Templated nanostructure sensors and methods of manufacture
Inventors
Biaggi-Labiosa, Azlin M. • Hunter, Gary W.
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-10294099-B1
Publication Date
2019-05-21
Expiration Date
2033-03-07
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Abstract
A microsensor and its method of manufacture are disclosed based on templated metal or metal oxide nanostructures. The microsensor includes an electrode that in one embodiment may be configured as a first sawtooth patterned electrode having a series of first peaks and first valleys and a second electrode that by be configured as a second sawtooth patterned electrode having a series of second peaks and second valleys where the second peaks generally align with the first peaks of the first electrode. A plurality of templated metal or metal oxide nanostructures connect on one side to the first electrode and on another side to the second electrode, where an electrical property of the microsensor changes in response to exposure to an environment to be monitored.
Core Innovation
The invention discloses a microsensor and its method of manufacture based on templated metal or metal oxide nanostructures. The microsensor includes electrodes with sawtooth patterns, and a plurality of templated nanostructures connecting these electrodes. The electrical properties of the microsensor change in response to exposure to an environment, allowing detection of certain gases.
The problem being solved addresses limitations in current chemical sensors involving nanostructured materials. Specifically, the challenge of controlling the structural and morphological properties of nanostructures such as nanotubes and nanowires limits their use in sensor applications. Additionally, semiconductor metal oxide sensors typically operate at high temperatures (350-450° C.), which results in high power consumption. The invention aims to produce sensors that are small, easy to batch fabricate, low cost, with low power consumption and decreased operating temperature while maintaining or improving sensitivity and selectivity.
The invention proposes using carbon-based templates such as carbon nanotubes, coated with metal or metal oxide materials, followed by heat treatment to remove the template leaving a nanostructure imprinted with the morphology of the carbon template. This templated nanostructure combines the advantageous crystal patterns and surface morphology of the template with the chemical and thermal durability of metal oxides. This method results in porous nanostructures with increased surface area accessible to gas molecules, enhancing sensitivity. The microsensor fabrication includes aligning these templated nanostructures between electrodes using dielectrophoresis, enabling room temperature operation and detection of gases such as methane with low power consumption and high stability.
Claims Coverage
The patent includes two independent claims directed to methods of manufacturing templated nanostructure microsensors, each featuring several inventive aspects.
Use of carbon-based template materials with metal oxide precipitate coating
The method provides a carbon-based template material with morphological sensing properties and coats it with a metal oxide precipitate, such as tin oxide, tungsten oxide, titanium dioxide, indium oxide, or others, imprinting the morphology into the precipitate coating.
Sacrificial removal of the carbon-based template by heat treatment
Heat treating the coated structure in an oxygen environment sacrifices the carbon template, leaving a metal oxide nanostructure that preserves the template morphology with a crystallite size less than twice the depletion layer depth.
Formation of microsensor structure by connecting spaced electrodes via nanostructures and burying contacts
Nanostructures of the metal oxide precipitate physically connect spaced electrodes patterned and aligned on a substrate. An upper electrode is deposited to bury contact points, enhancing electrical connection.
Alignment of nanostructures between electrodes using electric field and electrode patterning
Prior to depositing the upper electrode, the method aligns templated nanostructures between patterned physically spaced electrodes using dielectrophoresis with sawtooth patterned electrodes to preferentially position nanostructures between electrode tips.
The independent claims focus on templated metal oxide nanostructures imprinted from carbon-based templates, sacrificial removal of the template, electrode configuration connecting nanostructures, and alignment techniques employing patterned electrodes and electric fields to manufacture improved microsensors.
Stated Advantages
Low power consumption due to operation at room temperature without the need for heating.
Miniature size, low weight, and low cost enabling simple batch fabrication with high yield.
Enhanced sensitivity and selectivity due to porous nanostructures that allow gas molecules to interact with both interior and exterior surfaces.
Robust sensor structure enabled by microfabrication techniques, including batch fabrication of sawtooth patterned electrodes.
Long-term stability of sensor response demonstrated over extended testing periods.
Documented Applications
Environmental monitoring, specifically detection of methane gas.
Detection of various gases including hydrogen, propylene, hydrocarbon gases, carbon monoxide, nitrogen oxides, nitrogen tetraoxide, fluorines, chlorines, ammonia, hydrazine, formaldehyde.
Detection of biological molecules in aqueous environments such as cells, viruses, or proteins.
Toxic gas monitoring and explosive gas monitoring.
Detection of biological agents and biological molecules of interest.
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