Name: Rapid and Low-cost Prototyping of Medical Devices Using 3D Printed Molds for Liquid Injection Molding (Video) | JoVE Journal
Uploaded: 2014-06-27T15:00:00.000+00:00
Duration: 10 min 43 s
Description: Learn rapid prototyping of liquid elastomer medical devices using 3D printed molds for injection molding. This low-cost method enables custom device creation in resource-limited academic settings.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

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. Essentials of Polymer Science and Engineering. DEStech Publications. , Lancaster, PA. (2009).</li>
<li>Rosato, D. V., Rosato, M. G., Schott, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Reaction+Injection+Molding%5BTitle%5D)+AND+%22Plastics+Technology+Handbook+-+Volume%22%5BJournal%5D)">Reaction Injection Molding.</a> Plastics Technology Handbook - Volume. 2, 103-139 (2010).</li>
<li>Cybulski, E. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aCybulski%2C+E+%22Plastic+Conversion+Process%3A+A+Concise+and+Applied+Guide%22">Plastic Conversion Process: A Concise and Applied Guide</a>. , CRC Press: Boca. Raton, FL. (2009).</li>
<li>Ortiz, H. ernández, J,, Osswald, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Modeling+processing+of+silicone+rubber%3A+Liquid+versus+hard+silicone+rubbers%5BTitle%5D)+AND+%22Journal+of+Applied+Polymer+Science%22%5BJournal%5D)">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/pubmed?term=((Injection+Molds+and+Molding%3A+A+Practical+Manual%5BTitle%5D)+AND+%22%22%5BJournal%5D)">Injection Molds and Molding: A Practical Manual.</a> , 395, New York, NY. (1987).</li>
<li>Mueller, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Stereolithography-based+prototyping%3A+case+histories+of+applications+in+product+development%5BTitle%5D)+AND+%22Northcon+95.+IEEE+Technical+Applications+Conference+and+Workshops+Northcon.+%2C+305%E2%80%93310%2C+doi%3A10.1109%2FNORTHC.1995.485087%22%5BJournal%5D)">Stereolithography-based prototyping: case histories of applications in product development.</a> Northcon 95. IEEE Technical Applications Conference and Workshops Northcon. , 305–310, doi:10.1109/NORTHC.1995.485087. , (1995).</li>
<li>Hilton, P. Rapid Tooling: Technologies and Industrial Applications., 288, Press: Boca. , Raton, Florida. (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/pubmed?term=((Anisotropic+material+properties+of+fused+deposition+modeling+ABS%5BTitle%5D)+AND+%22Rapid+Prototyping+Journal%22%5BJournal%5D)">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/pubmed?term=((Rapid+investment+casting%3A+direct+and+indirect+approaches+via+fused+deposition+modelling%5BTitle%5D)+AND+%22The+International+Journal+of+Advanced+Manufacturing+Technology%22%5BJournal%5D)">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/pubmed?term=((Silicone+Rubber+Substrata%3A+A+New+Wrinkle+in+the+Study+of+Cell+Locomotion%5BTitle%5D)+AND+%22Science%22%5BJournal%5D)">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/pubmed?term=((Low-temperature+sterilization+using+gas+plasmas%3A+a+review+of+the+experiments+and+an+analysis+of+the+inactivation+mechanisms%5BTitle%5D)+AND+%22International+journal+of+pharmaceutics%22%5BJournal%5D)">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/pubmed?term=((Towards+BirthAlert+-+A+Clinical+Device+Intended+for+Early+Preterm+Birth+Detection%5BTitle%5D)+AND+%22IEEE+Trans+Biomed+Eng%22%5BJournal%5D)">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/pubmed?term=((Novel+device+to+trend+impedance+and+fluorescence+of+the+cervix+for+preterm+birth+detection%5BTitle%5D)+AND+%22Conf+Proc+IEEE+Eng+Med+Biol+Soc.+2013%2C+176%E2%80%939%2C+doi%3A10.1109%2FEMBC.2013.6609466%22%5BJournal%5D)">Novel device to trend impedance and fluorescence of the cervix for preterm birth detection.</a> Conf Proc IEEE Eng Med Biol Soc. 2013, 176–9, 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/pubmed?term=((Mechanical%2C+microscopical+and+fire+retardant+studies+of+ABS+polymers%5BTitle%5D)+AND+%22Polymer+Degradation+and+Stability%22%5BJournal%5D)">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/pubmed?term=((Chemical+Resistance+of+Geosynthetic+Materials%5BTitle%5D)+AND+%22Geotextiles+and+Geomembranes%22%5BJournal%5D)">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/pubmed?term=((The+influence+of+residual+stresses+on+the+mechanical+and+thermal+properties+of+injection+moulded+ABS+copolymer%5BTitle%5D)+AND+%22Journal+of+Materials+Science%22%5BJournal%5D)">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 °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 &amp; production, (2) mold assembly (3) elastomer mixing, (4) elastomer injection, and (5) elastomer curing &amp; demolding.
