Patent Publication Number: US-11022489-B2

Title: Portable multi-spectrometry system for chemical and biological sensing in atmospheric air

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/650,599, filed Mar. 30, 2018, entitled “PORTABLE MULTI-SPECTROMETRY SYSTEM FOR CHEMICAL AND BIOLOGICAL SENSING IN ATMOSPHERIC AIR,” the disclosure of which is expressly incorporated by reference herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used and licensed by or for the United States Government for any governmental purpose without payment of any royalties thereon. This invention (Navy Case 200,500) is assigned to the United States Government and is available for licensing for commercial purposes. Licensing and technical inquiries may be directed to the Technology Transfer Office, Naval Surface Warfare Center Corona Division, email: CRNA_CTO@navy.mil. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a portable multi-spectrometry system for chemical and biological sensing in atmospheric air. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a systems and methods to directly sample (real-time in the field) atmospheric air, including particles, aerosols, and spores, for potential pollutants and toxins, so results are obtained almost instantaneously; and depending on those results, actions can be taken immediately thereafter. 
     A variety of portable field-equipment is currently available with the detection technology based primarily on a theory of spectroscopy, electrochemistry, or chemical reactions. The spectroscopy method is preferred because (1) spectrometers are generally robust; (2) portable spectrometry equipment do not use chemicals; and (3) perform detection directly in atmospheric air. The theories portable spectrometers employ have included Particle-Light-Scattering (PLS), Infra-Red Absorption Spectrometry (IRAS), Molecular Absorption Spectrometry (MAS), Molecular Fluorescence Spectrometry (MFS), Raman Scattering Spectrometry (RSS), and Mass Spectrometry (MS). Each spectroscopic theory provides advantageous features as well as limitations in practical air analysis. Most commercially available portable spectrometers are designed and constructed for single-theory operation. 
     This invention describes a portable, spectrometric system that integrates multiple spectroscopy theories, combines their advantageous features, and fills the gaps for their limitations. The combined spectrometry system with operations for PLS, IRAS, MAS, MFS, RSS, and MS, will detect particles and chemicals, directly and sequentially, in the same air-stream. The results generated and the information provided from the multiple spectrometric detection will be complementary and will greatly increase the accuracy and reliability for the sensing. The design and construction for the system will be modular, that is, each module will contain a particular spectrometric function. The operator may select to assemble the sensing system for any single-function or for multiple-functions with a combination of two or more spectrometric modules. 
     According to a further illustrative embodiment of the present disclosure, a specific system can be used for biomolecule detection. The detection results will answer questions, such as: if the air contains biologicals or not; what are the biochemical molecular compositions; are there particles or not; if particles, are they biologics or not. 
     Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description of the drawings particularly refers to the accompanying figures in which: 
         FIG. 1  shows a block diagram of an exemplary design layout of a portable multi-spectrometry system. 
         FIG. 2  shows an exemplary light scattering spectrometer. 
         FIG. 3  shows an exemplary infrared absorption spectrometer. 
         FIG. 4  shows an exemplary simultaneous molecular absorption and molecular fluorescence spectrometer. 
         FIG. 5  shows an alternative exemplary simultaneous molecular absorption and molecular fluorescence spectrometer. 
         FIG. 6  shows an exemplary mini-mass spectrometer connected to an adaptor. 
         FIG. 7  shows an exemplary Raman scattering spectrometer with concentrator for atmospheric air. 
         FIG. 8  shows an exemplary assembled modular system. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The embodiments of the invention described herein are not intended to be exhaustive or to limit the invention to precise forms disclosed. Rather, the embodiments selected for description have been chosen to enable one skilled in the art to practice the invention. 
       FIG. 1  shows a block diagram of an exemplary design layout of a portable multi-spectrometry system  1 . Exemplary systems include a plurality of spectrometers placed sequentially such that the spectrometers can test the same testing sample  19 . Testing sample  19  enters the system through air inlet  3  and is drawn through the system by air pump  17 . The plurality of spectrometers can include a light scattering spectrometer  5 , an infrared (IR) absorption spectrometer  7 , a combined molecular absorption spectrometer and molecular fluorescence spectrometer  9 , a mass spectrometer  15 , and a Raman scattering spectrometer  13  connect to a concentrator  11 . If selected, light scattering spectrometers  5  should be placed in the first position of the series, and Raman scattering spectrometers  13  should be placed in the last position of the series. Because using a concentrator  11  affects the concentration of molecules in an air sample passing through an exemplary modular system, placing a Raman scattering spectrometer  13  in a position other than last could interfere with readings of subsequent spectrometers. Similarly, including multiple sets of Raman scattering spectrometers  13  and concentrators  11  can result in inaccurate readings of following Raman scattering spectrometers. Other spectrometers types can be placed interchangeably in any position without affecting performance. In some embodiments, multiple spectrometers of the same type can be placed within the series; these embodiments allow an operator to verify accuracy of spectrometers by comparing the results of duplicate spectrometers (e.g., comparing the readings of a first mass spectrometer to a second mass spectrometer). 
