Name: process of making three-dimensional microstructures using vaporization of a sacrificial component
Uploaded: 2013-11-02T17:00:00
Description: Watch this Scientific Journal Video about Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component at JoVE.com

This work was supported by the AFOSR Young Investigator Program under FA9550-12-1-0352 and a 3M Non-Tenured Faculty Award. The authors would like to thank Lalisa Stutts and Janine Tom for helpful discussion relating to this project. The authors thank the Calit2 Microscopy Center and Laser Spectroscopy Facility at the University of California, Irvine for allowing use of its facilities. Hodge Harland and the UCI Physical Sciences Machine Shop are acknowledged for the fabrication of tools. Poly(lactic) acid fibers were generously provided by Teijin Monofilament.

1. Catalyzing Sacrificial Fibers
<ol>
	<li>Wrap the desired amount of poly(lactic) acid fibers around the lower &#190; of customized spindle. Reduce fiber overlap to provide the maximum surface area exposure.</li>
	<li>Mix deionized H2O with 40 ml of Disperbyk 130 in a closed bottle and shake until a homogenous solution is obtained. Then place a 1,000 ml beaker in a water bath at 37 &#176;C and pour trifluoroethanol into the beaker. The amount of H2O and TFE to use depends on the PLA fiber diamete...

<ol>
	<li>Bellan, L. M., Singh, S. P., Henderson, P. W., Porri, T. J., Craighead, H. G., Spector, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+an+artificial+3-dimensional+vascular+network+using+sacrificial+sugar+structures.">Fabrication of an artificial 3-dimensional vascular network using sacrificial sugar structures.</a> Soft Matter. 5 (7), 1354 (2009).</li><li>Bellan, L. M., Strychalski, E. A., Craighead, H. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nano-channels+fabricated+in+polydimethylsiloxane+using+sacrificial+electrospun+polyethylene+oxide+nanofibers.">Nano-channels fabricated in polydimethylsiloxane using sacrificial electrospun polyethylene oxide nanofibers.</a> J. Vac. Sci. Technol. B Microelectron. Nanometer Struct. Process. Meas. Phenom. 26 (5), 1728 (2008).</li><li>Borenstein, J. T., Weinberg, E. J., Orrick, B. K., Sundback, C., Kaazempur-Mofrad, M. R., Vacanti, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfabrication+of+three-dimensional+engineered+Scaffolds.">Microfabrication of three-dimensional engineered Scaffolds.</a> Tissue Eng. 13 (8), 1837-1844 (2007).</li><li>Wu, H., Odom, T. W., Chiu, D. T., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+complex+three-dimensional+microchannel+systems+in+PDMS.">Fabrication of complex three-dimensional microchannel systems in PDMS.</a> J. Am. Chem. Soc. 125 (2), 554-559 (2003).</li><li>Trask, R. S., Bond, I. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomimetic+self-healing+of+advanced+composite+structures+using+hollow+glass+fibres.">Biomimetic self-healing of advanced composite structures using hollow glass fibres.</a> Smart Mater. Struct. 15 (3), 704-710 (2006).</li><li>Dong, H., Esser-Kahn, A. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+treatment+of+poly(lactic+acid)+fibers+to+enhance+the+rate+of+thermal+depolymerization.">Chemical treatment of poly(lactic acid) fibers to enhance the rate of thermal depolymerization.</a> ACS Appl. Mater. Interfaces. 4 (2), 503-509 (2012).</li><li>Esser-Kahn, A. P., Thakre, P. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+microvascular+fiber-reinforced+composites.">Three-dimensional microvascular fiber-reinforced composites.</a> Adv. Mater. 23 (32), 3654-3658 (2011).</li><li>White, S. R., Blaiszik, B. J., Kramer, S. L. B., Olugebefola, S. C., Moore, J. S., Sottos, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-healing+polymers+and+composites.">Self-healing polymers and composites.</a> Am. Sci. 99 (5), 392 (2011).</li><li>Nguyen, D. T., Leho, Y. T., Esser-Kahn, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+three-dimensional+microvascular+gas+exchange+unit+for+carbon+dioxide+capture.">A three-dimensional microvascular gas exchange unit for carbon dioxide capture.</a> Lab Chip. 12 (7), 1246 (2012).</li><li>Nguyen, D. T., Leho, Y. T., Esser-Kahn, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+membrane+thickness+on+a+microvascular+gas+exchange+unit.">The effect of membrane thickness on a microvascular gas exchange unit.</a> Adv. Funct. Mater. , (2012).</li></ol>

The introduction of the SnOx catalyst into the PLA fibers allows the fibers to depolymerize at a lower temperature. This prevents the degradation of the embedding resin, in this case PDMS. A custom spindle is required to properly mix the treatment solution (Figure 5A). The spindle is composed of six supporting rods surrounding a central core which attaches to a digital mixer. The fibers are wrapped around the support rods so that the surface area of the wrapping fibers in contact with the catalytic solut...

