The authors thank Sungwon Lim for intellectual contributions to device and mold design as well as Jambu Jambulingam and Rebecca Grossman-Kahn for creating intravaginal silicone probes using this process. This work is supported by the Bill and Melinda Gates Foundation, the Vodafone Americas Foundation, and the FDA (2P50FD003793).

<ol>
	<li>Painter, P. C., Coleman, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Essentials of Polymer Science and Engineering. DEStech Publications. , (2009).</li><li>Rosato, D. V., Rosato, M. G., Schott, 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=Reaction+Injection+Molding.">Reaction Injection Molding.</a> Plastics Technology Handbook - Volume. 2, 103-139 (2010).</li><li>Cybulski, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Plastic Conversion Process: A Concise and Applied Guide. , (2009).</li><li>Ortiz, H. e. r. n. &. #. 2. 2. 5. ;. n. d. e. z., J, T., Osswald, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modeling+processing+of+silicone+rubber:+Liquid+versus+hard+silicone+rubbers.">Modeling processing of silicone rubber: Liquid versus hard silicone rubbers.</a> Journal of Applied Polymer Science. 119, 10-1002 (2010).</li><li>Dym, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Injection+Molds+and+Molding:+A+Practical+Manual.">Injection Molds and Molding: A Practical Manual.</a> , (1987).</li><li>Mueller, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stereolithography-based+prototyping:+case+histories+of+applications+in+product+development.">Stereolithography-based prototyping: case histories of applications in product development.</a> Northcon 95. IEEE Technical Applications Conference and Workshops Northcon. , 305&#8211;310, doi:10.1109/NORTHC.1995.485087. , (1995).</li><li>Hilton, 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> Rapid Tooling: Technologies and Industrial Applications., 288, Press: Boca. , (2000).</li><li>Ahn, S. -. H., Montero, M., Odell, D., Roundy, S., Wright, P. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anisotropic+material+properties+of+fused+deposition+modeling+ABS.">Anisotropic material properties of fused deposition modeling ABS.</a> Rapid Prototyping Journal. 8 (4), 248-257 (2002).</li><li>Cheah, C. M., Tan, L. H., Feng, C., Lee, C. W., Chua, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+investment+casting:+direct+and+indirect+approaches+via+fused+deposition+modelling.">Rapid investment casting: direct and indirect approaches via fused deposition modelling.</a> The International Journal of Advanced Manufacturing Technology. 23 (1-2), 1-2 (2004).</li><li>Harris, A., Wild, P., Stopak, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silicone+Rubber+Substrata:+A+New+Wrinkle+in+the+Study+of+Cell+Locomotion.">Silicone Rubber Substrata: A New Wrinkle in the Study of Cell Locomotion.</a> Science. 208 (4440), (1980).</li><li>Moisan, M., Barbeau, J., Moreau, S., Pelletier, J., Tabrizian, M., Yahia, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-temperature+sterilization+using+gas+plasmas:+a+review+of+the+experiments+and+an+analysis+of+the+inactivation+mechanisms.">Low-temperature sterilization using gas plasmas: a review of the experiments and an analysis of the inactivation mechanisms.</a> International journal of pharmaceutics. (1-2), 226-221 (2001).</li><li>Etemadi, M., Chung, P., Heller, J., Liu, J., Rand, L., Roy, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+BirthAlert+-+A+Clinical+Device+Intended+for+Early+Preterm+Birth+Detection.">Towards BirthAlert - A Clinical Device Intended for Early Preterm Birth Detection.</a> IEEE Trans Biomed Eng. 10, (2013).</li><li>Etemadi, M., Chung, 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=Novel+device+to+trend+impedance+and+fluorescence+of+the+cervix+for+preterm+birth+detection.">Novel device to trend impedance and fluorescence of the cervix for preterm birth detection.</a> Conf Proc IEEE Eng Med Biol Soc. 2013, 176&#8211;9, doi:10.1109/EMBC.2013.6609466. , (2013).</li><li>Owen, S. R., Harper, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical,+microscopical+and+fire+retardant+studies+of+ABS+polymers.">Mechanical, microscopical and fire retardant studies of ABS polymers.</a> Polymer Degradation and Stability. 64, 449-455 (1999).</li><li>Cassidy, P. E., Mores, M., Kerwick, D. J., Koeck, D. J., Verschoor, K. L., White, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+Resistance+of+Geosynthetic+Materials.">Chemical Resistance of Geosynthetic Materials.</a> Geotextiles and Geomembranes. 11, 61-98 (1992).</li><li>Akay, M., Ozden, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+residual+stresses+on+the+mechanical+and+thermal+properties+of+injection+moulded+ABS+copolymer.">The influence of residual stresses on the mechanical and thermal properties of injection moulded ABS copolymer.</a> Journal of Materials Science. 30 (13), (1995).</li></ol>

None of the authors have any competing financial interests with respect to the work detailed in this article.

