Name: methane hydrate crystallization on sessile water droplets
Uploaded: 2021-05-26T15:00:00.000+00:00
Duration: 8 min 46 s
Description: Watch this Scientific Journal Video about Methane Hydrate Crystallization on Sessile Water Droplets at JoVE.com

NASA Exobiology grant 80NSSC19K0477 funded this research. We thank William Waite and Nicolas Espinoza for valuable discussions.

<ol>
	<li>Bohrmann, G., Torres, M. E., Schulz, H. D., Zabel, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gas+hydrates+in+marine+sediments.">Gas hydrates in marine sediments.</a> Marine Geochemistry. , 481-512 (2006).</li><li>Ruppel, C. D., Kessler, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+interaction+of+climate+change+and+methane+hydrates.">The interaction of climate change and methane hydrates.</a> Reviews of Geophysics. 55 (1), 126-168 (2017).</li><li>Hammerschmidt, E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+gas+hydrates+in+natural+gas+transmission+lines.">Formation of gas hydrates in natural gas transmission lines.</a> Industrial and Engineering Chemistry. 26, 851-855 (1934).</li><li>Ke, W., Kelland, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+hydrate+inhibitor+studies+for+gas+hydrate+systems:+a+review+of+experimental+equipment+and+test+methods.">Kinetic hydrate inhibitor studies for gas hydrate systems: a review of experimental equipment and test methods.</a> Energy &amp; Fuels. 30 (12), 10015-10028 (2016).</li><li>Kelland, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+kinetic+hydrate+inhibitors+from+an+environmental+perspective.">A review of kinetic hydrate inhibitors from an environmental perspective.</a> Energy &amp; Fuels. 32 (12), 12001-12012 (2018).</li><li>Walker, V. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antifreeze+proteins+as+gas+hydrate+inhibitors.">Antifreeze proteins as gas hydrate inhibitors.</a> Canadian Journal of Chemistry. 93 (8), 839-849 (2015).</li><li>Bruusgaard, H., Lessard, L. D., Servio, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology+study+of+structure+I+methane+hydrate+formation+and+decomposition+of+water+droplets+in+the+presence+of+biological+and+polymeric+kinetic+inhibitors.">Morphology study of structure I methane hydrate formation and decomposition of water droplets in the presence of biological and polymeric kinetic inhibitors.</a> Crystal Growth &amp; Design. 9 (7), 3014-3023 (2009).</li><li>Jung, J. W., Espinoza, D. N., Santamarina, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Properties+and+phenomena+relevant+to+CH4-CO2+replacement+in+hydrate-bearing+sediments.">Properties and phenomena relevant to CH4-CO2 replacement in hydrate-bearing sediments.</a> Journal of Geophysical Research. 115 (10102), 1-16 (2010).</li><li>Chen, X., Espinoza, D. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ostwald+ripening+changes+the+pore+habit+and+spatial+variability+of+clathrate+hydrate.">Ostwald ripening changes the pore habit and spatial variability of clathrate hydrate.</a> Fuel. 214, 614-622 (2018).</li><li>DuQuesnay, J. R., Diaz Posada, M. C., Beltran, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+gas+hydrate+reactor+design:+3-in-1+assessment+of+phase+equilibria,+morphology+and+kinetics.">Novel gas hydrate reactor design: 3-in-1 assessment of phase equilibria, morphology and kinetics.</a> Fluid Phase Equilibria. 413, 148-157 (2016).</li><li>Udegbunam, L. U., DuQuesnay, J. R., Osorio, L., Walker, V. K., Beltran, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+equilibria,+kinetics+and+morphology+of+methane+hydrate+inhibited+by+antifreeze+proteins:+application+of+a+novel+3-in-1+method.">Phase equilibria, kinetics and morphology of methane hydrate inhibited by antifreeze proteins: application of a novel 3-in-1 method.</a> The Journal of Chemical Thermodynamics. 117, 155-163 (2018).</li><li>Espinoza, D. N., Santamarina, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Water-CO2-mineral+systems:+Interfacial+tension,+contact+angle,+and+diffusion+-+Implications+to+CO2+geological+storage.">Water-CO2-mineral systems: Interfacial tension, contact angle, and diffusion - Implications to CO2 geological storage.</a> Water Resources Research. 46 (7537), 1-10 (2010).</li><li>Sloan, E. D., Koh, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Clathrate Hydrates of Natural Gases. 3rd edn. , (2007).</li><li>Makogon, I. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hydrates of natural gas. , 125 (1981).</li><li>Johnson, A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mainly+on+the+plane:+deep+subsurface+bacterial+proteins+bind+and+alter+clathrate+structure.">Mainly on the plane: deep subsurface bacterial proteins bind and alter clathrate structure.</a> Crystal Growth &amp; Design. 20 (10), 6290-6295 (2020).</li></ol>

There are no competing financial interests.

