Name: manufacturing of three-dimensionally microstructured nanocomposites through microfluidic infiltration
Uploaded: 2014-03-12T23:00:00
Duration: 14 min 24 s
Description: Watch this Scientific Journal Video about Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration at JoVE.com

The authors acknowledge financial support from FQRNT (Le Fonds Qu&#233;b&#233;cois de la Recherche sur la Nature et les Technologies). The authors would like to thank the consulting support of Prof. Martin Levesque, Prof. My Ali El Khakani and Dr. Brahim Aissa.

1. Fabrication of 3D Microfluidic Networks
<ol>
	<li>Melt the fugitive ink at 80 &#176;C and load it into a 3 ml syringe barrel. 
	Note: The fugitive ink is a binary mixture of a microcrystalline wax and a petroleum jelly with a weight proportion of 40:60.</li>
	<li>Choose a deposition nozzle depending on the desired filament diameter (e.g.&#160;internal diameter (ID) = 150 &#181;m).</li>
	<li>Install the nozzle on the syringe barrel containing the ink material and mount it onto the syringe holder of the dispensing robot.</li>
	<li>Use an Excel program to design the moving path of the dispensing robot for the fabrication of the desired 3D scaffold structure. 
	Note: The overall dimensions of the 3D ink structure and filaments&#39; spacing in a given layer can be easily programmed; in this case, the dimensions are 60 mm in length, 7.5 mm in width, and 1.7 mm in thickness with 0.25 mm horizontal spacing between each filament.</li>
	<li>Set the deposition pressure on the pressure regulator and the robot dispensing speed. 
	Note: The fugitive ink filament diameter varies depending on the nozzle diameter, deposition pressure, ink viscosity and dispensing speed. Here, the filament diameter is ~150 &#181;m for a deposition speed of 4.7 mm/sec at an extrusion pressure of 1.9 MPa.</li>
	<li>Start the fabrication of the microscaffold with the deposition of the ink-based filaments on an epoxy substrate, which leads to a 2D pattern (Figure 2a).</li>
	<li>Deposit the subsequent layers by successively incrementing the z-position of the dispensing nozzle by an amount equal to the diameter of the filaments (Figure 2b). 
	Note: Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built.</li>
	<li>Mix the two parts of epoxy (i.e.&#160;the resin and the hardener) used for the encapsulation and degas the epoxy mixture under vacuum for a defined time (here, 0.15 bar for 30 min) to remove the bubbles trapped during mixing of the epoxy components. 
	Note: The degassing time may vary with the gel time of the epoxy mixture. For a different epoxy system, the required degassing time may be shorter or longer.</li>
	<li>Load the epoxy resin into a 3 ml syringe barrel using a fluid dispenser by applying a negative pressure and then mount a fine nozzle (e.g.&#160;ID = 0.51 mm) into the syringe barrel.</li>
	<li>Place drops of epoxy over the inclined scaffold structure at its upper end using the same fluid dispenser and mounted nozzle to minimize the risk of bubble trapping during the epoxy encapsulation. 
	Note: The epoxy then flows into the empty spaces between filaments, driven by gravity and capillary forces.</li>
	<li>Continue placing drops of epoxy over the scaffold until the empty space between the scaffold filaments is completely filled.</li>
	<li>Let the encapsulating epoxy precure at room temperature for 24 hr and then put the structure in an oven for post-curing at 60 &#176;C (Figure 2c). 
	Note: A different cure schedule may be applied for a different epoxy system.</li>
	<li>Cut the excess parts of epoxy using a precision saw after complete curing.</li>
	<li>Drill two holes at two ends of the structure and insert two plastic tubes.</li>
	<li>Remove the fugitive ink from the structure as following:
	<ol>
		<li>Put the samples in an oven at 90 &#176;C for 30 min for the ink liquefaction (Figure 2d).</li>
		<li>Shortly after taking the samples out of the oven, wash the channel network with the suction of hot distilled water through the tubes attached to the opened channels for 5 min followed by hexane for another 5 min. 
		Note: The ink removal yields an interconnected 3D microfluidic network (Figure 5).&#160;Post-cleaning of the networks using hexane is performed in order to remove the possible residual traces of the ink from the channel walls.</li>
