Name: Rapid Formation and Testing of Self-expanding NiTi Frames with a Small Form Factor Suitable for Minimally Invasive Implants (Video) | JoVE Journal
Uploaded: 2025-03-07T12:00:00.000+00:00
Duration: 6 min 48 s
Description: Learn a low-cost fabrication technique for shape-setting nitinol frames using sacrificial fixtures. This method enables rapid prototyping and testing of self-expanding minimally invasive implants with complex geometries.

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

Research reported in this publication was supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health under Award Number R21EB030654. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. S. Alaie and J. Mata also thank the Department of Mechanical and Aerospace Engineering and the College of Engineering at New Mexico State University for their support. The authors&#160;thank Oscar Lara and Angel de Jesus Zuniga Ramirez for their contributions in generating Figure 2 and editing the references.&#160;The authors also thank Andrea Gonzalez Martinez and Jesus Armando Gil Parra for their contributions to the video demonstrations.

NOTE: See the Table of Materials for details related to all materials used in this protocol. Figure 1A shows an example of the copper/NiTi frame. Use safety gloves.
1. Iteration of a design of a NiTi frame/prototype
<ol>
	<li>Align NiTi wire inside copper tubes (or brass tubes; Figure 2A).
	<ol>
		<li>Select NiTi wire (0.008 in) and a copper tube (OD 1.00 mm x 400 mm).</li>
		<li>Turn on the stereoscope and visually look at the NiTi on the monitor and copper while manipulating them. Align the wire inside the tube. Push the wire fully into the tube.</li>
	</ol>
	</li>
	<li>Prepare 3D printed fixtures (Figure 2B-D).
	<ol>
		<li>Download one .STL file for the fixture/template (https://osf.io/54rm3/files/osfstorage). 
		NOTE: For some .STL file examples, see this repository (https://osf.io/54rm3/files/osfstorage).</li>
		<li>If any adjustment is needed, download the .SDLRD file from the same repository, make design adjustments in the propriety CAD software, and then export it as a .STL file. Alternatively, create a model in open-source CAD software and export a .STL file. 
		NOTE: For some .SDLRD or .FCSTD design examples, see this repository (https://osf.io/54rm3/files/osfstorage).</li>
		<li>Open the slicing software (e.g., Elegoo Cura) and import the .STL file. Select the object to be 3D printed and click on the bottom of the slice pane. Save the file. gcode and save it on a&#160;micro-sd card. Pull out the micro-SD card.</li>
		<li>Turn on the FDM 3d printer. Put in the micro-sd card. From the screen, select prepare | preheat | PLA. Select back | print. Select the .gcode file and then tap on print.</li>
		<li>Leave the machine to 3D print the part.</li>
		<li>After completion of the 3D printing, remove the printed part and cut any support part using pliers.</li>
		<li>File the part, where there are coarse edges, and mark the areas to be drilled with a marker.</li>
		<li>Drill holes in the 3D-printed geometry using a hand drill (Figure 2B). 
		CAUTION: Use safety gloves and safety glasses.</li>
		<li>Pass screws through the holes of the 3D printed part using a screwdriver (Figure 2C).</li>
	</ol>
	</li>
	<li>Form the 3D structure of the Cu/NiTi using the fixture and hand tools. Pass the wire through the holes and bend it over the screws step by step. If needed, bend the wire using hand tools (Figure 2D,E).
	<ol>
		<li>Hold NiTi/Cu and pass it through the central hole. Next, fold/bend the Cu tube using tweezers or pliers around all the screws to form the desired shape (Figure 2E).</li>
		<li>Unscrew the screws. Heat up to soften the 3D printed fixture (from step 1.2) using a soldering gun.</li>
		<li>Use scissors to cut the 3D-printed part. Remove the unwanted 3D part using tweezers or pliers (Figure 2F).</li>
	</ol>
	</li>
	<li>Heat treat the NiTi/Cu structure/frame (Figure 2G).
	<ol>
		<li>Turn on the furnace tube and monitor the temperature using a thermocouple. When the temperature reaches 500 &#176;C, place the Cu/NiTi frame in the furnace for 3 min. 
		NOTE: Use high-temperature gloves, lab coat, and safety face shield.</li>
		<li>Monitor the temperature using K-type thermocouples by placing the thermometer in the tube furnace.</li>
		<li>Take out the NiTi/Cu frame using a hook after 3 min (Figure 2H) and quench it in distilled water.</li>
	</ol>
	</li>
	<li>Etch the sacrificial copper tubes (Figure 2I).
	<ol>
		<li>Weigh ammonium persulfate on a scale. Weigh water in a glass container as well. Mix them such that the weight of ammonium persulfate is 23% of that of water. 
		NOTE: Do this process inside the fume hood and use a lab coat, safety glass, and safety gloves.</li>
		<li>Add ammonium persulfate to achieve a 23% weight ratio (ammonium persulfate to water). Stir the solution using a glass stirrer until the ammonium persulfate is dissolved. 
		NOTE: Do this process inside the fume hood and use a lab coat, safety glass, and safety gloves.</li>
		<li>Submerge the NiTi/Cu frames from step 1.3 into the solution for ~8 h to etch the copper (Figure 2I). 
