https://www.tpbin.com/Uploads/Subjects/643149a0-8194-4c67-bf05-73fae6f0d14f.pdf

Development of new metallic alloys for biomedical applications

This review gives a brief overview of microvalves, and focuses on the actuation mechanisms and their applications. One of the stumbling blocks for successful miniaturization and commercialization of fully integrated microfluidic systems was the development of reliable microvalves. Applications of the microvalves include flow regulation, on/off switching and sealing of liquids, gases or vacuums. Microvalves have been developed in the form of active or passive microvalves employing mechanical, non-mechanical and external systems. Even though great progress has been made during the last 20 years, there is plenty of room for further improving the performance of existing microvalves.

http://iopscience.iop.org/article/10.1088/0960-1317/16/5/R01/pdf

A review of microvalves

Martensitic transformation, shape memory effect and superelasticity of Ti-Nb binary alloys

Shape memory alloys (SMAs) with high transformation temperatures can enable simplifications and improvements in operating efficiency of many mechanical components designed to operate at tem...

High temperature shape memory alloys

The design of new low-cost Ti-alloys with high biocompatibility for implant applications, using ubiquitous alloying elements in order to establish the strategic method for suppressing utilization of rare metals, is a challenge To meet the demands of longer human life and implantation in younger patients, the development of novel metallic alloys for biomedical applications is aiming at providing structural materials with excellent chemical, mechanical and biological biocompatibility It is, therefore, likely that the next generation of structural materials for replacing hard human tissue would be of those Ti-alloys that do not contain any of the cytotoxic elements, elements suspected of causing neurological disorders or elements that have allergic effect Among the other mechanical properties, the low Young's modulus alloys have been given a special attention recently, in order to avoid the occurrence of stress shielding after implantation Therefore, many Ti-alloys were developed consisting of biocompatible elements such as Ti, Zr, Nb, Mo, and Ta, and showed excellent mechanical properties including low Young's modulus However, a recent attention was directed towards the development of low cost-alloys that have a minimum amount of the high melting point and high cost rare-earth elements such as Ta, Nb, Mo, and W This comes with substituting these metals with the common low cost, low melting point and biocompatible metals such as Fe, Mn, Sn, and Si, while keeping excellent mechanical properties without deterioration Therefore, the investigation of mechanical and biological biocompatibility of those low-cost Ti-alloys is highly recommended now lead towards commercial alloys with excellent biocompatibility for long-term implantation

Biocompatibility of Ti-alloys for long-term implantation.

Texture and shape memory behavior of Ti–22Nb–6Ta alloy

A microvalve with high operation temperature ranging up to 120 °C is presented, which is driven by a TiNiPd thin film microactuator. Fabrication is based on a hybrid integration concept. The main fabrication technologies are magnetron sputtering, photochemical micromachining, and thin film transfer. Infrared microscopy investigations of temperature profiles and force-deflection tests are performed to determine optimum operation conditions of the TiNiPd microactuator. Gas flow measurements demonstrate control of pressure differences up to 70 kPa. The high phase transformation temperatures allow a cooling time of the microactuator of 22 ms at room temperature resulting in a maximum operation frequency of the microvalve of 30 Hz.

A TiNiPd thin film microvalve for high temperature applications

The crystal structure of orthorhombic martensite in ternary TiNi-based compounds has been several times examined, although, in all cases, the structure was not completely solved as the positions of atoms in the unit cell remained unknown. In the present work, the X-ray patterns of TiNi-Cu and TiNi-Pd films were refined by the Rietveld method revealing important regularities in the location of Ti and Ni atoms. In particular, the (010) atomic planes in the orthorhombic martensite structure are always distorted and loose the planar centre of symmetry. This observation was confirmed by ab-initio calculations, where the atomic positions were varied in order to minimise the energy of electron bands.

Crystal structure of orthorhombic martensite in TiNi-Cu and TiNi-Pd intermetallics

Dynamic actuation properties of two types of high-speed microactuators utilizing Ti-Ni-based thin films were investigated. One type is a microactuator utilizing a Ti-Ni-Pd thin film which has high transformation temperatures. Cooling rate of a microactuator increases with increasing temperature difference between transformation and atmosphere temperatures, thus the increase in transformation temperature is effective to increase the actuation response. The other type is a microactuator using R-phase transformation of a Ti-Ni thin film which has a narrow transformation temperature hysteresis. The narrow transformation temperature hysteresis of the R-phase transformation is effective to increase the actuation response. Both types of actuators are promising for high response applications. The working frequency of the microactuators reached 100Hz in the two types of microactuators utilizing the martensitic transformation of the Ti-Ni-Pd thin film and the R-phase transformation of the Ti-Ni thin film.

K. Okutsu

Papers

Texture and shape memory behavior of Ti–22Nb–6Ta alloy

A TiNiPd thin film microvalve for high temperature applications

Crystal structure of orthorhombic martensite in TiNi-Cu and TiNi-Pd intermetallics

Characterization of High-Speed Microactuator Utilizing Shape Memory Alloy Thin Films