fascinating acoustic-induced sperm swimming behavior acoustotaxis in analogy with the well-known rheotaxis, in which sperm orientate to swim against a continuous fluid flow frequently generated by using an external pump in the microfluidic systems. Here, we benefit from the acoustotaxis for a pump-less separation of an effective highly motile sperm concentration from raw human semen samples at low volumes of up to 20–30 µL within a short period of about 4 minutes free from any centrifugation step. This sperm separation device exhibits a successful selection capability that leads to sperm progressive motility increase by 45 %, sperm curvilinear velocity by 23 %, sperm average path velocity by 69 %, and sperm linearity by 78 % in the selected cells in comparison with the raw sample. This acoustotaxic sperm selection separation approach provides an easy-to-use and effective method for the selection of highly motile sperm cells without adversely affecting sperm viability, paving the way for efficient and rapid sperm separation platforms, applicable for patients with low semen volumes, and up-scalable for a large volume of raw semen processing in a short time.

Microscale chemical imaging to characterize and quantify corrosion processes at the metal-electrolyte interface

We introduce an experimental setup to chemically image corrosion processes at metal-electrolyte interfaces under stagnant, confined conditions—relevant in a wide range of situations. The setup is based on a glass capillary, in which precipitation of corrosion products in the interfacial aqueous phase can be monitored over time with optical microscopy, and chemically and structurally characterized with microscopic synchrotron-based techniques (X-ray fluorescence, X-ray diffraction, and X-ray absorption spectroscopy). Moreover, quantification of precipitates through X-ray transmission measurements provides in-situ corrosion rates. We illustrate this setup for iron corrosion in a pH 8 electrolyte, revealing the critical role of O2 and iron diffusion in governing the precipitation of ferrihydrite and its transformation to goethite. Corrosion and coupled reactive transport processes can thus be monitored and fundamentally investigated at the metal-electrolyte interface, with micrometer-scale resolution. This capillary setup has potential applications for in-situ corrosion studies of various metals and environments.

Determination of brominated flame retardants in electrical and electronic equipment by micro-sample pretreatment technique combined with ion chromatography

A method for the determination of brominated flame retardants was established by micro sample pretreatment technology combined with ion chromatography. Using a sealed glass capillary as a micro reactor, the brominated flame retardants were debrominated by pyrolysis at 300 ℃ and absorbed by absorbing liquid, followed by ion chromatography determination. To improve the debromination efficiency, important factors including pyrolysis time and absorbing liquid were investigated. The linearity of the method was satisfactory over a Br− concentration of 0.05–100 mg/L and the determination coefficient was greater than 0.999. The limit of detection and limit of quantitation of bromide ion were 1.50 μg/L and 5.00 μg/L, respectively. The potential of the established method was assessed by applying it to the determination of total bromine in actual electrical and electronic equipment. The average recoveries (97.1–104.2 %) and the precision (3.1–7.5 %) were achieved by real samples spiked with three levels. This proposed method, with simple operation and low cost, could be a good supplementary for the oxygen bomb combustion-ion chromatography method for the determination of brominated flame retardants in electrical and electronic products.

Movement of oil droplets against salt concentration gradients in thin capillaries

Mobilization of residual oil droplets is the key process for enhanced oil recovery. Visualization of the droplet movement at a pore level provides insights on the underlying physical mechanisms. We couple a microfluidic droplet generator and a thin glass capillary to study the movement of oil droplets under salinity gradients with visualization of individual droplet movements. The driving forces that affect the movement of the droplets are discussed. We demonstrate experimentally that oil droplets in micro-confined channels can be mobilized and move against pressure under the concentration gradients of dissolved salts. The gradient-driven movement can be strong enough to drive a droplet through a narrow constriction in the middle of the capillary channel. The droplet movement can be understood by combining a Marangoni stress due to surfactant redistribution, electrostatic interaction and diffusiophoresis. This suggests that the abrupt change of salinity may be one of the physical mechanisms of smart waterflooding.