		NOTE: Do this process inside the fume hood and wear a lab coat, safety glass, and safety gloves.</li>
		<li>Visually monitor the copper etching. If they are not fully etched, dispose of the etchant, produce the fresh etchant (see steps 1.5.1 and 1.5.2), and pour the fresh one into the container.</li>
		<li>If the copper is fully etched, take it out using tweezers (Figure 2J) and wash the released NiTi frame in distilled water by triple-rinsing it. See Figure 1B for an example of a released NiTi frame after these steps.</li>
		<li>Turn on the microscope. Place the NiTi wire under the microscope; look for any undesirable curvature or dimensions.</li>
	</ol>
	</li>
</ol>
2. Covering the sides of the frame with films or fabric
<ol>
	<li>Spin coat the aromatic polyurethane elastomer (polycarbonate urethane is an alternative, see the Table of Materials; the complete protocol is provided elsewhere6).
	<ol>
		<li>Place a 4 inch silicon wafer in the oxygen plasma machine and plasma treat it for 2 min. Next, remove the wafer.</li>
		<li>Open the vacuum desiccator and pour a few drops of the silane (C8H4Cl3F13Si; see Table of Materials) into a plastic container in the desiccator.</li>
		<li>Place the wafer in the desiccator, close the lid, and apply vacuum to the desiccator.</li>
		<li>Close the desiccator valve and turn off the vacuum pump.</li>
		<li>Leave the desiccator for 2 h,&#160;afterward&#160;take out the silicon wafer.</li>
		<li>Place the wafer on the spin coater, center it, and pour some aromatic or aliphatic polyurethane elastomer dissolved in DMAc (see the Table of Materials) on its center.</li>
		<li>Spin-coat the wafer; then, remove the wafer and place it in the 80 &#176;C oven for 2 h, under a fume hood.</li>
		<li>After 2 h, take out the wafer and peel off the cured film using tweezers (use fingers if needed).</li>
		<li>Cut the peeled film into smaller pieces using scissors.</li>
	</ol>
	</li>
	<li>Heat press the aromatic polyurethane elastomer films on the NiTi frames.
	<ol>
		<li>Design a spacer for the heat processing procedure.</li>
		<li>Use the proprietary or open-source CAD software to design the spacer, export the .STL file in the environment, and slice the object to create gcode files (see step 1.2.3). Alternatively, download and use the spacer design provided (https://osf.io/54rm3/files/osfstorage).</li>
		<li>Start 3D printing the spacer by opening the .STL file in slicing the software (e.g., CHITUBOX), Alternatively, follow the 3D printing steps in 1.2.4, 1.2.5 instead of 2.2.4, 2.2.5, and 2.2.6. 
		NOTE: The spacer fabricated through the latter steps will have longer durability.</li>
		<li>Choose the object to be 3D printed, hit the slice pane and save the file in a .CBT format on a USB stick.</li>
		<li>Put the USB stick into the SLA 3D printer, pour photopolymer resin into the container of the 3D printer, turn on the 3D printer, choose print, and hit the triangle sign to start the 3D printing process.</li>
		<li>After the 3D printing process is finished remove the spacer from the print bed, place it for 10 minutes inside the UV LED system, then wash it in water, and store it for the next steps.</li>
		<li>Open the heat press.</li>
		<li>Laminate the polyurethane elastomer film on the spacer (Figure 2K), and place NiTi wire/frame around the spacer and on top of the film. Laminate a second film layer on the wire. Set the temperature at 240 &#176;F (If desired, add additional layers of elastomers between the two layers &#160;or between polyurethane and the spacer to avoid adhesion).</li>
		<li>Close the top of the press and lock it; wait for 60 s.</li>
		<li>Repeat the same process of heat pressing for the other side of the NiTi wire frame and the spacer.</li>
		<li>Cut the extra parts of the bonded film with scissors (Figure 2L).</li>
		<li>As an alternative to bonding thermoplastic materials, cover the NiTi wire frame by sewing PET fabrics. 
		NOTE: Figure 3 shows the frame covered by layers of a hemocompatible polymer. Here, the layers include an additional layer of micropatterned polydimethylsiloxane that is sandwiched between them.</li>
	</ol>
	</li>
</ol>
3. Testing frame deployment
<ol>
	<li>Hold a FR 12 catheter by hand (Figure 4A) and pass it through a dilator and a needle (Figure 4B,C).</li>
	<li>Secure a silicone piece on the holder (Figure 4E).</li>
	<li>Using the needle and dilator, create a hole in the silicone piece (Figure 4E).</li>
	<li>Pass the catheter through the hole gradually (Figure 4F) and retract the dilator and needle.</li>
	<li>Fold the NiTi frame and push it through the proximal end of the catheter (Figure 4G).</li>
	<li>Push the frame toward the distal end of the catheter using the polytetrafluoroethylene (PTFE) rod (Figure 4D).</li>
	<li>Dislodge the first side of the NiTi frame (Figure 4I).</li>
	<li>Retract the catcher (Figure 4H) and dislodge the second side of the NiTi frame on the other side of the silicone rubber (Figure 5).</li>
	<li>Examine the frame under the microscope to check for any type of failure or undesired deformations.</li>
</ol>

