Nitinol Springs Research Articles

DESIGN, IMPLEMENTATION, AND TESTING OF A 3D-PRINTED GRIPPER ACTUATED BY NITINOL SPRINGS

This article explores the use of shape memory alloy (SMA) materials in the creation of robot effectors. Specifically, we focus on the design and implementation of a gripper powered by nitinol springs. Nitinol, an alloy of nickel and titanium, can return to a pre-set shape when heated - a phenomenon known as the shape memory effect - which we utilize to control the gripper. The article showcases the design, construction, and testing of the gripper, including its speed and reliability in grasping different objects. Our findings indicate that the gripper was reliable solution, but further research is necessary to optimize its functions and control for more efficient results in practical applications.

Re-Evaluating the Long-Term Efficacy of Semi-Rigid Fixation Using a Nitinol Spring Rod in Lumbar Surgery: A Retrospective Study on an Effective Alternative for Reducing Adjacent Segment Disease

Adjacent segment disease (ASD) is a prevalent complication following lumbar fusion surgery, representing a significant challenge in spinal surgery. This study aimed to assess the long-term outcomes of Nitinol spring rod semi-rigid fixation, a potential alternative to traditional rigid fixation, in reducing the incidence of ASD. This retrospective case study evaluated 89 patients who underwent lumbar or lumbosacral surgeries using a combination of Bioflex® (a Nitinol spring rod dynamic stabilization system) and an interbody cage over 10 years of follow-up. The fusion status, adjacent segment disc height, mechanical complications, and re-operation rates were analyzed. The cohort had a median follow-up duration of 13.0 years. All patients achieved solid fusion at the final follow-up visit. One patient underwent revision surgery for clinical ASD (1.1%), and no patients required revision surgery due to mechanical problems. Radiological evidence of ASD was observed in 16.9% of the patients. This study’s findings suggest that semi-rigid fixation using Bioflex with an interbody cage is a possibly effective treatment strategy to prevent ASD. The technique potentially reduces the risk of ASD by allowing a degree of movement at the surgical site.

Low-cost prototyping of nitinol wires/frames using polymeric cores and sacrificial fixtures with application in individualized frames anchoring through the atrial septum

Self-expanding frames for minimally invasive implants are typically made from nitinol wires and are heat treated to maintain the desired shapes. In the process of heat treatment, nitinol structures are placed in a high-temperature oven, while they are confined by a fixture. During this process, nitinol exerts a high amount of force. Accordingly, a fixture requires high mechanical strength and temperature resistance; this is why fixtures are typically made from metals. The use of metal fixture also increases the turnaround time and cost. However, accelerating this process is beneficial in many applications, such as rapid development of medical implants that are patient-specific. Inspired by the use of sacrificial layers in microfabrication technology, here we propose a novel method for shape setting nitinol wires using a sacrificial metal fixture. In this process, the nitinol wires are first aligned inside copper hypotubes. Next, the forming process is done using hand-held tools to shape complex geometrical structures, annealing the nitinol reinforced by copper, and then selectively etching copper hypotubes in ammonium persulfate solutions. In this process, other sacrificial cores, which are 3D printed or cast from low-cost polymers, are also used. This combination of polymeric cores and minimal use of metals enables reducing the cost and the turnaround time. As a proof of concept, we showed that this process was capable of fabricating springs with mm or sub-mm diameters. The result showed a change of less than 5% in the intended diameter of the nitinol spring with diameters ranging from ~ 0.7 to 1.9 mm, which confirms copper as a suitable sacrificial fixture to obtain the desired complex geometry for nitinol. A metric, based on the elastic strain stored in copper is suggested to predict the possible variation of the intended dimensions in this process. Finally, to demonstrate the potential of this method, as proof of concept, we fabricated NiTi wire frames designed for anchoring through the atrial septum. These frames demonstrated septal defect occluders that were designed based on a patient’s cardiac image available in the public domain. This low-cost rapid fabrication technique is highly beneficial for a variety of applications in engineering and medicine with specific applications in rapid prototyping of medical implants.