       FIG. 2  shows an exemplary light scattering spectrometer  5 . Laser radiation (typically near IR) is generated by a laser-diode lamp  33 . The laser radiation is focused to the center of the air stream of sampling  19  by reflector  35  and focusing lens  37 ; particles in the air-stream scatter the incident laser light to the forward direction; a collection lens  39  gathers the forward scattered light onto a photo-diode detector  43  (e.g., a strip shape that detects the dimensional-imaged radiation effectively). A connector  31  connects laser-diode lamp  33  to a controlling driver and power supply, and cable  45  connects to a power supply transmits detection signals (see  FIGS. 8-9 ). A light mask/trap  41  blocks both the incident laser beam and the central-scattering light. Therefore, the scattering at the larger (higher) angles from a selective smaller-size group particles is detected. Change of the light mask  41  size selects the cut-off size-group (e.g., less than 20 micrometers) for detection. Biological air-particulates have a typical particle size of less than 15 micrometers. 
       FIG. 3  shows an exemplary infrared absorption spectrometer  7 . Because absorption spectrometric measurements in air are often interfered with by particles that scatter away light (the source radiation) from reaching the photo-detector, resulting in a false absorption signal, an optical integrating sphere  61  distributes and multiplies an input radiation homogeneously in the entire volume within the reflective-wall sphere. The use of integrating sphere  61  can prevent this interference because the integrating sphere  61  can enclose all the scattered light within the measurement system. The total light (photons) within the integrating sphere  61  is either absorbed by absorbing substances or reflected by non-absorbing particles in the sampling air  19 . A photodetector  69  can sense the diffused Infra-Red radiation from the integrating sphere  61  as reflectance. A lowered reflectance measurement, relative to a blank, indicates absorption. Illustratively, a two to four inch diameter integrating sphere that weighs about one pound may be used. The reflective coating determines the wavelength-range of radiation useful with a sphere. The photodetector  69  is positioned such that it will not directly view the input or the reflected source-radiation (from the opposite wall facing the source). Baffles can be used to shield the source radiation and/or the reflection from sphere-wall, for the detector to sense. Incorporation of baffles will reduce the efficiency of the sphere. The detector-location here is set to minimize viewing of the source radiation and reflection. 
     The sensing for biomolecules by IR-Absorption Spectrometry can be based on the Amide I band (band center 6060 nm) and/or Amide II band detection. A spectral narrow band-pass filter can select suitably centered wavelength of 6180 nm that includes ˜6060 nm to pass through, blocking over wavelengths between 400˜11,000 nm. The IR radiation source  67  provides approximately 1000 to 20,000 nm wavelength-range and that the ˜6180 nm band wavelengths along with 11,000-20,000 nm wavelengths pass through a first spectral narrow band filter  65 . A spectral short-pass filter  63  will allow only the ˜6180 nm band wavelengths to pass but will block the 11000-20,000 nm wavelengths. Therefore, only the ˜6180 nm band wavelengths which are the source radiation of interest for the IR Spectrometry for Bio-sensing. A second spectral narrow band filter  66  can be placed before photodetector  69  to further prevent false positive detections caused by light outside of wavelengths of interest. The inside-wall of the integrating sphere must be coated with a reflective surface (e.g., Infragold NIR-MIR Reflectance Coating) for the IR wavelengths of interest, in this example the approximately 6180 nm. The photodetector  69  must be able to sense the wavelengths of interest (˜6180 nm). A connector  68  connects IR radiation source  67  to a controlling driver and power supply. 
       FIG. 4  shows an exemplary simultaneous molecular absorption and molecular fluorescence spectrometer  9 . The photodetectors are positioned such that they will not directly view the input or the reflected source-radiation (from the opposite wall facing the source). An integrating sphere  71  is used for the previously described reasons. Baffles may need be used to shield the source radiation and/or the reflection from sphere-wall, for the detectors to sense. Incorporation of baffles will reduce the efficiency of the sphere. In the immediate front of fluorescence photodetector  77  is a spectral filter  75  that allows only the fluorescence radiation of interest to pass through and blocks the source radiation; a plano-convex collecting lens  73  collects a wide angle of fluorescence from the relatively central volume of sphere. In the immediate front of the radiation source  81  and the reflectance photodetector  87  are spectral filters  79 ,  80 , respectively, that allow only the source radiation (wavelength) of interest to pass through and block the fluorescence. Both the reflectance and the fluorescence photodetectors  87 ,  77  can be large diameter spot avalanche photodiodes. A connector  83  connects radiation source  81  to a controlling driver and power supply. 