Of all the steps described, careful mold design is the most critical to success. The mold master should be created as a solid body with external geometries equal to the final device. These geometries should be adjusted to account for any material shrinkage due to the chosen elastomer as well as 3D printer resolution and tolerances. Placement of mold parting lines and through-holes for threaded rods and screws are dependent on one another. Adding parting lines increases the number of linear and rotational degrees of freed...

Liquid injection molding (LIM) (also known as reaction injection molding) is often used to manufacture elastomeric devices from thermosetting elastomers, but high tooling and equipment costs require a great deal of up-front capital investment1. Furthermore, LIM can be technically challenging and expensive to implement in cases with complex geometry and requirements for overmolding. As a result, it is typically impractical to use traditional LIM in ultra-low volumes or with early-stage device designs that often incur iterative revisions.
The typical procedure for injection molding elastomeric materials involves injecting liquid monomers at pressures around 150 psi into a mold using specialized molding machinery2. Temperatures and pressures are controlled to ensure laminar flow and prevent air being trapped in the mold3. Raw materials are typically two-part cure systems, such as platinum cure silicone, that are kept in separate and temperature controlled chambers prior to injection. Both components of the raw material are pumped into a high-pressure mixing chamber that subsequently feeds into the mold cavity. Curing is achieved by the presence of a catalyst as well as temperatures around 150-200 &#176;C4. Molds are typically machined from steel or aluminum to precise tolerances to create a good seal around parting edges3,5. Unfortunately, this process is generally more suited to larger scale manufacturing given high mold tooling costs as well as the requirement for specialized injection and feedback control systems.
For rapid prototyping of polyurethane (PU) parts, it is possible to use stereolithography (SLA) to create a mold master and produce a silicone rubber mold6,7. However, this technique is not suitable for overmolding since it is difficult to achieve precise alignment of overmolded components, as the silicone is, by design, not a rigid structure. Furthermore, production of devices with complex geometries, such as invaginations or hollowed out sections, is difficult or impossible. The requirement for complex or precise mold parting lines and rigid thin elements are more often than not, incompatible with the liquid rubber molding process.
The aforementioned production-scale or late-stage prototyping processes are often impractical for early-stage medical device development in which a few devices need to be produced for proof-of-concept and feasibility in human studies, as is often the case in academic laboratory and start-up company environments. The lack of alternatives often means that even early-stage development would incur high costs, requiring many device developers to limit device functionality or put development on hold while additional funds are raised. This contributes to a dramatic slowing of the development process since a large fraction of medical devices require implementation of complex features. It is also difficult to fund the costly development of such devices since proof-of-concept data is often not yet established. We encountered this roadblock in a recent project within this lab, which involved the development of a silicone intravaginal probe with overmolded electrical and optical sensors that required a cup-like tip to conform to specified cervical geometries. The process described in this article documents our attempt to circumvent this vicious cycle and rapidly reach proof-of-concept for LIM medical devices.
The technique shown in Figure 1 deconstructs the LIM process into 5 main activities: (1) mold design &#38; production, (2) mold assembly (3) elastomer mixing, (4) elastomer injection, and (5) elastomer curing &#38; demolding.
<img alt="Figure 1" fo:content-width="6in" src="/files/ftp_upload/51745/51745fig1highres.jpg" width="600" /> 
Figure 1. Protocol Overview. Overview of the protocol, which involves: (1a) creating a mold using computer-aided design tools, (1b) 3D printing the mold pieces, (2) assembling the mold pieces using threaded rods and screws, (3) mixing liquid elastomer and loading it in a syringe, (4) injecting the liquid elastomer into the mold using a modified desiccator, (5a) curing the elastomer in a temperature-controlled oven, and (5b) demolding the cured elastomer device from the mold pieces.
Mold design involves development of a mold master in computer-aided design (CAD) software, subtraction of the mold master from a solid block and definition of mold parting lines. Mold pieces are created and then assembled using screws, rods, and nuts with overmolded components positioned in the mold cavity. Elastomer mixing involves combining parts A and B of raw material and degassing to remove potential void spaces in the material. Next, elastomer injection involves pressure-driven filling of the mold cavity, followed by elastomer curing in a temperature-controlled oven to ensure chemical crosslinking of the polymer chains.
Breaking down the injection molding process into these steps enables us to forego traditional LIM equipment in favor of low cost alternatives. For example, instead of machining a metal mold or casting a silicone rubber mold from a mold master, the molds created from the protocol described in this manuscript were created from acrylonitrile butadiene styrene (ABS) plastic using a fused-deposition modeling (FDM) 3D printer8,9. Compared to building metal molds or SLA molds, FDM is generally a cheaper and faster process. Fairly complex molds can be printed quickly on an in-house 3D printer, or cheaply produced by one of the many contract 3D printing services available. For example, a complex eight-piece 3D printed mold was used to cast the demonstrated intravaginal probe in the representative results section and shown in Figures 14&#160;and 15. All parts for this mold can be printed in approximately 1.5 days on an in-house 3D printer. Turnaround times for simpler molds can be a few hours. The overall length of time necessary to prototype a device using FDM 3D printers to create molds is similar to the time required to cast a mold out of silicone rubber and create a polyurethane prototype. However, using FDM 3D printers to create molds allows for several things that cannot easily be accomplished using a silicone mold: (1) many thermosetting elastomers can be used provided the 3D-printed mold can tolerate the required curing temperatures, (2) complex geometries can be created with the use of many different mold pieces and parting lines, and (3) use of rigid mold pieces allows precise and reproducible alignment of overmolded components within the mold cavity.
Instead of using a traditional LIM machine, which combines mixing, injection, and curing, it is possible to use a laboratory mixer to ensure homogenous mixing, a modified desiccator for injection, and a standard temperature-controlled oven for curing. The injection system was created using off-the-shelf components and involves the addition of a positive pressure supply line into the desiccator that connects to a syringe filled with mixed elastomer. Chamber pressurization in bench top desiccators is typically controlled by a three-way valve between the chambers, a vacuum supply line, and the atmosphere. The modified desiccator adds a positive pressure supply line feeding to the back of a syringe plunger. This enables the creation of a 40-50 psi pressure differential that is sufficient for liquid material injection into the mold cavity.
This technique allowed us to produce silicone intravaginal probes with overmolded electrical and optical sensors to collect proof-of-concept data for a Phase I clinical trial. Silicone was selected because of the need for biological inertness as well as the ability to sterilize with a variety of methods10,11. Furthermore, the device required a complex and unconventional cup-like geometry at the tip of the probe where sensors are located to interface with the cervix. Without the use of the described technique, it would have been a much more costly and lengthy process to produce these devices. This adaptation of the LIM process reduces cost and equipment requirements when compared to the traditional LIM process, making it practical to adopt a rapid and iterative approach to designing elastomeric devices.