Stirnol Engine: A combination of Nitinol (shape memory alloy) and Gamma Stirling Engine

Global pursuit to meet emergent energy demands necessitates finding simple and cost effective solutions. A promising solution is the application of renewable energy with thermo-mechanical conversion systems such as Stirling engines. Considerable effort is in hand at industry and academia domains to stimulate the development of Stirling technology. Foregoing, this paper focuses on modelling of Low Temperature Difference (LTD) gamma-type Stirling engine and investigating means of enhancing its performance through integration of Nitinol spring. The CFD models were comprehensively developed to simulate the engine, which have been subsequently validated through experimental data. The results reveal that addition of Nitinol Spring enhances the overall efficiency of engine demonstrating affirmative impact of shape memory alloy towards performance output of Stirling engine.

Effect of Material Change on Stirnol Engine: A Combination of NiTiNOL (Shape Memory Alloy) and Gamma Stirling Engine.

Population explosion, industrialization, and urbanization have accelerated energy requirements across the globe. This has led to the human quest to find simple and cost-effective energy solutions. A promising solution is the revival of the Stirling engine with the addition of Shape Memory Alloy NiTiNOL in it. The experimental results reveal that the addition of a NiTiNOL spring at the base plate of the Stirling engine enhances the overall efficiency of the engine, demonstrating some impact of the shape memory alloy toward the performance output of the Stirling engine. The newly modified engine has been named the STIRNOL ENGINE. The comparative study of Stirling and Stirnol engines reveals a minuscule efficiency improvement, yet there is a furtherance that opens a window for future researchers to get a lead and venture into this new field. We are confident that with more complex designs and better Stirling and NiTiNOL combinations, more efficient engines can be invented in the future. This research focuses on changing the material of the base plate of the Stirnol engine and ascertaining its performance differential through the integration of the NiTiNOL spring. A minimum of four types of materials are utilized for experimentation.

Stem cell activation during distraction enterogenesis in the murine colon.

Short bowel syndrome (SBS) is a devastating disease. We have proposed spring-mediated distraction enterogenesis for intestinal lengthening. Colonic lengthening is a potential treatment option for SBS to enhance fluid absorption capacity. We hypothesized that intraluminal spring-mediated colonic lengthening is associated with stem cell proliferation. C57BL/6 mice underwent placement of a gelatin-encapsulated compressed or uncompressed nitinol spring in a cecal segment. Animals were given clear liquid diet until postoperative day (POD) 7, followed by regular diet until POD 14. Cecal lengths were measured at euthanasia, and tissue was formalin fixed for histological processing. For Lgr5-GFP mice, immunohistochemistry against GFP was performed to localize Lgr5+ cells within crypts. Significant cecal lengthening with compressed springs and shortening with uncompressed springs were observed on POD 7 and 14. Mucosa of the compressed spring group was significantly thicker on POD 14. The density of Lgr5+ cells within the crypts in the compressed spring groups was higher than that in the uncompressed spring groups on both POD 7 and 14. Expandable springs can be used to lengthen the colon in the mouse model. Colonic lengthening was associated with gradual mucosal thickening and correlated with an increased density of stem cells within the crypts.

Experimental and numerical Comparison of traditional spring DVA and shape memory alloy actuated DVA for fixed beam vibration control

A desirable smart material that might be employed in dynamic vibration absorbers (DVA) as a stiffness adjustment element is shape memory alloy (SMA). This paper offers a numerical and experimental platform that examines the vibration of a stationary beam that has been operated by a SMA. In this study, a DVA is created using springs made of shape-memory alloy to eliminate vibration in a fixed beam. The system has a fixed beam secured by a C clamp. Real-time vibration was provided by the shaker with the help of a function generator. Results for the vibration's amplitude were recorded after the conventional spring with mass was mounted at a distance of 305.1 mm from the left end of the fixed beam. The SMA spring with mass was used in place of the conventional spring, and experiments were run at various frequencies. To record the results, the FFT and accelerometer were interfaced using Pulse software. The fixed beam with spring mass system is modelled in ANSYS Workbench R15.0 in accordance with the experimental setup. Over a range of frequencies, the results of a harmonic response analysis were compared. The experimental & analytical results are in good agreement when one SMA spring or two SMA springs connected in parallel or series are used to dampen the system effectively. The outcomes of this work can be utilised as a reference for designing DVA with a Nitinol spring as a stiffness tuning component in circumstances where smooth and continuous tuning of the absorber is required.

