Name: fabrication and visualization of capillary bridges in slit pore geometry
Uploaded: 2014-01-09T13:45:00
Description: Watch this Scientific Journal Video about Fabrication and Visualization of Capillary Bridges in Slit Pore Geometry at JoVE.com

The authors are grateful for the support of the National Science Foundation under Grant No. CMMI-00748094 and the ONR N000141110629.

The protocol text is broken up into three main sections: 1) the fabrication of the of the PDMS (polydimethylsiloxane) pillars, 2) the functionalization of the tops of the pillars, and 3) the formation and characterization of the capillary bridges.
1. Fabrication of the PDMS Pillars
This section details the fabrication of the PDMS pillars using die casting with a silicon/SU-8 mold.
<ol>
	<li>Fabrication of silicon/SU-8 mold
	<ol>
		<li>Place a clea...

<ol>
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Mater. 7, 189-193 (2008).</li><li>Mastrangeli, M., Ruythooren, W., Celis, J. -. P., Van Hoof, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Challenges+for+Capillary+Self-Assembly+of+Microsystems.">Challenges for Capillary Self-Assembly of Microsystems.</a> IEEE T. Compon. Pack. 1, 133-149 (2011).</li><li>Josell, D., Wallace, W. E., Warren, J. A., Wheeler, D., Powell, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Misaligned+flip-chip+solder+joints:+Prediction+and+experimental+determination+of+force-displacement+curves.">Misaligned flip-chip solder joints: Prediction and experimental determination of force-displacement curves.</a> J. Electron. Pack. 124, 227-233 (2002).</li><li>Lin, W., Patra, S. K., Lee, Y. 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The method presented here provides a way to create capillary bridges in slit pore geometry, and also a method for imaging these bridges so that their morphology can be analyzed and compared to simulation and theory.
This method incorporates physical relief as well as selective chemical patterning to create asymmetric wetting properties. If only a chemical heterogeneity is present, a liquid drop will stay pinned on the heterogeneity until the contact angle exceeds that of the less wettable (low...

The study of the shape and resulting forces caused by capillary bridges has been the subject of extensive studies2-7. Initially most efforts were focused, due to their simplicity, on axisymmetric capillary bridges. Often capillary bridges occurring in natural systems, such as those found in granular and porous media8,9&#160;and bridges employed in technological applications, such as for capillary self-assembly in flip chip technologies10-15 are asymmetric with nonuniform wetting properties on the interacting surfaces. The combination of improved lithography techniques along with the accessibility of simple numerical tools to model fluid interfaces allows for the creation and modeling of capillary bridges with increasing complexity.
Capillary bridges in slit-pore geometry offer an interesting compromise: the directional wetting properties lead to nonaxisymmetric bridges that retain some symmetry planes (which simplifies the analysis). They have been studied theoretically and numerically as a case study for porous media. Systematic experimental studies of capillary bridges in slit-pore geometry have, however, been limited. Here we present a method to create and characterize capillary bridges in slit pore geometry. Briefly, the method consists of 1) the fabrication of pillars to create a chemical and physical heterogeneity, 2) the design of a microstage to align and manipulate the bridges, and 3) the imaging of the capillary bridges either from the front or the sides to characterize their morphology. The characterization of the bridge morphology, along with comparisons to surface evolver simulations are provided in a separate publication1.