We have developed a method to form methane hydrate shells on sessile water droplets safely and share this method to machine and assemble a pressure cell rated to 10 MPa working pressure, as well as the pressurizing and cooling systems. The pressure cell is outfitted with a stage for the droplet containing embedded thermocouples, a sapphire window for visualizing the droplet, and a pressure transducer fixed to the top of the cell. The cooling system includes chilled ethylene glycol circulating through copper coils in a tank with 50% ethanol solution, in which the pressure cell is placed. A pressure pump pressurizes the gas from the cylinder to the pressure cell. The hydrate shell forms upon rapid temperature decrease with the addition of dry ice to the top of the pressure cell. We allow the shell to form for 2 h, during which we believe the gas permeates through stochastic cracking of the hydrate shell, and Ostwald ripening over a longer period. Indeed, this device could be used to study these phenomena.
The critical steps for this protocol include: 1) leak-test the pressure cell with water before pressurizing it with gas, 2) practice adding the water droplet onto the stage before inserting the sapphire window, 3) cool the droplet to be stable at ~2 &#176;C before pressurizing, 4) pressurize with a max flow rate of 10 mL min-1 to 5 MPa in 1 MPa increments, 5) close the outlet valve on the pressure pump (to the cell) to limit gas exchange with the pressure pump, 6) set the temperature, pressure, and time-lapse software to log every 1 s, 1 s, and 5 s (or less), respectively, before adding dry ice, 7) apply dry ice to the top of the cell continuously until a hydrate shell is observed in the time-lapse, 8) allow the hydrate shell to form for at least 1 h, 9) depressurize at the same speed as pressurizing.
During method development, we optimized variables and techniques, including the timing of cooling, pressurizing, depressurizing, droplet size, and the droplet insertion technique. There are a few limitations in using this method. One limitation is the resolution of droplet imaging due to the camera resolution and materials between the camera and droplet (tank, ethanol solution, thick sapphire window). Additionally, while other studies observe the surface droplet on a microscale7,9,10, this method only allows for macro-scale observations. A microscope lens attachment could be installed if there was interest in micro observations.
Another limitation to this method is not being able to measure the hydrate shell thickness precisely. However, the hydrate thickness can be estimated by subtracting the cross-sectional area before and after hydrate formation and calculating the gas consumption using the change in temperature during depressurization to determine the volume of hydrate formed. Another limitation is that this droplet cannot be viewed in 3D because there is only one side of the pressure cell containing a sapphire window. In contrast, other studies have used cells made entirely of&#160;sapphire to observe the droplet from multiple angles7. We also did not install a temperature-controlling stage10 or spectroscopic techniques; however, these could certainly be installed using this setup.
With this method, the morphology, dissociation pressure and temperature, and the change in temperature during hydrate dissociation can be observed with droplets containing additives or alternative stage substrates. This method is relatively cheap, and there are few thorough protocols for forming gas hydrate shells. Because high-pressure systems can be dangerous, we include safety tips for pressurizing and leak testing. Additionally, many setups do not allow the visualization of gas hydrate formation, or do so on a much smaller or much larger scale. Laboratory experiments are a major contributor to the understanding of naturally occurring gas hydrates and natural gas hydrates that can cause lethal gas pipeline explosions. This method can be used to quickly assess the effects of additives on the dissociation temperature and morphology and the ability of additives to eliminate the memory effect. Effective additives could be used as inhibitors in natural gas pipelines or to study the biological activity of deep-sea bacterial proteins6,15.

Gas hydrates are cages of hydrogen-bonded water molecules that trap guest gas molecules via van der Waals interactions. Methane hydrates form under high-pressure and low-temperature conditions, which occur in nature in the subsurface sediment along continental&#160;margins, under Arctic permafrost, and on other planetary bodies in the solar system1. Gas hydrates store several thousand gigatons of carbon, with important implications for climate and energy2. Gas hydrates can also be hazardous in the natural gas industry because conditions favorable for hydrates occur in gas pipelines, which can clog the pipes leading to fatal explosions and oil spills3.
Due to the difficulty of studying gas hydrates in situ, laboratory experiments are often employed to characterize hydrate properties and the influence of inhibitors and substrates4. These laboratory experiments are performed by growing gas hydrate at elevated pressure in cells of various shapes and sizes. Efforts to prevent gas hydrate formation in gas pipelines have led to the discovery of several chemical and biological gas hydrate inhibitors, including antifreeze proteins (AFPs), surfactants, amino acids, and polyvinylpyrrolidone (PVP)5,6. To determine the effects of these compounds on gas hydrate properties, these experiments have employed diverse vessel designs, including autoclaves, crystallizers, stirred reactors, and rocking cells, which support volumes from 0.2 to 106 cubic centimeters4.
The sessile droplet method used here and in previous studies7,8,9,10,11,12 involves forming a gas hydrate film on a sessile droplet of water inside a pressure cell. These vessels are made of stainless steel and sapphire to accommodate pressures up to 10-20 MPa. The cell is connected to a methane gas cylinder. Two of these studies used the droplet method to test AFPs as gas hydrate inhibitors compared to commercial kinetic hydrate inhibitors (KHIs), such as PVP7,11. Bruusgard et al.7 focused on the morphologic influence of inhibitors and found that droplets containing Type I AFPs have a smoother, glassy surface than the dendritic droplet surface without inhibitors at high driving forces.
Udegbunam et al.11 used a method developed to assess KHIs in a previous study10, which allows for the analysis of morphology/growth mechanisms, the hydrate-liquid-vapor equilibrium temperature/pressure, and kinetics as a function of temperature. Jung et al. studied CH4-CO2 replacement by flooding the cell with CO2 after forming a CH4 hydrate shell8. Chen et al. observed Ostwald ripening as the hydrate shell forms9. Espinoza et al. studied CO2 hydrate shells on various mineral substrates12. The droplet method is a relatively simple and cheap method to determine the morphologic effect of various compounds and substrates on gas hydrates and requires small amounts of additives due to the small volume. This paper describes a method for forming such hydrate shells on a droplet of water using a stainless-steel cell with a sapphire window for visualization, rated up to 10 MPa working pressure.

