Currently, SMA alloy, which has practical value in industry, can be divided into a NiTi-based memory alloy, a Cu-based memory alloy and a Fe-based memory alloy according to the composition of the three categories, but the most promising medical development is only a nitinol-based memory alloy, a nitinol-based alloy in addition to the characteristics common to other shape memory alloys, but also has excellent biocompatibility, wear resistance and corrosion resistance.Although there are several systematic studies of the biocompatibility of NITI-based alloys, such as some studies in which NiTi-based alloys are introduced only on animals (mice ,rabbits,dogs )for biocompatibility experiments and in vitro cytotoxicity experiments, however, some studies show that subcutaneous implantation of niti alloys leads to a minimal reaction of biological tissues, it can be assumed that the biocompatibility of niti alloy wire is the same as that of stainless steel, and it has the possibility of implantation into deep tissues.Excellent properties make NiTi-based alloys widely used in the field of medicine.
Application of nitinol shape memory alloy in therapeutic equipment
From the current research results, it follows that the strength of the shape restoration of the components of the NiTi shape memory alloy is proportional to the power of its characteristic size 2 ,and the surface area increases after reducing the characteristic size and accelerating cooling. These characteristics make it widely used in the field of medical devices, mainly in the following aspects.
The use of nitinol shape memory alloy as the driving force of the tubular mirror can be achieved by remote control of various complex movements of the tubes of the human body ,with this tubular mirror, surgeons can perform microsurgical operations on blood vessels and so on.
Researchers have invented a drug-releasing device that can be placed in the human body to eliminate pain and problems caused by prolonged injection.A miniature valve on the device for the release of drugs is activated by elements made of an alloy with a memory of the shape of nitinol.The opening and closing of the miniature valve is controlled by heating or cooling the nitinol memory alloy element.
Tactile gloves made of nitinol shape memory alloy, developed by American scientists, can reflect the magnitude of the force of touch and contact ,avoiding the phenomenon when doctors often make mistakes when performing microsurgical operations using micromachines or robots, because they do not feel a little on their hands during the control process.
Its main principle is:the output signal of the sensor is converted into a certain size of the heating current, so that the temperature of the nitinol shape memory alloy element regulates the amount of force acting on the doctor’s hand.
Miniature surgical forceps made of nitinol shape memory alloy were invented by American researchers for the surgical treatment of brain tumors in the event of a stroke.
Capillaries made of nitinol shape memory alloy are very soft in various parts of the human body, which can be injected into a certain part of the human body and other procedures can be performed.This feature takes advantage of the superelasticity characteristics of the memory alloy and the low elastic modulus.
There is a certain correspondence between the EMG signals on a person’s limbs and the action they want to achieve. However, the way people with disabilities use this signal to control the movement of prostheses can solve this problem with the help of such prostheses made of a nitinol shape memory alloy.The basic principle is to convert the EMG signal into the heating current of the nitinol shape memory alloy, and then control the heating current to regulate the temperature of the nitinol shape memory alloy element to control its shape
The need for continuous administration of anticoagulants, neutralizers and other portable artificial kidney systems for medicines requires that the flow rate of the drug injection pump is extremely small and reliable, made of a NiTi shape memory alloy.This pump is not only simple and compact, easy to operate, but also very reliable.
Application of Nitinol memory alloy in clinical departments
The main areas of application of nitinol in dentistry are orthodontic wire, dental implants and locking rings.For example, the study of nail suturing for the treatment of cracks on teeth.
Currently, the use of the SMA mesh structure to support the biliary tract with a large spiral angle can provide unhindered access to the biliary tract in the treatment of biliary stenosis or surgical resection of obstruction, prolong the survival time of patients and improve the quality of life.
Vascular surgery is a common disease in medical practice for thin aneurysms, so long-term development can lead to rupture of blood vessels, causing severe bleeding.The role of nitinol shape memory alloy in vascular surgery mainly consists in:
Therefore, intravascular SMA stents made of nitinol shape memory alloys can be used instead of hemangiomas with aneurysm parts.
Shape memory alloys are mainly used in orthopedics for the manufacture of orthopedic rods for the spine,curium nail concentrators, internal fixators and artificial joints.
SMA snoring device and Japanese scientists have developed SMA bones that use the SMA shape memory effect and superelasticity.The SMA anti-snoring device is used to fix the patient’s tongue or small tongue, to prevent the patient from blocking the respiratory passage during sleep; The SMA hearing bone can effectively transmit vibration to the ear, the general characteristics of the SMA and SMA anti-snoring device are easy to install, soft power, stable.
The brain aneurysm clamp made of SMA demonstrates the advantages of ease of use, stable and reliable clamping force and easy control during surgical treatment of a brain aneurysm.In addition, SMA brain aneurysm clamp at low temperature, the clamping force of the cerebral artery is very small, at this time it is easy to determine the position of the brain aneurysm clamp and whether the blood vessels are properly clamped, mistakes can be avoided.
The use of SMA at low temperatures with a small modulus of elasticity, good plasticity and other characteristics of the SMA stent in the treatment of various esophageal and tracheal stenoses in the process, is easy to install, reliable, and in case of surgical failure is also very easy to remove.Using the SMA shape restoration force at high temperatures, which can also be used as an artificial heart power source, the principle is simple, the memory of the reduction of the SMA wire attached to the outer wall of the artificial ventricle, the SMA wire that is energized after heating, it will lead to a contraction of the ventricle and produce a pumping effect.
The SMA stent is a kind of medical instrument used to treat urethral obstruction caused by prostatic hyperplasia, which easily damages other tissues and is incomparable with other materials.