Research On The PCM-compositebased Phase Change Microactuator Using Induction Heating

Microactuator is the important components of Micro-electromechanical Systems(MEMS),which has broad application prospect in micro chemical analysis,micro pharmacy control,space micro propulsion system,rabot and so on.Paraffin phase based microactuator,as one drive mode,can typically expands of up to 15%,and this expansion can produce both large driving force and large displacement.In addition,the paraffin phase based microactuator has the advantages of simple structure,convenient manufacture and low cost.Generally,a metal meandered resistive heater is adopted in paraffin-based microactuators.When the resistive heater was located outside the paraffin chamber,it takes too much time to conduct heat which means high power consumption and long actuation time.When the resistive heater was located inside the paraffin chamber,the heating speed and high heat conduction efficiency were improved.However,the electrical connection between the electrodes of power supply and electrical conductive paraffin wax inside the PCM chamber is required which means complex structure and difficult to fabricate.In addition,because paraffin wax has very low thermal conductivity and resistive heater produces uneven heating,the heating method is slow.This paper presents a new microactuator using induction heating.In this study,the heat was produced inside the phase change material(PCM)composite.So that,the heat transfer efficiency was improved,the heat loss was reduced and simplify the structure and fabrication process.In this paper,we introduce the design,fabrication,experiment step,result and discussion of this sampling device.In addition,a micro-fluidic chip based on the actuating principle was fabricated and tested.The main contents are as follows.In chapter one,the classification of traditional paraffin-based microactuators was made based on the heating method as well as the advantages and disadvantages of different kinds of microactuators were illustrated.In order to solve the weakness of traditional microactuator,the design of the PCM-composite-based microactuator with induction heating was proposed.In chapter two,with regard to the microactuator operating mechanism,this paper mainly expounds the theories of induction heating,composites characteristic,which can provide theoretical foundations for the design and performance testing of the microactuator.In chapter three,In order to optimize the structure and size parameters of the microactuator,the model was established by the finite element simulation software COMSOL,and simulation analysis was made on the magnetic strength and temperature of the composite.The influence of pivotal parameters such as winding number,wire diameter and size of composite material on the heating effect was studied.According to the result,we optimize the structure and dimension parameters of the micro-actuator.In chapter four,rely on MEMS technology,the fabrication process of microactuator was designed.With MEMS process,the sample was fabricated,and the experimental system was set up,which can test the important performance parameters of microactuator.Experiments show that about 140 ?m actuation height was realized in 5 second with an input power of 1.42 W at excitation frequency of 1 kHz.Since an induction heating method is adopted which means the microactuator has no superfluous wire.The microactuator has some advantages,such as ease of fabrication,small-sized,low cost,and eases of integration into Micro-Electro-Mechanical Systems(MEMS).In chapter five,an application of microactuator in microfluidics was studied.A normal closed microvalve was designed and fabricated,and the experimental system was set up,which can test the important performance parameters of microvalve.The experiments showed that the thermally actuated microvalve can close against a flow of 2.75 ?L/s within 8–10 s under a pressure of 10 kPa with an input power of 1.12 W.The microactuator has some advantages,such as simple control and high reliability.The microvalve is very suited for flow control in portable lab-on-a-chip systems where flow rate is large.