Cost-Effective Shape Setting of NiTi Wires Using Sacrificial Copper Fixtures

<ol><li>Smith, S., Hodgson, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Shape+setting+nitinol%5BTitle%5D)+AND+%22Proc+of+the+Mater+Process+Med+Devices+Conf%22%5BJournal%5D)">Shape setting nitinol.</a> Proc of the Mater Process Med Devices Conf. , 266-270 (2004).</li>
<li>Kapoor, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Nitinol+for+medical+applications%3A+A+brief+introduction+to+the+properties+and+processing+of+nickel+titanium+shape+memory+alloys+and+their+use+in+stents%5BTitle%5D)+AND+%22Johnson+Matthey+Tech+Rev%22%5BJournal%5D)">Nitinol for medical applications: A brief introduction to the properties and processing of nickel titanium shape memory alloys and their use in stents.</a> Johnson Matthey Tech Rev. 61 (1), 66-76 (2017).</li>
<li>Viscuso, S., Gualandris, S., De Ceglia, G., Visentin, V. Shape memory alloys for space applications. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aViscuso%2C+S+%22Shape+Mem+Alloy+Eng%22">Shape Mem Alloy Eng</a>. , Elsevier. 609-623 (2021).</li>
<li>Liu, X., Wang, Y., Yang, D., Qi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+effect+of+ageing+treatment+on+shape-setting+and+superelasticity+of+a+nitinol+stent%5BTitle%5D)+AND+%22Mater+Charact%22%5BJournal%5D)">The effect of ageing treatment on shape-setting and superelasticity of a nitinol stent.</a> Mater Charact. 59 (4), 402-406 (2008).</li>
<li>Dulal, H., Swan, T., Al'aref, S. J., Alaie, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Low-cost+prototyping+of+nitinol+wires%2Fframes+using+polymeric+cores+and+sacrificial+fixtures+with+application+in+individualized+frames+anchoring+through+the+atrial+septum%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">Low-cost prototyping of nitinol wires/frames using polymeric cores and sacrificial fixtures with application in individualized frames anchoring through the atrial septum.</a> Sci Rep. 13, 21853(2023).</li>
<li>Alaie, S., Robinson, S. S., Amiri Moghadam, A. A., Auge, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Advanced+manufacturing+of+patient+specific+occluders+for+the+left+atrial+appendage+with+minimally+invasive+delivery%5BTitle%5D)+AND+%22Adv+Eng+Mate%22%5BJournal%5D)">Advanced manufacturing of patient specific occluders for the left atrial appendage with minimally invasive delivery.</a> Adv Eng Mate. 22, 1901074(2020).</li>
<li>Robinson, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Patient-specific+design+of+a+soft+occluder+for+the+left+atrial+appendage%5BTitle%5D)+AND+%22Nat+Biomed+Eng%22%5BJournal%5D)">Patient-specific design of a soft occluder for the left atrial appendage.</a> Nat Biomed Eng. 2, 8-16 (2018).</li>
<li>Amiri Moghadam, A. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Toward+development+of+inflatable+stents+with+application+in+endovascular+treatments%5BTitle%5D)+AND+%22Adv+Funct+Mater%22%5BJournal%5D)">Toward development of inflatable stents with application in endovascular treatments.</a> Adv Funct Mater. 28 (51), 9(2018).</li>
<li>Chen, Y. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aChen%2C+Y+%22Design%2C+parameter+optimization+and+in+vitro+evaluation+of+implantable+medical+devices%22">Design, parameter optimization and in vitro evaluation of implantable medical devices</a>. , University of Pittsburgh. (2018).</li>
<li>Bernini, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Oversizing+of+self-expanding+nitinol+vascular+stents-a+biomechanical+investigation+in+the+superficial+femoral+artery%5BTitle%5D)+AND+%22Journal+of+the+Mechanical+Behavior+of+Biomedical+Materials%22%5BJournal%5D)">Oversizing of self-expanding nitinol vascular stents-a biomechanical investigation in the superficial femoral artery.</a> Journal of the Mechanical Behavior of Biomedical Materials. 132, 105259(2022).</li>
<li>Bernini, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surface+finishing+of+n+itinol+for+implantable+medical+devices%3A+A+review%5BTitle%5D)+AND+%22J+Biomed+Mater+Res+Part+B+Appl+Biomater%22%5BJournal%5D)">Surface finishing of n itinol for implantable medical devices: A review.</a> J Biomed Mater Res Part B Appl Biomater. 110 (12), 2763-2778 (2022).</li>
