Category Archives: General Instrumentation

AFM, interferometry, mass spectrometry, STEM, etc.

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

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

Digital Method for Real-Time Frequency Evaluation of Periodic Signals

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Summary:

Frequency counters typically count a frequency of a periodic signal by setting a set gate level. Each time the periodic signal crosses the gate level an event is generated. After calculating the number of events per second, the frequency is then calculated from the periodic signal. Unfortunately, this universal method has not demonstrated stability for frequency measurements. At The Ohio State University, we have created a reliable digital real-time method that detects frequency of a force signal from a microcantilever sensor in Magnetic Resonance Force Microscopy. Additionally, this method demonstrates sensitivity limited only by the displacement noise of a cantilever. Our high precision evaluation of the frequency of a periodic signal can be used as an extra option for any currently available digital signal processing hardware. A prototype is available for testing and evaluation under a confidentiality agreement.

Potential Applications:

  • Detection of biohazards at sensitive immigration and import/export points and at transportation sites
  • Counter intelligence and eavesdropping
  • Breathalizers
  • Any SFM system, MRFM, MRI, and microwave signals

Advantages:

  • Measures frequency shifts of resonator cantilever quickly thus offering increased sensitivity.
  • Continuously measures rather than sampling because it measures in small forces that are 6-7 magnitudes larger than what needs to be measured.
  • Accurately and directly calculates the frequency from the amplitude and the phase of an input signal.
  • The frequency signal is based upon a number of points less than the period of a signal.
  • Enables higher force sensitivity for force microscopy systems and for noise where force is detected through its influence upon the frequency of the oscillating mechanical force detector (microcantilever).
  • Solves the problem of limited bandwidth of amplitude detection.
  • Most effective sound frequency range is DC-1MHz.
  • One can resynchronize by re-inputing data that was taken out of the probe sequence so one can probe the system with the probe sequence.
  • Allows one to create a full MRFM measurement system including a self excitation circuit, a frequency detector, and RF modulation circuits and capable of generating modulation signals whose phase is locked to the cantilever signal.
  • Existing computers already use digital computers.
  • Digital read-out of frequency output time is 4 milliseconds; as computer boards improve, this technique’s speed improves.

Implementation of Light-Free Capacitive Displacement Detection for Magnetic Resonance Force Microscopy

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Summary:

Magnetic resonance signal is detected via displacement detection of a micromechanical cantilever. Usually, this is done by means of fiber-optical laser interferometry. However, in many systems, laser light disrupts magnetic resonance signal. At The Ohio State University, we are the first to implement MRFM with light-free capacitive displacement readout that can perform subsurface imaging on a nanometer scale.

Potential Applications:

  • Solid state quantum computer
  • Semiconducting devices
  • It can detect a range of magnetic resonance phenomena (EPR, NMR, FMR) making it applicable to various physical systems

Advantages:

  • The depth of probing can measure to the nanometer scale to image molecules.
  • Improved sensitivity could exceed optical techniques
  • Capacitive detection will eventually replace optical detection
  • There is no laser light to disrupt the magnetic resonance signal
  • Displacement detection is integrated into the device allowing it to be fabricated at the same time making it enabling for parallelization

Undetectable, Unjammable, and Interference-Free Ultra Wideband Radar System

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Summary:

Researchers at the Ohio State University have developed a virtually undetectable ultra wide band radar system that transmits pseudo random noise. On receive, the radar system cross-correlates a copy (possibly modified) of the original waveform with the receive signals. If a target reflects the signal (with modifications) then the radar will detect the reflection, the time delay, and Doppler. Thus the radar can tell the distance to a reflecting object and its relative speed. This is done using a waveform that will not interfere with other users of the spectrum. The noise waveform is extremely hard to detect. Researchers have further developed a system of storing the waveforms and performing the cross correlation at a particular time delay using a single memory device and no delay devices. This lends to the creation of a small, low cost, low power, stealthy radar that cannot be easily detected by conventional radar detection equipment and can be used for very short range applications. The radar can also be used to identify radar targets by using a pair of waveforms matched to the target radar impulse response. Thus the radar can also be used to detect only specific types of targets, as maybe required by the application.