	</ol>
	</li>
</ol>
2. Nanocomposite Preparation
Note: The nanocomposites are prepared by blending a dual cure (ultraviolet/heat curable) thermosetting resin, either an epoxy resin or a urethane-based resin and nanofillers (here, single-walled carbon nanotubes) at different loadings.
<ol>
	<li>Add the desired amount of nanotubes to a solution of 0.1 mM of a surfactant (zinc protoporphyrin IX) either in acetone or dichloromethane14 (Figure 6). 
	Note: Here, 150 mg of CNTs was added to the solution (~50 ml) in order to prepare a nanocomposite with a final nanotube concentration of 0.5% wt. It should be also mentioned that the use of high boiling temperature solvents like DMF should be avoided due to possible heat-curing of the UV-epoxy used in this study at temperatures above 60 &#176;C during the solvent evaporation.</li>
	<li>Sonicate the suspension in an ultrasonic bath for 30 min to debundle the nanotube aggregates (Figure 6). 
	Note: Additional efforts such as filtration or ultracentrifugation of the nanotube solution should be made to remove the remaining big clusters before mixing with the resin.</li>
	<li>Mix the resin (either epoxy or urethane) with the nanotube suspension over a magnetic stirring hot plate at a temperature slightly below the solvent boiling temperature (e.g.&#160;50 &#176;C for acetone solution) for 4 hr.</li>
	<li>Place the nanocomposite mixture into the ultrasonication bath and simultaneously apply the sonication and heating (40-50 &#176;C) for 1 hr (Figure 6).</li>
	<li>Let the residual solvent evaporate by heating the nanocomposite at 30 &#176;C for 12 hr and then at 50 &#176;C for 24 hr under vacuum (~0.1 bar).</li>
	<li>Shear mix the nanocomposite materials by passing them through a small gap between the rolls in a three-roll mill mixer in order to break large nanotube aggregates (Figure 6). Keep a portion of nanocomposite prior to three-roll mixing for baseline comparison.</li>
	<li>Set the three-roll mixing parameters (i.e.&#160;gaps and rotating speed). 
	Note: Here, a constant speed of 250 rpm is used for the apron roll. However, the gaps between rolls are reduced in three-step processing as follows: 5 passes at 25 &#181;m, 5 passes at 10 &#181;m, and 10 passes at 5 &#181;m, respectively.</li>
	<li>Degas the final mixture under vacuum of ~0.1 bar for 24 hr using a desiccator to remove the air bubbles trapped during the mixing.</li>
</ol>
3. Nanocomposite Infiltration (Injection)
<ol>
	<li>Load the nanocomposites, prepared in section 2, into a 3 ml syringe barrel using the fluid dispenser by applying a negative pressure.</li>
	<li>Insert a fine nozzle (e.g.&#160;ID = 0.51 mm) that fits into the plastic tubes attached to the opened channels (same tubes used for the ink removal) and mount it into the syringe barrel containing the nanocomposite materials.</li>
	<li>Set the desired pressure (i.e.&#160;positive pressure) on the pressure dispenser. 
	Note: Here, the nanocomposite injection pressure is set at 400 kPa. 
	Note: A vacuum (i.e.&#160;negative pressure) could be applied to the other end (i.e.&#160;outlet side) to assist the network filling. Once the pressure is applied, the microfluidic network, built in Protocol&#160;1, is filled by nanocomposite suspension, which enters the network through the plastic tubes.</li>
	<li>Shortly after the injection, expose the nanocomposite-filled composite beams to UV illumination of a UV lamp for 30 min for precuring. 
	Note: This precuring operation is thought to reduce the effect of Brownian motion on the CNTs possible orientation. It also reduces the heat-induced shrinkage (Figure 7)</li>
	<li>Post-cure the manufactured beams in the oven at, in the case of UV-epoxy, 80 &#176;C for 1 hr followed by 130 &#176;C for another 1 hr (Figure 7).</li>
	<li>Cut the excess epoxy parts using a saw and then polish the beams to the desired dimensions (here,&#160;~60 mm in length, ~6.8 mm in width, and ~1.6 mm in thickness of the beams were manufactured for ease of mechanical characterization).</li>
</ol>

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No conflicts of interest declared.