<table><tbody><tr><td>&lt;strong&gt;CAMERA AND LAPTOP&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Camera Body</td><td>Nikon</td><td>D7200</td><td>Name in Protocol: camera</td></tr><tr><td>Camera Control Pro 2 Software</td><td>Nikon</td><td></td><td>Name in Protocol: camera software</td></tr><tr><td>Laptop</td><td>HP Pavilion</td><td>hp-pavilion-laptop-14-ce0068st</td><td>Needs to be PC with plenty of storage (~ 1 Tb)&lt;br/&gt; Name in Protocol: laptop</td></tr><tr><td>Macrophotography Lens</td><td>Nikon</td><td>AF-S MICRO 105mm f/2.8G IF-ED Lens</td><td>Name in Protocol: lens</td></tr><tr><td>&lt;strong&gt;CONSUMABLES&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Deionized water</td><td></td><td></td><td>Name in Protocol: DI water</td></tr><tr><td>Dry Ice</td><td>VWR or grocery store</td><td></td><td>Buy just before nucleation&lt;br/&gt; Name in Protocol: dry ice</td></tr><tr><td>Ethanol</td><td></td><td></td><td>Name in Protocol: ethanol</td></tr><tr><td>Ethylene Glycol</td><td></td><td></td><td>Name in Protocol: ethylene glycol</td></tr><tr><td>&lt;strong&gt;COOLING SYSTEM&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>1/2 in. O.D. x 3/8 in. I.D. x 25 ft. Polyethylene Tubing</td><td>Everbilt</td><td>Model # 301844</td><td>For circulating coolant from chiller to copper coils in aquarium&lt;br/&gt; Name in Protocol: 3/8&amp;rdquo; (inner diameter) plastic tubing</td></tr><tr><td>Circulating chiller</td><td>Polyscience</td><td></td><td>Name in Protocol: chiller</td></tr><tr><td>Economical Flexible Polyethylene Foam Pipe Insulation</td><td>McMaster-Carr</td><td>4530K162</td><td>3/4&quot; thick wall; 1/2&quot; inner diameter; R Value 3; 6&#039; long&lt;br/&gt; Name in Protocol: foam pipe insulation</td></tr><tr><td>Plastic tubing</td><td></td><td></td><td>use any tubing that fits the airline connection in the lab and long enough to travel from the airline connection to the front of the aquarium</td></tr><tr><td>&lt;strong&gt;DATALOGGER&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Armature Multiplexer Module for 34970A/&lt;br/&gt; 34972A, 20-Channel</td><td>Keysight Technologies</td><td>34901A</td><td>Name in Protocol: datalogger multichannel</td></tr><tr><td>Benchvue or Benchlink software</td><td>Benchvue or Benchlink</td><td></td><td>Name in Protocol: temperature transducer software</td></tr><tr><td>Data Acquisition/Switch Unit. GPIB, RS232</td><td>Keysight Technologies</td><td>34970A</td><td>Name in Protocol: datalogger</td></tr><tr><td>USB/GPIB interface</td><td>Keysight Technologies</td><td>82357B</td><td>Name in Protocol: datalogger USB</td></tr><tr><td>datalogger multichannel</td><td></td><td></td><td></td></tr><tr><td>Schott Fostec -Llc 20510 Ace Fiber Optic Light Source</td><td>Schott Fostec</td><td>A20500</td><td>3115PS-12W-B20 115 V ~AC 50/60Hz 5/4.5 W&lt;br/&gt; Name in Protocol: light source unit</td></tr><tr><td>Schott Fostec light source guide - single bundle</td><td>Schott Fostec</td><td>A08031.40</td><td>Name in Protocol: fiber optic light source cable</td></tr><tr><td>&lt;strong&gt;METHANE GAS AND REGULATOR&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>1/4 OD in. x 20 ft. Copper Soft Refrigeration Coil</td><td>Everbilt</td><td>Model # D 04020PS</td><td>For pressurizing ISCO pressure pump. An additional pack is needed for coolant circulation, as listed below.&lt;br/&gt; Name in Protocol: high pressure-rated 1/4&amp;rdquo; copper pipe</td></tr><tr><td>Methane cylinder regulator</td><td>Airgas</td><td>Y11N114G350-AG</td><td>Name in Protocol: methane cylinder regulator</td></tr><tr><td>Methane gas cylinder</td><td>Airgas</td><td>ME UHP300</td><td>Name in Protocol: methane gas cylinder</td></tr><tr><td>&lt;strong&gt;PRESSURE PUMP&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>1/4 in.&amp;nbsp; flexible tubing, ~ 3 ft.</td><td></td><td></td><td>Connect to pump inlet for leak test&lt;br/&gt; Name in Protocol: 1/4&quot;&amp;nbsp; flexible tubing</td></tr><tr><td>260D Syringe Pump W/Controller</td><td>Teledyne Instruments Inc.</td><td>67-1240-520</td><td>Name in Protocol: pressure pump</td></tr><tr><td>Controller &amp;minus; Ethernet/USB</td><td>Teledyne Instruments Inc.</td><td>62-1240-114</td><td>Purchase if you would like to install Labview onto computer and control pressure pump remotely. We did not do this.