2.76/2.760 Multiscale Systems Design & Manufacturing. Fall Piezoelectricity-2

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1 2.76/2.760 Multiscale Systems Design & Manufacturing Fall 2004 Piezoelectricity-2

2 Ba 2+ O 2- Ti 4+ BaTiO3 P = 0.03A c Spontaneous polarization P( polar) P(nonpolar) / a 2 c : Polarization per unit cell volume a Figure by MIT OCW. HW1: Calculate the magnitude of spontaneous Polarization. a=3.992 A, c=4.036a 1e=1.602x10-19 C 0.06A 0.1A Dipole moment=σ charge x position shift = 8(2e/8)(0.06 x m) + 4e(0.1 x m) + 2(-2e/2)(-0.03 x m) = x C m Volume=a x a x c=64.3 x m 3 Spontaneous Polarization = C/ m 2

3 d 31 vs d 33 HW2: Compare generated voltages V31 (from d31mode), V33 (d33mode). Both have same cantilever dimension, but different electrodes. Assume, g33=2g31 tpzt=o.5 µ d=5 µ length=100 µ, width=50 µ Young s modulus of the beam= 65 Gpa, max strain=0.1% d33=200 pc/n K=1000 P Interdigitated Electrode PZT layer ZrO 2 layer Membrane layer

4 Principles of piezoelectric -e Stress(T) Piezoelectric effect -h c Strain(S) Electric field(e) g β -h ε Dielectric Displacement(D) d d -e g s Thermo-elastic effect Electro-thermal effect Entropy Temperature

5 Direct effect D = Q/A = Piezoelectricity dt E = -gt Converse effect S = de g = d/ ε = d/kε o D: dielectric displacement, electric flux density/unit area T: stress, S: strain, E: electric field d: Piezoelectric constant, [Coulomb/Newton]

6 Piezoelectric Charge Constants Electrical energy Actuator Mechanical energy Longitudinal (d 33 ) Transverse (d 31 ) Shear (d 15 ) Diagram removed for copyright reasons. Source: Piezo Systems, Inc. "Introduction to Piezo Transducers." Diagram removed for copyright reasons. Source: Piezo Systems, Inc. "Introduction to Piezo Transducers." E P T/T = d 33 E ΔL/L = d 31 E Shear strain = d 15 E

7 Coarse Positioning Screw Louse Beetle Courtesy of Friedrich-Alexander University. Used with permission. Source: "Scanning Tunneling Microscopy"

STM tip scanning Tripod x = d31v L h x V = d 31 L h Courtesy of Friedrich-Alexander University. Used with permission. Source: "Scanning Tunneling Microscopy" http://www.fkp.uni-erlangen.

8 STM tip scanning Tripod x = d31v L h x V = d 31 L h Courtesy of Friedrich-Alexander University. Used with permission. Source: "Scanning Tunneling Microscopy" For L=20mm, h=2mm, PZT-5H x =? V Resonant frequency=? PZT-5H d31: Angstrom/V d33: 5.93 A/V E: N/m2 Tc: 195 C Q: 65 ρ: 7.5g/cm3 C: 2.8 km/sec

Bimorph bender +V h/2 L 2 2 31 31 2 1 1 31 1 3 6 : 3 ) ( 0 ) ( 2 / 1 h L V d z V d h radius h dz z z M z z h V Ed = = = = = = = ± ρ σ α σ α σ σ σ Courtesy

9 Bimorph bender +V h/2 L : 3 ) ( 0 ) ( 2 / 1 h L V d z V d h radius h dz z z M z z h V Ed = = = = = = = ± ρ σ α σ α σ σ σ Courtesy of Friedrich-Alexander University. Used with permission. Source: "Scanning Tunneling Microscopy"

10 Tube scanner Piezo Tube with ¼ electrodes Courtesy of Friedrich-Alexander University. Used with permission. Source: "Scanning Tunneling Microscopy" +v δy y,θ -V L