<li>Funk, K. A., Hampshire, V. A., Schuh, J. C. Nonclinical safety evaluation of medical devices. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aFunk%2C+KA+%22Toxicol+Pathol%22">Toxicol Pathol</a>. , CRC Press. 95-152 (2018).</li>
<li>U.S. Food and Drug Administration. Non-clinical engineering tests and recommended labeling for intravascular stents and associated delivery systems - Guidance for industry and FDA staff. U.S. Food and Drug Administration. , Available from: 
 <a target="_blank" href="https://www.fda.gov/regulatory-information/search-fda-guidance-documents/non-clinical-engineering-tests-and-recommended-labeling-intravascular-stents-and-associated-delivery">https://www.fda.gov/regulatory-information/search-fda-guidance-documents/non-clinical-engineering-tests-and-recommended-labeling-intravascular-stents-and-associated-delivery</a> (2018).</li>
<li>Rokicki, R., Hryniewicz, T., Pulletikurthi, C., Rokosz, K., Munroe, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Towards+a+better+corrosion+resistance+and+biocompatibility+improvement+of+nitinol+medical+devices%5BTitle%5D)+AND+%22J+Mat+Eng+Perform%22%5BJournal%5D)">Towards a better corrosion resistance and biocompatibility improvement of nitinol medical devices.</a> J Mat Eng Perform. 24, 1634-1640 (2015).</li>
<li>Hryniewicz, T., Rokicki, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Modification+of+nitinol+biomaterial+for+medical+applications%5BTitle%5D)+AND+%22World+Scientific+News%22%5BJournal%5D)">Modification of nitinol biomaterial for medical applications.</a> World Scientific News. (96), 35-58 (2018).</li>
<li>Handa, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Hemocompatibility+comparison+of+biomedical+grade+polymers+using+rabbit+thrombogenicity+model+for+preparing+nonthrombogenic+nitric+oxide+releasing+surfaces%5BTitle%5D)+AND+%22J+Mater+Chem+B%22%5BJournal%5D)">Hemocompatibility comparison of biomedical grade polymers using rabbit thrombogenicity model for preparing nonthrombogenic nitric oxide releasing surfaces.</a> J Mater Chem B. 2 (8), 1059-1067 (2014).</li>
<li>Li, P., Wang, Y., Meng, F., Cao, L., He, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Effect+of+heat+treatment+temperature+on+martensitic+transformation+and+superelasticity+of+the+Ti49Ni51+shape+memory+alloy%5BTitle%5D)+AND+%22Materials%22%5BJournal%5D)">Effect of heat treatment temperature on martensitic transformation and superelasticity of the Ti49Ni51 shape memory alloy.</a> Materials. 12 (19), 2539(2019).</li>
<li>Duerig, T., Pelton, A., Stöckel, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((An+overview+of+nitinol+medical+applications%5BTitle%5D)+AND+%22Mat+Sci+and+Eng%3A+A%22%5BJournal%5D)">An overview of nitinol medical applications.</a> Mat Sci and Eng: A. 273, 149-160 (1999).</li>
<li>Kwok, D., Schulz, M., Hu, T., Chu, C., Chu, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Surface+treatments+of+nearly+equiatomic+niti+alloy+%28nitinol%29+for+surgical+implants%2C+biomedical+engineering%5BTitle%5D)+AND+%22Trends+in+Mater+Sci%22%5BJournal%5D)">Surface treatments of nearly equiatomic niti alloy (nitinol) for surgical implants, biomedical engineering.</a> Trends in Mater Sci. , 269-282 (2011).</li>
<li>Williams, K. R., Gupta, K., Wasilik, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Etch+rates+for+micromachining+processing-part+ii.+II%5BTitle%5D)+AND+%22J+of+Microelectromech+Syst%22%5BJournal%5D)">Etch rates for micromachining processing-part ii. II.</a> J of Microelectromech Syst. 12 (6), 761-778 (2003).</li>
<li>Yip, M. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Low-cost+and+rapid+shaping+of+nitinol+for+medical+device+prototyping%5BTitle%5D)+AND+%22ASME+Open+J+of+Eng%22%5BJournal%5D)">Low-cost and rapid shaping of nitinol for medical device prototyping.</a> ASME Open J of Eng. 2, 021027(2023).</li>
</ol>