</td></tr><tr><td>Smooth-Bore Seamless 316 Stainless Steel Tubing, 1/4&quot; OD, 0.035&quot; Wall Thickness, 1 Foot Long (x5)</td><td>McMaster-Carr</td><td>89785K824</td><td>Name in Protocol: 1/4&quot; pipe</td></tr><tr><td>Smooth-Bore Seamless 316 Stainless Steel Tubing, 1/8&quot; OD, 0.02&quot; Wall Thickness, 1 Foot Long (x4)</td><td>McMaster-Carr</td><td>89785K811</td><td>Name in Protocol: 1/8&quot; pipe</td></tr><tr><td>Stainless Steel Swagelok Tube Fitting, Reducing Union, 1/4 in. x 1/8 in. Tube OD (x4)</td><td>Swagelok</td><td>&amp;nbsp;SS-400-6-2</td><td>Name in Protocol: 1/8&amp;rdquo; to 1/4&amp;rdquo; adapter</td></tr><tr><td>&lt;strong&gt;PRESSURE CELL&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>316 Stainless Steel Nut and Ferrule Set (1 Nut/1 Front Ferrule/1 Back Ferrule) for 1/4 in. Tube Fitting (20)</td><td>Swagelok</td><td>&amp;nbsp;SS-400-NFSET</td><td>Used for fitting connections where necessary&lt;br/&gt; Name in Protocol: ferrule set</td></tr><tr><td>316L Stainless Steel Convoluted (FM) Hose, 1/4 in., 316L Stainless Steel Braid, 1/4 in. Tube Adapters, 60 in. (1.5 m) Length</td><td>Swagelok</td><td>SS-FM4TA4TA4-60</td><td>Connects pressure pump to pressure cell&lt;br/&gt; Name in Protocol: 1/4&quot; braided stainless steel flexible pressure-rated hose</td></tr><tr><td>ABAQUS</td><td>ABAQUS FEA</td><td></td><td>Name in Protocol: simulation software</td></tr><tr><td>Abrasion-Resistant Cushioning Washer for 7/8&quot; Screw Size, 0.875&quot; ID, 2.25&quot; OD, packs of 10 (x1)</td><td>McMaster-Carr</td><td>90131A107</td><td>Name in Protocol: 2.25&quot; rubber washer</td></tr><tr><td>Abrasion-Resistant Sealing Washer, Aramid Fabric/Buna-N Rubber, 3/8&quot; Screw Size, 0.625&quot; OD, packs of 10 (x1)</td><td>McMaster-Carr</td><td>93303A105</td><td>Used for illumination port</td></tr><tr><td>Acrylic Sheet | White 2447 / WRT31&lt;br/&gt; Extruded Paper-Masked (Translucent 55% (0.118 x 12 x 12)</td><td>Interstate Plastics</td><td>ACRW7EPSH</td><td>Machine a circle of acrylic to fit in the inner chamber of the pressure cell to serve as the background for imaging&lt;br/&gt; Name in Protocol: acrylic disc</td></tr><tr><td>AutoCAD</td><td>AutoCAD</td><td></td><td>Name in Protocol: engineering design software</td></tr><tr><td>Conax fitting</td><td>Conax Technologies</td><td>311401-011</td><td>TG(PTM2/)-24-A6-T, OPTIONAL 1/4&quot; NPT&lt;br/&gt; Name in Protocol: pressure seal connector</td></tr><tr><td>High Accuracy Oil Filled Pressure&lt;br/&gt; Transducers/Transmitters for General&lt;br/&gt; industrial applications (x2)</td><td>Omega Engineering, Inc.</td><td>PX409-3.5KGUSBH</td><td>Buy two so there is a backup.&lt;br/&gt; Name in Protocol: pressure transducer</td></tr><tr><td>HIGH PRESSURE CHAMBER&amp;nbsp; PARTS</td><td>Wither Tool, Die and Manufacturing Company</td><td></td><td>Machining for pressure cell parts as listed in CAD drawings (Figure S1)&lt;br/&gt; Name in Protocol: Part B = stainless steel washer</td></tr><tr><td>High-Strength 316 Stainless Steel Socket Head Screw, M5 x 0.80 mm Thread, 14 mm Long (x20)</td><td>McMaster-Carr</td><td>90037A119</td><td>Used for illumination port</td></tr><tr><td>High-Strength 316 Stainless Steel Socket Head Screw, M8 x 1.25 mm Thread, 25 mm Long (x20)</td><td>McMaster-Carr</td><td>90037A133</td><td>Name in Protocol: M8 stainless steel screws</td></tr><tr><td>Oil-Resistant Hard Buna-N O-Ring, 3/32 Fractional Width, Dash Number 120, packs of 50 (x1)</td><td>McMaster-Carr</td><td>5308T178</td><td>Name in Protocol: 1&quot; o-ring</td></tr><tr><td>Oil-Resistant Hard Buna-N O-Ring, 3/32 Fractional Width, Dash Number 128, packs of 50 (x1)</td><td>McMaster-Carr</td><td>5308T186</td><td>Name in Protocol: 1.5&quot; o-ring</td></tr><tr><td>Omega Inc. pressure transducer software</td><td>Omega Engineering, Inc.</td><td></td><td>Name in Protocol: pressure transducer software</td></tr><tr><td>Polycarbonate Disc</td><td>McMaster-Carr</td><td>8571K31</td><td>Listed in CAD drawings for illumination port, Fig. S1 Part E</td></tr><tr><td>Sapphire windows (x3)</td><td>Guild Optical Associates, Inc.