Approaches to Achieve Smarter Electroactive Materials and Devices

Open Access
Ren, Kailiang
Graduate Program:
Electrical Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
September 28, 2007
Committee Members:
  • Qiming Zhang, Committee Chair
  • Srinivas A Tadigadapa, Committee Member
  • Leslie Eric Cross, Committee Member
  • Zhiwen Liu, Committee Member
  • Christopher Rahn, Committee Member
  • Ferroelectric Polymer
  • Polymer Actuators
  • Energy Harvesting
  • Shape Memory Polymer
  • Self-healing.
In the last several decades, considerable research effects have been devoted to the smart materials, including piezoelectric and electrostrictive ceramics, electroactive polymers (EAP), magnetostrictive materials, shape-memory materials, and magneto-rheologic fluids. This has led to the development of several novel materials with high performance. It is the objective of this thesis to explore and expand these new opportunities. Especially, we will investigate and develop innovative approaches to address three applications: In chapter 2 and chapter 3, the energy harvesting using both the electrostrictive PVDF based polymers and 1-3 single crystal PMN-33PT/Epoxy composite are investigated. In addition to the high elastic energy density and high electromechanical conversion efficiency of these active materials, this study also explores the approaches of using smart electronics to significantly enhance the efficiency of the energy harvesting process. As an example, we demonstrate that when a properly phased and externally applied electric AC field is superimposed on the mechanical cycle, an output electrical energy density of 39mJ/cm3 and mechanical-to-electrical conversion efficiency of about 10% can be obtained from the P (VDF-TrFE) based electrostrictive polymers. For 1-3 single crystal PMN-33PT/Epoxy composite, under a mechanical stress of 88.9 MPa at 4 Hz, a harvested energy density of near 0.1 W/cc can be achieved. In chapter 4, the Braille actuators suitable for refreshable full page display and graphic display using the electrostrictive PVDF-based polymers are investigated. The current refreshable Braille display utilizes the piezoceramic actuator and the small strain level requires that the actuator is operated in the bimorph mode, resulting in a bulky device, low reliability, and not suitable for full page refreshable Braille display. An EAP compact Braille actuator was designed and fabricated with PVDF-TrFE-CFE terpolymer films wound on a spring core. The test results demonstrate that the EAP Braille actuator meets all the functional requirements of actuators for refreshable full Braille display, which offers compact size, reduced cost and weight. In chapter 5, we investigate the hybrid SMP/EAP actuator to create a new class of actuator which can maintain the high strain without electrical signal stimulus and can be reconfigured to different strain and shape. Since the strain generation and elastic modulus of two independent processes, this new actuator has the potential to reach much higher elastic energy density than any of the current solid state actuator materials. In the following, we will briefly introduce the smart materials to be investigated in my thesis.