Nanowire arrays for trace vapor preconcentration
Inventors
Giordano, Braden C. • Pehrsson, Pehr E. • Johnson, Kevin J. • Ratchford, Daniel • Field, Christopher • Yeom, Junghoon
Assignees
Publication Number
US-10501316-B2
Publication Date
2019-12-10
Expiration Date
2031-11-10
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Abstract
Disclosed herein is a method of providing a structure having two electrodes connected by nanowires, exposing the structure to an analyte that can adsorb onto the nanowires, and passing an electrical current through the nanowires to heat the nanowires to desorb the analyte. Also disclosed herein is an apparatus having the above structure; a current source electrically connected to the electrodes, and a detector to detect the analyte.
Core Innovation
The invention relates to a method and apparatus involving a structure having two electrodes connected by a plurality of nanowires perpendicular to the electrodes. The nanowires have a chemically selective surface that adsorbs analytes from a sample. An electrical current is passed through the nanowires to heat them via Joule heating, causing desorption of the adsorbed analyte for detection. The structure may have one or both electrodes with perforations that allow gases or liquids to flow rapidly through, enhancing analyte access to the nanowires.
The problem addressed is the challenge of creating sensor devices based on vertical nanowire arrays with efficient electrical connections to all nanowires and enabling rapid analyte diffusion. Existing approaches do not sufficiently allow for porous electrodes with controlled hole size and distribution that enable rapid analyte flow while maintaining electrical contact. Furthermore, current trace vapor detection methods, such as spectroscopic or chemical sensors, suffer from limitations in sensitivity, selectivity, response time, or instrument complexity. Eddy diffusion during desorption broadens analyte pulses and reduces detection precision. The invention aims to improve sensitivity, selectivity, and response speed through controlled nanowire array structures with porous electrodes and Joule heating for desorption.
The vertical silicon nanowire arrays offer high surface area for adsorption and the ability to selectively control nanowire dimensions, arrangement, and surface chemistry. The periodic perforated electrode enables rapid analyte transport through the array, and the electrical connection to all nanowires minimizes noise sources. Joule heating of the nanowires results in rapid, controlled desorption profiles that serve as unique thermal desorption spectra for analyte separation and detection. The method and apparatus enable integration with various multichannel detectors such as mass spectrometry or ion mobility spectrometry and can be expanded to matrices of arrays with different surface coatings for enhanced selectivity and sensitivity.
Claims Coverage
The patent discloses two independent claims covering a method and an apparatus involving nanowire structures with chemically selective surfaces and electrodes, describing their configuration and use for analyte adsorption and desorption.
Nanowire structures with chemically selective surfaces and dual electrodes
The method provides two or more structures each comprising a first electrode, a plurality of nanowires perpendicular to the electrode with chemically selective surfaces, and a second electrode in contact with the nanowires’ second end, where the different structures have chemically selective surfaces each selective for different analytes.
Heating nanowires by passing electrical current to cause analyte desorption
The method includes passing electrical current through the nanowires to heat them to desorb adsorbed analytes after exposure to a sample containing the target analyte.
Use of perforated or continuous second electrodes and periodic arrangement
The second electrode may be perforated or continuous, and the nanowires and perforations may be periodically arranged to enable efficient analyte flow and electrical contact.
Detection of desorbed analytes using various techniques
The method optionally includes detection of desorbed analytes by mass spectrometry, ion mobility spectrometry, fluorescence probes, cantilevers, chemiresistors, nanowire arrays, and optionally passing analytes through gas chromatography before detection.
Apparatus combining nanowire structures with current source and detector
The apparatus comprises two or more nanowire structures as described, each with electrodes and chemically selective surfaces, a current source electrically connected to the electrodes to pass heating current, and a detector configured to detect desorbed analytes.
The independent claims cover providing nanowire array structures with chemically selective surfaces and electrodes, passing current through the nanowires to heat them for desorption, and detecting the desorbed analyte using various detectors. The apparatus claim integrates these elements with a current source and a detector, optionally including multiple structures with different chemical selectivities.
Stated Advantages
The perforated top electrode allows rapid gas flow through the nanowire array, significantly improving sensor response time compared to non-porous electrodes.
The vertical nanowire arrays maximize sensor surface area and minimize noise sources such as wire-to-wire junction noise and 1/f noise, enhancing sensitivity and signal-to-noise ratio.
Joule heating of the nanowires enables rapid and controlled desorption of analytes, providing unique thermal desorption spectra that improve analyte separation and detection sensitivity.
Integration with multichannel detectors and the use of arrays with different coatings allows enhanced selectivity through differential sorption/desorption kinetics.
The method permits scalable fabrication of ordered nanowire arrays with controlled electrode perforations without the need for precise alignment, facilitating large-area production.
Use of silicon nanowires allows easy fabrication with existing techniques and compatibility with CMOS integration, reducing cost and complexity.
The method reduces total analysis time and instrument complexity compared to traditional analytical instrumentation by combining preconcentration and partial separation in one structure.
Documented Applications
Detection of trace explosives vapors including components of improvised explosive devices (IEDs) in complex environments.
Gas phase sensing of chemical warfare agents, toxic industrial chemicals (TICs), and chemical or biological agents.
Preconcentration and desorption of trace vapor analytes for downstream analysis by mass spectrometry, ion mobility spectrometry, or gas chromatography.
Arrays with different chemically selective surfaces providing unique desorption chromatograms for analyte identification.
Use as a meter dose vapor generator for vapor detector calibration by controlled loading and desorption of analytes.
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