1. Preparing the microfluidic flow cell
NOTE: For this protocol, a commercial microfluidic flow cell will be utilized. By using a commercial product that is designed for light penetration from an optical microscope, any challenges regarding brightfield illumination of the media will be minimized.
<ol>
	<li>Start preparing the microfluidic flow cell by covering the outlet with parafilm to seal one end of the channel so that the empty flow cell may be packed with polymeric powder. Before starting the experiment, confirm that the microfluidic channel is clean and dry.
	<ol>
		<li>Tape the metric paper ruler directly beneath the flow channel.</li>
		<li>Weigh the microfluidic flow cell with the parafilm and the ruler attached. The mass of the flow cell is the unpacked flow cell mass (mu).</li>
	</ol>
	</li>
</ol>
2. Packing the powder into the channel
<ol>
	<li>When packing the powder, use a plastic pipet to transfer the powder. Note that particles may adhere to the outside of the pipet tip, which is a result of tribocharging.
	<ol>
		<li>While introducing the powder into the channel, tap the flow cell at least five times to compact the powder. Continue packing until the powder reaches the beginning of the opening of the flow channel. 
		NOTE: Tapping compacts the powder within the channel with the goal of providing a reproducible diagnostic tool. For certain applications, this effort can be a higher, lower, or equivalent level of powder compaction than the compaction that is observed in the application of interest. If there are issues with the reproducibility of tapping or with packing powder within the application, consider performing ASTM D7481-1820.</li>
		<li>Remove the powder present on the outer surface of the flow cell with a wipe soaked in alcohol. 
		NOTE: Some types of particles can be hydrophobic, so water may not remove the particles well.</li>
	</ol>
	</li>
	<li>Once the powders are packed, visually inspect the flow cell for loosely packed powder. If the powder within the flow cell appears loosely packed (Figure 1), tap the flow cell five more times. If the powder packing appears consistent and compact, weigh the flow cell to measure the mass of the polymeric powder (mp - mu; see Equation 1).
	<ol>
		<li>Calculate the bulk packing density (&#961;) using the difference between the unpacked (mu) and packed flow cell mass (mp) and dividing it by the volume of the flow cell. The volume of the flow cell is then known [length (l): 50 mm, width (w): 5 mm, channel depth (h): 0.8 mm]. 
		<img alt="Equation 1" src="/files/ftp_upload/63494/63494eq01.jpg" style="margin: auto;" />&#160; &#160; &#160;Eq 1</li>
		<li>Confirm that the packing density is in the typical range of 0.45 g/mL to 0.55 g/mL for polymeric powders2,3,4,21. Leave the flow cells in the fume hood until steps 3 and 4 are completed. 
		CAUTION: Particles with a diameter of less than 10 &#181;m can penetrate into the lungs and potentially enter the bloodstream, which can cause health problems related to the pulmonary and cardiovascular systems. The polymeric powders that were used in this experiment have a particle diameter of approximately 50 &#956;m. Therefore, inhalation of the particles has less potential to cause health problems, but smaller particles are present even in narrow particle size distributions. For the safest environment, preparation of the flow cells should be done in a fume hood.</li>
	</ol>
	</li>
</ol>
3. Preparing the solvent
<ol>
	<li>Prepare a 75 wt% solution of ethanol in water. Note that the solvent will be referred to as the fluid in the rest of this manuscript. 
	&#8203;CAUTION: Make sure that the beaker used to prepare the solution is free from any surfactants, as surfactants will affect the results.</li>
</ol>
4. Preparing the white light table
<ol>
	<li>To prevent flooding the detector (camera) with too much light, cover the light table with an opaque material, such as a 3D printed cover in black polylactic acid (PLA) filament (Supplementary Figure 1). Ensure that the material has an opening that is the size of the microchannel (5 mm x 55 mm) to allow light to illuminate the powder. 
	NOTE: Too much light means the screen or monitor of the camera will appear white and the microchannel will not be visible. Therefore, the detector will be unable to focus the lens on the microchannel.</li>
	<li>To ensure that the camera on the mobile device can capture the contrast between the wet and dry powder, use the light table at a low to medium light intensity. 
	NOTE: High light intensity is at 100%. The other two settings are relative to the high light intensity; the setting for low light intensity is at ~30%, and medium light intensity is at ~65%.</li>
	<li>Align the camera on the mobile device directly above the light table. Confirm that the camera is perpendicular to the top of the light table (Figure 2).</li>