<table border="0" cellpadding="0" cellspacing="0" width="1434">
	<tbody>
		<tr>
			<td>ABS Model Material</td>
			<td>Stratasys</td>
			<td>P430</td>
			<td>Model Material for uPrint Plus SE (Step: Mold Design &#38; Production)</td>
		</tr>
		<tr>
			<td>Soluble Support Material</td>
			<td>Stratasys</td>
			<td>SR-30</td>
			<td>Support Material for uPrint Plus SE (Step: Mold Design &#38; Production)</td>
		</tr>
		<tr>
			<td>Underwater Silicone Sealant, 2.8 Oz Tube, Clear</td>
			<td>McMaster-Carr Supply Company</td>
			<td>7327A21</td>
			<td>Silicone RTV for sealing gaps at mold parting lines (Step: Mold Assembly)</td>
		</tr>
		<tr>
			<td>Tubing, 1/8&#34; ID, 1/4&#34; OD, 1/16&#34; Wall Thickness, Ultra-chemical-resistant Tygon PVC, Clear</td>
			<td>McMaster-Carr Supply Company</td>
			<td>5046K11</td>
			<td>Forms runner/sprue adapter between mold and syringe with elastomer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Coupling, Adapter, Straight, Male Quick-turn (Luer lock) X 1/8&#34; Tube Barb, Nylon</td>
			<td>McMaster-Carr Supply Company</td>
			<td>51525K123</td>
			<td>Connect runner/sprue between mold and syringe with elastomer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Coupling, Adapter, Staight, Female Quick-turn (Luer lock) X 1/8&#34; Tube Barb, Nylon</td>
			<td>McMaster-Carr Supply Company</td>
			<td>51525K213</td>
			<td>Connect runner/sprue between mold and syringe with elastomer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Cap, Female Quick-turn (Luer lock), Nylon</td>
			<td>McMaster-Carr Supply Company</td>
			<td>51525K315</td>
			<td>Cap to prevent silicone from leaking out of mold after injection (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Liquid Silicone Rubber (LSR) 30 - 10:1, Implant Grade</td>
			<td>Applied Silicone Corporation</td>
			<td>PN40029</td>
			<td>Substitute with the elastomer of your choice.&#160; This is the one used for the intravaginal probe (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Syringes (BD), 1mL Slip-Tip, non-sterile clean, bulk</td>
			<td>Cole-Parmer</td>
			<td>WU-07945-00</td>
			<td>Syringes for transfering elastomer material (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Syringes (BD), 1mL Slip-Tip, non-sterile clean, bulk</td>
			<td>Cole-Parmer</td>
			<td>WU-07945-04</td>
			<td>Syringes for transfering elastomer material (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Syringe, 20mL, Open Bore, Solid Ring Plunger and Grip</td>
			<td>Qosina Corporation</td>
			<td>C1200</td>
			<td>Syringes for transfering elastomer material.&#160; Open bore is used for very viscous elastomers. (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Needle (BD), Non-sterile Clean with Shields, 18 gauge X 1.5&#34; Lg., Stainless Steel, BD Bulk&#160;</td>
			<td>Cole-Parmer</td>
			<td>WU-07945-76</td>
			<td>Used for removing air column between syringe plunger and elastomer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Plastic Cups, 12 Oz., Clear</td>
			<td>Safeway</td>
			<td>N/A</td>
			<td>Used for mixing silicone in THINKY Mixer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Polyethylene Bag, Open-Top, Flat, 5&#34; Width X 6&#34; Height, 2-MIL Thk.</td>
			<td>McMaster-Carr Supply Company</td>
			<td>1928T68</td>
			<td>Used for mixing silicone in THINKY Mixer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Rubber Band, Latex Free, Orange, Size 64, 3-1/2&#34; L X 1/4&#34; W</td>
			<td>McMaster-Carr Supply Company</td>
			<td>12205T96</td>
			<td>Used for mixing silicone in THINKY Mixer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Parafilm Wrap, 4&#34;W</td>
			<td>Cole-Parmer</td>
			<td>EW-06720-40</td>
			<td>Used for mixing silicone in THINKY Mixer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Syringe Barrels with Stoppers, Luer Lock, Air Operated,&#160; 50mL</td>
			<td>EWD Solutions</td>
			<td>JEN-JG50A-15</td>
