Low Temperature Co-Fired Ceramics for Micro-Fluidics

The miniaturization of analytical instruments and packaging of novel sensors is an area that has attracted significant research interest and offers many opportunities for product commercialization. Low Temperature Co-fired Ceramics (LTCC) is a materials system composed of alumina and glass in an organic binder. LTCC is a good choice for sensor development because of the ease of incorporating features in the ‘green’ or unfired state such as electrical traces, fluidic pathways and passive electrical components. After a firing cycle, what remains is a robust, monolithic device with features embedded in the package. In order for LTCC to be a successful medium for small scale sensors or lab-in-package devices, fluid flow through channels and inlet/outlet ports must be perfected. Device inlet/outlet ports have been demonstrated by embedding sapphire tubes in LTCC, allowing external connections using compression fittings. Channels and cavities have been fabricated through the use of sacrificial carbon tapes and pastes. A field flow fractionation device used for separating or concentrating constituent components in a fluid and a multi-electrode electrochemical cell were fabricated with the techniques described in this paper

An extensional mode resonator for vibration harvesting

In an effort to identify techniques for harvesting energy from ambient vibrations, a prototype device that utilizes stretching piezoelectric film to support a proof mass, with an adjustable support that allows the resonant frequency of the device to be easily altered has been developed. This extensional mode resonator (XMR) device is described by a model developed in this work that predicts the power that is harvested as a function of the frequency and amplitude of the external vibration, the elastic and piezoelectric materials properties, and the device geometry. The model provides design guidelines for the effects of device geometry and applied tension through an adjustable support that suggest a strong dependence on mechanical damping and a weak dependence on frequency, as opposed to a bending cantilever device. The model predictions are compared to experimental measures from multiple configurations of the prototype device for frequencies between 60 Hz and 180 Hz, and at accelerations between 0.1 m/s2 and 25 m/s2. Up to 22 mW is generated from a device with a mass of ~82 g at 25 m/s2 acceleration, and over the range of frequencies tested the power harvested at 4 m/s2 is between 3 mW and 4 mW. The developed models are used as design tools for various configurations that are capable of over 100 mW at less than 3 m/s2 in one case to another that can generate more than 10 mW at 1 m/s2. Prototype configurations have been successfully tested as high as 80 m/s2 with power generated on the order of 40 mW

Mini- and Micro- Channel Devices in Low Temperature Cofired Ceramics

The miniaturization of analytical instruments and packaging of novel sensors is an area that has attracted significant research interest and offers many opportunities for product commercialization. Low Temperature Co-fired Ceramics (LTCC) is a materials system composed of alumina and glass in an organic binder. LTCC is a good choice for sensor development because of the ease of incorporating features in the \u27green\u27 or unfired state such as electrical traces, fluidic pathways and passive electrical components. After a firing cycle, what remains is a robust, monolithic device with features embedded in the package. In order for LTCC to be a successful medium for small scale sensors or lab-in-package devices, fluid flow through channels and inlet/outlet ports must be perfected. Device inlet/outlet ports have been demonstrated by embedding sapphire tubes in LTCC, allowing external connections using compression fittings. This research presents different methods of channel and cavity fabrication through the use of sacrificial carbon tapes and pastes. A field flow fractionation device used for separating or concentrating constituent components in a fluid and a multi-electrode electrochemical cell are featured as integral components to the successful implementation of a lab-in-package device

Sample Preparation for the Transmission Electron Microscope

The work of preparing samples for a Transmission Electron Microscope (TEM) can be complicated. In order to demystify the skill of preparing samples for the TEM, an illustrated guide is presented to serve as a learning tool to the new student in the laboratory. This guide will compare processing techniques for three different materials used in the Advanced Materials Laboratory: Tungsten, Lanthanum Calcium Ferrite and Graphite. A general outline is enhanced with material specific procedures to help reinforce the major concepts, identify common mistakes, and highlight the similarities among each material. Examples demonstrate the goals for each section of the procedure. Understanding the characteristics of each material directs the approach used to prepare the TEM sample. Generally, the harder the material is (Tungsten in this example) the more aggressive the initial steps of the procedure are. For the hardest of materials, each step of the procedure will take more time even starting with a higher degree of abrasive instruments, however, the procedure will regress into common methods shared by all materials. Preparing samples for the TEM can be a daunting task for any novice. Providing a detailed “how to” guide will accelerate the transition of the timid trainee to knowledgeable expert, saving many hours in preparation