The experimental procedure presented here is a new and flexible manufacturing method in order to tailor mechanical performance of polymer-based materials for material design purposes. Using this method, desired properties could be achieved based on the proper choice of components (i.e.&#160;infiltrated materials and main matrix) as well as engineering the composite structures. First, the technique enables the manufacture of a single material, composed of different thermosetting polymers, representing a unique temperature-dependent feature which is different than those of the components bulks15. Another advantage of the present technique over other nanocomposite fabrication techniques by which the nanofillers are uniformly distributed through whole matrix is the ability to spatially place the reinforcements at desired locations in these 3D-reinforced composite beams. Due to this positioning capability, a lower amount of possibly expensive nanofillers is needed to obtain a specific mechanical performance13. Since the reinforcement pattern obeys the original direct-writing of the ink scaffold, the filaments&#39; spacing in a given layer is limited to approximately ten times the ink filaments diameter owing to the viscoelastic properties of the fugitive ink. On the other hand, a small spacing may limit flow of liquid epoxy during the epoxy encapsulation step. Moreover, the ink filament&#39;s diameter should be large enough (e.g.&#160;above 50 &#181;m) for ease of fabrication (e.g.&#160;extrusion of high viscous ink) and subsequent manufacturing steps such as nanocomposite infiltration into the microfluidic networks.
Another potential of the present method might be the capability of aligning the individual CNTs or other nanofillers in the flow direction under shear flow16&#160;by nanocomposite infiltration at higher speeds/pressures, if the nanofillers are well-dispersed in during the nanocomposite mixing process. However, a high degree of alignment could only be achieved at very high infiltration pressures (due to small channel diameter), which may cause air entrapment in the network during the infiltration.
Representative optical images in Figure 6 show the nanocomposites prepared by the mixing procedure presented in Protocol&#160;2 (two images at the bottom of the figure). The observed dark spots are thought to be nanotube aggregates.&#160;For the ultrasonicated nanocomposite, the micron-size aggregates with a diameter of up to ~7 &#181;m are present while a drastic change of the size of the aggregates (with an average of ~1 &#181;m) is observed for the shear-mixed nanocomposite. Since the nanofiller dispersion affects the mechanical and electrical properties of the manufactured 3D nanocomposite beams, an improved dispersion should be achieved to take the full advantage of 3D positioning of nanofillers using the present manufacturing technique. Therefore, a further study is needed to systematically investigate the dispersion states of nanotubes and the use of other nanofillers, which can be more easily dispersed within the epoxy matrix.
The present manufacturing technique might enable the design of functional 3D nanocomposite products for microengineering application17. The technique is not limited to the materials used in this study. Therefore, the application of this technique could be extended by the utilization of other thermosetting materials and nanofillers. Among several applications, structural health monitoring, vibration absorption products and microelectronics can be mentioned.

Polymer nanocomposites using nanomaterials, especially carbon nanotubes (CNTs) incorporated into polymer matrices feature multifunctional properties1 for potential applications such as structural composites2, microelectromechanical systems3&#160;(e.g.&#160;microsensors), and smart polymers4. Several processing steps including CNT treatment and nanocomposite mixing methods may be required to desirably disperse CNTs into the matrix. Since the CNTs&#39; aspect ratio, their dispersion state and surface treatment mainly influence the electrical and mechanical performance, the nanocomposite processing procedure may vary depending on desired properties for a targeted application5. Moreover, for specific loading conditions, aligning CNTs along a desired direction and also positioning the reinforcements at desired locations enable further improvement of the mechanical and/or electrical properties of these nanocomposites.
A few techniques such as shear flow6-7and electromagnetic fields8&#160;have been used to align the CNTs along a desired direction in a polymer matrix. Moreover, CNT orientation induced by dimensional constraining, specifically in one-dimension (1D) and two-dimension (2D), has been observed during the processing/forming of nanocomposite materials9-11. However, new advances on the manufacturing processes are still needed to allow sufficient control of the three-dimensional (3D) orientation and/or positioning of the nanotube reinforcement during the manufacturing of a product for optimal conditions.
In this paper, we present a protocol for manufacturing 3D-reinforced composite beams via directed and localized in&#64257;ltration of a 3D micro&#64258;uidic network with polymer nanocomposite suspensions (Figure 1). First, the fabrication of a 3D interconnected microfluidic network is demonstrated, which involves the direct-write fabrication of the fugitive ink filaments12-13 on epoxy substrates (Figures 2a and 2b), followed by epoxy encapsulation (Figure 2c) and the sacrificial ink removal (Figure 2d). The direct-write method consists of a computer-controlled robot that moves a fluid dispenser along the x, y, and z axes (Figure 3). This technique provides a fast and flexible way to fabricate 3D microdevices for photonic, MEMS and biotechnology applications (Figure 4). Then, the nanocomposite preparation is demonstrated, along with its infiltration (or injection) into the porous network under different controlled and constant pressures to manufacture 3D-reinforced multiscale composites (Figures 2e and 2f). Finally, some representative results along with their potential applications are shown.

