This work has focused on the Mn-modified (1-x)BiFeO3-xBaTiO3 (BFBT) perovskite solid solution developed at the University of Kentucky. In this material the application of a large electrical DC field leads to an observed change in the local ferroelectric domain structure and enhanced low and high field piezoelectric properties. Specifically, application of a 40 kV/cm DC bias results in enhanced piezoelectric strain response, and a low-field d33 coefficient of 150 pC/N. Drawing from observations in other domain engineered ceramics, the application of a large DC bias in BiFeO3-BaTiO3 is believed to create an “engineered” ordered domain state leading to higher extrinsic and intrinsic contributions to the piezoelectric coefficient in BFBT ceramics. This is in strong contrast to the expected suppression of extrinsic contributions and reduction in the low field piezoelectric coefficient typically observed in ferroelectric ceramics at large DC bias. Evidence of this electric field induced engineered domain state can been observed in the weak residual banding of the domain structure observed by TEM following high field poling, shown below top. The resulting lead free BF-BT piezoelectric ceramic materials have the highest depolarization temperatures (Td) of any current piezoelectric ceramic material while maintain large piezoelectric coefficients when compared to alternative lead-free piezoceramic systems, shown below bottom.
Compact fluidic control and pumping in microfluidic systems remains a key barrier to the development and widespread application low-cost and portable microfluidic devices. This project resulted in all ceramic piezoelectric micropump incorporating cofired piezoelectric actuators into a self-contained package, see figure below top. This required the development of a suitable high performance low sintering temperature piezoelectric ceramic formulation. The addition of liquid phase sintering additives (LiBiO2 and CuO) to PbZrO3-Sr(K0.25,Nb0.75)O3 (PZT-SKN) produced a high performance piezoelectric (d33>400pC/N) which can be sintered at 900oC for 1 hour (~350 oC lower than traditional PZT based piezoelectric formulations). The analytical master sintering model was then used to assist in the development of a sintering process which would enable cofiring the developed material with commercially available low temperature cofire ceramic (LTCC) formulations. Finally, finite element modeling (FEM) was used to design on optimize a traveling wave peristaltic micropump. The resulting micropump has bidirectional pumping capabilities, and measured maximum flow rate of 450 μl/min and blocking pressure of 1.4 kPa when operated at 100 Vpp and 100 Hz, as shown below bottom.
This project is an integral component of the ONR DEPSCoR program “Development of Targeted Antioxidant Polymers (AOP) for the Prevention of Combat Trauma Related Ischemia/Repurfusion (I/R) Injury.” The overall aim of this program is the development of therapeutic polymers to which could be used to eliminate or reduced the impacts tourniquet application and subsequent release on remote tissues/organs. A key component of this effort is the development of an in-vitro cell culture platform to simulate, study I/R injury, and the potential therapeutic effects of the polymers being developed. The endothelium-on-chip (EOC) device we are developing is microfluidic ceramic chip incorporating an array of gold measurement electrodes to monitor the trans-epithelial electrical resistance (TEER) across a layer endothelial cells (EC) cultured within the chip, illustrated below. The measured TEER values provide a qualitative measure of EC activation associated with oxidative stress injury and activation of the inflammatory cascade associated with I/R injury. Ultimately, these devices may enable us to understand the role or ischemic preconditioning and therapeutic effects of AOP on reducing the negative consequences associated with tourniquet injury.
Richard E. Eitel, Assistant Professor
Department of Chemical and Materials Engineering
Office: 151 F. Paul Anderson Tower
Mailing: 177 F. Paul Anderson Tower
Lexington, KY 40506