1. Eelectric Energy Harvesting Through Piezoelectric Polymers Final Report – May 13 Don Jenket, II Kathy Li Peter Stone

2. Final Report May 13, 2004Eelectric Presentation Overview Objective Background Materials Choice & PVDF Properties Electrical Properties Strain-Voltage Relationships Circuitry Conclusions Future Suggestions Acknowledgements

3. Final Report May 13, 2004Eelectric Background 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 3.082 Objective: Demonstrate that piezoelectric materials can be used to harness power from airflow and determine the maximum amount of useful power that can be harvested with a single eel tail http://www.darpa.mil/dso/trans/energy/pa_opt.html

4. Final Report May 13, 2004Eelectric Materials Selection http://web.media.mit.edu/~testarne/TR328/node7.html

5. Final Report May 13, 2004Eelectric Poly(vinylidene fluoride) PVDF CC H H F F 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.http://www.psrc.usm.edu/macrog/pvdf.htm

6. Final Report May 13, 2004Eelectric 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 Davis, G.T., Mckinney, J.E., Broadhurst, M.G., Roth, S.C. Electric-filed-induced phase changes in poly(vinylidene fluoride). Journal of Applied Physics 49(10), Oct, 1978.  -phase (piezoelectric)  -phase (anti- parallel dipoles)

7. Final Report May 13, 2004Eelectric Poling - 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  -phase crystallites uniformly throughout the poled material Electromechanic coupling factor0.11 Young’s Modulus~2,500 MPa Melting Point175º C Depoling Temperature90º C Selected Properties of 40  m thick bioriented PVDF Table courtesy of K-Tech Corporation Reference: Piezoelectric SOLEF PVDF Films. K-Tech Corp., 1993.

8. Final Report May 13, 2004Eelectric Design Schematic Fan 0.005” Magnet Wire Kapton Tape Silver Paste Electrode PVDF Tail Weight Tail Holder Flagpole Electrical Output

9. Final Report May 13, 2004Eelectric Strain in a bending cantilever goes as: y is the distance from the neutral plane and R is the Radius of Curvature: at a distance l from the fixed end and the free end deflection is dz for a cantilever of total length, L. Thus for a cantilever of thickness, H Strain in a Cantilever

10. Final Report May 13, 2004Eelectric In 31 piezoelectric coupling: The charge induced due to the strain at point l: So the voltage induced across the surface is: This is simply the length-averaged voltage, leading to: Strain-Induced Voltage and

11. Final Report May 13, 2004Eelectric Displacement (cm) Radius of Curvature at Midpoint (m) Normal Strain (*10 -5 ) Voltage (mV) Expected Voltage* (mV) 0.0Inf0~200 0.51.920.5216455.4 1.00.961.0480110.81 1.50.641.56106166.21 2.00.482.08163221.61 2.50.3842.60202277.02 3.00.323.13232332.42 19.80.04820.72200 Strain-Induced Voltage

12. Final Report May 13, 2004Eelectric Strain-Induced Voltage

13. Final Report May 13, 2004Eelectric Oscillation Frequency Fan Off Fan On

14. Final Report May 13, 2004Eelectric Tail Capacitance C =  A/d A = 7.5 * 10 -4 m 2  (at < 0.1 kHz) = 11.5  o ±10% d = 4 *10 -5 m Calculated Capacitance Lower bound: 1719 pF Upper bound: 2099 pF Median: 1910 pF Actual Capacitance at 10-100 Hz: 1940 pF

15. Final Report May 13, 2004Eelectric Oscilloscope Data 2cm x 12cm Piezoelectric PVDF in Wind

16. Final Report May 13, 2004Eelectric Tail Power Output Resistance (  ) Peak Voltage Amplitude (mV) Power = V 2 /R (nW) 10 00035.1123 100 00091.784 1 000 00030191

17. Final Report May 13, 2004Eelectric Tail Current Output Resistance (  ) Voltage (mV) Current (  A) 10 00035.13.51 100 00091.70.917 1 000 0003010.301

18. Final Report May 13, 2004Eelectric Rectifier Circuit AC LED Capacitors Diodes

19. Final Report May 13, 2004Eelectric Increasing Voltage

20. Final Report May 13, 2004Eelectric Series Connection of 2 Tails

21. Final Report May 13, 2004Eelectric Series Connection of 3 Tails

22. Final Report May 13, 2004Eelectric Conclusions PVDF tails can successfully harness energy from air to useful electric output The electrical properties of 2 x 12 cm tails have been characterized Frequency and Capacitance Power and Current A relationship has been quantified between strain and voltage in this design Linear relationship Compares well with cantilever model A series connection of two tails in phase has been established to increase voltage One tail: ~300 mV amplitude Two tails: ~500 mV amplitude

23. Final Report May 13, 2004Eelectric Future Work Troubleshoot connections Successfully connect more than two tails in series to get useful voltages Exploit parallel connections to increase current Better piezoelectric materials Active Fiber Composites PZT fibers in an epoxy matrix Combine flexibility and good electromechanical coupling Currently, they are too stiff to be oscillated by natural forces

24. Final Report May 13, 2004Eelectric Acknowledgements Professor Yet-Ming Chiang Professor David Roylance Joe Parse & Yin-Lin Xie Joe Adario & David Bono