11 Tube scanner, deflection Curvature R = δy = 4 2 πdh 2d 31 V 2d31VL πdh 2 Resonant frequency 40KHz (z), 8 KHz(x,y), For a tube of 12.7mm L, 6.35 mm diameter, 0.51mm thick

12 Design of a Z-axis scanner Component schematic removed for copyright reasons. Physik Instrumente Z-positioner P , in page Ordering Number* Dimensions A x B x L [mm] Nominal Displaceme nt 100 V] (±10%) Max. Displaceme nt 120 V] (±10%) Blocking Force 120 V] Stiffness [N/µm] Electrical Capacitance [µf] (±20%) Resonant Frequency [khz] P x 3 x

13 Case 1: Piezoelectric micro-actuators Work / Volume (J/m3) Muscle Thermal expansion Electrostatic Electromagnetic 10 7 SMA Solidliquid 10 6 Thermopneumatic Thin film PZT PZT Positives 1. Low power and voltage for thin films 2. High force 3. Compact µ-bubble Cycling Frequency (Hz) Figure by MIT OCW Modified from P. Krulevitchet al, "Thin Film Shape Memory Alloy Microactuators, JMEMS Vol. 5, No pp

14 Leveraged Amplification h1 h2 h3 l1 g h h L0 L1

15 Bow Strain Amplifier US Patent pending, N. Conway, S. Kim

16 Amplification depends on 2 factors y θ x θ 0 = initial angle Figure by MIT OCW. y x = sinθ sinθ0 cosθ cosθ 0 = cot 1 2 ( θ + θ ) 0

17 Small angles yield enormous amplification y/ x y/ x θ 0 = 1º θ 25(deg) θ (deg) amplification

18 MIT Bow-actuator Nick Conway, MS 2003 Piezoelectric Amplifiers End effector Released Bottom PZT Top 4-bar linkage design Fixed substrate

19 Flexural pivots enable a parallel guiding linkage in a high aspect ratio structure. k θ YI L

20 Process Flow 1-4 mask process 1 Deposit oxide (SiO 2 ) layer on Si substrate 2 Deposit and pattern Pt/Ti bottom electrode layer (#1) 3 Spin-on PZT

21 4 Process Flow 2 Pattern then anneal PZT (#2) 5 Deposit top electrode (platinum) (#3) 6 Spin-on SU-8 (30 µm) and cure, expose, and develop (#4)

22 7 Process Flow 3 RIE oxide 8 XeF 2 etch away Si to release actuator

23 Finished Note: SU-8 nonconducting.

24 MEMS-Strain-Amplifier 500 µ Nick Conway, Micronanosystems Laboratory, MIT

25 Arrayed configurations Cellular analog digital actuation

Case: Piezoelectric Micro Power Generator Inter-digitated Electrode E 3 + - + - + -

26 Case: Piezoelectric Micro Power Generator Inter-digitated Electrode E PZT ZrO 2 membrane MIT Media Lab, Shoe Power MIT EECS, Chandrakasan Energy Amplifier

27 Comparison of Energy Scavenging Energy Source Solar (outdoor) Solar (indoor) Vibrations (piezoelectric) Vibrations (electrostatic) Acoustic noise Temperature gradient Batteries (non-rechargeable) Batteries (rechargeable) Hydrocarbon fuel (micro heat engine) Fuel cells (methanol) Power Density for 10 Years 15,000 µw/cm 3 6 µw/cm µw/cm 3 50 µw/cm µw/cm 3 (at 75 db) 15 µw/cm 3 (at 10 o Cgradient) 3.5 µw/cm 3 (45 µw/cm 3 one year life) 0 µw/cm 3 (7 µw/cm 3 one year life) 33 µw/cm 3 (330 µw/cm 3 one year life) 28 µw/cm 3 (280 µw/cm 3 one year life) Shad Roundy, Paul K. Wright, Jan Rabaey, Computer Communications xx(2003) 1 14