<img alt="3D printing process diagram: CAD design, mold assembly, elastomer mixing, injection, curing stages." fo:content-width="6in" src="/files/ftp_upload/51745/51745fig1highres.jpg" width="600" data-altupdatedat="1787630408000" data-alt="Figure 1"> 
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 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><tbody><tr><td>ABS Model Material</td><td>Stratasys</td><td>P430</td><td>Model Material for uPrint Plus SE (Step: Mold Design &amp;amp; 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 &amp;amp; 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&quot; ID, 1/4&quot; OD, 1/16&quot; 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&quot; 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&quot; 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.&amp;nbsp; This is the one used for the intravaginal probe (Step: Elastomer Mixing)</td></tr><tr><td>Syringes (BD), 1 ml 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), 1 ml 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, 20 ml, Open Bore, Solid Ring Plunger and Grip</td><td>Qosina Corporation</td><td>C1200</td><td>Syringes for transfering elastomer material.&amp;nbsp; Open bore is used for very viscous elastomers. (Step: Elastomer Mixing)</td></tr><tr><td>Needle (BD), Non-sterile Clean with Shields, 18 G x 1.5&quot; Lg., Stainless Steel, BD Bulk</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&quot; Width x 6&quot; 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&quot; L x 1/4&quot; 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&quot; 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,&amp;nbsp; 50 ml</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&#039; Lg x 1/4&quot; W, 0.0028&quot; Thk, 0.5 G/CC Specific Gravity</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 &amp;amp; Demolding)</td></tr><tr><td>Kimwipes</td><td>VWR</td><td>21903-005</td><td>&amp;nbsp;(Step: Curing &amp;amp; Demolding)</td></tr><tr><td>2-Propanol, J. T. Baker</td><td>VWR</td><td>JT9334-3</td><td>&amp;nbsp;(Step: Curing &amp;amp; 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 &amp;amp; Production)</td></tr><tr><td>Screw, Cap, Hex Head,&amp;nbsp; 1/4&quot;-28 , 2-1/2&quot; 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&quot;-28, 7/16&quot; Wd, 7/32&quot; Height, 18-8 Stainless Steel&amp;nbsp;</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&quot;-28, 1&quot; Lg, 18-8 Stainless Steel&amp;nbsp;</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>&amp;nbsp;(Step: Elastomer Mixing)</td></tr><tr><td>Desiccant Vacuum Canister, Reusable,&amp;nbsp; 10-3/4&quot; 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&quot; ID, 1/2&quot; OD, 1/8&quot; 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&quot; ID, 5/8&quot; OD, 1/8&quot; 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&quot; Tube ID X Vacuum Barb 1/4&quot; 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 &amp;amp; Tube, Worm-Drive, for 7/32&quot; to 5/8&quot; OD tube, 5/16&quot; 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&quot; to 3/4&quot; OD tube, 3/8&quot; 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&quot; 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&quot; 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&quot; OD, 1-1/2&quot; 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&quot; to 1-3/16&quot; Saw, 1/4&quot; 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&quot; Thru 6&quot; 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,&amp;nbsp; 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&quot; 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, 30/50 ml</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&quot; Dial, 1/4 NPT Male, Bottom Connector, 30&quot; 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&quot; Dial, 1/4 NPT Male, Center Back, 30&quot; 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&amp;nbsp;</td><td>Fisher Scientific</td><td>280A</td><td>Standard non-vacuum oven can be used (Step: Curing &amp;amp; Demolding)</td></tr><tr><td>Solidworks CAD</td><td>Dassault Syst&amp;egrave;mes</td><td>Solidworks Research Subscription</td><td>Other CAD Software can be used for mold master and mold design (Step: Mold Design &amp;amp; Production)</td></tr></tbody></table>

