Category Archives: Materials & Nanotechnology

Ceramics, composites, polymers, superconductors, thin films, etc.

A Novel Method for Fabricating Nano-fibrillar Ceramics

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Summary:

Researchers at the Ohio State University have discovered a novel fabrication technique for fabricating ceramic nano-fibrillar structures. Such structures can be used as reactive or catalytic surfaces for gas sensors and catalysts applications. Generally, gas sensors and catalysts require high exposed surface area to allow for efficient gas-solid reactions. Our newly developed nano-filaments are 50-100 nanometers in diameter and about 5 microns in length, which correspond to a high aspect ratio of 50/1 to 100/1 and therefore provides high surface area for gas-solid interaction, which is beneficial for chemical sensors and catalysts. The inventive process demonstrates the feasibility of a simple, low-cost method of fabricating nano-structured ceramics as a platform for these applications.

Potential Applications:

  • Catalysis and catalytic supports
  • Chemical sensors
  • Dielectrics
  • Solar cells

Advantages:

Large surface area for more efficient gas-solid reactions

A Gas-Assisted Resin Injection Technique for Bonding and Surface Modification of Microfluidic Devices

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Summary:

Polymer-based microfluidic systems have great potential for use in BioMEMS applications, because many polymers are low cost, biocompatible, and have good processibility as compared to silicon and ceramic materials. Packaging (e.g., sealing a platform with a lid) and surface modification (e.g., hydrophilicity, protein absorption, electric conductivity for electrokinetics), however, are challenging issues in the fabrication of polymer microfluidic platforms.

We recently developed a gas-assisted resin injection technique in our lab, which can achieve bonding and surface modification on microfluidic devices.

Potential Applications:

BioMEMS applications

Advantages:

Achieve bonding and surface modification on microfluidic devices

Uniform Electrochemical Reduction of Apertures to Submicron Dimensions using Commercial Biperiodic Metallic Mesh Arrays

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Summary:

Metallic meshes have unusual optical properties when the size of the holes is comparable to the wavelengths of light. Surface plasmons couple short-lived waves producing “extraordinary” transmission (Ebbesen, et al. 1998) and extraordinary absorptions by species on the surface of the channels. At The Ohio State University, we are able to detect radicals and intermediates of reactions catalyzed by coating the metal surface.

Potential Applications:

  • Physical separation based on size – several meshes could be configured in flows to separate materials such as cells, bacteria, or particles in the micron and submicron regime
  • Control of diffusion – such as in drug delivery application or keeping a sensor from saturating
  • Optical detection – such as bio-molecules passing through the channels in analytical separations by virtue of their unusual bandpass and surface enhanced optical properties
  • Unusual optical properties – the meshes serve as band-pass filters and beam splitters in the infrared (IR) region

Advantages:

  • In the IR region, we see surface plasmons on Ni (or Cr, Pt, Pd, and W) unlike the visible region where work focuses on Ag and Au
  • It is possible to measure lifetimes, dispersions, and resonance shifts of surface plasmons more accurately because of the capability of working in the IR region
  • Surface plasmons created from this process produce 1000-fold enhancements in the IR absorption spectra of monolayers and surface species
  • Stacking of the meshes creates rudimentary photonic crystals with the potential to serve as sensors for biomolecules on lipidbilayers
  • Detection of submonolayer densities of molecular species, like methoxy radical, is possible by using metal microarrays with subwavelength holes as substrates
  • Meshes allow researcher the time to tackle a biochemical problem before surface plasmons dissipate

Direct, Low Frequency Capacitance Measurement for Scanning Capacitance Microscopy

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Summary:

Scanning capacitance microscopy (SCM) circuits, used for such applications as semiconductor characterization (including dopant profiling, device characterization, and surface defect characterization), are typically not adapted for calibrated, low frequency measurements of absolute capacitance. In fact, these implementations of SCM generally do not measure capacitance directly. Rather, they measure the change in capacitance versus the change in voltage (dC/dV) by varying the probe-sample voltage V at frequencies greater than 10 kHz. This is due to a voltage dependant capacitance resulting from a voltage-dependant space change layer in the semiconductor substrate. The Ohio State University has developed a system and method for performing scanning capacitance microscopy using an atomic force microscope (AFM) that measures direct capacitance at a frequency less then 10 kHz. The system exhibits high sensitivity with very low noise. Recent advancements to this technology have resulted in even higher sensitivity by enabling direct measurements of absolute capacitance at higher frequencies. The design of the circuit has also been simplified, enabling the use of off-the-shelf components such as function generators. This straightforward design will shorten the investment of time and money needed to commercialize this powerful system.