The authors declare no conflicts of interest.

In this protocol, multiple steps require meticulous attention such as the heat treatment (annealing), etching, and design of 3D-printed fixtures. Large variations in temperature from 500 &#176;C 17 or the annealing time of NiTi can be detrimental to the superelasticity of the NiTi wire and to achieving the desired shapes18. Heat treatment with inaccurate conditions (temperature and time) can also lead to a loss of the superelastic property19. The etc...

NiTi wires are widely used in medical implants but require an initial shape-setting process during device fabrication1. Various devices are made from NiTi, including catheter tubes, guidewires, stone retrieval baskets, filters, needles, dental files, as well as other surgical instruments2. NiTi&#39;s biocompatibility, superelasticity, and fatigue resistance make it suitable for these applications. Additionally, it has applications in the automotive and aerospace industries3.
Usage of NiTi&#160;is limited due to its high cost and complex processes needed for shape-setting. In the shape-setting process, NiTi structures are traditionally exposed to high temperatures (about 500 &#176;C) while confined in a fixture4. This elevated temperature, as well as the stresses during the shape-setting process, requires a fixture with high mechanical strength. This is why typical fixtures are usually made from metals1. As such, the use of metal fixtures that are typically machined increases costs and poses challenges for the rapid prototyping and testing of NiTi structures. One alternative approach involves the use of reconfigurable fixtures constructed from pins and plates1, which simplifies the process; however, this process has limitations in the shaping of complex geometries. Accordingly, a low-cost, shape-setting process using low-cost materials and manufacturing is highly desirable for research that requires shape-setting NiTi frames.
To address the need for rapid prototyping of NiTi, we recently introduced a protocol utilizing low-cost 3D printed parts and crafted manufacturing for shape-setting NiTi wires5. This method incorporates sacrificial fixtures with a minimal mass. The fixture is shown to be beneficial in securing the NiTi wire during wire forming and shape-setting (heat treatment) processes. Copper tubes were employed as an accessible and low-cost material. It acts as a reinforcing sacrificial fixture and the standard wire bending techniques can be used for shape-setting complex structures. It was observed that the brass tubes could be used as an alternative. Ammonium persulfate was utilized in the final stage for the selective etching of copper, after the annealing process. This step finally released the shape-set NiTi wires. This approach illustrates the innovative use of sacrificial structures as spacers. When this approach is combined with additive manufacturing, the fabrication of complex shapes can be achieved.
In vitro deployment test is among the basic tests for assessing the feasibility of a self-expanding prototype implant, designed to be deployed through a catheter. These tests involve assessing if a self-expanding implant can successfully pass through a sheath/catheter with the required dimension. Such tests have been used in various transcatheter devices or implant prototypes; some examples include left atrial appendage occluders6,7, soft-stents8, NiTi flow diverter9, and NiTi stents10. These works highlight the need for a methodology for rapidly fabricating NiTi frames with complex topologies, which could self-expand through catheters thereby satisfying the preliminary requirements for a transcatheter implant.
The aim of this paper is to outline cost-efficient and well-crafted manufacturing methods, providing a detailed, step-by-step guide through each process. It focuses on demonstrating a variety of self-expanding NiTi wire frames suitable for implants and analyzes key aspects of the method needed to produce complex topologies using affordable and efficient techniques. This&#160;paper includes testing these frames and deploying them through a Fr-12 catheter in a benchtop setup that simulates transeptal implant delivery to the atrial septum. This test is similar to basic tests, employed by prior work6,8. This method demonstrated the capability of deployment of a prototype self-expanding frame after passing through a catheter. Ultimately, this methodology can help determine if a certain topology/design for a NiTi frame can meet the preliminary mechanical requirements for deployment through a specific catheter.
While this work&#160;focuses on the fabrication of prototypes for NiTi frames and the basic characterization of their topology and conformality, various other characterizations11 and regulatory safety tests12,13 are necessary for the development of implants. Some characterizations include characterization of surface properties/chemistry14, corrosion14, fatigue analysis13, hemocompatibility13, and biocompatibility15.

