Material Design, Processing, and Engineering Requirements for Magnetic Shape Memory Devices

For magnetic shape memory (MSM) alloys, a magnetic field stimulates a shape change. We use the shape change to build devices such as micro-actuators, sensors, and microfluidic pumps. Currently, (as a novel technology,) devices suffer from some material and magnetic driver shortcomings. Here we address the issues related to operating temperature, repeatability, failure, and magnetic driver development. To increase the operating temperature of the MSM material, we alloyed Fe and Cu to Ni-Mn-Ga. We showed that the element-specific contribution to the valence electron density as parameter systematically determines the effect of each element on the variation of the martensite transformation temperature of the 10M phase. To stabilize the material, we developed a micro-shotpeening process that adds stresses to the material surface, thereby inducing a fine twin microstructure. The treatment allowed nearly full magnetic-field-induced strain, and extended fatigue life of the material from only one thousand cycles in the electropolished state to more than one million cycles in the peened state. We measured the effect of the peening process on material actuation when in MSM pump configuration. In the polished state, the deformation was stochastic, with a sharp-featured, faceted shrinkage. In the treated state, the deformation was smooth and repeatably swept along the surface akin to a wave. To actuate the MSM micropump without electromotor, we developed a linear electromagnetic actuation device and evaluated its effectiveness in the switching mechanism of the material. By compressing the magnetic field between opposing coils, we generated a strong magnetic field, which caused a localized region to switch at selected poles. In the next iteration of the drive, we inserted the MSM sample between two linear pole arrangements of high pitch density to approximate a moving vertical field. The incremental stepping of the vertical field between poles caused translation of the switched region. The results of this dissertation demonstrate the suitability of MSM alloys for high-precision, persistent, and reliable actuators such as micropumps

Modeling and simulation of a wirelessly-powered thermopneumatic micropump for drug delivery applications

This paper presents modeling and finite element analysis of a thermopneumatic micropump with a novel design that does not affect the temperature of the working fluid. The micropump is operated by activating a passive wireless heater using wireless power transfer when the magnetic field is tuned to match the resonant frequency of the heater. The heater is responsible for heating an air-heating chamber that is connected to a loading reservoir through a microdiffuser element. The solution inside the reservoir is pumped through a microchannel that ends with an outlet hole. The thermal and pumping performances of the micropump are analyzed using finite element method over a low range of Reynold’s number ⩽ 10 that is suitable for various biomedical applications. The results demonstrate promising performance with a maximum flow rate of ∼2.86 μL/min at a chamber temperature of 42.5 ºC, and a maximum pumping pressure of 406.5 Pa. The results show that the developed device can be potentially implemented in various biomedical areas, such as implantable drug delivery applications

Micro Electromechanical Systems (MEMS) Based Microfluidic Devices for Biomedical Applications

Micro Electromechanical Systems (MEMS) based microfluidic devices have gained popularity in biomedicine field over the last few years. In this paper, a comprehensive overview of microfluidic devices such as micropumps and microneedles has been presented for biomedical applications. The aim of this paper is to present the major features and issues related to micropumps and microneedles, e.g., working principles, actuation methods, fabrication techniques, construction, performance parameters, failure analysis, testing, safety issues, applications, commercialization issues and future prospects. Based on the actuation mechanisms, the micropumps are classified into two main types, i.e., mechanical and non-mechanical micropumps. Microneedles can be categorized according to their structure, fabrication process, material, overall shape, tip shape, size, array density and application. The presented literature review on micropumps and microneedles will provide comprehensive information for researchers working on design and development of microfluidic devices for biomedical applications