			<td>Smaller syringes can be used if less elastomer is required, but make sure it is compatible with Air Operated Syringe Adapter in injection chamber (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Sealant Tape, Pipe Thread, 50&#39;Lg X 1/4&#34; W, .0028&#34; Thk, 0.5 G/CC Specific Gravity&#160;</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4591K11</td>
			<td>Teflon Tape for air-tight seals around at threads (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Scalpel Blades, Disposable, No. 22</td>
			<td>VWR</td>
			<td>21909-646</td>
			<td>Used for cutting tubing and demolding (Step: Curing &#38; Demolding)</td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>VWR</td>
			<td>21903-005</td>
			<td>&#160;(Step: Curing &#38; Demolding)</td>
		</tr>
		<tr>
			<td>2-Propanol, J. T. Baker</td>
			<td>VWR</td>
			<td>JT9334-3</td>
			<td>&#160;(Step: Curing &#38; Demolding)</td>
		</tr>
		<tr>
			<td>uPrint Plus SE 3D Printer</td>
			<td>Stratasys</td>
			<td>uPrint Plus SE</td>
			<td>Other 3D printers can be used (Step: Mold Design &#38; Production)</td>
		</tr>
		<tr>
			<td>Screw, Cap, Hex Head,&#160; 1/4&#34;-28 , 2-1/2&#34; Lg, 18-8 Stainless Steel</td>
			<td>McMaster-Carr Supply Company</td>
			<td>92198A115</td>
			<td>Screws used with nuts to compress mold (Step: Mold Assembly)</td>
		</tr>
		<tr>
			<td>Nut, Hex, 1/4&#34;-28, 7/16&#34; Wd, 7/32&#34; Height, 18-8 Stainless Steel&#160;</td>
			<td>McMaster-Carr Supply Company</td>
			<td>91845A105</td>
			<td>Screws used with nuts to compress mold (Step: Mold Assembly)</td>
		</tr>
		<tr>
			<td>Stud, Fully Threaded, 1/4&#34;-28, 1&#34; Lg, 18-8 Stainless Steel&#160;</td>
			<td>McMaster-Carr Supply Company</td>
			<td>95412A567</td>
			<td>Threaded-rods can be cut to desired length and are used with nutes to compress mold (Step: Mold Assembly)</td>
		</tr>
		<tr>
			<td>Planetary Centrifugal Mixer</td>
			<td>THINKY USA Inc.</td>
			<td>ARE-310</td>
			<td>Mixers are strongly recommended for fine mixing and to reduce degassing time, but hand mixing is fine (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Laboratory Weigh Scale</td>
			<td>Mettler-Toledo International Inc.</td>
			<td>EL602</td>
			<td>&#160;(Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Desiccant Vacuum Canister, Reusable,&#160; 10-3/4&#34; OD</td>
			<td>McMaster-Carr Supply Company</td>
			<td>2204K7</td>
			<td>This desiccator is used for degassing the elastomer (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Custom 3D-Printed Mixer-to-Cup Adapter</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Modeled in Solidworks CAD and 3D printed (Step: Elastomer Mixing)</td>
		</tr>
		<tr>
			<td>Tubing, Smooth Bore, 1/4&#34; ID, 1/2&#34; OD, 1/8&#34; Wall Thickness, High Purity Tygon PVC, Clear</td>
			<td>McMaster-Carr Supply Company</td>
			<td>5624K51</td>
			<td>Tubing outside of Desiccator (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Tubing, Smooth Bore, 3/8&#34; ID, 5/8&#34; OD, 1/8&#34; Wall Thickness, High Purity Tygon PVC, Clear</td>
			<td>McMaster-Carr Supply Company</td>
			<td>5624K52</td>
			<td>Tubing to adapt to Air/Vacuum Supply (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Reducer, Straight, Vacuum Barb 3/8&#34; Tube ID X Vacuum Barb 1/4&#34; Tube ID, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>44555K188</td>
			<td>Adapt Tubing outside Desiccator to Tubing leading to Air/Vacuum Supply (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Clamp, Hose &#38; Tube, Worm-Drive, for 7/32&#34; to 5/8&#34; OD tube, 5/16&#34; Wd., 316 SS</td>
			<td>McMaster-Carr Supply Company</td>
			<td>5011T141</td>
			<td>Used on tubing to create Air/Vacuum-tight seal at junctions (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Clamp, Hose, Smooth-Band Worm-Drive, for 1/2&#34; to 3/4&#34; OD tube, 3/8&#34; Wd., 304 SS</td>
			<td>McMaster-Carr Supply Company</td>
			<td>5574K13</td>
			<td>Used on tubing to create Air/Vacuum-tight seal at junctions (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Tee, Vacuum Barb 1/4&#34; Tube ID, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>44555K138</td>
