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.

Simon Nitinol下腔静脉滤器置入术15例报告

肺栓塞(PE)是一种发病急、致死率很高的疾病,多因下肢深静脉血栓(DVT)栓子脱落所致.下腔静脉滤器可以有效预防PE的发生.我们对2001年1月～2003年3月经股静脉放置Simon Nitinol下腔静脉滤器(SNF)的15例患者进行追踪随访,对其效果及使用中的问题进行分析.

Platelet Adhesion onto Nitinol Surfaces Modified by Microwave Cold-plasma

The macromolecular structures on nitinol surfaces were prepared by ECR microwave cold-plasma of tetraglyme conditions. The surface chemistry was characterized by high resolution ESCA. The results showed that the modified nitinol surfaces were built up mainly of -CH2-CH2-O- linkages and were particularly effective in preventing platelet adhesion.

Dynamic design of a nonlinear energy sink with NiTiNOL-steel wire ropes based on nonlinear output frequency response functions

A novel vibration isolation device called the nonlinear energy sink(NES)with NiTiNOL-steel wire ropes(NiTi-ST)is applied to a whole-spacecraft system.The NiTi-ST is used to describe the damping of the NES,which is coupled with the modified Bouc-Wen model of hysteresis.The NES with NiTi-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET)to concentrate the energy locally on the nonlinear oscillator,and then dissipates it through damping in the NES with NiTi-ST.The generalized vibration transmissibility,obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the future.An optimization analysis of the impact of system responses is performed using different parameters of NES with NiTi-ST based on the transmissibility of NOFRFs.Finally,the effects of vibration suppression by varying the parameters of NiTi-ST are analyzed from the perspective of energy absorption.The results indicate that NES with NiTi-ST can reduce excessive vibration of the whole-spacecraft system,without changing its natural frequency.Moreover,the NES with NiTi-ST can be directly used in practical engineering applications.

Three-dimensional photoelasticity analysis of Nitinol Patellar Concentrator for treating patellar fractures

Objective: To analyze the biomechanical elements of Nitinol Patellar Concentrator (NT-PC) in heating commi nuted patellar fractures. Methods: The epoxy resin three dimensional photoelasticity pobal model was loaded with Nitinol Patellar Connector and frozen. After dividing layer, photographing and tracing, iterative method was used to calculate the stress value of every tuteed node. Rasults: Stress values of 1 262 nodes scattered in 12 layers were obtained The stress distribution indicated that an overall stress field was yield when the NT-PC fixated the patellar model, and there existed fixative stress in the facies articularis and distal pole of the patellar model. Conclusion: The NT-PC has evident therapeutic effect for the comminuted patellar fractures. The existing stress is helpful in maintaining anatomical reduction and enhancing fracture healing.

Synthesis and Characterization of PEG-like Structures on Nitinol Surface under ECR-cold-plasma

The synthesis and characterization of PEG-like macromolecular structures on Nit inol surface from tri (ethylene glycol) dimethyl-ether under ECR-cold-plasma conditions were discussed. It was demonstrated that based on high-resolution ES CA, ATR-FTIR and contact angle investigations, the deposited PEG-like layers a re composed mainly of -CH 2-CH 2-O- linkages. These structures have a relati vely low contact angle. Compared to the unmodified surfaces, the plasma-treated Nitinol surfaces are more hydrophilic. Plasma enhanced coatings of PEG-like la yers can prevent Ni ion from releasing, thereby improving the biocompatibility o f Nitinol.