</td><td>Optical Grade Sapphire Window, C-Plane&lt;br/&gt; Diameter: 1.811&amp;rdquo; &amp;plusmn;.005&amp;rdquo;&lt;br/&gt; Thickness: .590&amp;rdquo; &amp;plusmn;.005&amp;rdquo;&lt;br/&gt; Surface Quality: 60/40&lt;br/&gt; Edges ground and safety chamfered</td><td>Buy three so there are two backups.&lt;br/&gt; Name in Protocol: sapphire window</td></tr><tr><td>Solid Thermocouple Wire FEP Insulation and Jacket, Type K, 24 Gauge, 50 ft. Length (x1)</td><td>McMaster-Carr</td><td>3870K32</td><td>Name in Protocol: thermocouples</td></tr><tr><td>Stainless Steel Integral Bonnet Needle Valve, 0.37 Cv, 1/4 in. Swagelok Tube Fitting, Regulating Stem (x4)</td><td>Swagelok</td><td>&amp;nbsp;SS-1RS4</td><td>Two will be used for the pressure pump as well.&lt;br/&gt; Name in Protocol: 1/4&quot; needle valves</td></tr><tr><td>Stainless Steel Pipe Fitting, Hex Nipple, 1/4 in. Male NPT (x2)</td><td>Swagelok</td><td>&amp;nbsp;SS-4-HN</td><td>Used for illumination port</td></tr><tr><td>Stainless Steel Swagelok Tube Fitting, Female Branch Tee, 1/4 in. Tube OD x 1/4 in. Tube OD x 1/4 in. Female NPT (x2)</td><td>Swagelok</td><td>&amp;nbsp;SS-400-3-4TTF</td><td>Used with pressure transducer&lt;br/&gt; Name in Protocol: branch tee fitting</td></tr><tr><td>Stainless Steel Swagelok Tube Fitting, Male Connector, 1/4 in. Tube OD x 1/4 in. Male NPT (x4)</td><td>Swagelok</td><td>&amp;nbsp;SS-400-1-4</td><td>Used on top port and side port leading to needle valves&lt;br/&gt; Name in Protocol: NPT screws</td></tr><tr><td>Stainless Steel Swagelok Tube Fitting, Port Connector, 1/4 in. Tube OD (x8)</td><td>Swagelok</td><td>&amp;nbsp;SS-401-PC</td><td>Use as tube connections between NTP and valve connections&lt;br/&gt; Name in Protocol: port connector fitting</td></tr><tr><td>&lt;strong&gt;TANK&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>1/4 OD in. x 20 ft. Copper Soft Refrigeration Coil</td><td>Everbilt</td><td>Model # D 04020PS</td><td>For circulating coolant&lt;br/&gt; Name in Protocol: 1/4&quot; copper pipe</td></tr><tr><td>10 gallon aquarium</td><td>Tetra</td><td></td><td>Name in Protocol: 10 gallon tank</td></tr><tr><td>2 oz. Waterweld</td><td>J-B Weld</td><td>Model # 8277</td><td>Name in Protocol: underwater sealant</td></tr><tr><td>3 in. x 25 ft. Foil Backed Fiberglass Pipe Wrap Insulation</td><td>Frost King</td><td>Model # SP42X/16</td><td>For wrapping around aquarium&lt;br/&gt; Name in Protocol: foil-lined fiberglass</td></tr><tr><td>3/8 7/8 in. Stainless Steel Hose Clamp (10 pack)</td><td>Everbilt</td><td>Model # 670655E</td><td>Name in Protocol: worm drive hose clamps</td></tr><tr><td>Styrofoam</td><td></td><td></td><td>Name in Protocol: insulating material</td></tr><tr><td>&lt;strong&gt;TOOLS&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>1-1/8 in. Ratcheting Tube Cutter</td><td>Husky</td><td>Model # 86-036-0111</td><td></td></tr><tr><td>1/2 in. to 1 in. Pipe Cutter</td><td>Apollo</td><td>Model # 69PTKC001</td><td></td></tr><tr><td>Adjustable wrench (x2)</td><td>Steel Core</td><td>Model # 31899</td><td>Need two wrenches with jaw at least 1&quot;</td></tr><tr><td>Allen wrench set</td><td>Home Depot</td><td></td><td></td></tr><tr><td>Duct tape</td><td></td><td></td><td>Name in Protocol: duct tape</td></tr><tr><td>Flexible tubing, like an IV line, to fit on the end of grainger probe (canula)</td><td></td><td></td><td>Name in Protocol: IV tube</td></tr><tr><td>Grainger 18 gauge probe</td><td>Grainger</td><td></td><td>For inserting droplet&lt;br/&gt; Name in Protocol: cannula</td></tr><tr><td>High Vacuum Grease</td><td>Dow corning</td><td></td><td>Apply to o-rings before inserting sapphire window&lt;br/&gt; Name in Protocol: vacuum grease</td></tr><tr><td>Klein Tools Professional 90 Degree 4-in-1 Tube Bender</td><td>Klein Tools</td><td>Model # 89030</td><td>Name in Protocol: tube bender</td></tr><tr><td>Snoop liquid leak detector</td><td>Swagelok</td><td>MS-SNOOP-8OZ</td><td>To detect leaks when pressurized when methane&lt;br/&gt; Name in Protocol: liquid leak detector</td></tr><tr><td>Suction cup</td><td>Home Depot</td><td></td><td>For removing tight fitting sapphire window&lt;br/&gt; Name in Protocol: suction cup</td></tr><tr><td>Teflon Tape</td><td></td><td></td><td>Name in Protocol: plumber&#039;s tape</td></tr><tr><td>Temflex 3/4 in. x 60 ft. 1700 Electrical Tape Black</td><td>3M</td><td>Model # 1700-1PK-BB40</td><td>Name in Protocol: electrical tape</td></tr></tbody></table>