Novel Materials for Transient Liquid Phase Ceramics and Metal Joining

Joining is an enabling technology for many ceramics applications. Often ceramics are only useful in a system of components, requiring that they be bonded in some fashion to other ceramic components of the same composition or dissimilar materials such as metals or other ceramics. This is particularly true in the practical applications of fuel cells, gas separation membranes, and sensors, where a wide variety of ceramic-ceramic and ceramic-metal joints are required. The objective of this project is to bond a metal to a ceramic by the formation of a liquid-phase ceramic that wets to the surface of the metal and the ceramic. This liquid phase diffuses into the metal and bulk ceramic, and as the chemical composition of the liquid changes, it becomes a solid. This process is known as transient liquid phase (TLP) sintering. Ideally, this solid will be the bond between a metal and a ceramic. There are a variety of existing methods for joining ceramics to themselves or other materials. These joining methods have the disadvantage of leaving behind an interfacial phase with thermal and physical properties inferior to that of the materials being joined and may degrade the environmental stability of the parent material. Consequently, industry and academia have sought for many years to develop joining methods which leave behind effectively no interfacial phase, or a compatible, refractory phase with virtually the same thermal expansion coefficient as the joined parts. Although this work has not yet yielded a successfully novel metal to ceramic joint, a new transient liquid phase ceramic, SrMoO4, has been synthesized. This ceramic was sintered at 830°C and possesses a melting temperature of over 1200°C. Additionally a baseline study of the environmental stability of metal-to-metal brazes was conducted. This work is in collaboration with the Central Metallurgical Research Institute of Egypt with the goal of extending the operating range of high temperature materials and increasing their operational life

Recrystallization Kinetics of 3C Silicon Carbide Implanted with 400 keV Cesium Ions

Polycrystalline 3C silicon carbide (SiC) was implanted at room temperature with 400 keV cesium ions to a dose of 1016 ions/cm2. The samples were annealed at 600°C–1000°C for times up to 48 h to observe changes in the implantation zone crystallinity and density. The implanted regions were characterized by transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS) before and after annealing. It is shown that the implantation resulted in a 217 ± 2 nm amorphous region with microstructural damage extending to ~250 nm below the surface. Recrystallization of the amorphous region was observed to begin at 725°C. Densification was determined indirectly through changes in the measured implantation zone thickness. Measurable thickness, or densification, of the implanted region was not observed until temperatures greater than ~800°C. The SiC recrystallization began at the interface between the amorphous, damaged region, and the underlying polycrystalline material. Image analysis was used to quantify the fraction of crystalline phase as a function of time and temperature. The recrystallization kinetics exhibited Arrhenius dependency with an apparent activation energy of 480 kJ/mol. SIMS demonstrated that 60%–70% of the cesium was retained within the recrystallized microstructure after thermal annealing

A Prototype Continuous Flow Polymerase Chain Reaction LTCC Device

There is a growing need for remote biological sensing in both laboratory and harsh field environments. Sensing and detection of biological entities such as anthrax, Ebola and other micro-organisms of interest involves sampling of the environment, amplification, analysis and identification of the target DNA. A key component of such a sensor is a low cost, portable, reusable, continuous flow polymerase chain reaction (PCR) thermal cycler. Fabrication with low temperature co-fired ceramics (LTCC) can provide a reusable low cost device capable of operating in a wide range of environments. The design and manufacture of a prototype continuous flow micro-fluidic PCR device using low temperature co-fired ceramic is presented. Initial modeling of flow characteristics and heat transfer was carried out in SolidWorks™. The prototype device employs resistance heaters below the channels, buried and surface thermocouples for temperature monitoring, and air gaps for thermal isolation

Strategies for Controlling the Spatial Orientation of Single Molecules Tethered on DNA Origami Templates Physisorbed on Glass Substrates: Intercalation and Stretching

Nanoarchitectural control of matter is crucial for next-generation technologies. DNA origami templates are harnessed to accurately position single molecules; however, direct single molecule evidence is lacking regarding how well DNA origami can control the orientation of such molecules in three-dimensional space, as well as the factors affecting control. Here, we present two strategies for controlling the polar (θ) and in-plane azimuthal (ϕ) angular orientations of cyanine Cy5 single molecules tethered on rationally-designed DNA origami templates that are physically adsorbed (physisorbed) on glass substrates. By using dipolar imaging to evaluate Cy5′s orientation and super-resolution microscopy, the absolute spatial orientation of Cy5 is calculated relative to the DNA template. The sequence-dependent partial intercalation of Cy5 is discovered and supported theoretically using density functional theory and molecular dynamics simulations, and it is harnessed as our first strategy to achieve θ control for a full revolution with dispersion as small as ±4.5°. In our second strategy, ϕ control is achieved by mechanically stretching the Cy5 from its two tethers, being the dispersion ±10.3° for full stretching. These results can in principle be applied to any single molecule, expanding in this way the capabilities of DNA as a functional templating material for single-molecule orientation control. The experimental and modeling insights provided herein will help engineer similar self-assembling molecular systems based on polymers, such as RNA and proteins