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			<td height="21" style="height:21px;width:163px;">Dispensing Robot</td>
			<td style="width:160px;">I &#38; J Fisnar</td>
			<td style="width:136px;">I &#38; J2200-4</td>
			<td style="width:147px;">-</td>
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		<tr height="41">
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			<td style="width:160px;">I &#38; J Fisnar</td>
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			<td style="width:147px;">JR-Point Dispensing</td>
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			<td height="21" style="height:21px;width:163px;">Syringe Barrel</td>
			<td style="width:160px;">Nordson EFD Inc.</td>
			<td style="width:136px;">7012072</td>
			<td style="width:147px;">3cc</td>
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		<tr height="41">
			<td height="41" style="height:41px;width:163px;">Dispensing Nozzle</td>
			<td style="width:160px;">Nordson EFD Inc.</td>
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			<td style="width:147px;">Stainless Steel Tip&#160;&#160; (ID: 0.51 mm)</td>
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		<tr height="41">
			<td height="41" style="height:41px;width:163px;">Dispensing Nozzle</td>
			<td style="width:160px;">Nordson EFD Inc.</td>
			<td style="width:136px;">7018424</td>
			<td style="width:147px;">Stainless Steel Tip&#160;&#160; (ID: 0.15 mm)</td>
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			<td height="21" style="height:21px;width:163px;">Fluid Dispenser</td>
			<td style="width:160px;">Nordson EFD Inc.</td>
			<td style="width:136px;">HP-7X</td>
			<td style="width:147px;">-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Fluid Dispenser</td>
			<td style="width:160px;">Nordson EFD Inc.</td>
			<td style="width:136px;">800</td>
			<td style="width:147px;">-</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Live camera</td>
			<td style="width:160px;">MediaCybernetics</td>
			<td style="width:136px;">QI, Cool, Color</td>
			<td style="width:147px;">12 Bit, Qimaging</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Live Camera Software</td>
			<td style="width:160px;">Image-pro Plus</td>
			<td style="width:136px;">-</td>
			<td style="width:147px;">Version 6</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Precision Saw</td>
			<td style="width:160px;">Buehler (IsoMet)</td>
			<td style="width:136px;">622-ISF-03604&#160;</td>
			<td style="width:147px;">&#160;Low-Speed Saw</td>
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			<td height="21" style="height:21px;width:163px;">Flexible plastic Tube</td>
			<td style="width:160px;">Saint-Gobain PRL Corp.</td>
			<td style="width:136px;">Tygon 177936</td>
			<td style="width:147px;">-</td>
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			<td height="21" style="height:21px;width:163px;">Stirring hot plate</td>
			<td style="width:160px;">Barnstead international</td>
			<td style="width:136px;">SP131825</td>
			<td style="width:147px;">-</td>
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			<td height="21" style="height:21px;width:163px;">Vacuumed-oven</td>
			<td style="width:160px;">Cole-Parmer</td>
			<td style="width:136px;">EW-05053-10</td>
			<td style="width:147px;">-</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Ultrasonic cleaner</td>
			<td style="width:160px;">Cole-Parmer</td>
			<td style="width:136px;">EW-08891-11</td>
			<td style="width:147px;">-</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Three-roll mill mixer</td>
			<td style="width:160px;">Exakt Technologies</td>
			<td style="width:136px;">Exakt 80E</td>
			<td style="width:147px;">-</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:163px;">Dynamic Mechanical Analyzer</td>
			<td style="width:160px;">TA Instruments</td>
			<td style="width:136px;">DMA Q800</td>
			<td style="width:147px;">-</td>
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			<td height="41" style="height:41px;width:163px;">UV-lamp</td>
			<td style="width:160px;">Cole Parmer</td>
			<td style="width:136px;">RK-97600-00</td>
			<td style="width:147px;">Intensity of 21mW/cm&#178;</td>
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</table>