Potential Applications:

This system is an ideal tool for semiconductor characterization. It is also useful for measuring a wide variety of dielectric films such as SiO2 grown on Si, or for dielectric films on other semiconductor substrates such as Si3N4, Al2O3, TiO2, and ZrO2. It may also be used to measure thin lubricant films such as perfluoropolyethers, a widely used class of compounds for MEMS and hard disk drive lubrication. Other suitable types of samples include self-assembled monolayers.

Advantages:

  • Enables direct capacitance measurements at low frequencies
  • Low noise
  • High sensitivity
  • Straightforward yet powerful design
  • Can also determine stray capacitance

Fabrication of Micro-devices with Sandwich Structure

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Summary:

A variety of ways are currently used to manufacture polymer microparticles. They include spray drying, phase separation, and emulsification. However, the microparticles produced by these methods are typically limited to shapes that are spherical, and the sizes of particles produced are uneven.

Researchers at the Ohio State University have discovered a novel way of fabricating uniform polymer microparticles that addresses these shortcomings of current fabrication methods. The disclosed techniques have the advantages of increase geometrical control and applicability to a wide variety of polymers.

Potential Applications:

Drug delivery

Advantages:

More control over shape and size of microparticles allows more targeted drug delivery

Novel Processing of Gas Sensors: Oxidation of Metallic Precursors

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Summary:

Researchers at the Ohio State University have discovered a novel processing method of gas sensors by the oxidation of metallic precursors. Gas sensors are present in automobiles and industrial operations in order to monitor levels of harmful gases that may be present. The operation and effectiveness of these gas sensors depend heavily on how much contact the gases make with the sensors, so it is desirable to make sensors with a large surface area.

We have discovered a method to manufacture free-standing, porous rutile foils having an open structure. This design greatly increases the available surface area for the gas sensors and allows more accurate and stable detection of gas levels. These ceramic bodies may also be able to filter out a species of liquids or solid particles in a fluid.

Potential Applications:

  • Automobile emission systems
  • Industry

Advantages:

  • Able to catalyze reactions
  • Freestanding
  • Can survive harsh environments

NOx Sensor with Improved Selectivity and Parts-Per-Billion Sensitivity

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Summary:

Nitrogen Oxides (NOx) present a host of environmental and health problems, including acid rain, urban smog, acidification of lakes and streams, and damage of forest soils.  The major source of NOx is from the combustion of fossil fuels, and NOx sensors are employed in the development of internal combustion engines in order to optimize combustion and minimize emissions.  Nitric Oxide is also an important biological molecule and its level in human breath is also an indication of many diseased states, including asthma.

Resistance-based electrochemical NOx sensors, while exhibiting good sensitivity, often react to many different gases, and selectivity suffers.  Potentiometric sensors offer a promising approach for NOx measurements in harsh environments, but often suffer from interference with other gases.

Researchers at The Ohio State University have developed a novel potentiometric NOx sensor that overcomes the interference limitations of previous potentiometric sensors.  This sensor is extremely selective to NOx in the presence of other gas species, and sensitivities have been confirmed in the parts-per-billion range!  The sensor is ideal for incredibly precise NOx measurements in environments as diverse as engines and for breath monitoring.

Potential Applications:

  • Medical diagnostics
  • Combustion optimization
  • Environmental NOx monitoring

Advantages:

  • Ridiculously high sensitivity (ppb range!)
  • Excellent selectivity
  • Will withstand extreme environments
  • Cost effective as potentiometric output does not require sophisticated support electronics

Technique for Single Sensor Differential Thermal Analysis

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Summary:

Researchers at The Ohio State University have developed a technique for single sensor differential thermal analysis (SS-DTA) that determines the solid-liquid and solid-state phase transformations during the actual processing of metals and alloys. The SS-DTA technique is based on single sensor temperature measurement and computerized acquisition of the thermal history in particular locations of the processed metal. The heat of reaction and temperatures of the phase transformation are measured by software that processes the thermal data. This new technique was verified by direct comparison to the classic differential thermal analysis (DTA) as well as dilatometry. It has been successfully applied for in-situ determining the solidification ranges and solid-state phase transformation temperatures in welded joints of various alloy steels, non-ferrous alloys and Ni-base superalloys, and for development of continuous cooling transformation diagrams. In addition, phase transformation behavior during weldability testing, post-weld heat treatment, and casting has also been measured. It has been successfully applied with a thermo-mechanical simulator. The SS-DTA technique is performed utilizing a device for the investigation of phase transformations (DIPT) that was also developed by The Ohio State University.