An Investigation of the Effects of Thermal Interference between Adjacent Nitinol Spring Actuators in a Tactile Display

Over the years, there has been increased research interest in the application of Nitinol as an actuator, due to its shape memory behaviour, simplicity, high power-to-weight ratio, compactness, and extreme high fatigue resistance to cyclic motion, and noiseless operation. Nitinol has found application in tactile displays which reproduce tactile parameters such as texture and shape, depending on the application. This paper presents the effects of thermal interference between adjacent Nitinol spring actuators in a tactile display. The tactile display is made of a 3 by 3 pin array whose spatial resolution was varied from 4 mm to 6 mm in steps of 1 mm while a current of 1.5 A was used to actuate 8 of the springs, and the centre spring was left unactivated to observe the thermal effects on it due to the heat gradient formed. A Finite Element (FE) model was developed using COMSOL Multiphysics and the results were further verified through experimentation. In both cases, there was visible thermal interference between actuators. The increase in spatial resolution saw a decrease in thermal interference by 12.7%. Using a fan to introduce forced convection, reduced the thermal interference in the simulation by 20% and during experimentation by 11%. The results of this research indicate a spatial resolution of 6 mm reduced the thermal inference to a negligible rate. However, thermal interference could not be eliminated with these two methods.

The effect of spring diameter on porcine ileal distraction enterogenesis.

Spring-mediated distraction enterogenesis has proven to be successful for intestinal lengthening. We aimed to evaluate the effect of spring diameter mismatch on intestinal adaptation. Juvenile mini-Yucatan pigs underwent placement of compressed nitinol springs with diameter of 10, 11, or 12mm into the ileal lumen. Pigs were euthanized on postoperative day 7. The lengths, histology, total area of blood vessels, and enteric ganglia were evaluated. All spring groups exhibited significant ileal lengthening. Across the different diameters, spring-expanded segments were similar in terms of ileal lengthening, crypt height, muscular thickness, blood vessels, and enteric ganglia area. Spring-mediated distraction enterogenesis is successful in the porcine ileum. A smaller diameter spring is as effective as a larger diameter spring in lengthening the ileum. Springs of varying diameters result in comparable structural changes in the ileum.

Internal plication for spring confinement to lengthen intestine in a porcine model.

Short bowel syndrome and its resultant nutritional deficiencies are the most common cause of intestinal failure. Significant intestinal lengthening using intraluminal springs is feasible in porcine models using an external plication technique. We hypothesize that an internal plication technique will yield significant intestinal lengthening, which may lead to future endoscopic spring placement. Uncompressed springs measuring 7.5 cm with a diameter of 1.0 cm were compressed to 2.0 cm. A gelatin-encapsulated compressed nitinol spring was inserted into the jejunal lumen of juvenile pigs and held in place with endoluminal sutures just proximal and distal to the spring-containing segment. A control segment distal to the spring was marked. Pigs were euthanized on postoperative day 7. Spring and control segments were collected for analyses. There was an average lengthening by 72% of the spring segment compared to the control segment. Two out of 7 springs stayed within both sets of plications and doubled in length. Histology showed normal mucosal integrity of the spring segment and plicated areas with similar muscular thickness but increased crypt depth and villus length compared to the control segment. Internal plication resulted in significant bowel lengthening. Five springs had slipped through proximal, distal or both sets of plications, resulting in less lengthening than those that remained fixed. A more consistent methodology for endoluminal suturing is needed to produce more lengthening.

