Nitinol wire

The Concentric Retriever (Concentric Medical Inc., Mountain View, CA), a flexible, nitinol wire with helical tapering coil loops (X5 and X6) that is used in conjunction with a balloon guide catheter (8 or 9 French) and a microcatheter, is the only device currently approved by the FDA for the endovascular treatment of stroke patients (Fig. 4.3). The second-generation devices (L5 and L6) differ from the X devices by the inclusion of a system of arcading filaments attached to a nontapering... 

Fig. 2. The Thermobile energy conversion device using two wheels and a strand of Nitinol wire loop Converting directly the thermal into mechanical energy (Wang, US Patent 4,275,561).

The characteristic feature of all Amplatzer devices is the nitinol wire mesh. There are two possible methods of implantation. Either the device is placed entirely into the appendage or the distal disc is expanded in the neck and the proximal disc in the left atrium. The risk of residual shunting around the device is increased when it is totally inserted into the LAA with no part protruding into the atrium. The Amplatzer occluder series holds the widest spectrum of device sizes (4 to 40 mm), The device is attached to a delivery cable and can simply be opened or recollapsed into the delivery catheter. Release is by unscrewing the device after first testing stability with simple traction. 

The memory metal, nitinol, is an alloy of nickel and titanium. It is called a memory metal because after being deformed, a piece of nitinol wire will return to its original shape. (See Qhem Matters, October 1993, pp. 4-7.) The structure of nitinol consists of a simple cubic array of Ni atoms and an inner penetrating simple cubic array of Ti atoms. In the extended lattice, a Ti atom is found at the center of a cube of Ni atoms the reverse is also true. 

Inferring Twisted nitinol-wire eyeglass frames unbend at room temperature. Is the transition temperature of the frames above or below room temperature ... 

Applying Design a simple lever that could be raised and lowered smoothly using nitinol wires. 

Inferring Twisted nitinol-wire eyeglass frames 2. Applying Design a simple lever that could be unbend spontaneously at room temperature. raised and lowered smoothly using nitinol... 

Problem In 1965 some scientists produced a very special nickel-titanium alloy which can remember its programmed form. They called this kind of alloy memory metal and the special compound Nitinol , because it was discovered in the Nickel-Titanium Naval Ordonnance Laboratory. The memory metals are often used in engines, motors and other pieces of equipment, for which it is important to have a certain form at a certain temperature, e.g. for closing a valve. The conversion temperature of the Nitinol composition NqTq is approximately 50°C. Samples of such memory metals, like nitinol wires, can be obtained from Educational Innovations (teachersource.com). 

Tip A nitinol wire can be reprogrammed to different shapes the new wire form has to be stabilized between two steel plates and heated red hot with a burner for several minutes. If an oven is available, the steel plates with the fixed wires can also be heated for 10 min at approximately 500°C. This new form always reemerges whenever the wire is reshaped at room temperature and then heated until the transformation temperature is exceeded. 

The MERCI Retriever (Concentric Medical, Inc., Mountain View, CA) is a flexible nitinol wire with coil... 

Nitinol has many medical applications, including hooks used by orthopedic surgeons to attach ligaments and tendons to bone and "baskets" to catch blood clots. In the latter case a length of Nitinol wire is shaped into a tiny basket and this shape is set at a high temperature. The... 

Schematic representation of the structure of the Amplatzer Septal Occluder device, showing the two disks with the waist constructed of nitinol wire. ... 

Das-Angel Wings /Guardian Angel Nitinol wire with knitted polyester Secundum ASD <20 mm Self-centering device Stent-like... 

Manufacturers of nitinol products are known to electropolish the surface of the nitinol wire to produce an oxidized surface layer that contains only titanium and oxygen. This reduces the potential for nickel allergy and toxicity problems. The alloy MP35N used in the CS/SF device is a quaternary of cobalt, nickel, chromium, and molybdenum, and is known to have high strength and corrosion resistance. Additionally, this metal has been found to be biocompatible and MR compatible. These are all desirable properties for an implantable device, but its nickel content should be noted and considered when dealing with patients who are allergic to nickel. 

The fabric used in the GHSO is an ePTFE membrane which is bonded to the nitinol wire used in the device. Membranes made from ePTFE are typically smooth, have low porosity (especially when compared to woven or knitted structures) and are biocompatible. Due to the chemical nature of ePTFE, tissue growth does not occur on the membrane. 

Recently, the Maitland group has returned to a thermosetting polyurethane system, developed in-house [48], and combined the technology with superelastic Nitinol wires with electro-resistive heating [49, 50]. In the most recent embodiment, the SMP is cast around a Nitinol wire in its predetermined coiled shape (Fig. 4). The... 

The Ultraflex nitinol stent comes in both covered and uncovered versions (Fig. 3.4). It has a significantly lower radial expansile force than the other stents but the covered version is much more flexible than any of the other covered stents and may therefore be placed across acutely angled stenoses (Repici et al. 2000). The stent is available with a 23-mm mid diameter and a 28-mm funnel-shaped proximal end and is mounted on a 16-F delivery catheter. The stent consists of a nitinol wire mesh with a polyurethane external membrane which leaves both stent ends bare for 1.5 cm for better fixation. 

Fig. 2.2. Polymeric composite with embedded Nitinol wires displaying large bending deformation when activated a beam configuration before activation, b deflected beam after SMA activation...

Strain gauge Wires providing NITINOL wires Swing path... 

NITINOL wire Strain gauges affixed Beam Plexiglass posts... 

The first controller implemented on the structure was the direct MRAC shown in Fig. 4.5. This gives a basis for comparison between direct and indirect control. Figure 4.6a shows a plot of the open-loop response envelope, the desired response envelope, and the closed-loop response achieved. As can be seen, the closed-loop system adapts to the reference-model response until the deadband is reached (after approximately 11s), at which point adaptation is turned off. The deadband is inherent to the Nitinol wire actuators. 

Figure 20.8 Image of an Amplatz canine duct occluder (ACDO), which shows the fine nitinol wire mesh used as an embolic device to completely occlude patent ductus arteriosus (PDA) in dogs.

A device with shape memory technology and osmotic delivery has been developed to treat patients who suffer from a painful bladder condition known as interstitial cystitis/bladder pain syndrome (TARIS Biomedical Inc., MA). The device was made of a dual-lumen silicone catheter with one lumen loaded with lidocaine, which continuously leached out as contacted with urine. The second lumen of the device contains superelastic nitinol wire in a predefined form, which provides the... 

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