	<li>Orient the camera on the mobile device so that the long axis of the mobile device aligns with the longest axis of the flow cell.</li>
</ol>
5. Starting the experiment
<ol>
	<li>Place the flow cell on the light table and focus the camera on the mobile device on the flow channel. 
	NOTE: For optimal results, a darker (reduced overhead lighting) recording space will typically provide better image resolution. If a dark space is not available, minimizing changes in overhead lighting (lights being turned on, turned off, or being dimmed) during recording should improve graphic signals and minimize undesired noise in the experiment.</li>
	<li>After focusing the camera on the mobile device, select the record button. Add 125 &#956;L of fluid to the open inlet of the microchannel using a pipet.</li>
	<li>Record the flow for 2 min or until all the powder is wetted visibly.</li>
</ol>
6. Analyzing the data
<ol>
	<li>Transfer the video file from the mobile device to the computer for easy access. Note that videos over 2 min may not load in the software at this time, as the file size can be excessively large.</li>
	<li>Download Tracker, a free software from the Physlets website22. This software can track position, velocity, and acceleration in the following video files: .mov, .avi, .mp4, .flv, .wmv, etc. For the following steps, please refer to Supplemental File. 
	NOTE: For Mac users, install the latest version of the software for the software to function properly. Additionally, Mac users may require a video engine (Xuggle), animated GIF files (.gif), or image sequences that consist of one or more digital images (.jpg, .png, or pasted from the clipboard).</li>
	<li>Once the software is installed, open the Tracker software. From the File menu, select Open File to load the transferred video file from step 6.1 on the desktop of the computer.</li>
	<li>Click the Clip Settings icon, which looks like the film strip, to define the Starting Frame and the Step Size. 
	NOTE: Placing the mouse over an icon will identify the icon.
	<ol>
		<li>Define the Starting Frame. The Starting Frame is defined as the frame in which the first contrast (the contrast between the wet and dry powder) is observed.</li>
		<li>Set the Step Size. Step Size refers to the frame step size, which the software would analyze. From prior experiments, the optimum Step Size is 10.</li>
	</ol>
	</li>
	<li>Click on the Calibration Tool, the icon with the blue ruler, to the right of the Clip Settings button. From New, select Calibration Stick.</li>
	<li>To zoom in on the ruler in the video, right-click on the area to magnify and Select Zoom in from the list. Once appropriately magnified, define the beginning and end of 1 mm on the ruler taped to the microchannel, and Type 1 mm to define the distance.</li>
	<li>Click on the Coordinate Axis Tool, which is the purple icon, to the right of the Calibration Tool. Set the Origin for the x- and y-axis, using the starting frame while doing this step.</li>
	<li>To define the initial point of analysis, create a Point Mass. Click on Create, then select Point Mass. Use Shift + Control to change the size of the rectangle. The initial point is where the inlet and the channel connect. 
	NOTE: The rectangle indicates the domain, defined by the user, that the software will scan to find the contrasting wet and dry powder. The boundary allows the user to define the region where the initial point will be observed.
	<ol>
		<li>Click on Search Next a couple of times to verify that the software is analyzing the correct area. If the software is functioning properly, click on Search and wait for the software to finish analyzing the video. If the software cannot automatically find a matching image intensity from the previous frame to the current frame, the software will stop and wait for the user to redefine the search area. 
		NOTE: For reproducibility and the ability to compare different experimental results, choose the fastest or the slowest point of the fluidic flow front (region of contrast between the wetted and dry powder) for every sample.</li>
		<li>If an analysis error is observed on the live plotted data on the right-hand side of the Tracker screen, click on the Data Point once on the step prior to the erred data point. On the main screen, modify the red rectangular search area location to search the region of interest and repeat step 6.8.1. 
		NOTE: If an error exists, right-click on the inaccurate data point and deselect the point for further analysis.</li>
	</ol>
	</li>
	<li>Once the analysis is complete, copy and paste the results into a spreadsheet. The results saved in the spreadsheet comprise the distance and time data.</li>
	<li>Plot the copied data in the spreadsheet as the distance of fluid transport through the powder bed as a function of time.</li>
</ol>