28 Energy Harvesting Concept with Piezoelectricity Vibration Acoustic Source High deformation in piezoelectric Electrical signal Energy Output Vibration/ acoustic amplitude Membrane amplitude charge/ voltage DC output voltage mechanical resonance piezoelectricity rectifying Energy conversion efficiency (η p ) η p = generated energy/input energy 65 to 78 % No voltage source needed Open circuit voltage: 3~15V JMM, 14, 717

29 Piezoelectrics V 33 = 2L / t pzt V V 31 3 V g 33 >2g 31 L~10t pzt

30 Device Design High strain: cantilever beam, proof mass High open-circuit voltage: d 33 interdigitated electrodes t L b

31 Device Modeling Governing equation for seismic excitation m z o = b m z o kz o + (EMC) m z i m V b 33 L δ + b mδ + kδ k = d 3t 4L 2 m z i Open Circuit Voltage of PMPG V s bd Y = be = 2 ε 33 ( 1 k ) δ 33 Y: Young s modulus δ: strain d: piezoelectric coeff. K 33 : coupling constant

32 Device Fabrication Si (a) Films deposition (CVD, spinning) Interdigitated Electrode (Ti/Pt) (c) Films patterning (RIE) Proof mass (b) Top electrode deposition (e-beam) and then lift-off (d) Proof mass (SU-8, spinning) PZT (Pb(Zr,Ti)O 3 ) ZrO 2 Membrane

33 Device Fabrication (II) (e) Cantilever release (XeF 2 etcher) (f) Packaging & PZT poling

Characterization of PZT films uniform grain sizes dielectric constant 1200 dielectric loss 1.2 1000 800 typical thinfilm PZT dielectric 0.8 0.4 500 nm 600 0.0 Intensity (A.U.

34 Characterization of PZT films uniform grain sizes dielectric constant 1200 dielectric loss typical thinfilm PZT dielectric nm Intensity (A.U.) XRD peaks of PZT film PZT(001) ZrO 2 (111) PZT(011) ZrO 2 (200) PZT(111) Pt(111) PZT(002) Pt(200) PZT(210) PZT(211) Polarization (µc/cm 2 ) frequency (khz) Before poling After poling θ Applied voltage (V)

35 PZT characterization High performance PZT thin film -d 33 =200 pc/n, d 31 =-100 pc/n, -ε=1200, -tanδ=0.02 at 15 khz

36 Cantilever Bow Control Photos removed for copyright reasons. Source: Jeon, Y.B., R. Sood, J.H. Joeng and S.G. Kim. Piezoelectric Micro Power Generator for Energy Harvesting. Sensors and Actuators A: Physical, accepted for publication, ZrO 2 (0.05um)/ thermal oxide(0.4um) ZrO 2 (0.05um)/ PECVD oxide(0.4 um) ZrO 2 (0.05um)/ PECVD oxide(0.1um)/ LPCVD nitride(0.4um) (A) (B) (C) Towards Tensile stress Towards High elastic modulus

37 Cantilever Bow Control (II) Cantilever Beam Structure PZT ZrO 2 SiO 2 Variable Membrane Cantilever Curvature [1/m] (B) (A) -200 MPa -100 MPa 0 MPa 100 MPa 200 MPa (C) Elastic Modulus of Bottom Layer [GPa]

38 Fabricated PMPG devices Photos removed for copyright reasons. Source: Jeon, Y.B., R. Sood, J.H. Joeng and S.G. Kim. Piezoelectric Micro Power Generator for Energy Harvesting. Sensors and Actuators A: Physical, accepted for publication, Top view of PMPG SEM image of PMPG Multiple cantilever device SEM image of PMPG

39 Set-up for measurement Charge Amplifier Voltage Amplifier: X-Z-θ translation Laser Vibrometer Laser beam PMPG OPTICS TABLE Piezoelectric Shaker

Resonant Response of Cantilever Tip Tip Displacement [µm] 5 4 3 2 1 13.9kHz 21.9kHz 48.