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

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="Cup and handle feature sketches, diagram of revolved cut regions with Y-axis and mold edge indicated." fo:content-width="5in" src="/files/ftp_upload/51745/51745fig2highres.jpg" width="500" data-altupdatedat="1787630408000" data-alt="Figure 2"> 
Figure 2. 2D CAD Sketches. A) 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) Teardrop-shaped 2D sket...

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 ...

The overall goal of this procedure is to create a liquid elastomer device with a custom geometry using 3D printed mold pieces. This is accomplished by first designing the desired mold geometry in CAD software and 3D printing the mold pieces. The second step is to assemble the mold pieces into a full mold next liquid elastomer prepared and injected into the mold cavity.The final step is curing the liquid elastomer and removing the resultant device from the mold. Ultimately, this technique enables rapid creation of small scale and low cost medical devices in a resource limited environment that would typically only be possible in an industry or larger scale manufacturing setting. The main advantage of this technique over traditional liquid injection molding is that it enables creation of elastomer devices in a resource limited or academic setting.One may use this technique to create prototype medical devices for use in clinical studies to assess the feasibility of new medical technologies. The ability to rapidly validate new medical devices at cost and with a quick iteration cycle drastically reduces the barriers to device development and proof of ization. The method we specifically is to embed electrical and optical sensors in an intravaginal probe device designed to scan human cervical tissue.Generally, individuals new to this technique may initially struggle because of the design constraints involved in the use of 3D printed materials and multiple mold pieces to create a mold. We hope that our demonstration of this technique will help guide any future attempts to design a mold and carry out the necessary steps to yield any desired elastomeric device. The first step is to use computer aided design software to design a to scale mold master.Here in solid works is the Intravaginal probe master. It has a cup like structure at one end and a handle and a separate CAD file. Extrude a rectangle into a rectangular prism, large enough to enclose the mold master.Import the mold master file into the file with the rectangular prism. Align the mold master such that it is centered and completely encased within the prism. Combine the files and use a subtraction operation to create the mold cavity.Next, define the pieces of the mold to create a bilateral parting line. Start in the right plain view. Define a rectangular 2D sketch that extends from the base of the cup like structure to the top of the probe handle.Apply cuts in the positive and negative X directions. This will yield bilateral symmetric mold parts to create a radial parting line. Start in the right plain view.Use a 2D sketch to create a radially symmetric parting line that includes the Y axis and passes through internal regions of the cup like geometry. Use a revolved cut on the sketch to isolate a radially symmetric mold part to hold the mold together. Define through holes by defining a circular 2D sketch with a standard clearance hole size corresponding the rod or screw to be used.Then apply the extruded cut feature to the sketch. Both vertical and horizontal through holes are created to fully constrain the mold pieces. After defining all parting lines in through holes, use the same procedure to define an entry point for the elastomer A gate toward the bottom of the mold cavity.Also, incorporate vents for excess elastomer to drain from the mold. Isolate each mold piece by suppressing or unsuppressed features. Now save each mold piece as a file compatible with the 3D printer to be used.When done, load the files into the 3D printer and wait until they are done about one day for this mold and setup. After the printing is done and the pieces have been cleaned, assembly is the next step. Bring the mold pieces together along with any components that will be overmolded.Here.The overmolded components are stainless steel tubing and electronics. For this mold, place threaded rods in some through holes and hold them in place with two jammed nuts on one end to help provide scaffolding when adding a piece, always be certain to align the through