manufacturing of three-dimensionally microstructured nanocomposites through microfluidic infiltration

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite in&#64257;ltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink.&#160;Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built using this method. The resulting tubular micro&#64258;uidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g.&#160;single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e.&#160;materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Figures 8a and 8b show a representative image of manufactured beams and an optical image of its cross-section, consisting of nine layers of the nanocomposite filaments.
Figures 8c and 8d show typical SEM images of a manufactured beams fracture surface and a higher magnification image of filled channels (i.e.&#160;embedded nanocomposite microfibers), respectively. Since no debonding is seen at the channels wall, it is fair to say that the surrounding epoxy and the infiltrated materials are well adhered as a result of proper cleaning of the channels with hexane after the ink removal.
Figure 9 shows a representative optical image of a beam broken during the mechanical testing in which hexane is not used during the ink removal. Fiber debonding, as a result of poor mechanical interface is observed which might be due to fugitive ink traces remained after network cleaning.
Figure 10 shows the storage modulus, E&#39;, of the molded bulk epoxy samples (as benchmarks) and the 3D-reinforced beams. The results show unique trends for the manufactured beams which are the combination of the embedded and surrounding epoxy materials with superior properties with the presence of only ~0.18 wt. % CNTs.
Figure 11 shows the three-point bending test results of the manufactured composite beams using a DMA.&#160;As a result of CNTs positioning, the flexural modulus of the 3D reinforced beams showed an increase of 34% compared to the pure epoxy-infiltrated (whole epoxy) beams.
<img alt="Figure 1" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig1highres.jpg" width="500" /> 
Figure 1. Schematic representation of a 3D-reinforced nanocomposite manufactured by the microinfiltration approach. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig1highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 2" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig2highres.jpg" width="500" /> 
Figure 2. Schematic representation of the manufacturing of 3D-reinforced beams. (a) Ink filament direct deposition using a dispensing robot,&#160;(b) Deposition of several layers on top of each other by incrementing the dispensing nozzle in z-direction,&#160;(c) Filling the pore space between filaments&#160;using a low viscosity resin,&#160;(d) Taking the ink out of the network by its liquefaction, resulting in the fabrication of microfluidic channels. (e) Filling the empty network with the nanocomposite suspension followed by curing, and (f) Cutting the excess epoxy parts. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig2highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 3" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig3highres.jpg" width="500" /> 
Figure 3. A photo of the robotic deposition stage consisting of a computer-controlled robot, a dispensing apparatus, and a live camera. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig3highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 4" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig4highres.jpg" width="500" /> 
Figure 4. A few images of microstructures manufactured by the direct-write assembly. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig4highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 5" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig5highres.jpg" width="500" /> 
Figure 5. An isometric view and a SEM image the 3D-connected microfluidic empty network. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig5highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 6" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig6highres.jpg" width="500" /> 
Figure 6. Nanocomposite mixing strategies including nanotube noncovalent functionalization, ultrasonication, and/or three-roll mill mixing which lead to nanotube dispersions with different qualities (optical images of nanocomposite films). <a href="https://www.jove.com/files/ftp_upload/51512/51512fig6highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 7" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig7highres.jpg" width="500" /> 
Figure 7. Nanocomposite curing under UV illumination of a UV-lamp followed by post-curing in the oven. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig7highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 8" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig8highres.jpg" width="500" /> 
Figure 8. (a) Isometric image of a 3D-reinforced beam, (b) Typical cross-section of a nanocomposite-injected beam, (c) A beam surface fracture SEM image, and (d) A close-up view of (c). <a href="https://www.jove.com/files/ftp_upload/51512/51512fig8highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 9" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig9highres.jpg" width="500" /> 
Figure 9. Fracture surface image of a polyurethane nanocomposite-infiltrated beam. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig9highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 10" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig10highres.jpg" width="500" /> 
Figure 10. Temperature-dependent mechanical properties (storage modulus) of the bulk epoxies and the manufactured beams using a dynamic mechanical analyzer. <a href="https://www.jove.com/files/ftp_upload/51512/51512fig10highres.jpg" target="_blank">Click here to view larger image.</a>
<img alt="Figure 11" fo:content-width="6in" src="/files/ftp_upload/51512/51512fig11highres.jpg" width="500" /> 
Figure 11. Quasi-static mechanical properties (flexural) of the bulk epoxies and the manufactured beams (three-point bending test). <a href="https://www.jove.com/files/ftp_upload/51512/51512fig11highres.jpg" target="_blank">Click here to view larger image.</a>