Generation of Porcine Ileum Through Spring-Mediated Mechanical Distraction

IntroductionShort bowel syndrome is a devastating gastrointestinal disorder in which decreased bowel length results in inadequate absorption causing nutritional deficiencies. Current treatment options are accompanied by significant morbidity. We have proposed spring-mediated distraction enterogenesis as a method to lengthen bowel with success seen in porcine jejunum. We hypothesize that spring-mediated distraction enterogenesis can be demonstrated in porcine ileum with preservation of ileal structure and function. Materials and methodsLaparotomy was performed on juvenile female mini-Yucatan pigs and a gelatin-encapsulated compressed nitinol spring was inserted into the ileal lumen and affixed proximally and distally. A control segment distal to the spring segment was marked with sutures. Postoperatively, pigs were placed on a liquid diet and euthanized on postoperative day 7. Spring and control segments were measured and processed for immunohistochemistry to evaluate for the presence of vitamin B12–intrinsic factor cotransporter, chromogranin A-producing cells, and 5-HT producing cells. ResultsAll seven pigs survived to postoperative day 7 with no adverse effects. On average, pigs gained 84.3 ± 66.4 g/d. Spring segments lengthened 1.5 ± 0.7 cm with a relative lengthening by 128% ± 56%, which was statistically significant when compared to control (P < 0.01). The average density of chromogranin-A cells in control compared to spring segments was not significantly changed (2.9 ± 1.1 cells/mm versus 3.2 ± 1.2 cells/mm, P = 0.17). Both vitamin B12–intrinsic factor cotransporter and 5-HT producing cells were present in both control and lengthened ileum. ConclusionsIntraluminal nitinol springs significantly lengthened porcine ileum. The increase in density of enteroendocrine cells may indicate enhanced endocrine function of the lengthened ileum.

Distraction enterogenesis in the murine colon

Background/PurposeDistraction enterogenesis with intraluminal spring technology has been successfully used to lengthen segments of murine small intestine. We hypothesized that biocompatible springs could also be used to lengthen murine large intestine. MethodsAge and weight matched C57BL/6 mice underwent surgical insertion of nitinol spring-loaded capsules into the cecum. Segment lengths were measured at initial spring placement and at euthanasia after 7 and 14 days. Histologic adaptations were evaluated at scarification. ResultsCecal segments loaded with compressed springs lengthened an average of 150%, which was significantly longer than control segments loaded with either empty capsules or uncompressed springs. Muscularis layers tended to be thicker in the compressed spring groups compared to control groups. ConclusionsInsertion of a compressed nitinol spring into the cecum results in significant colonic lengthening in a mouse model. The ability to increase cecum length serves as proof of concept that distraction enterogenesis technology may be feasibly applied to large intestinal models. The use of distraction enterogenesis technology shows promise for application to clinical models in the treatment of pediatric intestinal disease.

Investigation of Post-Processing of Additively Manufactured Nitinol Smart Springs with Plasma-Electrolytic Polishing.

Additive manufacturing of Nitinol is a promising field, as it can circumvent the challenges associated with its conventional production processes and unlock unique advantages. However, the accompanying surface features such as powder adhesions, spatters, ballings, or oxide discolorations are undesirable in engineering applications and therefore must be removed. Plasma electrolytic polishing (PeP) might prove to be a suitable finishing process for this purpose, but the effects of post-processing on the mechanical and functional material properties of additively manufactured Nitinol are still largely unresearched. This study seeks to address this issue. The changes on and in the part caused by PeP with processing times between 2 and 20 min are investigated using Nitinol compression springs manufactured by Laser Beam Melting. As a benchmark for the scanning electron microscope images, the differential scanning calorimetry (DSC) measurements, and the mechanical load test cycles, conventionally fabricated Nitinol springs of identical geometry with a medical grade polished surface are used. After 5 min of PeP, a glossy surface free of powder adhesion is achieved, which is increasingly levelled by further polishing. The shape memory properties of the material are retained without a shift in the transformation temperatures being detectable. The decreasing spring rate is primarily attributable to a reduction in the effective wire diameter. Consequently, PeP has proven to be an applicable and effective post-processing method for additively manufactured Nitinol.

Mechanical lengthening of porcine small intestine with decreased forces

Introductionshort bowel syndrome is marked by inadequate intestinal surface area to absorb nutrients. Current treatments are focused on medical management and surgical reconfiguration of the dilated intestine. We propose the use of spring-mediated distraction enterogenesis as a novel intervention to increase intestinal length. Given our previous success lengthening intestinal segments using springs with spring constant ~7 N/m that exerts 0.46 N or higher, we sought to determine the minimal force needed to lengthen porcine small intestinal segments, and to explore effects on intestine over time. MethodsJuvenile Yucatan pigs underwent laparotomy with enterotomy to introduce nitinol springs intraluminally (n = 21 springs). Bowel segments (control, spring-distracted) were retrieved on post-operative day (POD) 7 and 14, and lengths measured. Thickness of cross-sectional intestinal layers were measured using H&E, and submucosal collagen fiber orientation measured using trichrome stained sections. Resultsall pigs survived to POD7 and 14. Spring constants of at least 2 N/m exerting a minimum force of 0.10 N significantly lengthened intestinal segments (p <0.0001). The stronger the spring force, the greater the induced thickness of various intestinal layers at POD7 and 14. Collagen fiber orientation was also more disordered because of stronger springs. Conclusiona spring constant of approximately 2 N/m exerting 0.10 N and greater significantly lengthens intestinal segments and stimulates intestinal structural changes at POD7 and 14. This suggests a decreased force is capable of inducing spring-mediated distraction enterogenesis.