The relationship of hemorheological blood values and blood velocity of microcirculatory bloodstream in rats` skin vessels

Non-invasive study of blood rheology is relevant, but quite complex issue. When systemic blood viscosity and hematocrit levels deviate, blood flow indicators in different parts of microvasculature change. Purpose of the study – research of blood flow characteristics in skin microcirculatory bloodstream of rats obtained by high-frequency ultrasound Dopplerography (HFUD) with given changes in rheological blood indicators. The studies were carried out on pubescent male Wistar rats. 3 experimental groups were formed. Group 1 (n = 21) “Hemodilution” – viscosity 1.99 ± 0.02 mPa*s, hematocrit 31.48 ± 0.31%. Group 2 (n = 32) “Reference values” – animals with unchanged blood levels – viscosity 2.84 ± 0.03 mPa*s, hematocrit 41.60 ± 0.3%. Group 3 (n = 32) “Erythrocytosis” – viscosity 3.95 ± 0.04 mPa*s, hematocrit 54.56 ± 0.23%. Dynamic blood viscosity in vitro studies were carried out on oscillatory viscometer. In order to evaluate hematocrit level heparinized whole blood was centrifuged in glass capillaries using; hematocrit values were assessed taking into account sedimentation of formed elements column using a hematocrit reader card. Blood flow in skin microcirculatory bloodstream of rats` left thigh area was estimated by HFUD method using Minimax-Doppler-K hardware and software system, with ultrasound transducer (frequency 20 MHz). Statistical analysis showed the models are correct. Blood indicators of the animals in three experimental groups differed statistically and significantly in terms of blood viscosity and hematocrit. Discriminant analysis was used to determine the relations between rheological blood parameters and characteristics of blood velocity in microcirculatory bloodstream which made it possible to identify the most significant characteristics of blood flow that tend to change depending on altered blood composition. These include: mean systolic velocity Vas (p 0.01), mean velocity Vam (p 0.001), mean volume velocity Qam (p 0.001), vascular resistance index RI (p 0.01) and the percentage of blood cells moving in low-speed H' (p = 0.03). The reliability of selected characteristics was checked with one-way analysis of variance; and their significance in determining membership in “Hemodilution”, “Reference values” or “Erythrocytosis” groups according to HFUD data was confirmed. Based on this analysis classification functions were generated for non-invasive dynamic blood viscosity determination according to ultrasound Dopplerography data.

Micro Reference Electrode with an Ultrathin Ionic Path.

Reference electrode (RE) plays the core role in accurate potential control in electrochemistry. However, nanoresolved electrochemical characterization techniques still suffer from unstable potential control of pseudo-REs, because the commercial RE is too large to be used in the tiny electrochemical cell, and thus only pseudo-RE can be used. Therefore, microsized RE with a stable potential is urgently required to push the nanoresolved electrochemical measurements to a new level of accuracy and precision, but it is quite challenging to reproducibly fabricate such a micro RE until now. Here, we revisited the working mechanism of the metal-junction RE and clearly revealed the role of the ionic path between the metal wire and the borosilicate glass capillary to maintain a stable potential of RE. Based on this understanding, we developed a method to fabricate micro ultrastable-RE, where a reproducible ultrathin ionic path can form by dissolving a sandwiched sacrificial layer between the Pt wire and the capillary for the ion transfer. The potential of this new micro RE was almost the same as that of the commercial Ag/AgCl electrode, while the size is much smaller. Different from commercial REs that must be stored in the inner electrolyte, the new RE could be directly stored in air for more than one year without potential drift. Eventually, we successfully applied the micro RE in the electrochemical tip-enhanced Raman spectroscopy (EC-TERS) measurement to precisely control the potential of the working electrode, which makes it possible to compare the results from different laboratories and techniques to better understand the electrochemical interface at the nanoscale.

Method of Detecting Liquid Meniscus in Capillary Using Ultraviolet Sensor

The accuracy of determining the physical and chemical properties of a liquid, in particular, assessing the viscosity of the liquid used, is considered an important technical problem in medicine, food, oil, chemical industries, as well as in other areas that determine the quality and safety of human life and activity. For example, assessing the viscosity of the liquid used is a key stage in the design of hydraulic systems. Today, the improvement of methods for determining the viscosity of a liquid is on the path to automation (digitalization) of measurement instruments and methods. In this area, the activities of metrologists and engineers are consistent with the national program «Digital Economy of the Russian Federation» adopted in 2017. The article discusses the capillary method for determining the kinematic viscosity of a liquid as the most accurate of all possible methods at present. The method is based on determining the time of liquid flow between two marks, which are applied to the walls of a glass capillary viscometer forming a measuring tank. One of the main problems of this method is that all stages of measurement are performed by a person, even recording the moment when the liquid meniscus crosses the mark, which is a violation of one of the key principles of process automation – independence of execution, which only implies monitoring the operation of the system. Since ready-made solutions do not fit the laboratory’s measurement tasks, the management decided to develop and conduct a study of an information and measuring system that will carry out the process of detecting the liquid meniscus at the mark level, as well as recalculate the measured time interval into the kinematic viscosity value. The key decision in this development is the choice of a sensor for detecting the liquid meniscus. Based on the literature review, it was decided to use a photoelectric sensor. A study of the transmission spectra of liquids used in this method was conducted to select the wavelength at which the sensor will operate. Thus, a type of photoelectric sensor designed to operate in the UV range has been selected to automate the method of detecting the liquid meniscus when it crosses a mark applied to a capillary tube. The article is addressed to metrologists who perform verification and calibration of glass capillary viscometers, specialists in the field of experimental and theoretical viscometry. The method proposed by the authors can become the basis for further improvement of the method for measuring the kinematic viscosity of a liquid.