Watch this Scientific Journal Video about Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration at JoVE.com

Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration

Three-dimensional (3D) microstructured composite beams are fabricated through the directed and localized infiltration of nanocomposites into 3D porous microfluidic networks. The flexibility of this manufacturing method enables the utilization of different thermosetting materials and nanofillers in order to achieve a variety of functional 3D reinforced nanocomposite macroscopic products.

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite ...

manufacturing-three-dimensionally-microstructured-nanocomposites

Research

JoVE Journal

Chemistry

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Transport of Surface-modified Carbon Nanotubes through a Soil Column

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, electronics and biomedical applications. Due to their accelerating production and use, CNTs constitute a potential environmental risk if they are released to soil and groundwater systems. It is therefore essential to improve the current understanding of environmental fate and transport of CNTs. The transport and retention of CNTs in both natural and artificial media have been reported in literature, but the findings widely vary and are thus not conclusive. There are a number of physical and chemical parameters responsible for variation in retention and transport. In this study, a complete procedure of selected multiwalled carbon nanotubes (MWCNTs) is presented starting from their surface modification to a complete set of laboratory column experiments at critical physical and chemical scenarios. Results indicate that the stability of the commercially available MWCNTs are critical with their attached surface functional group which can also influence the transport and retention of MWCNT through the surrounding medium.

Surface properties of a nanoparticle are important for their interaction with the surrounding medium. Therefore the surface modification of carbon nanotubes can be critical for their transport and retention through porous media. Here, lab scale column experiments are used to understand the possible transport and retention of these nanoparticles.

Carbon nanotubes (CNTs) are widely manufactured nanoparticles, which are being utilized in a number of consumer products, such as sporting goods, ...

Laboratory Production of Biofuels and Biochemicals from a Rapeseed Oil through Catalytic Cracking Conversion

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil (HGO) for production of transportation fuels through a fluid catalytic cracking (FCC) route. Cracking experiments are performed with a fully automated reaction unit at a fixed weight hourly space velocity (WHSV) of 8 hr-1, 490-530 &#176;C, and catalyst/oil ratios of 4-12 g/g. When a feed is in contact with catalyst in the fluid-bed reactor, cracking takes place generating gaseous, liquid, and solid products. The vapor produced is condensed and collected in a liquid receiver at -15 &#176;C. The non-condensable effluent is first directed to a vessel and is sent, after homogenization, to an on-line gas chromatograph (GC) for refinery gas analysis. The coke deposited on the catalyst is determined in situ by burning the spent catalyst in air at high temperatures. Levels of CO2 are measured quantitatively via an infrared (IR) cell, and are converted to coke yield. Liquid samples in the receivers are analyzed by GC for simulated distillation to determine the amounts in different boiling ranges, i.e., IBP-221 &#176;C (gasoline), 221-343 &#176;C (light cycle oil), and 343 &#176;C+ (heavy cycle oil). Cracking of a feed containing canola oil generates water, which appears at the bottom of a liquid receiver and on its inner wall. Recovery of water on the wall is achieved through washing with methanol followed by Karl Fischer titration for water content. Basic results reported include conversion (the portion of the feed converted to gas and liquid product with a boiling point below 221 &#176;C, coke, and water, if present) and yields of dry gas (H2-C2's, CO, and CO2), liquefied petroleum gas (C3-C4), gasoline, light cycle oil, heavy cycle oil, coke, and water, if present.