Potential Applications:

  • Development of new alloys and welding consumables.
  • Investigation of microstructure evolution under actual processing conditions of thermal and thermo-mechanical processing.
  • Study of microstructure-property relationships and material fabricability.
  • Development and testing of procedures for thermal and thermo-mechanical processing of metals and alloys.

Advantages:

  • Applicable at non-equilibrium heating and cooling rates and in actual processing conditions.
  • Applicable and highly sensitive to the entire range of solid-liquid and solid-state phase transformations in metal and alloys and to the magnetic transformation (in ferrous alloys).
  • Fast, simple and cost-effective; Applicable as a more sensitive and accurate alternative or back up to dilatometry in simulation equipment.
  • Potential for measuring precipitation and recrystallization reactions and for quantifying the volume fraction of formed phases.

IP Status:

US pending

Device for Investigation of Phase Transformations in Metals and Alloys

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Summary:

Researchers at The Ohio State University have developed a device for investigating phase transformations (DIPT) in metals and alloys that is capable of reproducing, over laboratory scale specimens, the actual thermal histories of liquid, solid-liquid and solid-state processing. The thermal simulation devices currently available are not capable of studying the solid-liquid phase transformations and have limited usefulness for studying the non-equilibrium solid-state phase transformations that occur during thermal and thermo-mechanical processing. This has resulted in a lack of practically applicable phase transformation data for the modern structural alloys. The DIPT, however, has a broad field of application in the investigation of the melting and solidification phenomena and the solid-state phase transformations in metals and alloys under simulated processing conditions and in some fabricability tests. It provides a powerful tool for the development of alloys, consumables and filler metals for a wide range of processing applications such as welding, surfacing, hardfacing, brazing, soldering, surface melting, casting, etc. The DIPT simulates processing with complete or partial melting, or without melting, and determines the solid-liquid and solid-state phase transformation temperatures by single sensor differential thermal analysis (SS-DTA). SS-DTA is a novel technique that is based on single sensor temperature measurement and computerized acquisition of the thermal history. The phase transformation temperatures are measured by software processing of the thermal data. The DIPT has been successfully applied for measurement of solidification ranges, formation of eutectic phases, and solid state phase transformations in various steels and Ni-base super alloys.

Potential Applications:

Materials producers and processing companies as well as research and educational institutions

Advantages:

  • Reproduces the actual thermal histories of liquid, solid-liquid and solid-state processing over laboratory scale specimens.
  • Determines the solid-liquid and solid state phase transformation temperatures under a wide range of simulated processing conditions.
  • Provides a fast and economical tool for alloy development and a competitive alternative to the available simulation equipment.
  • Utilizes the highly sensitive and versatile single sensor differential thermal analysis (SS DTA).

IP Status:

US pending

A Novel Method for Fabricating Shaped monolithic Ceramics and Ceramic Composites: Displacive Compensation of Porosity (DCP)

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Summary:

Refractory ceramics can exhibit several enhanced properties relative to refractory metals and alloys, such as corrosion resistance, high temperature stability in oxidizing atmospheres, specific strength and stiffness, creep resistance, and wear resistance. However, the brittleness of ceramic bodies renders the fabrication of shaped components tedious and expensive. Such brittleness also necessitates the use of reinforcements to enhance damage tolerance. The present invention describes a new reaction-based method for fabricating shaped, reinforced ceramic bodies that involves a minimum number of low-cost processing steps: the Displacive Compensation of Porosity (DCP) process.

Potential Applications:

Manufacturing of materials that retain their strength at high temperatures.

Advantages:

Low cost Smaller number of steps to manufacture refractory ceramics; easier to manufacture.