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J., Rajput, F., Tufenkji, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transport+of+two+metal+oxide+nanoparticles+in+saturated+granular+porous+media:+Role+of+water+chemistry+and+particle+coating.">Transport of two metal oxide nanoparticles in saturated granular porous media: Role of water chemistry and particle coating.</a> Water Research. 46 (4), 1273-1285 (2012).</li><li>Giordano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effective+medium+theory+for+dispersions+of+dielectric+ellipsoids.">Effective medium theory for dispersions of dielectric ellipsoids.</a> Journal of Electrostatics. 58 (1-2), 59-76 (2003).</li><li>Toloni, I., Lehmann, F., Ackerer, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+the+effects+of+water+velocity+on+TiO2+nanoparticles+transport+in+saturated+porous+media.">Modeling the effects of water velocity on TiO2 nanoparticles transport in saturated porous media.</a> Journal of Contaminant Hydrology. 171, 42-48 (2014).</li><li>Dang-Vu, T., Hupka, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+porous+materials+by+capillary+rise+method.">Characterization of porous materials by capillary rise method.</a> Physicochemical Problems of Mineral Processing. 39, 47-65 (2005).</li><li>Huang, W. 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K., Hassanizadeh, S. M., Kleingeld, P. J., Imhof, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+colloids+transport+during+two-phase+flow+using+a+novel+polydimethylsiloxane+micro-model.">Study of colloids transport during two-phase flow using a novel polydimethylsiloxane micro-model.</a> Journal of Colloid and Interface Science. 401, 141-147 (2013).</li><li>Health and environmental effects of particulate matter (PM). EPA Available from: <a target="_blank" href="https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm">https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm</a> (2021)</li><li>Bridge, J. W., Banwart, S. A., Heathwaite, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+quantitative+measurement+of+colloid+transport+in+mesoscale+porous+media+using+time+lapse+fluorescence+imaging.">Noninvasive quantitative measurement of colloid transport in mesoscale porous media using time lapse fluorescence imaging.</a> Environmental Science &amp; Technology. 40 (19), 5930-5936 (2006).</li><li>ASTMInternational. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Standard+test+methods+for+determining+loose+and+tapped+bulk+densities+of+powders+using+a+graduated+cylinder.">Standard test methods for determining loose and tapped bulk densities of powders using a graduated cylinder.</a> ASTMInternational. , (2018).</li><li>Donovan, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Microfluidic investigations of capillary flow and surface phenomena in porous polymeric media for 3D printing. , (2019).</li><li>. 34;Try Tracker Online.&amp;#34; Tracker Video Analysis and Modeling Tool for Physics Education Available from: <a target="_blank" href="https://physlets.org/tracker/">https://physlets.org/tracker/</a> (2022)</li><li>Janssen, P. H. M., Depaifve, S., Neveu, A., Francqui, F., Dickhoff, B. H. 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The authors have nothing to disclose.