Effect of Laser Cladding Processing Parameters on Nitinol’s Clad Dimensions, Microstructure, and Hardness

Nickel Titanium alloy (Nitinol) is characterized by its good mechanical properties, good damping properties in addition to its distinctive shape-memory effect and superelasticity effect besides its great bio-mechanical compatibility and corrosion resistance. These properties have empowered its applications, particularly within the bio-medical and aerospace industry. Despite these exceptional properties, the manufacturing of Nitinol by conventional methods is exceptionally troublesome and costly and consequently must be inspected. Therefore, additive manufacturing specifically laser-based ones were used recently. In this research, the effect of processing parameters of laser cladding/laser direct deposition on Nitinol’s Microstructure, Hardness and Clad Dimensions was evaluated. Systematic characterization of Nitinol samples was done utilizing Optical Microscopy and Vickers hardness tester. Samples of Nitinol were synthesized with different processing parameters using laser cladding and its properties were investigated and compared to one another to get the optimum processing parameters to synthesize a near net shape, fully dense Nitinol component with reliable properties. The results showed that there’s a processing parameter window at which the alloy possesses its best mechanical and functional properties which were of Laser power of value 1.25 Kw, Scan speed of 1.5 m/min and powder deposition rate of 1.5/1.5 RPM, these conditions resulted in the formation of martensite phase which is responsible for its functional properties with 40% volume fraction and a hardness value of 598 HV.

ANALYSIS OF NICKEL CONTENT AFTER IMPLANTING NITINOL IN DOGS

The content of nickel of nitinol alloy isabout 50%, it is higher than that of 316 L stainless steel for surgical implantation, and lower than that of nickel based alloy for prosthetic dentistry. Nitinol alloy is implanted to the dog’s body, the effect of nickel in nitinol to the animal’s body is explored by the analyzing the trace element of nickel in the dog’s hair before and after implantation. Experimental results show that after 2 years implantation of nitinol alloy, the nickel content in the hair is not markedly increased. By measuring the weight, height and length of the animal periodically, and contrasting with normal data, no impairment of growth of the animal is observed. The ability of the animal to distinguish men and objects is also normal. The weighing test of the alloy sample taken out after 2 years implantation, shows that its anti-corrosion effect belongs to the very strong grade. It shows that during the long period of nitinol implantation into the animal’s body, there is no evidence that the free nickel or nickel compound present in tissue is harmful to the animal.

Evaluation of the Surface of Nitinol after MR Polishing Process

Nitinol is used in various industries, especially for biomaterials. Generally, the surface integrity of sub-micron level and non-surface flaw is required in nitinol for biomaterial. However, surface flaws, such as scratches, pits, and residual stress, can occur on the polished surface, and it is difficult to remove these surface flaws. The corrosion is accelerated continuously and causes bad influence in the body. Therefore, in this study, conventional polishing and MR polishing were used to minimize the corrosion and residual stress when the nitinol is used as biomaterial. X-ray diffraction and Tafel extrapolation were used to investigate the residual stress and the corrosion, and the strain hardening was investigated by nanoindentation. Surface integrities were also evaluated by SEM image and surface roughness results. As a result, the increased residual stress in conventional polishing was decreased by MR polishing. The result of corrosion test was improved from ?301 mV to ?280 mV. The residual stress was improved from ?38.18 MPa to ?31.17 MPa. Finally, it is certified that MR polishing can be used to minimize surface flaws and to improve the corrosion properties.

Combined application of Robicsek procedure and thermoreactive nitinol clips for treating a patient with sternal dehiscence

Postopereative sternal dehiscence is one of the most important complications of median sternotomy which may cause pulmonary dysfunction and mediastinitis. We are reporting a patient with sternal dehiscence after coronary artery bypass surgery that underwent application of thermoreactive nitinol clips in addition to Robicsek procedure. Using thermoreactive nitinol clips method together with Robicsek procedure may be a valuable technique for preventing recurrent sternal dehiscence for patients who are candidates of noninfective recurrent sternal dehiscence.

