A PMMA valveless micropump using electromagnetic actuation

We have fabricated and characterized a polymethylmethacrylate (PMMA) valveless micropump. The pump consists of two diffuser elements and a polydimethylsiloxane (PDMS) membrane with an integrated composite magnet made of NdFeB magnetic powder. A large-stroke membrane deflection (~200μm) is obtained using external actuation by an electromagnet. We present a detailed analysis of the magnetic actuation force and the flow rate of the micropump. Water is pumped at flow rates of up to 400µl/min and backpressures of up to 12mbar. We study the frequency-dependent flow rate and determine a resonance frequency of 12 and 200Hz for pumping of water and air, respectively. Our experiments show that the models for valveless micropumps of A. Olsson et al. (J Micromech Microeng 9:34, 1999) and L.S. Pan et al. (J Micromech Microeng 13:390, 2003) correctly predict the resonance frequency, although additional modeling of losses is necessar

VALVELESS PIEZOELECTRIC MICROPUMP FOR FUEL DELIVERY IN DIRECT METHANOL FUEL CELL (DMFC) DEVICES

Fuel cell has been considered as an important technology that can be used for various power applications. For portable electronic devices such as laptops, digital cameras, cell phones and etc., direct methanol fuel cell (DMFC) is a very promising candidate as power source. Compared with conventional batteries, DMFC can provide a higher power density with a long-lasting life and the recharging is almost instant. However, many issues related to the design, fabrication and operation of miniaturized DMFC power systems still remain unsolved. Fuel delivery is one of the key issues that will determine the performance of DMFC. To maintain a desired performance, an efficient fuel delivery system is required to provide adequate amount of fuel for consumption and remove carbon dioxide generated from fuel cell devices at the same time. In this dissertation, a novel fuel delivery system combined with miniaturized DMFC is presented. The core component of this system is a piezoelectric valveless micropump that can convert the reciprocating movement of a diaphragm activated by a piezoelectric actuator into pumping effect. Nozzle/diffuser elements are used to direct the flow from inlet to outlet. As for DMFC devices, the micropump system needs to meet some specific requirements: low energy consumption but sufficient fuel flow rate. Based on theoretical analysis and experimental study, the effect of piezoelectric materials properties, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole fuel cell system will be discussed. As a result, a viable design of micropump system for fuel delivery in DMFC devices can be achieved and some further improvements will be mentioned as well

HIGH PERFORMANCE PIEZOELECTRIC MATERIALS AND DEVICES FOR MULTILAYER LOW TEMPERATURE CO-FIRED CERAMIC BASED MICROFLUIDIC SYSTEMS

The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications

Design, simulation and validation of an equivalent circuit model for a valveless piezoelectric micropump

Proyecto de Graduación (Maestría en Ingeniería en Electrónica) Instituto Tecnológico de Costa Rica, Escuela de Electrónica, 2016.Equivalent electric circuit models are commonly used in microfluidics to represent the dynamic behavior of fluidic components in terms of their equivalent electric counterparts. FEM simulation tools are widely used for solving complicated problems, usually involving coupled physics. In this work a hybrid electric circuit model –HECM– and a complete FEM simulation are used to characterize a piezoelectric valveless micropump –PVM–. The model is considered hybrid because the parameters of the lumped elements are obtained using analytic solutions or FEM simulations depending of each case. Results of those two approaches – HECM and FEM simulations– are compared to experimental results obtained from the fabrication of a number of equal prototypes. The prototypes are fabricated using a technique called GAG –glass adhesive glass– which uses a combination of glass and adhesive layers to create a flow path. The HECM was 5 times faster in obtaining the required results and it was more accurate to describe the behavior of the PVM

Finite element modeling in the design and optimization of portable instrumentation

Finite element modeling method (FEM) is a powerful numerical analysis method that is widely used in various engineering and scientific domains. In this thesis, we have utilized FEM to study structural analysis, heat transfer, and fluid flow in the instrumentation design and optimization. In particular, we have designed and optimized a portable micro-dispenser for bio-medical applications and a portable enclosure device for industrial applications. In the micro-dispenser study, our proposed model is comprised of a permanent mainframe and a disposable main tank, which can hold a bulk volume of sample fluid as an off-chip reservoir. The height of the micro-dispenser and the diameter of the passive valve have been analytically designed upon the physical properties of the fluid sample. A Peltier thermoelectric device supported by a fuzzy logic controller is dedicated to controlling the temperature within the micro-dispenser. As an extension, we have also explored another piezoelectric-based actuator, which is further optimized by genetic algorithm and verified by FEM simulations. Furthermore, in the enclosure study, we have proposed a design and optimization methodology for the self-heating portable enclosures, which can warm up the inner space from -55°C for encasing the low-cost industrial-class electronic devices instead of expensive military-class ones to work reliably within their allowed operating temperature limit. By considering various factors (including hardness, thermal conductivity, cost, and lifetime), we have determined to mainly use polycarbonate as the manufacturing material of the enclosure. The placement of the thermal resistors is studied with the aid of FEM-based thermal modeling. In summary, despite the distinct specialties and diverse applications in this multi-disciplinary research, we have proposed our design methodologies based on FEM. The design efficacy has been not only demonstrated by the FEM simulations, but also validated by our experimental measurements of the corresponding prototypes fabricated with a 3D printer

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