Design of a passive mechanical system actuated by the nitinol helical springs for shading and sustainable development purposes of the buildings☆

Dynamic elements have always enabled humans to create adaptable systems that can adjust to the alternating exterior circumstances. Buildings, as one of the largest man-made objects, during the past decades and by the advent of numerous mechanical and electrical devices, have been continuously possessing dynamic components. Dynamic building skins have been recently developed for the main aim of energy control and visual comfort adjustment of the buildings, based on the alternating external conditions. These aims were typically fulfilled by mechanically- or electrically-derived, manual, or automatic systems; but these components require active energy source and control systems; in other words, they are not green-energy-based. Shape memory alloys, such as Nitinol helical springs, have been considered a novel replacement for these systems due to their lighter weight, smaller volume, passive actuation, and lower operating costs. This paper aims to propose a novel dynamic mechanical system for shading purposes, installed on the external side of the building skin, and actuated via the Nitinol helical springs, and by absorbing the solar energy. Initially, the theoretical, geometrical, and numerical formulations of the components and the Nitinol springs are established and then implemented inside a Python script. Further, the obtained numerical results are verified via a proper experimental campaign, designed and controlled by the Arduino microcontroller board and relevant components and sensors. Finally, it has been illustrated that there is a good agreement between the numerical and experimental results.

Mesenteric neovascularization during spring-mediated intestinal lengthening

BackgroundShort gut syndrome, a condition characterized by inadequate absorption of nutrients owing to decreased bowel length, has minimal avenues for treatment. We have proposed spring-mediated distraction enterogenesis to lengthen bowel in porcine jejunum as a treatment for short gut. We aim to evaluate the extent of mesenteric neovascularization in segments of lengthened bowel via spring-mediated enterogenesis. MethodsFemale juvenile Yucatan pigs underwent laparotomy and insertion of gelatin-encapsulated compressed nitinol springs, held in place with plication sutures, into the jejunum. At surgery and sacrifice, macroscopic mesenteric blood vessels were counted between the plication sites. Histologic samples of the mesentery were obtained to evaluate microscopic vasculature. ResultsA statistically significant increase in macroscopic mesenteric blood vessels was seen after intestinal lengthening (before: 1.9 ± 0.7 vessels, after: 4.7 ± 1.2 vessels, p = 0.001). A statistical significance is also seen in the density of arterioles (control: 3.0 ± 3.0 vessels/mm, spring: 7.0 ± 9.0 vessels/mm, p = 0.01) and venules (control: 4.0 ± 3.0 vessels/mm, spring: 8.0 ± 8.0 vessels/mm, p = 0.003). ConclusionIntestinal segments lengthened by intraluminal springs demonstrated total greater number of macroscopic vessels and microscopic blood vessels per length of mesentery as compared to control. This suggests local changes within the mesentery to recruit blood supply to growing intestine. Level of evidenceN/A Type of studyTreatment study.

Intestinal adaptation following spring insertion into a roux limb in mice

Background/PurposeIntraluminal springs have recently been shown to lengthen segments of intestine in a process known as distraction enterogenesis. We hypothesized that biocompatible springs could be used to lengthen defunctionalized murine small intestine and would lead to identifiable intestinal adaptations at the molecular level. MethodsAge and weight matched C57BL/6 mice underwent surgical insertion of nitinol spring-loaded capsules into a Roux limb of jejunum. Segment lengths were measured at initial spring placement and at euthanasia after 14 and 21 days. Histology and gene expression of the Roux limb were evaluated at scarification and compared to untreated control segments. ResultsIntestinal segments loaded with compressed springs lengthened an average of 240%, which was significantly longer than control segments loaded with either empty capsules or uncompressed springs. Muscularis thickening was greater in spring-treated mice compared to controls without springs. Crypt depth and Lgr5+ expression was greater in mice that received compressed spring treatments when compared to control groups. ConclusionsInsertion of a compressed nitinol spring into a Roux limb results in significant intestinal lengthening, smooth muscle thickening, and Lgr5+ expression in a mouse model. The ability to increase small bowel length in a defunctionalized murine model may be used to understand the mechanism of distraction enterogenesis.