Nitinol Stenting in Post-Traumatic Pseudo-Aneurysm of Internal Carotid Artery

Background: A pseudoaneurysm of the internal carotid artery (ICA) at its cervicl part, is a rare and often lethal com-plication after cervical trauma. The treatment of choice is anticoagulation. Patients with a contraindication for anticoagulation or those who do not improve with standard treatment, warrant either a surgical repair or stent placement.Stent placement posses both short and long term risks such as immediate ischemic events, in-stent stenosis and stent breakage, thus the choice of stent type is critical. Advances in stent technology have made cervical stent placement a viable option. We report our experience with the LEO + (Balt Extrusion, Montmorency, France) nitinol flexible self expanding stent for post-traumatic ICA aneurysms. Methods: 5 patients suffering a post-traumatic cervical ICA pseudo-aneurysms refractory to standard treatment were treated with nitinol braided flexible self expanding stent. This stent has a shape memory and superelasticity virtues making it suitable. Diagnosis was made with CT angiography and confirmed by catheter angiography. All procedures were preformed under local anesthesia. Time between trauma and treatment ranged six days to over five years. Follow-up was performed by CT angiography or conventional angiography. Results: Five patients, having eight aneurysms were treated using 12 stents. In all cases, appropriate stent placement was achieved. No immediate or late complications, as well as no neurological sequele reported at 6 months. Radiological follow-up exams demonstrated complete pseudoaneurysm closure. Conclusion: Stent placement can be a safe and definitive treatment option for patients to conventional medical treatment.

Self-Expanding Nitinol Stent for Treatment of Tracheal Stenosis Caused by Pulmonary Hypertension:1 case report

A 38 year-old man was admitted because of half a year of recurrent bouts of eough and shortness of breath and 20 days of hemoptysis. He had been apparently healthy until the illness. In the recent 6 months, the dyspnea and fatigue gradually onset and became more severe, the hemoptysis being 100-200 mL per day. Spells of chest pain are associated with coughing. Despite accepting antibiotic and antispasmodic therapy in a hospital, there was no obvious improvement and he was transferred to our hospital. Physical examination on admission: He was in acute distress and anemic face With P 110/min., R 30/min., T36. 8oC and Bp 100/60 mmHg. There were Wheezes, medium and fine

Three dimensional finite element analysis of anatomic distal radius Nitinol memory connector treating distal radius fracture

Objective: To study the memory biomechanical character of anatomic distal radius Nitinol memory connector (DRMC) in treating distal radius fracture. Methods: Establishing three dimensional model and finite element analysis, we calculated the stress in and around the fracture faces when distal radius fracture was fixated with DRMC. Results: Axial holding stress produced by holding part of DRMC on distal radius was 14.66 MPa. The maximum stress of holding part was 40-70 MPa, the minimum stress was 3-7 MPa,and the stress of compression part was 20-40 MPa. Conclusion: The distribution of stress produced by DRMC around the fracture line is reasonable, and axial holding stress can help stabilize fracture during earlier period. The existence of longitudal compression and memory effect can transfer fixated disused section into developed section and enhance fracture healing.

Effect of temperature on nitinol electropolishing

Electropolishing has been used in TiNi alloy in several fields for its special characteristics, but its essential details and electropolishing mechanism have not been reported yet as a demand from business competition, which, to a great degree, restricts the application and extension of the electropolishing technology. In this paper, effect of temperature on nitinol electropolishing is explored. Studies on the effect of the temperature on the electropolishing process show that the higher the temperature is, the bigger the electropolishing rate is, following a near Gauss law. The relationship between the temperature and surface roughness follows near parabolic law, the relationship between the temperature and surface reflectivity follows near Sigmoidal law.

Advancing Nitinol: From heat treatment to surface functionalization for nickel-titanium (NiTi) instruments in endodontics

Nickel-titanium(NiTi)alloy has been extensively researched in endodontics,particularly in cleaning and shaping the root canal system.Research advances have primarily focused on the design,shape,and geometry of the NiTi files as well as metallurgy and mechanical properties.So far,extensive investigations have been made surrounding surface and thermomechanical treatments,however,limited work has been done in the realm of surface functionalization to augment its performance in endodontics.This review summarizes the unique characteristics,current use,and latest developments in thermomechanically treated NiTi endodontic files.It discusses recent improvements in nano-engineering and the possibility of customizing the NiTi file surface for added functionalization.Whilst clinical translation of this technology has yet to be fully realized,future research direction will lie in the use of nanotechnology.