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.

In situ counter-diffusion crystallization and long-term crystal preservation in microfluidic fixed targets for serial crystallography.

Compared with batch and vapor diffusion methods, counter diffusion can generate larger and higher-quality protein crystals yielding improved diffraction data and higher-resolution structures. Typically, counter-diffusion experiments are conducted in elongated chambers, such as glass capillaries, and the crystals are either directly measured in the capillary or extracted and mounted at the X-ray beamline. Despite the advantages of counter-diffusion protein crystallization, there are few fixed-target devices that utilize counter diffusion for crystallization. In this article, different designs of user-friendly counter-diffusion chambers are presented which can be used to grow large protein crystals in a 2D polymer microfluidic fixed-target chip. Methods for rapid chip fabrication using commercially available thin-film materials such as Mylar, propyl-ene and Kapton are also detailed. Rules of thumb are provided to tune the nucleation and crystal growth to meet users' needs while minimizing sample consumption. These designs provide a reliable approach to forming large crystals and maintaining their hydration for weeks and even months. This allows ample time to grow, select and preserve the best crystal batches before X-ray beam time. Importantly, the fixed-target microfluidic chip has a low background scatter and can be directly used at beamlines without any crystal handling, enabling crystal quality to be preserved. The approach is demonstrated with serial diffraction of photoactive yellow protein, yielding 1.32 Å resolution at room temperature. Fabrication of this standard microfluidic chip with commercially available thin films greatly simplifies fabrication and provides enhanced stability under vacuum. These advances will further broaden microfluidic fixed-target utilization by crystallographers.

Density, thermal expansion, dynamic viscosity of halogenated arenes

Purpose. Experimental study of the density, thermal expansion and dynamic viscosity of halogenated arenes at temperatures from 293.15 to 343.15 K and atmospheric pressure 97.992 kPa.Methods. Density was determined by the pycnometric method, viscosity by the capillary method. A quartz pycnometer type PZh2 with a nominal capacity of 10 ml and a glass capillary viscometer type VPZh-2 with a nominal capillary diameter of 0.34 mm were used. The mass of liquids was measured using an electronic scale VSL-200/0.1A with a division value of 0.0001 g. Numerical methods were used to process the experimental results.Results. Experimental data were obtained on the density, coefficient of volumetric thermal expansion and dynamic viscosity of liquid o-xylene, ethylbenzene, fluorobenzene, chlorobenzene, bromobenzene, toluene, o-fluorotoluene, mfluorotoluene, p-fluorotoluene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, 2,4-dichlorotoluene, 2,6-dichlorotoluene. Density and dynamic viscosity data are approximated by a third-degree polynomial. Data on the coefficient of volumetric thermal expansion are obtained from approximated measured density data. The maximum estimate of the measurement error for density was 0.13 %, for dynamic viscosity – 3.5 %. The maximum calculation error for the coefficient of thermal expansion is estimated at 3 %.Conclusion. Mathematical processing of the obtained experimental data on density and dynamic viscosity made it possible to obtain analytical relations in the form of power polynomials that allow calculating the values of these quantities at any temperature from the studied temperature range and atmospheric pressure with an error not exceeding the error of experimental determination. The calculated values are in good agreement with the data provided in the reference and scientific literature. The experimental data obtained complement the information on the properties of some of the liquids under consideration, for which the dependences of density and viscosity on temperature are poorly understood. The substances under study are used in various sectors of the economy and are therefore technically important liquids. The measurement results can be used in condensed matter physics, for the analysis of liquid hydrocarbons, and can be useful in the chemical industry.

A Visual Distance-Based Capillary Immunoassay Using Biomimetic Polymer Nanoparticles for Highly Sensitive and Specific C-Reactive Protein Quantification.