Temperature-responsive biometamaterials for gastrointestinal applications.

We hypothesized that ingested warm fluids could act as triggers for biomedical devices. We investigated heat dissipation throughout the upper gastrointestinal (GI) tract by administering warm (55°C) water to pigs and identified two zones in which thermal actuation could be applied: esophageal (actuation through warm water ingestion) and extra-esophageal (protected from ingestion of warm liquids and actuatable by endoscopically administered warm fluids). Inspired by a blooming flower, we developed a capsule-sized esophageal system that deploys using elastomeric elements and then recovers its original shape in response to thermal triggering of shape-memory nitinol springs by ingestion of warm water. Degradable millineedles incorporated into the system could deliver model molecules to the esophagus. For the extra-esophageal compartment, we developed a highly flexible macrostructure (mechanical metamaterial) that deforms into a cylindrical shape to safely pass through the esophagus and deploys into a fenestrated spherical shape in the stomach, capable of residing safely in the gastric cavity for weeks. The macrostructure uses thermoresponsive elements that dissociate when triggered with the endoscopic application of warm (55°C) water, allowing safe passage of the components through the GI tract. Our gastric-resident platform acts as a gram-level long-lasting drug delivery dosage form, releasing small-molecule drugs for 2 weeks. We anticipate that temperature-triggered systems could usher the development of the next generation of stents, drug delivery, and sensing systems housed in the GI tract.

Intestinal lengthening via multiple in-continuity springs

BackgroundShort bowel syndrome is a debilitating condition with few effective treatments. Spring-mediated distraction enterogenesis can be used to lengthen intestine. The purpose of this study is to determine whether multiple springs in series can safely increase the total amount of lengthening. MethodsJuvenile mini-Yucatan pigs each received three nitinol springs placed within their jejunum. Plication was used to narrow the intestine around each spring to secure them. Compressed springs were used in the experimental group, while uncompressed springs were used in the control group. The intestine was examined 3 weeks later for lengthening and histologic changes. ResultsAll pigs tolerated diets postoperatively with continued weight gain, and no dilation or obstruction of the intestine was observed. Segments of intestine that contained compressed springs had a significant increase in length from 2.5 cm to 3.9 ± 0.2 cm per spring, compared to segments containing control springs that showed no change (p < 0.001). ConclusionsIntestinal plication can be safely used to secure multiple springs in series to achieve intestinal lengthening without compromising intestinal function. Using several springs at once allows for a greater amount of total lengthening. This is a promising model that has potential in the treatment of short bowel syndrome.

A New Automatically Fixating Stone Basket (2.5F) Prototype with a Nitinol Spring for Accurate Ureteroscopic Stone Size Measurement.

IntroductionIntraoperative assessment of stone size is crucial for the successful and safe extraction of stones. The first automatically fixating measuring stone basket prototype showed a mismatch between the steel spring and the nitinol basket; therefore, to improve this prototype, the steel spring was replaced with a nitinol spring and a modified scale was implemented on the basket handle for accurate intraoperative stone size measurement.MethodsThe proposed tipped basket was composed of nitinol. A standard handle with a spring-supported self-closing mechanism (2.5 F, Urotech®) was used, and a modified nonlinear millimeter scale was established on the handle. The grasping force was provided by the new nitinol spring mechanism in the handgrip. Various colors associated with the stone size were applied on the scale.ResultsThe material difference between the basket and the spring was eliminated. The measuring scale ranged from 2 mm (green) through 5 mm (yellow) to 8 mm (red), and the scale was nonlinear because of the nonlinear relationship between the diameter of the stone and the distance marked on the scale.ConclusionThe proposed automatically fixating stone basket with a nitinol spring has the potential to improve the safety and effectiveness of endourological stone retrieval. Further validation of this new scale and basket should follow.