Smart materials
• Piezoelectric materials • Shape memory materials • Magnetostriction materials • Electrostriction materials
w.wang 107 Qualitative comparison of different “smart technology
Active Shape-Memory Alloys Magnetostrictive Materials Piezoelectric Materials System
Driving Thermal field Magnetic field Electric field Force
Materials TiNi, TiPd TbFe, (TbDy)Fe, SmFe PZT, Quartz
Advantages •Large forces •High energy density •Contact-less control via magnetic field •High bandwidth •High material strength •High frequencies •High frequencies •High Elasticity •High temperature range •Low power Actuation
Limitations •Low bandwidth •Low frequencies •Generation of magnetic field equipment •Limited Strains •High hysteresis intensive •Auxiliary Equipment •Limited temperature •Limited strains needed range •Low material tensile strength •Low material tensile •Typically brittle materials strength •Typically brittle materials •Limited temperature range w.wang 108 w.wang 109 ucla w.wang 110 ucla ucla w.wang 111 w.wang 112 w.wang ucla113 ucla w.wang 114 w.wang ucla115 Piezoelectric materials
Ceramics: • PZT (Lead-Zirconate-Titanate or
Pbx(Ti, Zr)1-xO3 ) * quartz • Thin fims- ZnO, AlO
Polymers: • PVDF (poly vinylidene flouride) • PTF (polymer thick film) w.wang 116 Ceramic versus polymer
•Ceramic Polymer - high stiffness - acoustic impedance - Higher curie point less matching with water likely to depole - Flexible can be formed intocomplex shape - Low dieletric constant
w.wang 117 Piezoelectric materials
Advantage: • Reversible (use as sensor or actuator) • Actuation mechanism is highly resistive to environmental effect (e.g. humidity, temperature) • Very easy to control small (sub-micron) displacements with applied voltages. • High stiffness. • Very fast response. • 100's of N loads easy. • E to100GPa w.wang 118 Piezoelectric materials
Disadvantages: • Small displacements. 30ppm typical. Attempts to use long actuators doesn't work - stacks and bimorphs help. • Non-linear response and exhibit high-hysterisis and creep. Many commercial products overcome these through control techniques. • High electric fields can cause breakdown and failure. • requires a high voltage for displacement in the micron regime, however the problem can be partially alleviated by implementing a bimorph w.wang 119 Piezoelectric materials
w.wang 120 Piezoelectric material
w.wang 121 w.wang 122 ucla ucla w.wang 123 ucla w.wang 124 Piezoelectric materials
•STM AFM • Camera film plane control, lens motor • Mirror control, micro-actuator (fluid) • Acoustic wave generation-Speaker • Ski active vibration damper (K2) • Power generator • Ultrasonic transducer (image, range finder,hydrophone, microphone,bubble) w.wang 125 Piezoelectric materials application
Optics, Photonics and Measuring Technology Precision Mechanics and Mechanical Engineering • Image stabilization • Vibration cancellation • Scanning microscopy • Structural deformation • Auto focus systems •Interferometry • Out-of-roundness grinding, drilling, turning • Fiber optic alignment & switching • Tool adjustment • Fast mirror scanners • Wear correction • Adaptive and active optics • Needle valve actuation • Laser tuning • Mirror positioning •Micro pumps • Holography • Linear drives • Stimulation of vibrations • Piezo hammers Disk Drive • Knife edge control in extrusion tools • MR head testing • Micro engraving systems • Pole tip recession • Disk spin stands • Shock wave generation • Vibration cancellation Life Science, Medicine, Biology Microelectronics • Patch-clamp drives • Nano-metrology • Gene technology • Wafer and mask positioning • Micro manipulation • Critical Dimensions measurement • Microlithography • Cell penetration • Inspection systems • Micro dispensing devices • Vibration cancellation • Audiophysiological stimulation • Shock wave generation w.wang 126 Piezo speaker (PZT)
w.wang 127 Piezo speaker
w.wang 128 Piezoeletric energy scavenging in shoe (PVDF)
low-power, wireless application: •Store charge over several footsteps •When capacitor full, discharge through: regulator, 12-bit encoder, 310 Mhz ASK transmitter •Transmits 12-bit digital RFID from shoe to vicinity every 3-5 steps w.wang 129 •Enables smart building to track occupant location Smart structure composite (PZT/steel)
w.wang 130 Piezoelectric rotary motor
w.wang 131 Cricket jump
By Timothy S. Glenn and Nesbit W. Hagood at MIT
w.wang 132 Piezoelectric linear motor
w.wangEDO model PDA 130 133 Inch worm motors
w.wang 134 PVF2 Bimorph actuator
w.wang 135 micropump
w.wang 136 Spark generator (PZT)
w.wang 137 Different shape of PZT bimorph
Spiral or helical shape
w.wang 138 bimorph
Principle setup of piezoelectric bimorph w.wang 139 Piezoelectric effect (sensor)
External force results in a electric potential
w.wang 140 Piezoelectric effect (actuator)
Applied electric potential results in a deformation w.wang 141 Parallel and serial connection
Parallel design Serial design actuator sensor w.wang 142 Normal displacement versus voltage
w.wang 143 Electromechanical behavior
w.wang 144 Polymer thick film
History: • low-cost carbon-filled resistors • touch-membrane switches (touch pad, touch screen) • flexible circuits or connectors (laptops, calculators, cell phone) Advantages: • Flexible, withstand large strains • cured at temperatures below 200 oC
w.wang 145 • Carbon filler (pressure/force sensor, humidity sensor) • Silver or copper filler (conducting strip, temperature sensor) -conducting elastomer •Piezoelectric filler -Lead zirconate titanate (PZT) grains dispersed in a polymer matrix create a polymer-ceramic composite
w.wang 146 w.wang 147 Smart materials
• Vibration monitoring (chair, highway, smartcard) • Smart cloth, virtual reality sensors • Tactile sensors
w.wang 148 MEMS devices-inkjet printer head (ZnO ultrasound device)
USC
w.wang Micromachined Acoustic-Wave Liquid Ejector W.-C. 149Wang Liquid Ejector
D Rising Liquid Beam Diameter Cylinder at Focal Plane Surface Liquid/Air Tension Interface
Acoustic Wave Droplet Formation due to Focused Acoustic Wave Function of Radiation Pressure & Surface Tension Radiation Pressure (2If/Va) Droplet Diameter ~ Beam Diameter at Focal Plane
w.wang Micromachined Acoustic-Wave Liquid Ejector W.-C. 150Wang Fabricated Device (Micromachined Lensless Liquid Ejector) 100 µm
Transducer Specifications RF Frequency: 300 MHz ZnO Thickness: 10.55 µm Focal Length: 400 µm Half-Wave-Band Sources: 7 Predicted Droplet Diameter: 5 µm USC w.wang Micromachined Acoustic-Wave Liquid Ejector W.-C. 151Wang Time evolution of the liquid ejection process produced by our 600MHz SFAT with an RF pulsewidth of 30µsec
80 µm 30 µm
60 µm 15 µm USC
w.wang Micromachined Acoustic-Wave Liquid Ejector W.-C. 152Wang Piezoelectric Sensor
• Microphone • Bimorph sensor • Ultrasonic sensor (SAW, Bulk wave)
w.wang 153 Micromachined Piezoelectric Ultrasonic Transducers on Dome-Shaped-Diaphragm in Silicon Substrate
USC
w.wang 154 Fabrication Steps
USC
w.wang 155 Sound Pressure comparison between dome-shaped and flat diaphragm
USC
w.wang 156 Medical Ultrasound Application (PZT)
w.wang 157