<table><tbody><tr><td>304 SS Hypotubes&lt;br/&gt; Generic Name: Needle</td><td>Tegra Medical</td><td></td><td></td></tr><tr><td>3D printed frame for testing&lt;br/&gt; Generic Name: PLA filament</td><td>R3D</td><td></td><td></td></tr><tr><td>3D printed polymeric part for heat press&lt;br/&gt; Generic Name: PLA filament</td><td>R3D&amp;nbsp;</td><td></td><td></td></tr><tr><td>Ammonium Persulfate&lt;br/&gt; Generic Name: Ammonium Persulfate</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>Chronoflex AR 22%&lt;br/&gt; Generic Name: Polyurethane</td><td>AdvanSource biomaterials</td><td></td><td>aromatic polycarbonate urethane elastomer&amp;nbsp;</td></tr><tr><td>Copper Web Type Electrodes (1.00 mm x 400 mm)&lt;br/&gt; Generic Name: Copper Tube</td><td>Holepop edm supplies &amp;amp;electrodes</td><td></td><td></td></tr><tr><td>Dilator&lt;br/&gt; Generic Name: Dilator</td><td>QOSINA</td><td></td><td></td></tr><tr><td>Ecoflex 00-30&lt;br/&gt; Generic Name: Ecoflex 00-30</td><td>Smooth-on</td><td></td><td>silicone</td></tr><tr><td>Fr 12 or 13 Catheter&lt;br/&gt; Generic Name: Sheath</td><td>QOSINA</td><td></td><td></td></tr><tr><td>Nickel Titanium Wire (0.008)&lt;br/&gt; Generic Name: NiTi Wire</td><td>Malin Co.&amp;nbsp;</td><td></td><td></td></tr><tr><td>PTFE Teflon rod 1/8&quot; Diameter x 36&quot;&lt;br/&gt; Generic Name: Polytetrafluoroethylene&amp;nbsp;</td><td>Sterling Seal &amp;amp; Supply, Inc. (STCC)</td><td></td><td></td></tr><tr><td>Tecoflex&lt;br/&gt; Generic Name: Thermoplastic Polyurethane</td><td>Lubrizol</td><td></td><td>aliphatic polyurethane elastomer&amp;nbsp;</td></tr><tr><td>Trichloro(1H,1H,2H,2H-tridecafluoro-n-octyl)silane&lt;br/&gt; Generic Name: C&lt;sub&gt;8&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;Cl&lt;sub&gt;3&lt;/sub&gt;F&lt;sub&gt;13&lt;/sub&gt;Si</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>Dimethylacetamide (DMAC)&lt;br/&gt; Generic Name: Dimethylacetamide</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>SOLIDWORKS&lt;br/&gt; Generic Name: Proprietary CAD software</td><td>Dassault Syst&amp;egrave;mes</td><td></td><td></td></tr><tr><td>FreeCAD&lt;br/&gt; Generic Name: Open Source CAD software</td><td>freecad.org</td><td></td><td></td></tr><tr><td>ABS Like Photopolymer Resin&lt;br/&gt; Generic Name: Photopolymer Resin</td><td>ELEGOO</td><td></td><td></td></tr></tbody></table>

rapid formation and testing of self-expanding niti frames with a small form factor suitable for minimally invasive implants

Rapid Formation and Testing of Self-expanding NiTi Frames with a Small Form Factor Suitable for Minimally Invasive Implants