This paper presents an experimental method to produce biofuels and biochemicals from canola oil mixed with a fossil-based feed in the presence of a catalyst at mild temperatures. Gaseous, liquid, and solid products from a reaction unit are quantified and characterized. Conversion and individual product yields are calculated and reported.

The work is based on a reported study which investigates the processability of canola oil (bio-feed) in the presence of bitumen-derived heavy gas oil ...

Characterizing Electron Transport through Living Biofilms

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under physiologically relevant conditions.1 These measurements are performed on living biofilms in aqueous medium using source and drain electrodes patterned on a glass surface in a specialized configuration referred to as an interdigitated electrode (IDA) array. A biofilm is grown that extends across the gap connecting the source and drain. Potentials are applied to the electrodes (ES and ED) generating a source-drain current (ISD) through the biofilm between the electrodes. The dependency of electrical conductivity on gate potential (the average of the source and drain potentials, EG = [ED + ES]/2) is determined by systematically changing the gate potential and measuring the resulting source-drain current. The dependency of conductivity on gate potential provides mechanistic information about the extracellular electron transport process underlying the electrical conductivity of the specific biofilm under investigation. The electrochemical gating measurement method described here is based directly on that used by M. S. Wrighton2,3 and colleagues and R. W. Murray4,5,6 and colleagues in the 1980&#39;s to investigate thin film conductive polymers.

A protocol for measuring electrical conductivity of living microbial biofilms under physiologically relevant conditions is presented.

Here we demonstrate the method of electrochemical gating used to characterize electrical conductivity of electrode-grown microbial biofilms under ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables the silk proteins to be compact and ordered by shearing and elongation forces. Here, a biomimetic microfluidic channel was designed to mimic the specific geometry of the spinning duct of the silkworm. Regenerated silk fibroin (RSF) spinning doped with high concentration, was extruded through the microchannel to dry-spin fibers at ambient temperature and pressure. In the post-treated process, the as-spun fibers were drawn and stored in ethanol aqueous solution. Synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) technology was used to investigate the microstructure of single RSF fibers, which were fixed to a sample holder with the RSF fiber axis normal to the microbeam of the X-ray. The crystallinity, crystallite size, and crystalline orientation of the fiber were calculated from the WAXD data. The diffraction arcs near the equator of the two-dimensional WAXD pattern indicate that the post-treated RSF fiber has a high orientation degree.

A protocol for the microfluidic spinning and microstructure characterization of regenerated silk fibroin monofilament is presented.

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion co-flow device to generate uniform high-viscosity droplets in a low-viscosity fluid. The microfluidic capillary device has a common co-flow structure with its exit connecting to a wider tube. Elongated droplets of the low-viscosity fluid are first encapsulated by the high-viscosity fluid in the co-flow structure. As the elongated low-viscosity droplets flow through the exit, which is treated to be wetted by the low-viscosity fluid, phase inversion is then induced by the adhesion of the low viscosity droplets to the tip of the exit, which results in the subsequent inverse encapsulation of the high-viscosity fluid. The size of the resultant high-viscosity droplets can be adjusted by changing the flow rate ratio of the low-viscosity fluid to the high-viscosity fluid. We demonstrate several typical examples of the generation of high-viscosity droplets with a viscosity up to 11.9 Pas, such as glycerol, honey, starch, and polymer solution. The method provides a simple and straightforward approach to generate monodisperse high-viscosity droplets, which may be used in a variety of droplet-based applications, such as materials synthesis, drug delivery, cell assay, bioengineering, and food engineering.