Natural systems use extensive vascular networks to facilitate many biological functions. Mass transport can be achieved efficiently in such systems due to high surface area to volume ratios and optimized packing structures. While many synthetic fabrication techniques can produce microvascular structures, none can produce large-scale microvasculature while maintaining complexity and compatibility with existing manufacturing methods1-5. Structures such as the avian lung provide an inspiration. How do we fabricate structures of this complexity for enhancing mass transport?
The Vaporization of a Sacrificial Component (VaSC) can produce large-scale, complex microvascular structures6-7. This method uses the thermal depolymerization and evaporative removal of poly(lactic) acid fibers to form hollow channels that are the inverse of the fiber template. This is a sacrificial technique compatible with existing manufacturing methods. Meter long, cylindrical microchannel patterns can be formed using this fabrication process. This can be used to create vascularized devices such as self-healing polymers and 3D microvascular carbon capture units7-10.
The carbon capture units were inspired by the avian lung that provides an efficient gas-exchange-to-weight ratio owing to its use in flight. The parabronchus is composed of hexagonally patterned microchannels, which provides high gas exchange rates and structurally stable gas exchange units. In order to create exchange units with microscale features aligned in three-dimensions, we developed a method of independently tensioning fibers using a custom designed tension board with guitar tuners and laser-micromachined plates. Each fiber is held in place by external tension and the pattern is set by the placement of holes in the plate through which the fibers run.

<table border="1">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Reagent</td>
		</tr>
		<tr>
			<td>Tin (II) oxalate</td>
			<td>Sigma-Aldrich</td>
			<td>402761</td>
			<td></td>
		</tr>
		<tr>
			<td>Disperbyk 130</td>
			<td>BYK Additives &#38; Instruments</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Trifluoroethanol</td>
			<td>Halocarbon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Malachite Green (technical grade)</td>
			<td>Sigma-Aldrich</td>
			<td>M6880</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide (&#8805;98%, pellets)</td>
			<td>Sigma-Aldrich</td>
			<td>S5881</td>
			<td></td>
		</tr>
		<tr>
			<td>Polydimethylsiloxane (PDMS)</td>
			<td>Dow Corning</td>
			<td>3097358-1004</td>
			<td>Distributed from Ellsworth Adhesives</td>
		</tr>
		<tr>
			<td>Poly(lactic) acid fibers</td>
			<td>Teijin Monofilament</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Material</td>
		</tr>
		<tr>
			<td>RW 20 Digital Mixer</td>
			<td>IKA</td>
			<td>3593001</td>
			<td></td>
		</tr>
		<tr>
			<td>Desiccator Jar</td>
			<td>Pyrex</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum Oven</td>
			<td>Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Third Hand</td>
			<td>Jameco Electronics</td>
			<td>26690</td>
			<td>Plate holder</td>
		</tr>
		<tr>
			<td>Glue Gun</td>
			<td>Stanley</td>
			<td>GR20L</td>
			<td></td>
		</tr>
		<tr>
			<td>PLA Spindle</td>
			<td></td>
			<td></td>
			<td>Custom made</td>
		</tr>
		<tr>
			<td>Tensioning Board</td>
			<td></td>
			<td></td>
			<td>Custom made</td>
		</tr>
	</tbody>
</table>

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.

This procedure provides a method of fabricating microvascular structures embedded within a resin. These structures can conform to a variety of patterns (Figure 2). The structure of the microvascular network is only limited by the structures that can be formed with the sacrificial fibers.
Using a parallel arrangement of microvascular channels, gas transport between fluid streams is facilitated as gases traverse a permeable inter-channel membrane. These devices can be fabricated...

Watch this Scientific Journal Video about Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component at JoVE.com

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

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 ...

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