Master of Science

thesisThis thesis presents the design and optimization of a biologically inspired wet shape memory alloy (SMA) actuated pump that can provide thermal energy via fluidic convection to actuate external wet SMA subsystems. Furthermore, the pump draws from its own fluidic output to assist in the actuation of its own internal SMA actuators. A thorough analysis of the previous wet SMA robotic heart is conducted by searching for opportunities for improvement. Methods of improving the pump's output-to-input ratio included modifying the pumping chambers, actuation cycle timing, implementing electrical actuation, and continuously adding heat to the system. Dynamic modeling was performed to provide a baseline indicator of what was to be expected during actual implementation and testing. The effects of changing various parameters were explored to determine optimal configurations. Key parameters affecting performance include mechanical advantage, actuator length, flow durations, and water temperature. Implemented design changes and testing confirmed the modeling results. Continuous heating of the hot water within the pressurized accumulator greatly enhanced the pump's performance. Using only fluidic induced actuation, the output-to-input ratio peaked at 1.4. The pump reached an output-to-input ratio of 2.1 with the aid of electrical actuation. This is the first successful implementation of a self-sustaining thermofluidically powered SMA pump. Furthermore, unlike other SMA micropumps that typically output 1 mL/min or less, this pump is capable of a macroscale net output of 66 mL/min. While the pump's output exceeds the required input, the power efficiency and power density of the pump do not compare to that of the human heart due to the amount of power required to keep the hot water continuously heated. Viable options for improving efficiency and power density include minimizing pump mass, optimizing pumping chamber design, and reducing the amount of heat necessary to keep the hot water at an elevated temperature

Modeling, simulation, and fabrication of a PZT valveless micropump

A micropump is one of the most important elements in a micro-total analysis system used for rapid chemical and biological analysis. To date, different kinds of micropumps have been designed, fabricated, tested, and implemented. Among them, a PZT valveless micropump is receiving increasing attentions due to its unique advantages over a conventional check-type micropump. A valveless micropump is short of fatigue and wear of movable part. Without movable parts in the device may avoid high-pressure drop across the valves. It is expected that a valveless micropump has higher reliability and a longer lifetime. In particular, a valveless micropump is unique for delivering solutions with particles. Diffuser and nozzle elements direction dependent flow characteristics are quantitatively studied and summarized. From diffuser and nozzle flow characteristics, the working principle of the valveless micropump is presented. Based on fluidic mechanics and solid mechanics, a dynamic model for the PZT actuated valveless micropump is developed. The flow rate and backpressure are the most important performances for the valveless micropump. Considering nonlinear pressure loss in the nozzle, a numerical simulation method is chosen to study the valveless micropump performance. The simulation is studied in low frequency domain. The effects of several key parameters on the micropump performances are discussed. These key parameters include passive plate dimensions, PZT dimensions, and nozzle dimensions. An optimized micropump design is presented following the numerical simulation. The optimized dimensions for the micropump include 500 microns for the membrane thickness, 25 mm for the membrane radius, 80 microns for the nozzle neck and 400 microns for the nozzle length. The fabrication process for the valveless micropump is also implemented. Two major problems associated with the fabrication process were experimentally investigated. The fabrication process is revised accordingly

Frequency-controlled wireless passive microfluidic devices

Microfluidics is a promising technology that is increasingly attracting the attention of researchers due to its high efficiency and low-cost features. Micropumps, micromixers, and microvalves have been widely applied in various biomedical applications due to their compact size and precise dosage controllability. Nevertheless, despite the vast amount of research reported in this research area, the ability to implement these devices in portable and implantable applications is still limited. To date, such devices are constricted to the use of wires, or on-board power supplies, such as batteries. This thesis presents novel techniques that allow wireless control of passive microfluidic devices using an external radiofrequency magnetic field utilizing thermopneumatic principle. Three microfluidic devices are designed and developed to perform within the range of implantable drug-delivery devices. To demonstrate the wireless control of microfluidic devices, a wireless implantable thermopneumatic micropump is presented. Thermopneumatic pumping with a maximum flow rate of 2.86 μL/min is realized using a planar wirelessly-controlled passive inductor-capacitor heater. Then, this principle was extended in order to demonstrate the selective wireless control of multiple passive heaters. A passive wirelessly-controlled thermopneumatic zigzag micromixer is developed as a mean of a multiple drug delivery device. A maximum mixing efficiency of 96.1% is achieved by selectively activating two passive wireless planar inductor-capacitor heaters that have different resonant frequency values. To eliminate the heat associated with aforementioned wireless devices, a wireless piezoelectric normally-closed microvalve for drug delivery applications is developed. A piezoelectric diaphragm is operated wirelessly using the wireless power that is transferred from an external magnetic field. Valving is achieved with a percentage error as low as 3.11% in a 3 days long-term functionality test. The developed devices present a promising implementation of the reported wireless actuation principles in various portable and implantable biomedical applications, such as drug delivery, analytical assays, and cell lysis devices