A phase-inversion co-flow device is demonstrated to generate monodisperse high-viscosity droplets above 1 Pas, which is difficult to realize in droplet microfluidics.

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion ...

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 ...

Negative Additive Manufacturing of Complex Shaped Boron Carbides

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for high wear, high hardness, and lightweight material applications such as armors. To overcome this challenge, negative additive manufacturing (AM) is employed to produce complex geometries of boron carbides at various length scales. Negative AM first involves gelcasting a suspension into a 3D-printed plastic mold. The mold is then dissolved away, leaving behind a green body as a negative copy. Resorcinol-formaldehyde (RF) is used as a novel gelling agent because unlike traditional hydrogels, there is little to no shrinkage, which allows for extremely complex molds to be used. Furthermore, this gelling agent can be pyrolyzed to leave behind ~50 wt% carbon, which is a highly effective sintering aid for B4C. Due to this highly homogenous distribution of in situ carbon within the B4C matrix, less than 2% porosity can be achieved after sintering. This protocol highlights in detail the methodology for creating near fully dense boron carbide parts with highly complex geometries.

A method called negative additive manufacturing is used to produce near fully dense complex shaped boron carbide parts of various length scales. This technique is possible via the formulation of a novel suspension involving resorcinol-formaldehyde as a unique gelling agent that leaves behind a homogenous carbon sintering aid after pyrolysis.

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for ...

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. We successfully developed a method to quantitatively and easily measure Cu(I) in a plating solution and used it for evaluation of the solution. In this paper, a quantitative absorption spectrum measurement and a time-resolved injection measurement of Cu(I) concentrations by a color reaction are described. This procedure is effective as a method to reproduce and elucidate the phenomenon occurring in the plating bath in the laboratory. First, the formation and accumulation process of Cu(I) in solution by electrolysis of a plating solution is shown. The amount of Cu(I) in the solution is increased by electrolysis at higher current values &#8203;&#8203;than the usual plating process. For the determination of Cu(I), BCS (bathocuproinedisulfonic acid, disodium salt), a reagent that selectively reacts with Cu(I), is used. The concentration of Cu(I) can be calculated from the absorbance of the Cu(I)-BCS complex. Next, the time measurement of the color reaction is described. The color reaction curve of Cu(I) and BCS measured by the injection method can be decomposed into an instantaneous component and a delay component. By analysis of these components, the holding structure of Cu(I) can be clarified, and this information is important when predicting the quality of the plating film to be produced. This method is used to facilitate the evaluation of the plating bath in the production line.

Here, accumulation of cuprous ions in a copper sulfate plating solution in a model experiment and an analysis based on quantitative measurements are described. This experiment reproduces the accumulation process of cuprous ions in the plating bath.

Knowledge of the behavior of cuprous ions (monovalent copper ion: Cu(I)) in a copper sulfate plating bath is important for improving the plating process. ...

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry

On-surface synthesis has recently been regarded as a promising approach for the generation of new molecular structures. It has been particularly successful in the synthesis of graphene nanoribbons, nanographenes and intrinsically reactive and instable, yet attractive species. It is based on the combination of solution chemistry aimed at preparation of appropriate molecular precursors for further ultra-high vacuum surface assisted transformations. This approach also owes its success to an incredible development of characterization techniques, such as scanning tunneling/atomic force microscopy and related methods, which allow detailed, local characterization at atomic scale. While the surface-assisted synthesis can provide molecular nanostructures with outstanding precision, down to single atoms, it suffers from basing on metallic surfaces and often limited yield. Therefore, the extension of the approach away from metals and the struggle to increase productivity seem to be significant challenges toward wider applications. Herein, we demonstrate the on-surface synthesis approach for generation of non-planar nanographenes, which are synthesized through a combination of solution chemistry and sequential surface-assisted processes, together with the detailed characterization by scanning probe microscopy methods.

A combination of solution and surface assisted synthesis opens new directions in the atomically precise synthesis of nanostructures. Scanning tunneling microscopy (STM) supplemented by non-contact atomic force microscopy (nc-AFM) enables detailed characterization of newly designed and generated carbon-based nano-objects.