Richard E. Eitel

Progress in engineering high strain lead-free piezoelectric ceramics

Abstract Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The ‘structural engineering’ approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications.

Suppressing iron oxide nanoparticle toxicity by vascular targeted antioxidant polymer nanoparticles

The biomedical use of superparamagnetic iron oxide nanoparticles has been of continued interest in the literature and clinic. Their ability to be used as contrast agents for imaging and/or responsive agents for remote actuation makes them exciting materials for a wide range of clinical applications. Recently, however, concern has arisen regarding the potential health effects of these particles. Iron oxide toxicity has been demonstrated in in vivo and in vitro models, with oxidative stress being implicated as playing a key role in this pathology. One of the key cell types implicated in this injury is the vascular endothelial cells. Here, we report on the development of a targeted polymeric antioxidant, poly(trolox ester), nanoparticle that can suppress oxidative damage. As the polymer undergoes enzymatic hydrolysis, active trolox is locally released, providing a long term protection against pro-oxidant agents. In this work, poly(trolox) nanoparticles are targeted to platelet endothelial cell adhesion molecules (PECAM-1), which are able to bind to and internalize in endothelial cells and provide localized protection against the cytotoxicity caused by iron oxide nanoparticles. These results indicate the potential of using poly(trolox ester) as a means of mitigating iron oxide toxicity, potentially expanding the clinical use and relevance of these exciting systems.

Synthesis and characterization of poly(antioxidant β-amino esters) for controlled release of polyphenolic antioxidants

Attenuation of cellular oxidative stress, which plays a central role in biomaterial-induced inflammation, provides an exciting opportunity to control the host tissue response to biomaterials. In the case of biodegradable polymers, biomaterial-induced inflammation is often a result of local accumulation of polymer degradation products, hence there is a need for new biomaterials that can inhibit this response. Antioxidant polymers, which have antioxidants incorporated into the polymer backbone, are a class of biomaterials that, upon degradation, release active antioxidants, which can scavenge free radicals and attenuate oxidative stress, resulting in improved material biocompatibility. In this work, we have synthesized poly(antioxidant β-amino ester) (PAβAE) biodegradable hydrogels of two polyphenolic antioxidants, quercetin and curcumin. The degradation characteristics of PAβAE hydrogels and the antioxidant activity of PAβAE degradation products were studied. Treatment of endothelial cells with PAβAE degradation products protected cells from hydrogen-peroxide-induced oxidative stress.

Active Optical Fiber Alignment with a Piezoelectric Ultrasonic Motor Integrated Into Low Temperature Cofired Ceramics

The major goal of this research was to integrate an ultrasonic motor into a ceramic package for an active optical fiber alignment. Two degrees of freedom ultrasonic motor was successfully cofired with commercial low temperature cofired ceramic green tapes as well as with silver electrodes without encountering serious delamination, camber, and inter diffusion issues. High-power piezoelectric ceramics that can be sintered at 900°C was used for the ultrasonic motor. The motor successfully achieved fiber-to-laser optical alignment. Once alignment was achieved, a pre-stressed structure maintained the position of the fiber without any external electrical field or adhesive material. This package design provided a unique ability to adjust and realign an optical fiber.

An integrated multilayer ceramic piezoelectric micropump for microfluidic systems

A package-level peristaltic piezoelectric micropump has been designed and fabricated in utilizing multilayer ceramic fabrication methods. The device was fabricated using commercially available low-temperature cofired ceramic materials and a custom-designed low-temperature cofired ceramic compatible piezoelectric ceramic composition. The assembled multilayer pump structure was sintered in single cofiring step. Performance testing resulted in observed unloaded bidirectional flow rates of 450 µL/min and a blocking pressure of 1.4 kPa when the pump was operated at a voltage of 100 Vpp (with a phase difference of 120°) with a frequency of 100 Hz. It was further shown that incorporation of diffuser elements into the microfluidic interconnects was used to increase the blocking pressure capabilities at the expense of flow rate and bidirectional flow characteristics. Alternatively, by maintaining a uniform channel width but varying channel cross section width over height ratio (W/H), an unloaded flow rate of 630 µL/min with an enhancement of blocking pressure (1.55 kPa) was achieved for W/H = 3 (and the same drive conditions as above). The resulting multilayer ceramic-based piezoelectric micropump offers a compact planar pump design, with significant performance advantages, and design flexibility compared to competing micropump technologies.

Biocompatibility Evaluation of Human Umbilical Vein Endothelial Cells Directly onto Low-Temperature Co-fired Ceramic Materials for Microfluidic Applications

Expansion of Low-Temperature Co-fired Ceramic materials into microfluidic systems technology has many beneficial applications due to their ability to combine complex three dimensional structures with optical, fluidic, electrical functions. Evaluations of the biocompatibility of these Low-Temperature Co-fired Ceramic materials are vital for expanding into biomedical research. The few biocompatibility studies on Low-Temperature Co-fired Ceramics generally show negative cellular response to thick film pastes used in generating the electronic circuitry patterns. In this study, biocompatibility of Human Umbilical Vein Endothelial Cells was examined on Heraeuss Low-Temperature Co-fired Ceramic tape and two of their conductive pastes. The biocompatibility was assessed by monitoring cellular attachment and viability up to three days. This study examines the idea of leachates being detrimental to cells due to a study that suggests the possibility of harmful leachates. Results indicate difficulty in initial attach...

Improved Trans-endothelial Electrical Resistance Sensing using Microfluidic Low-Temperature Co-fired Ceramics

Trans-endothelial Electrical Resistance (TEER) and cellular impedance measurements are widely used to evaluate the barrier properties and functional change of endothelial cell monolayers. In the current work, low temperature cofired ceramics (LTCC) are applied enabling the incorporation of TEER and impediametric measurements in an integrated microfluidic chip. LTCC materials are an ideal substrate for biomedical and cell-based microfluidics due to their biocompatibility and ability to combine complex three dimensional structures with optical, fluidic, and electrical functionality. Multilayer microfluidic ceramic devices incorporating gold measurement electrodes where prepared using standard LTCC manufacturing procedures. The sensitivity of the resulting LTCC devices were compared to systems currently on the market for TEER measurements. These results indicate the LTCC device is able to effectively detect the growth of an endothelial cell monolayer. Results further evaluate endothelial cell viability using...

Biocompatible low temperature co-fired ceramic for biosensors

Low temperature co-fired ceramic (LTCC) electronic packaging materials are applied for their ease of fabrication, three dimensional features and integration of multifunctional component, such as optical and electrical functions. For these reasons LTCC is attractive for biomedical microfluidics and Lab-on-a-Chip systems. However, commercial LTCC systems, optimized for microelectrics applications, are not designed for biomedical applications, and have unknown cytocompatibility. In the current work, LTCC has been developed starting with materials of known composition and biocompatibility. The developed LTCC, fabricated from a lime silicate glass and pure alumina, exhibits low sintering temperature (<1000°C) and high density. Alumina reacts with the glass and forms anorthite type crystalline phase CaAl2Si2O8 at temperature 900°C. A commercial gold electrode paste has also been co-fired with the LTCC, with no delamination, cracks nor camber observed. In-vitro biocompatibility of LTCC has been evaluated using h...

P1–33: Thermal properties of alumina cathode heater potting materials

Dispenser cathodes must operate at specific temperatures while applying specific heater powers. Designs to accomplish this have traditionally been empirically derived. In order to apply more systematic FEA methods better knowledge of the unique materials used in the heater package is needed. This investigation was launched to evaluate the thermal properties of the alumina materials used to encapsulate heaters.