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			<td height="43" style="height:43px;width:167px;">99.999% Gold wire</td>
			<td style="width:84px;">Kurt J. Lesker</td>
			<td style="width:91px;">EVMAU40040</td>
			<td style="width:84px;"></td>
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			<td height="43" style="height:43px;width:167px;">Acetone</td>
			<td style="width:84px;">Pharmco-AAPER</td>
			<td style="width:91px;">C1107283</td>
			<td style="width:84px;"></td>
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			<td height="25" style="height:25px;width:167px;">Dimethyl sulfoxide</td>
			<td style="width:84px;">Fisher</td>
			<td style="width:91px;">D128-500</td>
			<td style="width:84px;"></td>
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			<td height="43" style="height:43px;width:167px;">Ethanol (200 proof)</td>
			<td style="width:84px;">Pharmco-AAPER</td>
			<td style="width:91px;">111000200</td>
			<td style="width:84px;"></td>
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			<td height="43" style="height:43px;width:167px;">Hydrochloric acid</td>
			<td style="width:84px;">EMD</td>
			<td style="width:91px;">HX0603-4</td>
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			<td height="43" style="height:43px;width:167px;">Hydrogen peroxide (30%)</td>
			<td style="width:84px;">EMD</td>
			<td style="width:91px;">HX0635-3</td>
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			<td height="43" style="height:43px;width:167px;">Isopropyl alcohol</td>
			<td style="width:84px;">Fisher</td>
			<td style="width:91px;">L-13597</td>
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			<td height="43" style="height:43px;width:167px;">Mercapto hexadecanoic acid (90%)</td>
			<td style="width:84px;">Sigma-Aldrich</td>
			<td style="width:91px;">448303-1G</td>
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			<td height="64" style="height:64px;width:167px;">Mercapto-propyl-trimethoxy-silane (MPTS)</td>
			<td style="width:84px;">Gelest</td>
			<td style="width:91px;">Sim6476-O-100GM</td>
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			<td height="22" style="height:22px;width:167px;">Milli-Q DI water</td>
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			<td height="43" style="height:43px;width:167px;">Nitrogen (gas)</td>
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			<td style="width:91px;">UN1066</td>
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			<td height="43" style="height:43px;width:167px;">Oxygen (gas)</td>
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			<td style="width:91px;">UN1072</td>
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			<td height="43" style="height:43px;width:167px;">Silicon wafers (4 in)</td>
			<td style="width:84px;">WRS Materials</td>
			<td style="width:91px;">CC8506</td>
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			<td height="43" style="height:43px;width:167px;">SU-8 2002 (negative photo resist)</td>
			<td style="width:84px;">MicroChem</td>
			<td style="width:91px;">SU82002</td>
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			<td height="43" style="height:43px;width:167px;">SU-8 2050 (negative photoresist)</td>
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			<td style="width:91px;">SU82050</td>
			<td style="width:84px;"></td>
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			<td height="43" style="height:43px;width:167px;">SU-8 Developer solution</td>
			<td style="width:84px;">MicroChem</td>
			<td style="width:91px;">Y020100 4000L1PE</td>
			<td style="width:84px;"></td>
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		<tr height="64">
			<td height="64" style="height:64px;width:167px;">Sulfuric acid</td>
			<td style="width:84px;">J.T. Baker</td>
			<td style="width:91px;">9681-03</td>
			<td style="width:84px;"></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:167px;">Poly dimethy sulfoxide (PDMS)</td>
			<td style="width:84px;">Dow Corning</td>
			<td style="width:91px;">Sylgard -184</td>
			<td style="width:84px;"></td>
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		<tr height="22">
			<td height="22" style="height:22px;width:167px;">Toluene</td>
			<td style="width:84px;">Omnisolv</td>
			<td style="width:91px;">TX0737-1</td>
			<td style="width:84px;">
			
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fabrication and visualization of capillary bridges in slit pore geometry

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and functionalized to render their top surfaces hydrophilic. The combination of a physical feature (the pillar) with a chemical boundary (the hydrophilic film on the top of the pillar) provides both a physical and chemical heterogeneity that pins the triple contact line, a necessary feature to create stable long but narrow capillary bridges. The substrates with the pillars are attached to glass slides and secured into custom holders. The holders are then mounted onto four axis microstages and positioned such that the pillars are parallel and facing each other. The capillary bridges are formed by introducing a fluid in the gap between the two substrates once the separation between the facing pillars has been reduced to a few hundred micrometers. The custom microstage is then employed to vary the height of the capillary bridge. A CCD camera is positioned to image either the length or the width of the capillary bridge to characterize the morphology of the fluid interface. Pillars with widths down to 250 &#181;m and lengths up to 70 mm were fabricated with this method, leading to capillary bridges with aspect ratios (length/width) of over 1001.

Description of the experimental device
The experimental device can be broken up into four main parts: 1) the top substrate stage, 2) the bottom substrate stage, 3) the syringe/ syringe xyz-translation stage and 4) the camera/optics and camera holder. The details of each follow:
<ol>
	<li>Top substrate stage. A digital translation stage is attached to a P-series mounting clamp via a custom machined connector piece. The mounting clamp is connected to a variable height P-post, w...

Watch this Scientific Journal Video about Fabrication and Visualization of Capillary Bridges in Slit Pore Geometry at JoVE.com

Fabrication and Visualization of Capillary Bridges in Slit Pore Geometry

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. The creation of capillary bridges relies on the formation of pillars to provide a directional physical and chemical heterogeneity to pin the fluid. Capillary bridges are formed and manipulated using microstages and visualized using a CCD camera.

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and ...

fabrication-visualization-capillary-bridges-slit-pore

Research

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Engineering

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography

X-ray microtomography was used to image, at a resolution of 6.6 &#181;m, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space of a carbonate rock at pressures and temperatures representative of typical formations used for CO2 storage. Chemical equilibrium between the CO2, brine and rock phases was maintained using a high pressure high temperature reactor, replicating conditions far away from the injection site. Fluid flow was controlled using high pressure high temperature syringe pumps. To maintain representative in-situ conditions within the micro-CT scanner a carbon fiber high pressure micro-CT coreholder was used. Diffusive CO2 exchange across the confining sleeve from the pore-space of the rock to the confining fluid was prevented by surrounding the core with a triple wrap of aluminum foil. Reconstructed brine contrast was modeled using a polychromatic x-ray source, and brine composition was chosen to maximize the three phase contrast between the two fluids and the rock. Flexible flow lines were used to reduce forces on the sample during image acquisition, potentially causing unwanted sample motion, a major shortcoming in previous techniques. An internal thermocouple, placed directly adjacent to the rock core, coupled with an external flexible heating wrap and a PID controller was used to maintain a constant temperature within the flow cell. Substantial amounts of CO2 were trapped, with a residual saturation of 0.203 &#177; 0.013, and the sizes of larger volume ganglia obey power law distributions, consistent with percolation theory.