Nitinol 60形状记忆合金高温变形特性研究

采用Gleeble-3500热模拟试验机对轧态Nitinol 60形状记忆合金进行等温恒应变速率拉伸试验,基于动态材料模型的加工图技术,研究了该合金在650~850℃和0.01~1 s^(-1)范围内的高温变形特性,并优化了其适宜的高温变形参数范围。结果表明,加工图中失稳区位于低温、高应变速率区,范围为650~776℃、0.075~1 s^(-1),对应的失稳现象为局部塑性流动。加工图中有2个η峰值区,范围分别为690~750℃、0.01~0.026 4 s^(-1)和750~838℃、0.01~0.050 5 s^(-1),η最大值分别达到了0.36和0.38,对应的变形机制均为动态再结晶,这2个区域为Nitinol 60合金适宜的热拉伸变形工艺参数范围。

New nitinol endovascular stent-graft system for abdominal aortic aneurysm with finite element analysis and experimental verification

Abdominal aortic aneurysm(AAA) is one of the most common and catastrophic manifestations of the acute aortic syndrome that can be treated with endovascular aneurysm repair(EVAR) which requires a specially designed stent-graft system.In this work, a self-expanding nickel–titanium(nitinol) stent-graft system is aiming at AAA using finite element analysis(FEA) methods to analyze both fatigue behaviors and radial forces.Based on the systematic analysis of the parametric variations, a final stent-graft system was developed by the selection and arrangement of the individual stent components, targeting an optimal performance for the treatment of AAA.Experimental tests, animal tests and clinical trials were carried out to confirm the results.Both animal trials and clinical trials showed comparable curative effects with Medtronic Endurant stent-graft(SG) systems.

镍钛泡沫合金对成骨细胞生物活性的影响

目的观察镍钛泡沫合金(PNT)在体外实验对细胞的生物安全性。方法选择PNT和镍钛致密合金(NiTi)材料(中南大学材料科学工程学院提供),以及纯钛(Ti)(宁波慈北医疗器械有限公司,中国);MC3T3-E1来源于中国科学院典型培养物保藏委员会细胞库。用PNT、NiTi、Ti 3种合金的浸提液,培养小鼠前成骨细胞MC3T3-E1。用CCK-8法检测细胞的增殖活性,碱性磷酸酶法测定细胞的分化能力,流式细胞术检测细胞早期凋亡情况。结果PNT组细胞增殖能力在第1天、第3天、第7天均明显小于NiTi组(P<0.001)和Ti组(P<0.001)。PNT组细胞分化能力在第1天、第3天、第7天均明显小于NiTi组(P<0.001)和Ti组(P<0.001)。PNT组细胞的凋亡细胞百分比在第1天、第3天、第7天均明显高于NiTi组细胞(P=0.001)和Ti组细胞(P<0.001)。结论PNT对细胞的增殖和分化的影响明显大于NiTi组和Ti组,更明显地抑制了细胞的增殖与分化能力,更容易导致细胞早期凋亡。

Fabrication of Intracranial Vascular Nitinol Alloy Stents with Improved Mechanical Property and Endothelialization Function

Intracranial vascular stenting has been widely used for ischemic stroke.However,there are complication risks with stent implantation,such as poor wall apposition,stent migration,thromboembolism and stent restenosis,due to the mismatched radial force and conformability of the stents."Therefore,a novel intracranial vascular nitinol stent was fabricated in order to improve mechanical property and endothelialization function.The bending moment of the stents was calculated to be 0.346 N mm,which shows improved conformability.The radial force of the stents evaluated by the flat plate test was0.0112 N/mm,within the range of the commercially available stent force(0.0065-0.0116 N/mm).Furthermore,the TyrIle-Gly-Ser-Arg(YIGSR)peptide derived from laminin was grafted onto the stent surfaces to promote endothelialization on vascular stents evaluated by the proliferation,adhesion and migration of human umbilical vein endothelial cells in vitro.The nitinol stents with improved mechanical property and endothelialization function are expected to reduce the recurrence risk of ischemic stroke after implantation.