The low-cost daily monitoring of C-reactive protein (CRP) levels is crucial for screening acute inflammation or infections as well as managing chronic inflammatory diseases. In this study, we synthesized novel 2-Methacryloyloxy ethyl phosphorylcholine (MPC)-based biomimetic nanoparticles with a large surface area to develop a visual CRP-quantification assay using affordable glass capillaries. The PMPC nanoparticles, synthesized via reflux precipitation polymerization, demonstrated multivalent binding capabilities, enabling rapid and specific CRP capture. In the presence of CRP, PMPC nanoparticles formed sandwich structures with magnetic nanoparticles functionalized with CRP antibodies, thereby enhancing detection sensitivity and specificity. These sandwich complexes were magnetically accumulated into visible and quantifiable stacks within the glass capillaries, allowing for the rapid, sensitive, and specific quantification of CRP concentrations with a detection limit of 57.5 pg/mL and a range spanning from 0 to 5000 ng/mL. The proposed visual distance-based capillary biosensor shows great potential in routine clinical diagnosis as well as point-of-care testing (POCT) in resource-limited settings.

ZnO-modified glass capillaries as a portable photocatalytic reactor for real-time measurements

Abstract Here, we have developed a photocatalytic reactor using glass capillaries which acts both as a flow cell and a thin film-supported photocatalyst due to the Zinc Oxide (ZnO) nanostructures grown on the inner surface of the glass capillaries. The structural, morphological, elemental, and optical characteristics of the ZnO nanostructures were investigated through characterization methods such as x-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive x-ray spectroscopy (EDAX), UV–Visible spectroscopy, and Raman spectroscopy. Further, dye-sensitized ZnO nanostructures were used for photocatalytic application under visible light irradiation. A custom-made setup is developed using ZnO-modified glass capillaries for simultaneous decay and measurement of the dye degradation process under visible LED light. This developed model could have future technological applications in designing portable photocatalytic reactors that can accurately monitor the dye degradation process using real-time measurements.

Exploration of Materials for Three-Dimensional NMR Microcoil Production via CNC Micromilling and Laser Etching.

The excellent versatility of 5-axis computer numerical control (CNC) micromilling has led to its application for prototyping NMR microcoils tailored to mass-limited samples (reducing development time and cost). However, vibrations during 5-axis milling can hinder the creation of complex 3D volume microcoils (i.e., solenoids and saddle coils). To address these limitations, a high-resolution NSCNC ELARA 4-axis milling machine was developed with the extra precision required for making complex 3D volume microcoils. Upon investigating the performance of resonators made with various copper-coated dielectrics, resonators with poly(methyl methacrylate) (PMMA) provided the best SNR/line shape. Thus, complex 1.7 mm microcoil designs were machined from Cu-coated PMMA. A milled 6.4 mm solenoid also provided 6.6× the total carbon signal for a 13C-labeled broccoli seed compared to a commercial inverse 5 mm NMR probe (demonstrating potential for larger coil designs). However, the manufacture of coils <1.7 mm with copper-coated PMMA rods was challenging as ∼0.5 mm of remaining PMMA was needed to retain their structural integrity. To manufacture smaller microcoils, both a solenoid and saddle coil (both with 1 mm O.D., 0.1 mm thick walls) were etched from Cu-coated glass capillaries using a UV picosecond laser that was mounted onto an NSCNC 5-axis MiRA7L. Both resonators showed excellent signal and identified a wide range of metabolites in a 13C-labeled algae extract, while the solenoid was further tested on two copepod egg sacs (∼4 μg of total sample). In summary, the flexibility to prototype complex microcoils in-house allows laboratories to tailor microcoils to specific mass-limited samples while avoiding the costs of cleanrooms.

Capillary effects of submicron heterogeneities in aqueous solutions of sugars. The additional mechanism of microfluidics

In this paper, we study submicron heterogeneities (SMH) that spontaneously form in aqueous solutions of sugars: glucose, fructose and sucrose, with a concentration of 0.5 mol%. These solutions were passed through glass capillaries with a diameter of about 6 and 13 µm, which led to a decrease in the concentration of SMH without significantly changing their size. For capillaries of smaller diameter, this effect is more pronounced. The decrease in the concentration of SMH is not associated with their mechanical destruction or adsorption on the surface of capillaries. This phenomenon is explained by the destruction of SMH as a result of their interaction with the hydrophilic surface of the capillary. The fundamental differences between the presence of SMH in microfluidic conditions and bulk reservoirs are discussed. This phenomenon should be taken into account in microfluidics.

Study on the Effect of a Sudden Jump in Wettability on Two-Component Liquid Flow in Sudden Contraction Devices.