NiTiNOL (commonly referred to as nitinol or NiTi) wires feature exceptional shape memory and super-elastic characteristics, while shape-setting is often a costly process. Among the steps in&#160;this process, heat treatment requires exposure to high temperatures for shape-setting. Traditionally, metal fixtures are used for this purpose.&#160;However, their manufacturing costs can be significant, which is unideal&#160;for iterating prototypes. This work demonstrates a recently introduced approach using sacrificial fixtures made of copper tubes, which eliminates the need for expensive fixtures. These copper tubes allow for the formation of complex geometries, and they offer a scaffold for various phases of the fabrication process. Moreover, ammonium persulfate is used&#160;for selective copper etching, which simplifies the production of NiTi frames. This work&#39;s findings confirm the effectiveness of this technique and&#160;demonstrate&#160;the successful shape-setting of NiTi wires for self-expanding frames. This methodology paves the way for future research, allowing for rapid prototyping of NiTi wireframes for various applications, especially those in medical devices.

NiTi frames were shape-set into various topologies using low-cost plastic fixtures and hand tools (Figure 1). In protocol steps 1.1 to 1.4 (Figure 1A), NiTi/Cu frames were formed into complex topologies. Following protocol step 1.5, Cu was etched to release the NiTi frames (Figure 1B). Here, the Cu fixture was completely etched away, allowing the NiTi frame to be released using low-cost jigs/fixtures that were 3D printed (step 1.2)....

This work illustrates a low-cost fabrication technique for shape-setting nitinol wires/frames with a small form factor using sacrificial fixtures. The technique is demonstrated for the fabrication of self-expanding frames designed for minimally invasive implants with complex shapes.

NiTiNOL (commonly referred to as nitinol or NiTi) wires feature exceptional shape memory and super-elastic characteristics, while shape-setting is often a ...

Prototyping medical implants with self-expanding nitinol frames involves time consuming design and fabrication processes before testing. Innovative technologies can reduce this timeline, enabling faster prototype design, fabrication, and testing. Traditional technologies work best for mass production.However, cost-effective techniques are needed for rapid iteration of various prototypes, especially those made from nitinol in the initial phase of implant development. This protocol allows for fast iteration of nitinol frames and testing them for transcatheter delivery. It also allows the assessment of whether a frame or stent meets the minimum requirements for self-expansion.That is specifically demonstrated in designing frames for an implant to be anchored on the atrial septum using 12 French characters. Our research lab develops proof of concept implantable pressure sensors for remote monitoring of patients'biomarkers with heart failure. We are interested in innovative designs that do not use electronics.We also leverage advanced manufacturing technologies and artificial intelligence in engineering novel proof of concept implants. To begin, select a nickel-titanium wire and a copper tube. Turn on the stereoscope and manipulate the nickel-titanium wire and copper tube shown on the monitor while visually inspecting them.Align the wire inside the tube and push it fully into the tube. To prepare 3D printed fixtures, download the STL file for the fixture or template. If any adjustments are needed, download the SDLRD file from the same repository.Make design adjustments in proprietary CAD software and export it as STL file. Then open the slicing software and import the STL file. Select the object to be 3D printed and click on the pane of slice.Save the file as a G-code file and save it on a micro SD card. After that, pull out the micro SD card. Now, turn on the FDM 3D printer and insert the micro SD card.From the screen, select Prepare, then Preheat and choose PLA. Then select Back and print. Choose the G-code file and tap Print.Wait for the machine to 3D print the part. After the completion of the 3D printing, remove the printed part, and using pliers, cut any support structures. Then file the part where there are coarse edges.And with a marker, mark the areas to be drilled. Using a hand drill, drill holes in the 3D printed geometry. Pass screws through the holes of the 3D printed part using a screwdriver.Now hold the nickel-titanium and copper frame and pass it through the central hole. Using tweezers or pliers, fold or bend the copper tube around all the screws to form the desired shape. Then unscrew the screws.Using a soldering gun, heat the 3D printed fixture to soften it. After that, employ tweezers or pliers to remove the unwanted parts. Then turn on the furnace tube and monitor the temperature using a Thermocable.When the temperature reaches 500 degrees Celsius, place the copper and nickel-titanium frame in the furnace for three minutes. Afterward, using a hook, take out the nickel-titanium and copper frame and quench it in distilled water. To etch the copper, submerge the nickel-titanium and copper frames in the ammonium persulfate solution for approximate eight hours.Once the copper is fully etched, use tweezers to remove the frame and triple rinse the released nickel-titanium frame in distilled water. Then turn on the microscope and place the nickel-titanium wire under it to check for any undesirable curvature or dimensions. Begin by designing and printing a nickel-titanium frame for minimally invasive implants.To cover the sides of the frame With thermoplastic films, open the heat press and laminate the polyurethane elastomer film on the spacer using a fluoropolymer film to avoid polyurethane adhering to the spacer. Place the nickel-titanium wire or frame around the spacer and on top of the film. Then laminate a second polyurethane film and another layer of fluoropolymer film.Set the temperature to 240 degrees Fahrenheit. After that, close the top of the press, lock it and wait for 60 seconds. Finally, cut the extra parts of the bonded film with scissors.To begin, design a nickel-titanium frame and cover the sides with hemocompatible elastomer. Hold a French 12 catheter by hand and pass it through a dilator and a needle. Next, secure a silicone piece on the holder.Using the needle and dilator, create a hole in the silicone piece. Then gradually pass the catheter through the hole and retract the dilator and needle. Fold the nickel-titanium frame and push it through the proximal end of the catheter.Using the polytetrafluoroethylene rod, push the frame toward the distal end of the catheter, then dislodge the first side of the frame. Now retract the catheter and dislodge the second side of the nickel-titanium frame on the other side of the silicone rubber. Then examine the frame under the microscope to check for any type of failure or undesired deformation.