The protocol that is provided is highly dependent on the material characteristics of the particles that are chosen. Material properties impacting flow include particle size distribution2,3,4,5,11,21, particle surface roughness11, chemical properties at the particle surface2...

Inkjet-based binder jetting into powder media represents an important technology in additive manufacturing (3D printing). The binder jetting process begins with the deposition of functional fluids into powder media using a scanning inkjet printing process. Specifically, an inkjet print head translates over the powder surface, depositing the liquid binding agent onto a powder surface, and thereby forming a solid part in a layer-by-layer fashion1. Inkjet-based binder jetting technologies generally include sand, metal powders, and polymeric powders. However, to expand the materials&#39; space in binder jetting, a fundamental approach to investigating fluid-powder and powder-powder interactions, tribology, powder packing density, and particle aggregation is required. Specifically, for fluid-powder interactions, a critical need exists for the ability to image fluid flow through powder beds in real-time. This promises to be a powerful tool for researchers to include as a characterization technique and potentially as a screening method for different combinations of fluids and powders2,3,4, as well as more complex systems, such as concrete 3D-printing systems that utilize particle-bed methods.
The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an active area of investigation in microfluidic and millifluidic studies. Probing intermolecular interactions by imaging techniques can be challenging, as little work has been done to probe these types of interactions under the conditions of unsaturated and unsteady fluid flow. Many of the studies that are reported in the literature have focused on a saturated, pre-wetted, porous media, such as glass bead5,6,7,8,9,10,11,12 and soils13,14,15,16,17,18. This technique provides a non-invasive approach, resulting in high temporal and spatial resolution2,3,4,19. Furthermore, the developed technique provides a novel method for characterizing and quantifying nano-scale and micron-scale particle transport in a variety of porous media, focusing on polymeric powders.
The proposed technique utilizes a mobile device to record unsaturated, unsteady fluidic transport through porous polymeric media with particle dimensions that are representative of the powders used in 3D printing systems that utilize fluidic powder-bed fusion technologies. This technique is advantageous as the flow cells are cost-effective, reusable, small, and easily handled, illustrating the dominant aspects of frugal science. The ability to implement these simple experiments into a field study is very straightforward, eliminating the complications, cost, and time that are required in optical microscopy. Given the ease of creating the setup, the access to quick results, and the minimal number of sample requirements, this technique is an optimal platform for diagnostic screening.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>&#181;-Slide I Luer</td>
			<td>ibidi</td>
			<td>80191</td>
			<td>Microfluidic flow cell</td>
		</tr>
		<tr>
			<td>Beaker</td>
			<td>Southern Labware</td>
			<td>BG1000-800</td>
			<td>Glassware</td>
		</tr>
		<tr>
			<td>CALIBRE 301-58 LT Natural Polycarbonate Resin</td>
			<td>TRINSEO LLC</td>
			<td>CALIBRETM 301-58 LT</td>
			<td>Natural polycarbonate resin</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma Aldrich</td>
			<td>1.00983</td>
			<td>Solvent</td>
		</tr>
		<tr>
			<td>Fume Hood</td>
			<td>Kewaunee</td>
			<td>Supreme Air LV Fume Hoods</td>
			<td>Used with 92 FPM at 18&#34; opening</td>
		</tr>
		<tr>
			<td>iPhone 7 plus</td>
			<td>Apple</td>
			<td></td>
			<td>Camera</td>
		</tr>
		<tr>
			<td>Opaque 3D printed material</td>
			<td></td>
			<td></td>
			<td>The CAD drawing is provided in the supplemental file</td>
		</tr>
		<tr>
			<td>ORGASOL&#160; 2002 ES 6 NAT 3</td>
			<td>ARKEMA</td>
			<td>A12135</td>
			<td>Polyamide powder</td>
		</tr>
		<tr>
			<td>Pipet</td>
			<td>VWR</td>
			<td>10754-268</td>
			<td>Disposable Transfer Pipet</td>
		</tr>
		<tr>
			<td>Pipette</td>
			<td>Globe Scientific Inc.</td>
			<td>3301-200</td>
			<td>Pipette that can hold 125 &#181;L of fluid</td>
		</tr>
		<tr>
			<td>Polystyrene</td>
			<td>Advanced Laser Materials, LLC.</td>
			<td>PS200</td>
			<td>Polystyrene for sintering</td>
		</tr>
		<tr>
			<td>Tracker</td>
			<td></td>
			<td></td>
			<td>Video analysis and modeling tool</td>
		</tr>
		<tr>
			<td>VariQuest 100 White Light Model 3-3700</td>
			<td>FOTODYNE</td>
			<td>&#160;3-3700</td>
			<td>White light</td>
		</tr>
		<tr>
			<td>Water</td>
			<td></td>
			<td></td>
			<td>Distilled water</td>
		</tr>
	</tbody>
</table>

frugal imaging technique of capillary flow through three-dimensional polymeric printing powders

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in microfluidic and millifluidic studies. With the advent of three-dimensional (3D) printing, a new domain of materials has emerged, thereby increasing the demand for novel polymers. Specifically, polymeric powders, with average particle sizes on the order of a micron, are experiencing a growing interest from academic and industrial communities. Controlling material tunability at the mesoscopic to microscopic length scales creates opportunities to develop innovative materials, such as gradient materials. Recently, a need for micron-sized polymeric powders has been growing, as clear applications for the material are developing. Three-dimensional printing provides a high-throughput process with a direct link to new applications, driving investigations into the physio-chemical and transport interactions on a mesoscale. The protocol that is discussed in this article provides a non-invasive technique to image fluid flow in packed powder beds, providing high temporal and spatial resolution while leveraging mobile technology that is readily available from mobile devices, such as smartphones. By utilizing a common mobile device, the imaging costs that would normally be associated with an optical microscope are eliminated, resulting in a frugal-science approach. The proposed protocol has successfully characterized a variety of combinations of fluids and powders, creating a diagnostic platform for quickly imaging and identifying an optimal combination of fluid and powder.

In the section on analyzing data, the data for the time-lapsed images in Figure 3 illustrate the 75 wt% ethanol solution infiltrating the polycarbonate (PC) powder. Fluorescein was added to the solution to enhance the image quality for this publication. In the time-lapse images, the time-resolved process begins when the fluid is added to the inlet. Time, t, starts as soon as the fluid begins to penetrate the channel. The series of images demonstrates the progression of the fluid and...