methane hydrate crystallization on sessile water droplets

This paper describes a method to form methane hydrate shells on water droplets. In addition, it provides blueprints for a pressure cell rated to 10 MPa working pressure, containing a stage for sessile droplets, a sapphire window for visualization, and temperature and pressure transducers. A pressure pump connected to a methane gas cylinder is used to pressurize the cell to 5 MPa. The cooling system is a 10 gallon (37.85 L) tank containing a 50% ethanol solution cooled via ethylene glycol through copper coils. This setup enables the observation of the temperature change associated with hydrate formation and dissociation during cooling and depressurization, respectively, as well as visualization and photography of the morphologic changes of the droplet. With this method, rapid hydrate shell formation was observed at ~-6 &#176;C to -9 &#176;C. During depressurization, a 0.2 &#176;C to 0.5 &#176;C temperature drop was observed at the pressure/temperature (P/T) stability curve due to exothermic hydrate dissociation, confirmed by visual observation of melting at the start of the temperature drop. The "memory effect" was observed after repressurizing to 5 MPa from 2 MPa. This experimental design allows the monitoring of pressure, temperature, and morphology of the droplet over time, making this a suitable method for testing various additives and substrates on hydrate morphology.

With this method, a gas hydrate shell on a droplet can be monitored visually through a sapphire window of the pressure cell and via temperature and pressure transducers. To nucleate the hydrate shell after pressurizing to 5 MPa, dry ice can be added to the top of the pressure cell to induce a thermal shock to trigger rapid hydrate crystallization. There is a clear morphologic difference upon dry ice-forced hydrate shell formation. The water droplet transitioned from a smooth, reflective surface (Figure 3A) to an opaque hydrate shell with a slightly dendritic surface (Figure 3B). The addition of 100 &#181;g mL-1 Type I AFP altered the hydrate morphology by inducing ridged edges along the droplet and protrusions from the top of the droplet (Figure 3C,D).
After the hydrate shell developed for ~1 h, the cell was depressurized to 2 MPa (Supplemental&#160;Video S3). During depressurization, there was a 0.2 &#176;C to 0.5 &#176;C drop in temperature near the P/T stability curve13 (Figure 4) due to exothermic hydrate dissociation. Hydrate dissociation was confirmed by visual melting through time-lapse imaging at the beginning of the decrease in temperature, noted by stars in Figure 4. After complete hydrate dissociation, we repressurized the cell to observe the morphology and melting temperature with the &#34;memory effect&#34;14, the phenomenon in which hydrate forms faster after hydrate has already formed in the system (Supplemental Video S4). Upon re-pressurization, a hydrate shell reformed within a couple of minutes after reaching 5 MPa, and we observed the same temperature decrease at the stability curve during dissociation.
Negative controls with no droplet and with a droplet that did not form a hydrate shell (Figure 4, Trials 4 and 5) showed no decrease in temperature during depressurization. Upon depressurization below 2 MPa, we observed gas bubbling within the droplet from rapid degassing. Because the apex of each temperature decrease was above the previously established P/T stability curve13 (hydrate stability curve #1 in Figure 4), a regression curve was calculated based on the apex P/T of these trials (P [kPa] = EXP(38.98+-8533.8/T [K]), hydrate stability curve #2 in Figure 4).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62686/62686fig01.jpg" /> 
Figure 1:&#160;Pressure cell. The stage on which the droplet sits and the embedded thermocouples are revealed by removing the sapphire window and overlying rubber and steel washers. All parts and connections are labeled. Top left inset: stage shown from above with central and side stage embedded thermocouples. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/62686fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62686/62686fig02.jpg" /> 
Figure 2:&#160;Methane hydrate experimental setup. (A) The fume hood in which the experimental setup is located. (B) The gas cylinder is connected via a copper coil to the pressure pump. Highlighted from panel (A) are (C)&#160;the assembled pressure cell, (D) the 10-gallon (37.85 L) tank without the insulation or solution, (E)&#160;the pressure pump, and (F, G, H)&#160;zoomed-in images ofpressure pump connections. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/62686fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/62686/62686fig03.jpg" /> 
Figure 3:&#160;Methane hydrate shells. Representative images of the droplet before (A) and after (B) a methane hydrate shell formed on a deionized water droplet and before (C) and after (D) a hydrate shell formed on a droplet containing 100 &#181;g mL-1&#160;Type I antifreeze protein. Scale bars = 5 mm. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/62686fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/62686/62686fig04.jpg" /> 
Figure 4:&#160;Pressure-temperature stability diagram. Pressure and temperature data during depressurization are shown with P/T stability curves of methane hydrate (#1 from Sloan and Koh 200713 and #2 calculated from taking a regression curve from hydrate melting peaks from this study). Trials with successfully formed hydrate shells on DI water droplets are Trials 1, 2, and 3. Trial 4 was a negative control with no droplet on the stage. The droplet in trial 5 was another negative control in which no hydrate shell was formed. Stars indicate when visual hydrate melting began during depressurization. Trial 1 has a resolution of 30 s (a data point every 30 s); other trials have a resolution of 1 s. Abbreviations: T = trial; M.E. = memory effect; P/T = pressure-temperature; DI = deionized; res = resolution. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/62686fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplemental Figure S1: CAD images for machining the pressure cell. Parts A-F of the pressure cell are labeled with their part letter and dimensions. Abbreviation: CAD = computer-aided design. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/62686_FigS1.pdf" target="_blank">Please click here to download this File.</a>
Supplemental Figure S2: Pressure and temperature data over time for Trials 2-4. Trials 2 and 3 were regular deionized water droplets that formed hydrate shells. Trial 4 was a negative control in which no droplet was present. The trials are lined up at the first depressurization, which occurs at time zero. A small drop in temperature occurs at the beginning of depressurization due to the gas mixing with the pressure pump. A larger temperature drop occurs due to the hydrate melting after the initial pressure drop, as shown in trials 2 and 3. The temperature fluctuation at the end of trial 4 is due to the opening of the valve leading to complete depressurization, which also occurs at the end of trials 2 and 3. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/62686_FigS2.pdf" target="_blank">Please click here to download this File.</a>
Supplemental Table S1: Allowable stress (MPa) of the machined pressure cell. Abbreviation: FS = factor of safety. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/Table_S1.xlsx" target="_blank">Please click here to download this Table.</a>
Supplemental Table S2: Factor of safety for the machined pressure cell. Abbreviation: FS = factor of safety. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/Table_S2.xlsx" target="_blank">Please click here to download this Table.</a>
Supplemental Video S1: Strain. Video of the strain simulation on machined pressure cell. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/Video_S1_strain.mov" target="_blank">Please click here to download this Video.</a>
Supplemental Video S2: Stress. Video of the stress simulation on machined pressure cell. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/Video_S2_stress.mov" target="_blank">Please click here to download this Video.</a>
Supplemental Video S3: Trial 3 of hydrate shell dissociation. Time-lapse video of hydrate shell dissociation at 25x speed. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/Video_S3_Trial 3 dissociation_25x.mp4" target="_blank">Please click here to download this Video.</a>
Supplemental Video S4: Trial 3 of memory effect nucleation. Time-lapse video of hydrate shell formation by memory effect after repressurizing from 2 MPa to 5 MPa at 10x speed. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/62686/Video_S4_Trial 3 memory effect nucleation_10x.mp4" target="_blank">Please click here to download this Video.</a>

Watch this Scientific Journal Video about Methane Hydrate Crystallization on Sessile Water Droplets at JoVE.com

Methane Hydrate Crystallization on Sessile Water Droplets

We describe a method to form gas hydrate on sessile water droplets to study the effects of various inhibitors, promoters, and substrates on the hydrate crystal morphology.

This paper describes a method to form methane hydrate shells on water droplets. In addition, it provides blueprints for a pressure cell rated to 10 MPa ...

methane-hydrate-crystallization-on-sessile-water-droplets

Nanyang Technological University

Research

JoVE Journal

Environment

2.3K Views.  Georgia Institute of Technology. We describe a method to form gas hydrate on sessile water droplets to study the effects of various inhibitors, promoters, and substrates on the hydrate crystal morphology. 

Video: Methane Hydrate Crystallization on Sessile Water Droplets

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

Herein the procedures for plasma enhanced chemical vapor deposition of perfluoroalkanes on microporous materials such as metal-organic frameworks to enhance their stability and hydrophobicity are described. Furthermore, breakthrough testing of milligram quantities of samples is described in detail.

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

Chemistry

Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample

Methane hydrates (MHs) are present in large amounts in the ocean floor and permafrost regions. Methane and hydrogen hydrates are being studied as future energy resources and energy storage media. To develop a method for gas production from natural MH-bearing sediments and hydrate-based technologies, it is imperative to understand the thermal properties of gas hydrates.
The thermal properties' measurements of samples comprising sand, water, methane, and MH are difficult because the melting heat of MH may affect the measurements. To solve this problem, we performed thermal properties' measurements at supercooled conditions during MH formation. The measurement protocol, calculation method of the saturation change, and tips for thermal constants' analysis of the sample using transient plane source techniques are described here.
The effect of the formation heat of MH on measurement is very small because the gas hydrate formation rate is very slow. This measurement method can be applied to the thermal properties of the gas hydrate-water-guest gas system, which contains hydrogen, CO2, and ozone hydrates, because the characteristic low formation rate of gas hydrate is not unique to MH. The key point of this method is the low rate of phase transition of the target material. Hence, this method may be applied to other materials having low phase-transition rates.