40 Resonant Response of Cantilever Tip Tip Displacement [µm] kHz 21.9kHz 48.5kHz 1 st mode at 13.9 khz 2 nd mode at 21.9 khz Frequency [khz] 3 rd mode at 48.5 khz

Variation of load resistance Schottky diodes: smallest forward voltage drop

41 Power Generation First mode of resonance at 13.9 khz with 14 nm amplitude Rectifying the AC signal, then store the charge Variation of load resistance Schottky diodes: smallest forward voltage drop 10 nf mylar cap: low leakage current Load voltage (V c ) 2.28V Source current (µv) 0.4µA Time (sec) Time (sec)

42 Measurement of generated power Proof mass Interdigitated electrode PZT ZrO 2 Generated Voltage (V c,v) Si Generated voltage (V c ) Generated power (P L ) at 13.9kHz Power Delivered To Load (P L, µw) 0.8 3V 1µW Resistive Load (R L,M-Ohms) Resistive Load (R L, ΜΩ ) at 13.9kHz Y. Jeon, R. Sood, and S.G. Kim, Hilton Head Conference 2004

43 Summary Characteristic Li/MnO 2 Li/LiCoO 2 PMPG Nominal OCV 3.1 V 4 V 3V Internal Construction Spiral Thin Film MEMS Packaging Hermeticity Nonhermetic Nonhermetic Excellent Energy Density 637 Wh/L 0.8 mwh/cm mwh/cm 2 Operating Temperature -20~60 o C -50~180 o C -20~80 o C Storage Conditions 10 years 60,000 cycles (charge/discharge) Infinite Energy conversion efficiency (η p ) η p = generated energy/input energy 65 to 78 % No voltage source needed Open circuit voltage: 3V

44 Power depends on Resonant Frequency Internal Capacitance and Resistance External Capacitance and Load Resistance Mechanical damping Membrane structure Electrode shape Bow control? Multi-cantilever Multiple bridges? New Design for Efficient Power Harvesting

45 In progress, High resonant frequency products Bridge Structures vs. Cantilevers Smart bearings Low resonant frequency structures Scavengers Monolithic Device Design Mechanical Rectifiers

46 Self-supportive Wireless Sensors Design and fabrication Concept prove New Design & PMPG integration N P RF circuit Storage Rectifier Generator On chip RFID with PMPG and Sensor RF transmitter + PMPG + Sensor

47 Wireless Sensing Applications RF transmitter + PMPG + sensor Network data transfer Reader Dashboard display with RF receiver RF transmitter with pressure sensor and power generator in tires Vehicle Industrial process (i.e. pipeline) Industrial process (i.e. pipeline) Self-supportive Sensors

48 Can we avoid disasters? Belgian gas pipe blast kills 15, destroys plants Photo removed for copyright reasons GHISLENGHIEN (Belgium) July 30 - A huge blast on a leaking gas pipeline in Belgium on Friday sent giant fireballs in the air and catapulted bodies hundreds of metres in the biggest industrial disaster in the country's recent history. At least 15 people were killed and more than 100 injured when the explosion ripped through the underground pipeline in the industrial zone of Ghislenghien, near the town of Ath, 40 km (25 miles) southwest of Brussels. PICTURE shows the cut gas pipeline which exploded at an industrial estate in Ghislenghien, southern Belgium, July AFPpix.

Outline. 4 Mechanical Sensors Introduction General Mechanical properties Piezoresistivity Piezoresistive Sensors Capacitive sensors Applications

Outline. 4 Mechanical Sensors Introduction General Mechanical properties Piezoresistivity Piezoresistive Sensors Capacitive sensors Applications Sensor devices Outline 4 Mechanical Sensors Introduction General Mechanical properties Piezoresistivity Piezoresistive Sensors Capacitive sensors Applications Introduction Two Major classes of mechanical