Eelectric Energy Harvesting Through Piezoelectric Polymers Formal Design Review

1. EelectricEnergy Harvesting Through Piezoelectric PolymersFormal Design Review Don Jenket, II Kathy Li Peter Stone

2. Presentation Overview • Project Goals • Choice of Materials • Choice of Processing Techniques • Device Architecture • Future Tests • Revised Timeline Eelectric

3. Objective • DARPA Objective: Convert mechanical energy from a fluid medium into electrical energy. • Fluid flow creates oscillations in an eel body • Creates strain energy that is converted to AC electrical output by piezoelectric polymers • AC output is stored and/or utilized • 3.082 Objective: Harness enough power from air flow to operate a L.E.D. Eelectric

4. PVDF- Poly(vinylidene fluoride) F H C C F H n • Properties • Chemically Inert • Flexible • High Mechanical Strength • Production • React HF and methylchloroform in a refrigerant gas • Polymerization from emulsion or suspension by free radical vinyl polymerization References: http://www.psrc.usm.edu/macrog/pvdf.htm, Accessed on: 3-9-04; Piezoelectric SOLEF PVDF Films. K-Tech Corp., 1993. Eelectric

5. Piezoelectric PVDF • Molecular Origin • Fluorine atoms draw electronic density away from carbon and towards themselves • Leads to strong dipoles in C-F bonds • Piezoelectric Model of PVDF (Davis 1978) • Piezoelectric activity based upon dipole orientation within crystalline phase of polymer • Need a polar crystal form for permanent polarization a-phase (anti-parallel dipoles) b-phase (piezoelectric) Reference: Davis, G.T., Mckinney, J.E., Broadhurst, M.G., Roth, S.C. Electric-filed-induced phase changes in poly(vinylidene fluoride). Journal of Applied Physics49(10), October, 1978. Eelectric

6. Piezoelectric PVDF • Poled by the Bauer Process • Biaxially stretch film: Orients some crystallites with their polar axis normal to the film • Application of a strong electric field across the thickness of the film coordinates polarity • Produces high volume fractions of b-phase crystallites uniformly throughout the poled material Selected Properties of 40 mm thick bioriented PVDF Table courtesy of K-Tech Corporation Reference: Piezoelectric SOLEF PVDF Films. K-Tech Corp., 1993. Eelectric

7. Tensile Testing of PVDF • Cross-sectional Area of the Film Tested: 1 cm X 40 microns = 4 X 10-7 m2 • Measured strain: .063 • Force at .063 strain: 3.95 lbs. • Elastic Modulus Calculated: 2.56 GPa Clamp Rubber PVDF E = se-1 Eelectric

8. Electrodes and Wires • Desired Properties • Electrodes • High Conductivity • Flexibility • Won’t oxidize • Wires • Ease of Attachment • Flexibility • The Process • Attach Electrodes using RF Magnetron Sputtering • Sputter 40 nm thick Gold electrodes on sample • Attach 3 mil copper wire with silver paste Eelectric

9. Schematic of Sputtering Sample Holder Rotates Sample Holder; Sample faces down Vacuum Pump Load-Lock Chamber Load-Lock Arm Vacuum Pump Main Chamber Sputter Guns Adapted From: Twisselmann, Douglas J. The Origins of Substrate-Topography-Induced Magnetic Anisotropy in Sputered Cobalt Alloy Films. MIT Doctoral Thesis, February, 2001 Eelectric

10. Sputtering Apparatus Sample Holder Load-Lock Chamber Main Chamber Vacuum Pump Eelectric

11. Sputtering Target Eelectric

12. “Eel Tail” Schematic 6-10 cm Top View 2 cm Cu Wire Gold Electrode Cu Wire 0.04 mm Silver paste 6-10 cm 2 cm Side View Front View Eelectric

13. Air Flow Testing of Eel Tail • For cost purposes, used unpoled PVDF • Thickness of PVDF film: 74 mm. • Can visually inspect eel oscillations • Wave forms • Estimate flexure and strain • Tested 2 cm by {5,6,7,8,9,10} cm tails Copper “Fin” Fan PVDF 2 cm Length= 5-10 cm Eelectric

14. Air Flow Testing of Eel Tail • 2cm x 6cm PVDF Eelectric

15. Air Flow Testing of Eel Tail • 2cm x 10cm PVDF Eelectric

16. Piezoelectric Response in Air Flow • 2cm x 6cm Piezoelectric PVDF Eelectric

17. Estimation of Piezoelectric Response • If we model the tail as a cantilever: V = 3/8 * (t/L)2 * h31 * dz, t= thickness; L = Length; dz = bending radius and h31 = g31*(c11 + c12)+ g33*c13 g31 = 6*10-12/11eo [V*m/N] c11 = 3.7 GN*m-2 L = 6 cm g33 = -0.14 [V*m/N] c12 = 1.47 GN*m-2 t = 40 mm dz = 3 cm c13 = 1.23 GN*m-2 Equation taken from: Herbert, J.M., Moulson, A.J. Electroceramics: Materials, Properties, Applications. Chapman and Hall: London, 1990. Piezoelectric Constants taken from: Roh, Y. et al. Characterization of All the Electic, Dielectric and Piezoelectric Constants of uniaxially oriented poled PVDF films. IEEE Transactions on Ultrasonics, Ferroelectics and Frequency Control.49(6) June 2002. Eelectric

18. Estimation of Piezoelectric Response • Estimated voltage: 0.7322 V • Voltage Measured in Air Field: 0.207 V • Voltage required to bias Ge-doped diode: 0.2 V • Sources of Error in Estimation • Cantilever does not account for oscillation • Wave form of eel is not a cantilever; looks more like a sinusoid. Eelectric

19. Rectifier Design ACin Reference: http://www.mcitransformer.com/i_notes.html Eelectric

20. Proposed Integrated Design Fan Storage Circuit Rectifier Electronics Housing Eelectric

21. Future Research • Dynamic Mechanical Testing (DMA) - ? • Oscilloscope • Quantified wave forms (peak amplitude) • Frequency • Continued Air Stream Testing • Possible water system (time permitting) • Environmental Protection stiffens the eel • Understanding vortex shedding Eelectric

22. Project Timeline Eelectric