We present a protocol for measuring the thermal properties of synthetic hydrate-bearing sediment samples comprising sand, water, methane, and methane hydrate.

Methane hydrates (MHs) are present in large amounts in the ocean floor and permafrost regions. Methane and hydrogen hydrates are being studied as future ...

Experimental Study of the Relationship Between Particle Size and Methane Sorption Capacity in Shale

The amount of adsorbed shale gas is a key parameter used in shale gas resource evaluation and target area selection, and it is also an important standard for evaluating the mining value of shale gas. Currently, studies on the correlation between particle size and methane adsorption are controversial. In this study, an isothermal adsorption apparatus, the gravimetric sorption analyzer, is used to test the adsorption capacity of different particle sizes in shale to determine the relationship between the particle size and the adsorption capacity of shale. Thegravimetric method requires fewer parameters and produces better results in terms of accuracy and consistency than methods like the volumetric method. Gravimetric measurements are performed in four steps: a blank measurement, preprocessing, a buoyancy measurement, and adsorption and desorption measurements. Gravimetric measurement is presently considered to be a more scientific and accurate method of measuring the amount of adsorption; however, it is time-consuming and requires a strict measuring technique. A Magnetic Suspension Balance (MSB) is the key to verify the accuracy and consistency of this method. Our results show that adsorption capacity and particle size are correlated, but not a linear correlation, and the adsorptions in particles sieved into 40 - 60 and 60 - 80 meshes tend to be larger. We propose that the maximum adsorption corresponding to the particle size is approximately 250 &#181;m (60 mesh) in the shale gas fracturing.

We use an isothermal adsorption apparatus, the gravimetric sorption analyzer, to test the adsorption capacity of different particle sizes of shale, in order to find out the relationship between particle size and the adsorption capacity of shale.

The amount of adsorbed shale gas is a key parameter used in shale gas resource evaluation and target area selection, and it is also an important standard ...

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as well as the magnitude of actuation. In addition, it is possible to vary the type of actuation from elongation to contraction depending on the director profile induced to the droplets during the flow in the capillary, which again depends on the microfluidic process and its parameters. Furthermore, particles of more complex shapes, like core-shell structures or Janus particles, can be prepared by adjusting the setup. By the variation of the chemical structure and the mode of crosslinking (solidification) of the liquid crystalline elastomer, it is also possible to prepare actuating particles triggered by heat or UV-vis irradiation.

This article describes the microfluidic process and parameters to prepare actuating particles from liquid crystalline elastomers. This process allows the preparation of actuating particles and the variation of their size and shape (from oblate to strongly prolate, core-shell, and Janus morphologies) as well as the magnitude of actuation.

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation ...

Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a temperature regulator, visualization techniques, and inner pressure measurements. The temperature control system contains a low-cost, programmable temperature regulator made with solid-state Peltier components. Along with the temperature control system, we incorporated visualization techniques and internal pressure measurements to study hydrate formation and inhibition in the presence of nonionic surfactants. We studied the hydrate-inhibiting ability of nonionic surfactants (sorbitane monolaurate, sorbitane monooleate, PEG-PPG-PEG, and polyoxyethylenesorbitan tristearate) at low (i.e., 0.1 CMC), medium (i.e., CMC), and high (i.e., 10 CMC) concentrations. Two types of crystals were formed: planar and conical. Planar crystals were formed in plain water and low surfactant concentrations. Conical crystals were formed in high surfactant concentrations. The results of the study show that conical crystals are the most effective in terms of hydrate inhibition. Because conical crystals cannot grow past a certain size, the hydrate growth rate as a conical crystal is slower than the hydrate growth rate as planar crystal. Hence, surfactants that force hydrates to form conical crystals are the most efficient. The goal of the protocol is to provide a detailed description of an experimental system that is capable of investigating the cyclopentane hydrate crystallization process on the surface of a water droplet in the presence of surfactant molecules.

We present a protocol to study the formation of hydrates in the presence of nonionic surfactants on the interface of a water droplet submerged in cyclopentane. The protocol consists of building a low-cost, programmable, temperature regulator. The temperature control system is combined with visualization techniques and internal pressure measurements.

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a ...

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO2/Si/SiO2 Wafers for Green Desalination

Desalination through direct contact membrane distillation (DCMD) exploits water-repellent membranes to robustly separate counterflowing streams of hot and salty seawater from cold and pure water, thus allowing only pure water vapor to pass through. To achieve this feat, commercial DCMD membranes are derived from or coated with water-repellent perfluorocarbons such as polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF). However, the use of perfluorocarbons is limiting due to their high cost, non-biodegradability, and vulnerability to harsh operational conditions. Unveiled here is a new class of membranes referred to as gas-entrapping membranes (GEMs) that can robustly entrap air upon immersion in water. GEMs achieve this function by their microstructure rather than their chemical make-up. This work demonstrates a proof-of-concept for GEMs using intrinsically wetting SiO2/Si/SiO2 wafers as the model system; the contact angle of water on SiO2 is &#952;o &#8776; 40&#176;. Silica-GEMs had 300 &#956;m-long cylindrical pores whose diameters at the (2 &#956;m-long) inlet and outlet regions were significantly smaller; this geometrically discontinuous structure, with 90&#176; turns at the inlets and outlets, is known as the &#34;reentrant microtexture&#34;. The microfabrication protocol for silica-GEMs entails designing, photolithography, chrome sputtering, and isotropic and anisotropic etching. Despite the water loving nature of silica, water does not intrude silica-GEMs on submersion. In fact, they robustly entrap air underwater and keep it intact even after six weeks (&#62;106 seconds). On the other hand, silica membranes with simple cylindrical pores spontaneously imbibe water (&#60; 1 s). These findings highlight the potential of the GEMs architecture for separation processes. While the choice of SiO2/Si/SiO2 wafers for GEMs is limited to demonstrating the proof-of-concept, it is expected that the protocols and concepts presented here will advance the rational design of scalable GEMs using inexpensive common materials for desalination and beyond.

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO2/Si/SiO2 Wafers for Green Desalination

Presented here is a stepwise protocol for realizing gas-entrapping membranes (GEMs) from SiO2/Si wafers using integrated circuit microfabrication technology. When silica-GEMs are immersed in water, the intrusion of water is prevented, despite the water-loving composition of silica.

