Eelectric Energy Harvesting Through Piezoelectric Polymers Formal Design Review Don Jenket, II Kathy Li Peter Stone

Formal Design Review March 11, 2004Eelectric Presentation Overview Project Goals Choice of Materials Choice of Processing Techniques Device Architecture Future Tests Revised Timeline

Formal Design Review March 11, 2004Eelectric 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 Objective: Harness enough power from air flow to operate a L.E.D.

Formal Design Review March 11, 2004Eelectric PVDF- Poly(vinylidene fluoride) 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: Accessed on: ; Piezoelectric SOLEF PVDF Films. K-Tech Corp.,

Formal Design Review March 11, 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 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 Physics 49(10), October,  -phase (piezoelectric)  -phase (anti- parallel dipoles)

Formal Design Review March 11, 2004Eelectric 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  -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.

Formal Design Review March 11, 2004Eelectric Tensile Testing of PVDF Cross-sectional Area of the Film Tested: 1 cm X 40 microns = 4 X m 2 Measured strain:.063 Force at.063 strain: 3.95 lbs. Elastic Modulus Calculated: 2.56 GPa E =   -1 Clamp Rubber PVDF

Formal Design Review March 11, 2004Eelectric 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

Formal Design Review March 11, 2004Eelectric Schematic of Sputtering Vacuum Pump Main Chamber Load-Lock Chamber Sample Holder; Sample faces down Sample Holder Rotates Sputter Guns Load-Lock Arm Adapted From: Twisselmann, Douglas J. The Origins of Substrate-Topography-Induced Magnetic Anisotropy in Sputered Cobalt Alloy Films. MIT Doctoral Thesis, February, 2001

Formal Design Review March 11, 2004Eelectric Sputtering Apparatus Load-Lock Chamber Vacuum Pump Main Chamber Sample Holder

Formal Design Review March 11, 2004Eelectric Sputtering Target

Formal Design Review March 11, 2004Eelectric “Eel Tail” Schematic Top View Side ViewFront View Cu Wire 6-10 cm 2 cm 6-10 cm 2 cm 0.04 mm Cu Wire Silver paste Gold Electrode

Formal Design Review March 11, 2004Eelectric Air Flow Testing of Eel Tail For cost purposes, used unpoled PVDF Thickness of PVDF film: 74  m. Can visually inspect eel oscillations Wave forms Estimate flexure and strain Tested 2 cm by {5,6,7,8,9,10} cm tails Fan PVDF Copper “Fin” Length= 5-10 cm 2 cm

Formal Design Review March 11, 2004Eelectric Air Flow Testing of Eel Tail 2cm x 6cm PVDF

Formal Design Review March 11, 2004Eelectric Air Flow Testing of Eel Tail 2cm x 10cm PVDF

Formal Design Review March 11, 2004Eelectric Piezoelectric Response in Air Flow 2cm x 6cm Piezoelectric PVDF

Formal Design Review March 11, 2004Eelectric Estimation of Piezoelectric Response V = 3/8 * (t/L) 2 * h 31 *  z, t= thickness; L = Length;  z = bending radius and h 31 = g 31 *(c 11 + c 12 )+ g 33 *c 13 g 31 = 6* /11  o [V*m/N]c 11 = 3.7 GN*m -2 L = 6 cm g 33 = [V*m/N]c 12 = 1.47 GN*m -2 t = 40  m  z = 3 cmc 13 = 1.23 GN*m -2 Equation taken from: Herbert, J.M., Moulson, A.J. Electroceramics: Materials, Properties, Applications. Chapman and Hall: London, 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 If we model the tail as a cantilever:

Formal Design Review March 11, 2004Eelectric Estimation of Piezoelectric Response Estimated voltage: V Voltage Measured in Air Field: 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.

Formal Design Review March 11, 2004Eelectric Rectifier Design AC in Reference:

Formal Design Review March 11, 2004Eelectric Proposed Integrated Design Fan Rectifier Storage Circuit Electronics Housing

Formal Design Review March 11, 2004Eelectric 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

Formal Design Review March 11, 2004Eelectric Project Timeline