Potential Applications:

  • Speed radar gun manufacturers seeking an undetectable radar gun
  • Simple moving vehicle/person/object with identification potential (automotive lane change warning)
  • Highway management to evaluate strength of material, or helicopter air to air warning systems
  • Low cost ground penetration radar for pipes, land mine detection, or probing human bodies
  • Low cost building penetration radar (security systems at casinos and airports)
  • Cross section instrumentation radar with inverse synthetic aperture imaging radar ability
  • Moving Radar, synthetic aperture radar systems

Advantages:

  • Robust with reference to interference or jamming – thus undetectable and hard to intercept
  • Unlikely to interfere with other noise radar systems or other radar systems in the same band
  • Low cost, small, light weight, and can be used for very short-range applications
  • Can be trained to be target specific (with the ability to specify multiple targets)
  • Would require no license to operate in civilian bands, and is fully coherent in amplitude and phase

Condensation reducing Petri dish or culture container

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Summary:

Condensation on the inside lid of Petri dishes is a universal problem in the laboratory. Condensation problems result when the temperature of the inside lid of a container falls below the temperature inside the container itself. Condensation can take the form of either a light fog or large water droplets. When large water droplets form, they can drop from the lid onto the contents of the container, displacing the contents and creating water-soaked microenvironments. When a light condensation is formed, the contents of the container are often obscured, which makes critical observations difficult and photo documentation of the contents of the dish can be very frustrating.

Researchers at The Ohio State University have eliminated condensation in Petri dishes by a simple modification in Petri dish design. By increasing the thickness of the polystyrene in the top portion of a standard Petri dish lid, the lid was buffered from small temperature changes and condensation was reduced or eliminated. The side walls of the Petri dish remain the same thickness so condensation will preferentially form on the side walls, and water droplets run down the side wall to be reabsorbed by the medium in the dish.

The invention does not require large changes in manufacturing basics. Containers will still be manufactured from polystyrene, which is optically clear, inexpensive and a good insulator (low thermal conductivity). The new Petri dish lid will be thicker on the top surface and sides of the lid should remain the same thickness.

Potential Applications:

All laboratories and other research and development facilities

Advantages:

  • Condensation is virtually eliminated
  • Does not require major manufacturing changes
  • Made with inexpensive materials

Multiwell Miroprocessing Basket

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Summary:

Researchers at the Ohio State University have developed a Multiwell Microprocessing Basket that allows simultaneous, quick, and safe processing of several groups of small/delicate specimens for light and electron microscopy, including preparations for immunolabeling, fluorescence and confocal laser scanning microscopy, with minimal handling of the specimens and minimal quantities of fixatives, antibodies, buffers, fluorescent dyes and other reagents used. This device is particularly useful, economic, and time saving, when processing very small/delicate specimens that are in danger of being lost/damaged during various preparation steps for light, fluorescence or electron microscopy. Such specimens may include, but are not restricted to, small pieces/sections of animal or plant tissue, small insects or insect organs, mites, other small animals, pelleted or aggregated microorganisms and cell cultures.

Potential Applications:

Laboratory work in immunolabeling, florscence and confocal laser scanning microscopy.

Advantages:

  • Requires minimal quantities of fixatives, antibodies, buffers, fluorescent dyes and other reagents.
  • Can process upt to 24 different samples simultanuosly without loss or damage to specimens.

Printed circuit emulation of anisotropic media for generating slow waves and field amplification in microwave and antenna components

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Summary:

For the first time ever, researchers at the Ohio State University have been able to use simple microwave circuit components to emulate the extraordinary propagation phenomena traditionally encountered in periodic assemblies of bulk anisotropic dielectric and gryomagnetic ferrite materials. The researchers have been able to realize degenerate band edge resonances as well as frozen modes using uniquely invented, cost effective, and easy to manufacture microstrip transmission lines arrangements (Printed Circuit technology). The field growth and amplification effects of these remarkable modes allows for miniaturization of microwave and optical circuit components such as coupled lines, delay elements, printed antennas, and antenna arrays. These microwave circuits can also be coupled with mature circuit optimization tools to quickly design metamaterials displaying the same electromagnetic modes. The proposed microwave circuits can be further extended to solid state semiconductor optoelectronics devices via standard IC manufacturing technology.

Potential Applications:

  • Miniaturization of microwave and optical circuit components such as coupled lines, delay elements, phase shifters, printed antennas, antenna arrays, and solid state semiconductor optoelectronic devices
  • Efficient metamaterial design
  • Frequency mixing and modulation applications

Advantages:

  • Compared to metamaterials, realizing the same modes is much easier and significantly less expensive
  • Easy to manufacture in volume production since it is based on printed circuit technology
  • Easy retrofit with existing manufacturing processes
  • Very cost effective

Ultrasonic Cleaning of Inorganic Cross-flow Filtration Membranes

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Summary:

A system has been developed which utilizes ultrasound to remove cake layer fouling from inorganic membranes. The system also prevents the sedimentation of patricles onto the membrane surface and reduces the concetration polarization near the membrane pore sizes. Inorganic membranes offer the potential of easier cleaning than polymeric membranes and the inorganic membranes are much more resistant to degradation by cavitation mechanisms generated by the ultrasound.

Potential Applications:

  • Any area where inorganic membranes are used to remove particles are colloids, such as:
  • Removal of yeast cells from beer
  • Seperation of whey proteins in the dairy industry

Advantages:

  • Removes cake layers without physically touching material
  • Reduces the concentration polarization