holes. When the mold is completed, put the remaining screws and rods in place and secure all rod ends with nuts.Next, prepare to create a channel into the mold gate. Use a barbed to male lure lock adapter. Insert it into the gate of the mold cavity.Make sure there is a tight fit. Obtain about four inches of silicone tubing with barb to female lure lock adapters. Attach to each end, connect this tubing to the adapter and the mold cavity gate.After this step is completed, the injection chamber should be prepared. Proceed with elastomer mixing. After preparing the injection chamber, use the mold volume to determine the needed quantities of elastomer components, part A and B.Then ready a disposable plastic cup, a plastic bag, and several rubber bands.Placed a plastic on a way scale and tear it. Pour the required quantities of part A and part B into the cup. Color master batches are also added here.Seal the cup opening by pulling a plastic bag over it. Secure the bag with three to four rubber bands. Next, place the cup in a centrifugal mixer mix for two minutes to ensure homogenous mixing and an additional one to two minutes on the DGAs setting.Meanwhile, to create the elastomer injection syringe, start with a 50 milliliter syringe with a male lure lock. Use a female lure lock cap to seal the bottom. Then secure the seal with para film and one rubber band.Retrieve the elastomer and transfer it from the plastic cup into the 50 milliliter syringe. Before adding the plunger position a syringe needle to help avoid trapping air in the syringe. Place the needle sharp side down along the syringe wall without touching the elastomer.Then put the syringe plunger into the syringe until there is no visible air column between the plunger and elastomer. The next step is to inject the elastomer into the mold. Remove the female cap on the syringe containing the prepared elastomer and connect the exposed male lure lock syringe tip to the female adapter leading to the gate of the assembled mold.The assembly is now ready for the injection chamber. Secure the air operated syringe adapter of the injection chamber to the back of the syringe, plays both the mold and the syringe in their respective positions. Cover the injection chamber and ensure an airtight seal is formed.This is the schematic representation of the system. After covering the injection chamber, the next step is to isolate the chamber and make certain the vacuum source is continuous with the chamber and the syringe plunger. Then slowly draw a vacuum until about negative 14.5 PSI is achieved.Maintain this pressure and break continuity between the vacuum source and the syringe plunger while establishing a connection with the positive air supply. Gradually ramp up positive pressure from the air supply until at least 25 to 35 PSI is achieved. In a few seconds, wait until the syringe plunger has reached the bottom of the syringe before returning the system to atmospheric pressure.When the mold is recovered, detach the tubes from the mold gate. Place a female lure lock cap on the male adapter to prevent the flow of elastomer. For curing.Place the mold in a temperature controlled oven. The device in this video is cured at 70 degrees Celsius for five hours. At the end of the curing time, remove the mold from the oven and allow the device to cool to room temperature.Then demold the device vice. This medical grade instrument was completed in about two days, including printing the mold pieces. A view into the cup like region shows six electrodes and the end of the receptacle for a fiber optic probe.All overmolded features the entrance for the fiber optic probe and A USB cable for the electrodes are at the rear. With this technique, we have manufactured over 40 intra vaginal probe devices for data collection. In a clinical study, this particular device has allowed us to study the use of cervical fluorescence and impedance to monitor pregnancy.For signs of preterm birth, It's important to remember to design the mold carefully choose parting lines, and through holes such. The fully assembled mold is constrained both linearly and rotationally, while also allowing easy removal of the fully cured device. Once master, this technique can take a couple of hours or a day, depending on the specific geometry or complexity of the desire to elastomeric device.We've shown that this is a feasible method of developing prototypes of therapeutic and diagnostic medical devices, but the procedure can be applied to the development of elastomeric devices and many other applications.

