Investigation on Laser assisted actuation of shape memory alloy based micro-valve

Abstract

This research highly focuses towards development of a Shape Memory Alloy based micro valve and actuation using LASER. Numerous Micro valve designs have been reported with a variety of actuation mechanisms such as piezoelectric, silicon rubber, etc. [1] , but the use of these micro valves have been limited. Here LASER is used as actuation medium because of noncontact type and low power energy density source.The micro valve is designed and fabricated to control small amounts of fluid flow of the order of µL/sec. Single way trained NiTi Shape Memory Alloy is used in this micro valve. EDX test and DSC test has been performed to get details of properties of NiTi SMA. In the LASER actuation work, detailed parametric studies have been performed by actuating the one way trained SMA at various Laser fluence, actuation time and spot diameter of Laser .Scanning Electron Microscope test has been performed to check for ablation. A micro-valve array for fluid flow control on macroscopic level is described. The micro-valve array is based on innovative design such that flow rate across micro-valve array can be varied with number of micro-valve opened with each micro-valve is laser actuated and spring returned.The actuation of SMA using LASER shows that the maximum deflection obtained for optimum LASER fluence of 25.48mJ/cm² is 7.29 mm, The flow measurement was performed using an air meter at pressure difference ranging from 1KPa to 5KPa with minimum rate of flow 325 µL/sec. Index Terms-Micro valve, Shape memory alloy (SMA), LaserActuation, Characterization I INTRODUCTIONA Shape memory alloys (SMAs) exhibit peculiar thermomechanical, thermo-electrical and thermo-chemical behaviors under mechanical, thermal, electrical and chemical conditions. Among all shape memory materials, Nitinol (Ni-Ti) shape memory alloys (SMAs) with their superior thermo-mechanical and thermo-electrical characteristics have found many applications in different fields of engineering and science [1]. A number of MEMS valves have been demonstrated using thermal [2], electromagnetic [3], pneumatic [4,5] and thermopneumatic actuation [6].The potential for precise control of fluid flow on a small scale has motivated the development of micro valves and micro pumps using various technologies. Such devices are potentially important in applications that include biomedical dosing, biochemical reaction systems, micro fluidic mixing and regulation. Normally opened valve allow flow when not actuated and obstruct flow when powered. The antithesis is true for normally closed valves, staying closed when not powered. Since micro valves typically operate under high pressures and controlled flow rates are desired, a strong and robust actuator that can generate required displacements is required. SMAs are excellent candidates for satisfying these criteria, and their use in micro valves will be discussed in detail here.In this work, LASER assisted actuation of SMA based micro-valve is investigated designed, fabricated, and tested. Such devices exhibit a linear scalable valve fu...

Actuation Mechanism of Microvalves: A Review

“…Due to some special properties, many materials and creatures are used to actuate microvalves. Actuation mechanisms of phase change materials are discussed, including polymer (hydrogel [93][94][95][96], sol-gel [97]), paraffin [98][99][100][101][102][103], alloy (low melting point alloy [104][105][106] and shape memory alloy [107][108][109][110][111][112]). Compared with the traditional mechanically active microvalves, these phase change microvalves are relatively new and cheap.…”

“…For example, the hydrophilia of TiO 2 is utilized in the light actuated microvalves by irradiating ultraviolet (UV) [117][118][119]. The shape memory effect of shape memory alloy is an attractive actuation principle for the development of microvalves, since it allows simple and compact structures with high output forces, which are capable of controlling high pressure differences and flows [107][108][109][110][111][112]. Due to the high sensitivity of temperature, low melting point alloy phase changes with the change of temperature [104][105][106].…”

“…The array of this type microvalve for flow control on macroscopic level was also presented. The flow flux about the microvalve array could be varied with opened valve number [112]. The comparison between low melting point alloy and SMA is displayed in Table 8.…”

Fabrication of Pneumatic Microvalve for Tall Microchannel Using Inclined Lithography

“…Owing to their simplicity and compactness, pneumatic pressure-controlled microvalves are widely used. In the case of flow damming methods, examples include the deformation of the channel [ 8 , 9 ] and insertion of a partition [ 10 ]. Microvalves that utilize the deformation technique are quite common, primarily because of their simplicity and ease of fabrication.…”