We present a methodology for the imaging of multiple fluid phases at reservoir conditions by the use of x-ray microtomography. We show some representative results of capillary trapping in a carbonate rock sample.

X-ray microtomography was used to image, at a resolution of 6.6 &#181;m, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space ...

Dynamic Pore-scale Reservoir-condition Imaging of Reaction in Carbonates Using Synchrotron Fast Tomography

Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve geologic seals and allow CO2 to escape. However, the dissolution processes at reservoir conditions are poorly understood. Thus, time-resolved experiments are needed to observe and predict the nature and rate of dissolution at the pore scale. Synchrotron fast tomography is a method of taking high-resolution time-resolved images of complex pore structures much more quickly than traditional &#181;-CT. The Diamond Lightsource Pink Beam was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 hours. The images were segmented and the porosity and permeability were measured using image analysis and network extraction. Porosity increased uniformly along the length of the sample; however, the rate of increase of both porosity and permeability slowed at later times.

Synchrotron fast tomography was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 &#181;m resolution over a period of 2 h.

Underground storage permanence is a major concern for carbon capture and storage. Pumping CO2 into carbonate reservoirs has the potential to dissolve ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Wicking Tests for Unidirectional Fabrics: Measurements of Capillary Parameters to Evaluate Capillary Pressure in Liquid Composite Molding Processes

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify their influence on void formation in composite parts. Wicking in a fibrous medium described by the Washburn equation was considered equivalent to a flow under the effect of capillary pressure according to the Darcy law. Experimental tests for the characterization of wicking were conducted with both carbon and flax fiber reinforcement. Quasi-unidirectional fabrics were then tested by means of a tensiometer to determine the morphological and wetting parameters along the fiber direction. The procedure was shown to be promising when the morphology of the fabric is unchanged during capillary wicking. In the case of carbon fabrics, the capillary pressure can be calculated. Flax fibers are sensitive to moisture sorption and swell in water. This phenomenon has to be taken into account to assess the wetting parameters. In order to make fibers less sensitive to water sorption, a thermal treatment was carried out on flax reinforcements. This treatment enhances fiber morphological stability and prevents swelling in water. It was shown that treated fabrics have a linear wicking trend similar to those found in carbon fabrics, allowing for the determination of capillary pressure.

An experimental method to measure geometrical parameters and the apparent advancing contact angles describing capillary wicking in unidirectional synthetic and natural fabrics is proposed. These parameters are mandatory for the determination of the capillary pressures that must be taken into account for liquid composite molding (LCM) applications.

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present an advanced method for fabricating ultra-thin color films with improved characteristics. The proposed process addresses several fabrication issues, including large area processing. Specifically, the protocol describes a process for fabricating ultra-thin color films using an electron beam evaporator for oblique angle deposition of germanium (Ge) and gold (Au) on silicon (Si) substrates.&#160; Film porosity produced by the oblique angle deposition induces color changes in the ultra-thin film. The degree of color change depends on factors such as deposition angle and film thickness. Fabricated samples of the ultra-thin color films showed improved color tunability and color purity. In addition, the measured reflectance of the fabricated samples was converted into chromatic values and analyzed in terms of color. Our ultra-thin film fabricating method is expected to be used for various ultra-thin film applications such as flexible color electrodes, thin film solar cells, and optical filters. Also, the process developed here for analyzing the color of the fabricated samples is broadly useful for studying various color structures.

We present a detailed method for fabricating ultra-thin color films with improved characteristics for optical coatings. The oblique angle deposition technique using an electron beam evaporator allows improved color tunability and purity. Fabricated films of Ge and Au on Si substrates were analyzed by reflectance measurements and color information conversion.

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present ...

Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste sample. The pore solution is expressed from a fresh paste sample using a pressurized nitrogen gas system. The pore solution is then immediately transferred to a syringe to minimize evaporation and carbonation. After that, assembled testing containers are used for the X-ray fluorescence (XRF) measurement. These containers consist of two concentric plastic cylinders and a polypropylene film which seals one of the two open sides. The pore solution is added into the container immediately prior to the XRF measurement. The XRF is calibrated to detect the main ionic species in the pore solution, in particular, sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-), to calculate sulfate (SO42-) using stoichiometry. The hydroxides (OH-) can be calculated from a charge balance. To calculate the electrical resistivity of the solution, the concentrations of the main ionic species and a model by Snyder et al. are used. The electrical resistivity of the pore solution can be used, along with the electrical resistivity of concrete, to determine the formation factor of concrete. XRF is a potential alternative to current methods to determine the composition of pore solution, which can provide benefits in terms of reduction in time and costs.

This protocol describes the procedure to express fresh pore solution from cementitious systems and the measurement of its ionic composition using X-ray fluorescence. The ionic composition can be used to calculate pore solution electrical resistivity, which can be used, together with concrete electrical resistivity, to determine the formation factor.

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste ...