Surface acoustic wave based wireless mems actuators
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Surface acoustic wave based wireless mems actuators

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Describes about the principle and working of a general SAW sensor, and also describes about the SAW based wireless microactuator for the biomedical applications

Describes about the principle and working of a general SAW sensor, and also describes about the SAW based wireless microactuator for the biomedical applications

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    Surface acoustic wave based wireless mems actuators Surface acoustic wave based wireless mems actuators Presentation Transcript

    • Surface Acoustic Wave based Wireless MEMS Actuators for Biomedical Applications by Sukanta Bhattacharyya Registration # 1651210007
    • Agenda Introduction Surface Acoustic Wave (SAW) sensor Device Design SAW sensor operation SAW based wireless microactuator Material selection Fabrication process flow Operation Advantage and disadvantage Applications Conclusion References Surface Acoustic Wave based wireless MEMS actuator 2 Thursday, November 07, 2013
    • Introduction Micro-Electro-Mechanical Systems (MEMS) technology has made it possible to fabricate small size, and high performance implantable devices to meet critical medical and biological needs such as in–vivo drug delivery, Lab–on–a–Chip (LoC), surface acoustic wave devices, polymerase chain reaction (PCR) etc. Actuators are one of the important components in BioMEMS, especially for fluid manipulation Surface Acoustic Wave (SAW) devices are used to develop micromachines such as ultrasonic micromotors and fluid transfer methodologies such as flexural micropumps Surface Acoustic Wave based wireless MEMS actuator 3 Thursday, November 07, 2013
    • Surface Acoustic Wave (SAW) sensor Surface acoustic wave sensor is a class of MEMS device which is based on the modulation of surface acoustic waves to sense a physical phenomenon. Surface Acoustic Wave based wireless MEMS actuator 4 Thursday, November 07, 2013
    • Device Design The basic surface acoustic wave device consists of a piezoelectric substrate, an input interdigitated transducer (IDT) on one side of the surface of the substrate, and a second, output interdigitated transducer on the other side of the substrate. The space between the IDTs, across which the surface acoustic wave will propagate, is known as the delayline. Surface Acoustic Wave based wireless MEMS actuator 5 Thursday, November 07, 2013
    • Surface Acoustic Wave (SAW) sensor Fig 1: Surface Acoustic Wave sensor Surface Acoustic Wave based wireless MEMS actuator 6 Thursday, November 07, 2013
    • SAW sensor operation SAW technology is based on the piezoelectric effect. Fig 2: Surface Acoustic Wave sensor operation Surface Acoustic Wave based wireless MEMS actuator 7 Thursday, November 07, 2013
    • SAW sensor operation contd.. Input Interdigitated Transducer (IDT) transduces electric signal to acoustic waves when the two ends of IDT are subjected to sinusoidal signal. Alternating polarity(+-) develops between the fingers of IDT resulting in generation of electric field. Direction of electric field changes alternatively between the adjacent set of fingers creating alternate regions of tensile strain and compressive strain (mechanical vibrations) thus producing mechanical waves. Waves produced at the surface of the piezoelectric substrate known as surface acoustic waves. Surface Acoustic Wave based wireless MEMS actuator 8 Thursday, November 07, 2013
    • SAW sensor operation contd.. Acoustic waves propagate through the region of delay line between the two IDTs. At the output end the propagated waves are picked up by the output IDT. Waves are converted back to electric signal by piezoelectric effect which is then measured and calibrated. Surface Acoustic Wave based wireless MEMS actuator 9 Thursday, November 07, 2013
    • SAW based wireless microactuator Fig 3: SAW based wireless microactuator Surface Acoustic Wave based wireless MEMS actuator 10 Thursday, November 07, 2013
    • Material selection The SAW based microactuator is similar to the normal SAW sensor only differing in the actuator part. SAW substrate: The SAW substrate is generally made of quartz. Lithium Niobate (LiNbO3) is also used as it is best suited for Rayleigh wave propagation. IDT: Made of highly conductive low cost materials such as copper (Cu), aluminum (Al), gold (Au), tungsten (W), and titanium (Ti). Surface Acoustic Wave based wireless MEMS actuator 11 Thursday, November 07, 2013
    • Material selection contd.. Microactuator: A thin conductive plate (conductive material) is placed over the output IDT with a small air gap in between that acts as the actuator. Also made of materials such as Silicon (Si) or Silicon Nitride (Si3N4) and the bottom surface of the microactuator can be coated with a thin conductive material such as Gold, Platinum or Aluminium. Input IDT is connected to a micro-antenna for wireless interrogation. Surface Acoustic Wave based wireless MEMS actuator 12 Thursday, November 07, 2013
    • Fabrication Process flow Surface Acoustic Wave based wireless MEMS actuator 13 Thursday, November 07, 2013
    • Operation Working principle is similar to that of normal SAW sensor. Only difference is that the wireless SAW uses the RF waves as the exciting source for the generation of Rayleigh waves at the input IDT that propagate in the forward direction towards the output IDT. RF is an electromagnetic wave having a frequency between 3 kHz to 300 GHz The RF signal is fed to the SAW device through the microstrip antenna Surface Acoustic Wave based wireless MEMS actuator 14 Thursday, November 07, 2013
    • Rayleigh waves are a type of surface acoustic wave that travel on solids. They can be produced in materials in many ways, such as by a localized impact or by piezoelectric transduction. Rayleigh waves include both longitudinal and transverse motions that decrease exponentially in amplitude as distance from the surface increases. Fig 4: Ray Leigh waves Surface Acoustic Wave based wireless MEMS actuator 15 Thursday, November 07, 2013
    • Actuation mechanism: electrostatic actuation A thin conductive plate is placed on top of the output IDT, which is separated by an air–gap. The conductive plate does not alter the mechanical boundary conditions of the SAW substrate, but causes the surface to be equipotential and the propagating electric potential to be zero at the surface of the conductive plate. As a result, an electrostatic force is generated between the conductive plate and the output IDT in the SAW device causing micro deformations or microactuation in the conductive plate Surface Acoustic Wave based wireless MEMS actuator 16 Thursday, November 07, 2013
    • Advantages • • • • • • • High biocompatibility Reliable Low power operation Small size Simplicity fabrication Cost effectiveness Fast fluid actuation Surface Acoustic Wave based wireless MEMS actuator 17 Thursday, November 07, 2013
    • Disadvantage One disadvantage of SAW is that Rayleigh waves are surfacenormal waves, making them poorly suited for liquid sensing. When a SAW sensor is contacted by a liquid, the resulting compressional waves cause an excessive attenuation of the surface wave. Surface Acoustic Wave based wireless MEMS actuator 18 Thursday, November 07, 2013
    • Applications Widely used in micro fluidics for studying the manipulation of fluids. Also used to develop micromachines such as ultrasonic micromotors and fluid transfer methodologies such as flexural micropumps Surface Acoustic Wave based wireless MEMS actuator 19 Thursday, November 07, 2013
    • Conclusion A brief introduction about the SAW sensor is highlighted at the beginning stating the device layout and working principle which is followed by a detailed explanation about the wireless based SAW microactuator. We talked about the fabrication process that is involved in the making of such a device and later we focused on some merits and demerits of the SAW based microactuator. Surface Acoustic Wave based wireless MEMS actuator 20 Thursday, November 07, 2013
    • References 1. 2. 3. 4. 5. Surface Acoustic Wave Based Wireless MEMS Actuators for Biomedical Applications Don W. Dissanayake, Said Al Sarawi and Derek Abbott, The School of Electrical and Electronic Engineering, The University of Adelaide Australia. SA 5005 A Fabrication Study of a Surface Acoustic Wave Device for Magnetic Field Detection by Matthew L. Chin www.google.com www.wikipedia.com Google images Surface Acoustic Wave based wireless MEMS actuator 21 Thursday, November 07, 2013
    • THANK YOU Surface Acoustic Wave based wireless MEMS actuator 22 Thursday, November 07, 2013