rapid-low-cost-prototyping-medical-devices-using-3d-printed-molds-for

Research

JoVE Journal

Bioengineering

A bioprinter was used to create patterned hydrogels based on a sacrificial mold.  The poloxamer mold was backfilled with a second hydrogel and then eluted, leaving voids which were filled with a third hydrogel. This method uses fast elution and good printability of poloxamer to generate complex architectures from biopolymers.

Printing Thermoresponsive Reverse Molds for the Creation of Patterned Two-component Hydrogels for 3D Cell Culture

In this article we describe different techniques for microfluidic rapid prototyping platforms. The proposed techniques are based on ultraviolet (UV) sensitive and temperature curing epoxies, polydimethylsiloxane (PDMS) based tubing, wire-bonding, and anisotropic adhesive films. The assembling procedures presented are developed for both one-time use devices as well as reusable microfluidic systems.

High Throughput Microfluidic Rapid and Low Cost Prototyping Packaging Methods

This protocol describes a platform for fabricating self-assembled tissue rings in variable sizes using a customized 3D-printed plastic mold. PDMS negatives are cured in the 3D-printed mold; then agarose is cast in the cured PDMS negatives. Cells are seeded into the resulting agarose wells where they aggregate into tissue rings.

Fabrication of Custom Agarose Wells for Cell Seeding and Tissue Ring Self-assembly Using 3D-Printed Molds

Herein we present a rapid, facile, and low-cost method for fabricating custom polydimethylsiloxane molds that can be used for producing hydrogel-based engineered tissues with complex geometries. We additionally describe results from mechanical and histological assessments conducted on engineered cardiac tissues produced using this technique.

Custom Engineered Tissue Culture Molds from Laser-etched Masters

A protocol for fabricating injection molding inserts for complex geometry with micro features on surfaces employing Additive Manufacturing (AM) is presented.

A Soft Tooling Process Chain for Injection Molding of a 3D Component with Micro Pillars

Here we present a protocol to construct a pressure-controlled syringe pump to be used in microfluidic applications. This syringe pump is made from an additively manufactured body, off-the-shelf hardware, and open-source electronics. The resulting system is low-cost, straightforward to build, and delivers well-regulated fluid flow to enable rapid microfluidic research.

Three-dimensional Printing of Thermoplastic Materials to Create Automated Syringe Pumps with Feedback Control for Microfluidic Applications

The aim of this work is to design and construct a reservoir-based melt extrusion three-dimensional printer made from open-source and low-cost components for applications in the biomedical and food printing industries.

Design of an Open-Source, Low-Cost Bioink and Food Melt Extrusion 3D Printer

This project allows small laboratories to develop an easy-to-use platform for the fabrication of precise multilayer microfluidic devices. The platform consists of a three-dimensionally printed microscope mask alignment adapter using which multilayer microfluidic devices with alignment errors of &lt;10 µm were achieved.

Design and Development of a Three-Dimensionally Printed Microscope Mask Alignment Adapter for the Fabrication of Multilayer Microfluidic Devices

We demonstrate the use of patterned aerosol adhesives to construct 3D paper microfluidic devices. This method of adhesive application forms semi-permanent bonds between layers, enabling single-use devices to be non-destructively disassembled after use and to ease folding complex nonplanar structures.

Using Adhesive Patterning to Construct 3D Paper Microfluidic Devices

A high-throughput microarray method for the identification of polymers which reduce bacterial surface binding on medical devices is described.

High-throughput Identification of Bacteria Repellent Polymers for Medical Devices

Learn rapid prototyping of liquid elastomer medical devices using 3D printed molds for injection molding. This low-cost method enables custom device creation in resource-limited academic settings.

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

Explore More Videos