Bucky gel actuator for morphing applications

Since the demonstration of Bucky Gel Actuator (BGA) in 2005, a great deal of effort has been exerted to develop novel applications for electro-active morphing materials. Three-layered bimorph nanocomposite has become an excellent candidate for morphing applications since it can be easily fabricated, operated in air, and driven with few volts. There has been limited published study on the mechanical properties of BGA. In this study, the effect of three parameters: layer thickness, carbon nanotube type, and weight fraction of components, on the mechanical properties was investigated. Samples were characterized via nano-indentation and DMA. It was found that BGA composed of 22 wt% single-walled carbon nanotubes and 45 wt% ionic liquid exhibited the highest hardness, adhesion, elastic and storage moduli. Most of BGA potential applications would require control over one BGA output: displacement. In this study, various sets of experiments were designed to investigate the effect of several parameters on the maximum lateral displacement of BGA. Two input parameters: voltage and frequency, and three material/design parameters: carbon nanotube type, thickness, and weight fraction of constituents, were selected. A new thickness ratio term was also introduced to study the role of individual layers on BGA displacement. In addition, an important factor in the design of BGA-based devices, lifetime, was investigated. Finally, possible degradation of BGA was studied by repeating displacement measurements after several weeks of being stored. Based on displacement studies, a new model was established utilizing nonlinear regression to predict BGA maximum displacement based on the effect of these parameters. This model was verified by comparing its predictions with other reported results in the literature. The model displayed a very good fit with various reported cases of BGA samples made with different types of CNT and ionic liquid. Microfluidics is a promising field of application for BGA. A brief literature review on the electroactive mechanisms used in microfluidics is presented. Preliminary force studies proved that BGA has the capability to be employed as a microvalve. A flow regulator utilizing a BGA microvalve was designed and fabricated. Flow rate measurements showed the capability of BGA-valve in manipulating the flow rate in different ranges

Optimal Design and Operation for a No-Moving-Parts-Valve (NMPV) Micro-Pump with a Diffuser Width of 500 μm

A no-moving-parts-valve (NMPV) with a diffuser width of D = 500 microns was investigated in this study by numerical simulations at Reynolds numbers, ReD, ranging from 20 to 75, and expansion valve angles ranging from 30° < θ1 < 57° and 110° < θ2 < 120°. The Dp,i value, 1.02 < Dp,i < 1.14, is larger within the proposed range of the expansion valve angles. A flow channel structure with a depth of 500 micron is manufactured using yellow light lithography in this study. From prior analyses and experiments, it is found that piezoelectric films work better at a buzz driving frequency of f < 30Hz and the best operating frequency is at a driving frequency of f = 10Hz because it produces the largest net flow. In addition, the expansion angles θ1 = 30° and θ2 = 120° are the best expansion angles because they produce the largest net flow. These related results are very helpful for the actual design of no-moving-parts-valve micro-pump

COMSOL Simulation of MEMS Piezoelectrically Actuated Micropump

In this poster, the design and COMSOL simulation of a piezoelectric micropump with dome-shaped diaphragms and diffuser-nozzle fluid rectifiers is reported. The micropump uses piezoelectric ZnO film (less than 10μm thick) to actuate the vibration of a parylene dome diaphragm, so that microfluid can be pumped in and out of the chamber. The device is to be fabricated on silicon substrate with an IC-compatible process. Piezoelectric ZnO film is sputter-deposited on a parylene dome diaphragm with its C-axis oriented perpendicular to the dome surface. The micropump utilizes two symmetric dome diaphragms for improved pumping rate. Diffuser-nozzle elements are integrated with piezoelectrically actuated dome diaphragms to form a multi-chip micropump. Due to the MEMS (Microelectromechanical Systems) technology used, the proposed micropump has very small size (10×10×1.6mm3) and consumes extremely low power. It also shows negligible leakage up to 700 Pa static differential pressure. The function of the proposed micropump is verified with COMSOL simulation