Watch this Scientific Journal Video about Frugal Imaging Technique of Capillary Flow Through Three-Dimensional Polymeric Printing Powders at JoVE.com

Frugal Imaging Technique of Capillary Flow Through Three-Dimensional Polymeric Printing Powders

The proposed technique will provide a novel, efficient, frugal, and non-invasive approach for imaging fluidic flow through a packed powder bed, yielding high spatial and temporal resolution.

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in ...

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1.2K Views.  South Dakota School of Mines & Technology. The proposed technique will provide a novel, efficient, frugal, and non-invasive approach for imaging fluidic flow through a packed powder bed, yielding high spatial and temporal resolution.

Video: Frugal Imaging Technique of Capillary Flow Through Three-Dimensional Polymeric Printing Powders

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth.&#160;However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras1. The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera&#8217;s field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation.
Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop.&#160;DFP systems can also achieve the same measurement resolution as the camera.&#160;For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in1-5). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30&#160;Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame6,7.&#160;Binary defocusing DFP methods can achieve even greater speeds8.
Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis9, facial animation10, cardiac mechanics studies11, and fluid surface measurements, but many other potential applications exist.&#160;This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces.&#160;It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques.

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

The Vaporization of a Sacrificial Component (VaSC) process is used to fabricate microvascular structures. This procedure uses sacrificial poly(lactic) acid fibers to form hollow microchannels with precise 3D geometric positioning provided by laser micromachined guide plates.

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material ...

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.

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 ...

Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute transport in rivers and many important biogeochemical processes. To improve understanding of these processes through visual demonstration, we created a hyporheic flow simulation in the multi-agent computer modeling platform NetLogo. The simulation shows virtual tracer flowing through a streambed covered with two-dimensional bedforms. Sediment, flow, and bedform characteristics are used as input variables for the model. We illustrate how these simulations match experimental observations from laboratory flume experiments based on measured input parameters. Dye is injected into the flume sediments to visualize the porewater flow. For comparison virtual tracer particles are placed at the same locations in the simulation. This coupled simulation and lab experiment has been used successfully in undergraduate and graduate laboratories to directly visualize river-porewater interactions and show how physically-based flow simulations can reproduce environmental phenomena. Students took photographs of the bed through the transparent flume walls and compared them to shapes of the dye at the same times in the simulation. This resulted in very similar trends, which allowed the students to better understand both the flow patterns and the mathematical model. The simulations also allow the user to quickly visualize the impact of each input parameter by running multiple simulations. This process can also be used in research applications to illustrate basic processes, relate interfacial fluxes and porewater transport, and support quantitative process-based modeling.

This manuscript describes how to create regular bedforms in a flume, visualize flow through the bedforms, and use computer simulations to simulate the hyporheic flow. The computer simulations compare well with the experimental observations. This coupled simulation and experiment is well-suited for both research and educational purposes.

Advective exchange between the pore space of sediments and the overlying water column, called hyporheic exchange in fluvial environments, drives solute ...

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data acquisition times with high spatial resolution. In the electronics industry there is serious interest in performing failure analysis on 3D microelectronic packages, many which contain multiple levels of high-density interconnections. Often in tomography there is a trade-off between image resolution and the volume of a sample that can be imaged. This inverse relationship limits the usefulness of conventional computed tomography (CT) systems since a microelectronic package is often large in cross sectional area 100-3,600 mm2, but has important features on the micron scale. The micro-tomography beamline at the Advanced Light Source (ALS), in Berkeley, CA USA, has a setup which is adaptable and can be tailored to a sample&#39;s properties, i.e., density, thickness, etc., with a maximum allowable cross-section of 36 x 36 mm. This setup also has the option of being either monochromatic in the energy range ~7-43 keV or operating with maximum flux in white light mode using a polychromatic beam. Presented here are details of the experimental steps taken to image an entire 16 x 16 mm system within a package, in order to obtain 3D images of the system with a spatial resolution of 8.7 &#181;m all within a scan time of less than 3 min. Also shown are results from packages scanned in different orientations and a sectioned package for higher resolution imaging. In contrast a conventional CT system would take hours to record data with potentially poorer resolution. Indeed, the ratio of field-of-view to throughput time is much higher when using the synchrotron radiation tomography setup. The description below of the experimental setup can be implemented and adapted for use with many other multi-materials.

For this study synchrotron radiation micro-tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron&#39;s high flux and brightness the sample was imaged in just 3 min&#160;with an 8.7 &#181;m spatial resolution.