			<td>Tee Junction between Vacuum, Three-way T-valve on Desiccator, and Three-way L-valve (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Tee, 1/4 NPT Female X Female X Male, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>50785K222</td>
			<td>Tee Junction between Pressure Gauge, Chamber, and Three-way L-valve (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Valve, Ball, Straight, T-Handle, 1/4 NPT Female X Male, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4082T42</td>
			<td>Three-way L-valve (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Adapter, Straight, Vacuum Barb 1/4&#34; ID Tube X 1/4 NPT Male, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>44555K132</td>
			<td>Adapter for Three-way L-valve-to-Tubing (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Saw, Hole, Bimetal. 1-3/8&#34; OD, 1-1/2&#34; Cutting Depth</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4066A25</td>
			<td>Used to cut holes in Desiccator for throughwall fittings (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Arbor, 9/16&#34; to 1-3/16&#34; Saw, 1/4&#34; Hex</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4066A76</td>
			<td>Used to cut holes in Desiccator for throughwall fittings (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Arbor Adapter for 1-1/4&#34; Thru 6&#34; Dia Hole Saws</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4066A77</td>
			<td>Used to cut holes in Desiccator for throughwall fittings (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Straight, Through-Wall, 1/2 NPT Female, Polypropylene</td>
			<td>McMaster-Carr Supply Company</td>
			<td>36895K141</td>
			<td>Throughwall fittings leading to Pressure/Vacuum Gauges (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Adapter, Straight, Reducing,&#160; Bushing, Hex, 1/2 NPT Male X 1/4 NPT Female, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4429K422</td>
			<td>Reducing tube diameter inside the Desiccator to adapt to Air-operated Syringe System (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Adapter, Straight, Reducing, Bushing, Hex, 1/4 NPT Male X 1/8 NPT Female, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4757T91</td>
			<td>Reducing tube diameter inside the Desiccator to adapt to Air-operated Syringe System (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Coupling, Adapter, Straight, Vacuum Barb 1/4&#34; ID Tube X 1/8 NPT Female, Brass</td>
			<td>McMaster-Carr Supply Company</td>
			<td>44555K124</td>
			<td>Reducing tube diameter inside the Desiccator to adapt to Air-operated Syringe System (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Syringe Adapters, Air Operated, 30/50mL</td>
			<td>EWD Solutions</td>
			<td>JEN-JG30A-X6</td>
			<td>Air operated syringe adapter on the inside of the Desiccator; must be compatible with syringes used to hold elastomer (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Gauge, Dual-Scale Vacuum, 2-1/2&#34; Dial, 1/4 NPT Male, Bottom Connector, 30&#34; Hg-0, Steel Case</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4002K11</td>
			<td>Vacuum Gauge (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Gauge, Dual-Scale Vacuum and Compound, 3-1/2&#34; Dial, 1/4 NPT Male, Center Back, 30&#34; Hg-0, 100 PSI, Steel Case</td>
			<td>McMaster-Carr Supply Company</td>
			<td>4004K616</td>
			<td>Pressure Gauge leading to Air-operated Syringe System (Step: Elastomer Injection)</td>
		</tr>
		<tr>
			<td>Oven, Vacuum, Isotemp, Economy&#160;</td>
			<td>Fisher Scientific</td>
			<td>280A</td>
			<td>Standard non-vacuum oven can be used (Step: Curing &#38; Demolding)</td>
		</tr>
		<tr>
			<td>Solidworks CAD</td>
			<td>Dassault Syst&#232;mes</td>
			<td>Solidworks Research Subscription</td>
			<td>Other CAD Software can be used for mold master and mold design (Step: Mold Design &#38; Production)</td>
		</tr>
	</tbody>
</table>