Desalination through direct contact membrane distillation (DCMD) exploits water-repellent membranes to robustly separate counterflowing streams of hot and ...

Engineering

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

The computational study of the formation and growth of atmospheric aerosols requires an accurate Gibbs free energy surface, which can be obtained from gas phase electronic structure and vibrational frequency calculations. These quantities are valid for those atmospheric clusters whose geometries correspond to a minimum on their potential energy surfaces. The Gibbs free energy of the minimum energy structure can be used to predict atmospheric concentrations of the cluster under a variety of conditions such as temperature and pressure. We present a computationally inexpensive procedure built on a genetic algorithm-based configurational sampling followed by a series of increasingly accurate screening calculations. The procedure starts by generating and evolving the geometries of a large set of configurations using semi-empirical models then refines the resulting unique structures at a series of high-level ab initio levels of theory. Finally, thermodynamic corrections are computed for the resulting set of minimum-energy structures and used to compute the Gibbs free energies of formation, equilibrium constants, and atmospheric concentrations. We present the application of this procedure to the study of hydrated glycine clusters under ambient conditions.

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

The atmospheric concentrations of weakly bound molecular clusters can be computed from the thermochemical properties of low energy structures found through a multi-step configurational sampling methodology utilizing a genetic algorithm and semi-empirical and ab initio quantum chemistry.

The computational study of the formation and growth of atmospheric aerosols requires an accurate Gibbs free energy surface, which can be obtained from gas ...

A Microfluidic Approach for the Study of Ice and Clathrate Hydrate Crystallization

An accurate mechanistic description of water crystallization is challenging and requires a few key elements: superb temperature control to allow the formation of single microscopic crystals and a suitable microscopy system coupled to the cold stage. The method described herein adds another important feature that includes exchanging solutions around ice and clathrate hydrate crystals. The described system comprises a combination of unique and home-developed instruments, including microfluidics, high-resolution cold stages, and fluorescence microscopy. The cold stage was designed for microfluidic devices and allows for the formation of micron-sized ice/hydrate crystals inside microfluidic channels and the exchange of solutions around them. The temperature resolution and stability of the cold stage is one millikelvin, which is crucial for controlling the growth of these small crystals. This diverse system is used to study the different processes of ice and hydrate crystallization and the mechanism by which the growth of these crystals is inhibited. The protocol describes how to prepare microfluidic devices, how to grow and control microscopic crystals in the microfluidic channels, and how the utilization of the flow of liquids around ice/hydrate crystals affords new insights into the crystallization of water.

The present protocol describes the crystallization of microscopic ice crystals and clathrate hydrates in microfluidic devices, enabling liquid exchange around the formed crystals. This provides unparalleled possibilities to examine the crystallization process and binding mechanisms of the inhibitors.

An accurate mechanistic description of water crystallization is challenging and requires a few key elements: superb temperature control to allow the ...

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb monoliths (MHMs) with micrometer-scale channels are expected as efficient platforms for reactions and separations because of their large surface areas. Up to now, MHMs have been prepared by a unidirectional freeze-drying (UDF) method only from very limited precursors. Herein, we report a protocol from which a series of MHMs consisting of different components can be obtained. Recently, we found that cellulose nanofibers function as a distinct structure-directing agent towards the formation of MHMs through the UDF process. By mixing the cellulose nanofibers with water soluble substances which do not yield MHMs, a variety of composite MHMs can be prepared. This significantly enriches the chemical constitution of MHMs towards versatile applications.

Here, we present a general protocol to prepare a variety of microhoneycomb monoliths (MHMs) in which fluid can pass through with an extremely low pressure drop. MHMs obtained are expected to be used as filters, catalyst supports, flow-type electrodes, sensors and scaffolds for biomaterials.

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb ...

Bioengineering

Entropy and Solvation

The process of surrounding a solute with solvent is called solvation. It involves evenly distributing the solute within the solvent. The rule of thumb for determining a solvent for a given compound is that like dissolves like. A good solvent has molecular characteristics similar to those of the compound to be dissolved. For example, polar solutions dissolve polar solutes, and apolar solvents dissolve apolar solutes. A polar solvent is a solvent that has a high dielectric constant (&#1013; &#8805; 15); an apolar solvent is one with a low dielectric constant. The dielectric constant is defined by the electrostatic law, which gives the interaction energy E between two ions with respective charges q1 and q2 separated by a distance r. A polar solvent effectively separates or shields ions from one another. Therefore, the tendency of oppositely charged ions to associate is less in a polar solvent than it is in an apolar solvent.
In the case of a hydrocarbon and water, one is polar (water), and the other is apolar (hydrocarbon). On the introduction of hydrocarbon molecules in water, the water molecules along the hydrocarbon&#8211;water interface form a shell-like arrangement called the solvent shell around each hydrocarbon molecule. The water within these shell-like arrangements is more ordered and has lower entropy compared to the water in the solvent. Since any system in nature tries to achieve a state of maximum entropy, the system tries to minimize the interactions between hydrocarbon and water, resulting in the formation of separate hydrocarbon and water layers. This entropy-driven separation between hydrocarbon and water is termed the hydrophobic effect.
Since entropy is the driving factor of the insolubility of hydrocarbons in water, the system&#39;s temperature also influences the process, for example, in gas hydrates or clathrates, one of the largest reserves of natural gas. Gas hydrates are crystalline solid forms of water and gas. They form when methane and water freeze under high pressures and low temperatures.&#160; The hydrocarbon molecules are enclosed within stable cages of ice, which has relatively large open spaces within its crystal structure. The hydrocarbon molecules fit within these holes, making it possible to predict the maximum size of the hydrocarbon molecules that can form clathrates.

Entropia i solwatacja

The process of surrounding a solute with solvent is called solvation. It involves evenly distributing the solute within the solvent. The rule of thumb for ...

Methane Hydrate Crystallization on Sessile Water Droplets

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Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample

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Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO₂/Si/SiO₂ Wafers for Green Desalination

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

A Microfluidic Approach for the Study of Ice and Clathrate Hydrate Crystallization

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

Entropia i solwatacja