rapid-formation-testing-self-expanding-niti-frames-with-small-form

Research

JoVE Journal

Engineering

In this video, we will demonstrate modification techniques for porous metallic implants to improve their functionality and to control cell migration. Techniques include development of pore gradients to control cell movement in 3D and production of basement membrane mimics to control cell movement in 2-D. Also, a HPLC-based method for monitoring implant integration in-vivo via analysis of blood proteins is described.

Multi-Scale Modification of Metallic Implants With Pore Gradients, Polyelectrolytes and Their Indirect Monitoring In vivo

Insertion of flexible neural microelectrode probes is enabled by attaching probes to rigid stiffeners with polyethylene glycol (PEG). A unique assembly process ensures uniform and repeatable attachment. After insertion into tissue, the PEG dissolves and the stiffener is extracted. An in vitro test method evaluates the technique in agarose gel.

Insertion of Flexible Neural Probes Using Rigid Stiffeners Attached with Biodissolvable Adhesive

An improved method to mechanically test bone anchorage to candidate implant surfaces is presented. This method allows for alignment of the disruption force exactly perpendicular, or parallel, to the plane of the implant surface, and provides an accurate means to direct the disruption forces to an exact peri-implant region.

An Improved Mechanical Testing Method to Assess Bone-implant Anchorage

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.

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

Bioactive and mechanically reliable metal scaffolds have been fabricated through a method which consists of two processes, dynamic freeze casting for the fabrication of porous Ti, and coating and densification of the Ti scaffolds. The densification process is simple, effective and applicable to the fabrication of functionally graded scaffolds.

Fabrication of Mechanically Tunable and Bioactive Metal Scaffolds for Biomedical Applications

In the protocol, we present a method to manufacture a small caliber stent-graft by sandwiching a balloon expandable stent between two electrospun nanofibrous polyurethane layers.

Fabrication of Small Caliber Stent-grafts Using Electrospinning and Balloon Expandable Bare Metal Stents

Using a 3D printer, a shape memory polymer filament is extruded to form a branched tubular structure. The structure is patterned and shaped such that it can contract into a compact form once folded and then return to its formed shape when heated.

4D Printed Bifurcated Stents with Kirigami-Inspired Structures

This protocol describes a method for rapid manufacturing of soft pneumatic actuators and robots with a thin form factor. The fabrication method starts with lamination of thermoplastic polyurethane (TPU) sheets followed by laser cutting/welding of a two-dimensional pattern to form actuators and robots.

Rapid Manufacturing of Thin Soft Pneumatic Actuators and Robots

This protocol describes the fabrication of an implantable integrated imaging window using 3D laser printing. The window consists of a system of microlenses coupled with micro-scaffolds. The method involves two-photon polymerization (2PP) of the biocompatible photoresist SZ2080 in a continuous sequence, optimizing manufacturing efficiency and alignment between the different components.

Microfabrication of Implantable Optics Integrated in a Microstructured Imaging Window for Advanced In Vivo Imaging

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

Construction and Testing of Coin Cells of Lithium Ion Batteries

Learn a low-cost fabrication technique for shape-setting nitinol frames using sacrificial fixtures. This method enables rapid prototyping and testing of self-expanding minimally invasive implants with complex geometries.

Rapid Formation and Testing of Self-expanding NiTi Frames with a Small Form Factor Suitable for Minimally Invasive Implants

Explore More Videos