rapid and low-cost prototyping of medical devices using 3d printed molds for liquid injection molding

Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using traditional liquid injection molding processes can be an expensive process due to tooling and equipment costs. As a result, it has traditionally been impractical to use liquid injection molding for low-cost, rapid prototyping applications. We have devised a method for rapid and low-cost production of liquid elastomer injection molded devices that utilizes fused deposition modeling 3D printers for mold design and a modified desiccator as an injection system. Low costs and rapid turnaround time in this technique lower the barrier to iteratively designing and prototyping complex elastomer devices. Furthermore, CAD models developed in this process can be later adapted for metal mold tooling design, enabling an easy transition to a traditional injection molding process. We have used this technique to manufacture intravaginal probes involving complex geometries, as well as overmolding over metal parts, using tools commonly available within an academic research laboratory. However, this technique can be easily adapted to create liquid injection molded devices for many other applications.

<img alt="Figure 2" fo:content-width="5in" src="/files/ftp_upload/51745/51745fig2highres.jpg" width="500" /> 
Figure 2. 2D CAD Sketches. A)&#160;2D Sketch that can be radially revolved about the Y-axis to produce a cup-like feature similar to the one on the intravaginal probe device. B)&#160;Teardrop-shaped 2D sketch that can be extruded out of the plane into a prism-like structure that forms the handle of the intravaginal probe device. ...

Watch this Scientific Journal Video about Rapid and Low-cost Prototyping of Medical Devices Using 3D Printed Molds for Liquid Injection Molding at JoVE.com

Rapid and Low-cost Prototyping of Medical Devices Using 3D Printed Molds for Liquid Injection Molding

We have devised a method for low-cost and rapid prototyping of liquid elastomer rubber injection molded devices by using fused deposition modeling 3D printers for mold design and a modified desiccator as a liquid injection system.

Biologically inert elastomers such as silicone are favorable materials for medical device fabrication, but forming and curing these elastomers using ...

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Research

JoVE Journal

Bioengineering

19.7K Views.  University of California, San Francisco. We have devised a method for low-cost and rapid prototyping of liquid elastomer rubber injection molded devices by using fused deposition modeling 3D printers for mold design and a modified desiccator as a liquid injection system.