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

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 ...

Three-Dimensional Ultrasonic Needle Tip Tracking with a Fiber-Optic Ultrasound Receiver

Ultrasound is frequently used for guiding minimally invasive procedures, but visualizing medical devices is often challenging with this imaging modality. When visualization is lost, the medical device can cause trauma to critical tissue structures. Here, a method to track the needle tip during ultrasound image-guided procedures is presented. This method involves the use of a fiber-optic ultrasound receiver that is affixed within the cannula of a medical needle to communicate ultrasonically with the external ultrasound probe. This custom probe comprises a central transducer element array and side element arrays. In addition to conventional two-dimensional (2D) B-mode ultrasound imaging provided by the central array, three-dimensional (3D) needle tip tracking is provided by the side arrays. For B-mode ultrasound imaging, a standard transmit-receive sequence with electronic beamforming is performed. For ultrasonic tracking, Golay-coded ultrasound transmissions from the 4 side arrays are received by the hydrophone sensor, and subsequently the received signals are decoded to identify the needle tip&#39;s spatial location with respect to the ultrasound imaging probe. As a preliminary validation of this method, insertions of the needle/hydrophone pair were performed in clinically realistic contexts. This novel ultrasound imaging/tracking method is compatible with current clinical workflow, and it provides reliable device tracking during in-plane and out-of-plane needle insertions.

Accurate and efficient visualization of invasive medical devices is extremely important in many ultrasound-guided minimally invasive procedures. Here, a method for localizing the spatial position of a needle tip relative to the ultrasound imaging probe is presented.

Ultrasound is frequently used for guiding minimally invasive procedures, but visualizing medical devices is often challenging with this imaging modality. ...

Simultaneous Measurement of Turbulence and Particle Kinematics Using Flow Imaging Techniques

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine micro-organisms, and/or sediments in the ocean, or fluidized bed reactors and combustion processes in engineered systems. In order to study the effect of turbulence on the kinematics of particles in such flows, simultaneous measurements of both the flow and particle kinematics are required. Non-intrusive, optical flow measurement techniques for measuring turbulence, or for tracking particles, exist but measuring both simultaneously can be challenging due to interference between the techniques. The method presented herein provides a low cost and relatively simple method to make simultaneous measurements of the flow and particle kinematics. A cross section of the flow is measured using a particle image velocimetry (PIV) technique, which provides two components of velocity in the measurement plane. This technique utilizes a pulsed-laser for illumination of the seeded flow field that is imaged by a digital camera. The particle kinematics are simultaneously imaged using a light emitting diode (LED) line light that illuminates a planar cross section of the flow that overlaps with the PIV field-of-view (FOV). The line light is of low enough power that it does not affect the PIV measurements, but powerful enough to illuminate the larger particles of interest imaged using the high-speed camera. High-speed images that contain the laser pulses from the PIV technique are easily filtered by examining the summed intensity level of each high-speed image. By making the frame rate of the high-speed camera incommensurate with that of the PIV camera frame rate, the number of contaminated frames in the high-speed time series can be minimized. The technique is suitable for mean flows that are predominantly two-dimensional, contain particles that are at least 5 times the mean diameter of the PIV seeding tracers, and are low in concentration.

The technique described herein offers a low cost and relatively simple method to simultaneously measure particle kinematics and turbulence in flows with low particle concentrations. The turbulence is measured using particle image velocimetry (PIV), and particle kinematics are calculated from images obtained with a high-speed camera in an overlapping field-of-view.

Numerous problems in scientific and engineering fields involve understanding the kinematics of particles in turbulent flows, such as contaminants, marine ...

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent properties has been of great interest for the development of novel device applications. Here, fabrication of 3D, microscale, hollow polyhedrons (cubes) consisting of a few layers of 2D graphene or graphene oxide sheets via an origami-like self-folding process is described. This method involves the use of polymer frames and hinges, and aluminum oxide/chromium protection layers that reduce tensile, spatial, and surface tension stresses on the graphene-based membranes when the 2D nets are transformed into 3D cubes. The process offers control of the size and shape of the structures as well as parallel production. In addition, this approach allows the creation of surface modifications by metal patterning on each face of the 3D cubes. Raman spectroscopy studies show the method allows the preservation of the intrinsic properties of the graphene-based membranes, demonstrating the robustness of our method.

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

Here, we present a protocol for fabrication of 3D graphene-based polyhedrons via origami-like self-folding.