This study experimentally investigated the effect of wettability and sudden changes in flow area on liquid-liquid extraction operation. The wall surface wettability has been altered by connecting the glass capillary (hydrophilic) and poly(tetrafluoroethylene) (PTFE)-coated capillary (hydrophobic) together in four different arrangements. In all of the arrangements, a 2 mm inner diameter tube of 35 cm length is used upstream, while a 1 mm inner diameter tube of 35 cm length is used downstream. Acetic acid mixed with toluene and water is used as a test fluid. Various flow patterns are observed: slug, droplet, slug with the droplet, and encapsulated drop in slug. The extraction efficiency is observed to be the maximum when the hydrophobic tube is used upstream, followed by a hydrophilic tube downstream. Due to the contraction effect, the specific surface area of the slug increases from 1.6 to 2.7 times. Further numerical simulations have been run using open CFD software OpenFoam to see the inner flow physics at the maximum efficiency due to a sudden jump in wettability. The presence of a recirculating zone downstream just after the plane of area change leads to the formation of encapsulated drop and enhances circulation within the slug.

Multifactorial optimization enables the identification of a greener method to produce (+)-nootkatone

The natural aroma compound (+)-nootkatone was obtained in selective conversions of up to 74 mol% from inexpensive (+)-valencene substrate by using a comparatively greener biocatalytic process developed based on modifications of the previously published Firmenich method. Buffer identity and concentration, pH, temperature and downstream work-up procedures were optimized to produce a crude product in which >90 % of (+)-valencene had been converted, with high chemoselectivity observed for (+)-nootkatone production. Interestingly, the biotransformation was carried out efficiently at temperatures as low as 21 ºC. Surprisingly, the best results were obtained when an acidic pH in the range of 3–6 was applied, as compared to the previously published procedure in which it appeared to be necessary to buffer the pH optimally and fixed throughout at 8.5. Furthermore, there was no need to maintain a pure oxygen atmosphere to achieve good (+)-nootkatone yields. Instead, air bubbled continuously at a low rate through the reaction mixture via a submerged glass capillary was sufficient to enable the desired lipoxygenase-catalyzed oxidation reactions to occur efficiently. No valencene epoxide side-products were detected in the organic product extract by a standard GCMS protocol. Only traces of the anticipated corresponding α- and β-nootkatol intermediates were routinely observed.

Growth Kinetics and Porous Structure of Surfactant-Promoted Gas Hydrate.

Surfactants present in tiny amounts in the aqueous phase are known to be efficient gas hydrate promoters; yet, the promotion mechanisms are still not fully understood. Understanding and directing those mechanisms is key to the implementation of gas-hydrate-based applications such as gas storage and separation, secondary refrigeration or water treatment, and desalination. In this work, the growth at the water/gas interface and the porous structure of surfactant-promoted methane hydrate are observed by optical microscopy and Raman imaging in glass capillaries used as optical cells. Hollow crystals are continuously generated and expelled from the methane/water meniscus into the water or surfactant solution, where they ultimately form the skeleton of a porous medium filled with the solution. Unprecedented information is gathered over a range of scales from the molecular scale (crystal structure and cage filling) to the mesoscale (crystal morphologies, growth habits and pore sizes) and macroscale (rates and amounts of water and gas converted into hydrate and hydrate porosity). Following an early steady-state growth regime, a sudden order-of-magnitude increase of the conversion rate occurs, which is related to gaseous methane microbubbles being directly incorporated across the meniscus in the aqueous solution and later converted to methane hydrate. An assessment and comparison are made of the mechanisms and performance of two common anionic surfactants known to be efficient gas hydrate promoters, SDS (sodium dodecyl sulfate) and AOT (dioctylsulfosuccinate sodium or AerosolOcTyl). AOT provides a quicker but more limited conversion into hydrate than SDS, suggesting that it is more appropriate for continuous flow processes while SDS is better suited for gas storage applications. Raman spectra reveal that cage filling by methane of structure I methane hydrate is not affected by surfactants.

Adaptive optics in an oblique plane microscope.

Adaptive optics (AO) can restore diffraction-limited performance when imaging beyond superficial cell layers in vivo and in vitro, and as such, is of interest for advanced 3D microscopy methods such as light-sheet fluorescence microscopy (LSFM). In a typical LSFM system, the illumination and detection paths are separate and subject to different optical aberrations. To achieve optimal microscope performance, it is necessary to sense and correct these aberrations in both light paths, resulting in a complex microscope system. Here, we show that in an oblique plane microscope (OPM), a type of LSFM with a single primary objective lens, the same deformable mirror can correct both illumination and fluorescence detection. Besides reducing the complexity, we show that AO in OPM also restores the relative alignment of the light-sheet and focal plane, and that a projection imaging mode can stabilize and improve the wavefront correction in a sensorless AO format. We demonstrate OPM with AO on fluorescent nanospheres and by imaging the vasculature and cancer cells in zebrafish embryos embedded in a glass capillary, restoring diffraction limited resolution and improving the signal strength twofold.