       FIG. 5  shows an alternative exemplary simultaneous molecular absorption and molecular fluorescence spectrometer  9  using a mini-spectrometer for monitoring both reflectance and fluorescence wavelengths. Plano-convex lenses are placed between the integrating sphere and mini-spectrometer. A Laser Diode Emits ˜275 nm Radiation, and the mini-spectrometer can monitor both the ˜275 nm radiation and fluorescence wavelength of ˜345 nm simultaneously. 
       FIG. 6  shows an exemplary mini-mass spectrometer  15  connected to an adaptor  121 . The mini-mass spectrometer  15 , operating with reduced internal-pressure, draws some of the air into its ionization section of the mass spectrometer, for subsequent analysis. Biological molecules/toxins have very high molecular weight typically several to many-tens of thousands Daltons mass unit; and that the type of mass spectrometer (MS) most suitable for detection employs a time-of-flight (TOF) separation-sector. 
       FIG. 7  shows an exemplary Raman scattering spectrometer  13  with concentrator  11 . The Raman Effect is very weak and therefore a concentrated sample and a relatively high laser power density for excitation are desired. The mini-Raman-spectrometer  13  is integrated with a laser and optical components such as a notch spectral filter and a dichroic filter that allows the same optical lens-set to be used for laser reaching the sample and for Raman scattering collected back into the spectrometer. A near IR laser (e.g., 830 nm wavelength) can be used for excitation and will minimize or avoid fluorescence from samples. Collection filter or membrane can be used to concentrate the sample by collecting chemicals, aerosols, spores, particles, airborne materials on the filter or membrane. The filter or membrane material can be chosen such that, when it is illuminated with a laser, it will not emit light that could interfere spectrally for the Raman Shift spectral region of interest. O-rings  135  can be used to keep the filter or membrane fit between the top and bottom parts of the concentrator. Lenses  137  between the mini-Raman-spectrometer  13  and concentrator  11  can be used for high light collection. In some exemplary embodiments, multiple Raman spectrometers  13  can be placed around a single concentrator. 
       FIG. 8  shows an exemplary assembled modular system with an air inlet  3 , a light scattering spectrometer  5 , an infrared absorption spectrometer  7 , a spectral filter molecular absorption and spectral filter molecular fluorescence spectrometer  9 , a mass spectrometer  15 , a Raman scattering spectrometer  13  with a concentrator  11 , and an air pump  17 . A battery supply  151  can be a centralized unit with one battery. All of the control and signal processing electronics and software can be centralized within a signal processor  153 . A display allows the signal processor to show various data and readings. All of the components of the modular system can fit in a system container that is approximately the size of a suitcase, and the entire modular system can weigh less than thirty pounds. The system generates complementary information, providing very high confidence for fast and accurate field-detection in air, and answering the questions: if the air contains biologicals or not; what are the biochemical molecular compositions; are there particles or not; if particles, are they biologics or not. The modular systems may be adapted to unmanned ground or aerial vehicles (e.g., air-drones, etc.) for operations. 
     In an exemplary method of operation, an exemplary portable multi-spectrometry system can be using in a controlled environment to test air samples having known quantities of molecules. The controlled readings can be used to generate a database of known values. The database of known values can be stored within the portable multi-spectrometry system or an external computer storage medium (e.g., for upload to additional portable multi-spectrometry system units). A portable multi-spectrometry system can compare field readings to the database of known values to determine the presence of biological and chemical molecules. 
     In an exemplary method of operation, an exemplary portable multi-spectrometry system can be used to test unknown air samples. An unknown air sample enters the system through an air inlet and is drawn through the system by an air pump. The unknown air sample passes through a plurality of spectrometers, wherein each spectrometer generates a reading which is transferred to a processor. The plurality of readings can be analyzed (e.g., manually or automatically) to determine the presence of biological and chemical molecules in the unknown air sample. In exemplary methods, each reading can be compared to each other for consistency. If a particular reading is determined to be incorrect, inconsistent, or unreliable, the corresponding spectrometer can be replaced at the point of use. Because each individual spectrometer is light-weight (e.g., less than 30 pounds), modular, and interchangeable, the spectrometers can be quickly replaced or rearranged. 
     In an exemplary method of operation, an exemplary portable multi-spectrometry system having testing spectrometers comprising multiple of one type of spectrometer (e.g., three infra-red absorption spectrometers occupying the second, third, and fourth positions) can test a known or unknown sample of air. The readings from the testing spectrometers can be compared to each other to ensure consistency and accuracy of the testing spectrometers. Exemplary methods can use this method to test for active usage (e.g., in a field setting) or test large quantities of spectrometers for future usage (e.g., in a factory or warehouse setting). 
     Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the spirit and scope of the invention as described and defined in the following claims.