Patent Publication Number: US-2021190746-A1

Title: Multi-element, ultra-low swap chemical pre-concentrator

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to chemical pre-concentrators and more particularly to a multi-element, ultra-low SWaP chemical pre-concentrator. 
     BACKGROUND OF THE DISCLOSURE 
     Long term autonomous and continuous monitoring of an airborne chemical environment has become a priority for various applications. The size, weight, and power (SWaP) requirements of prior systems are not compatible with such requirements. 
     Wherefore it is an object of the present disclosure to overcome the above-mentioned shortcomings and drawbacks associated with the conventional chemical pre-concentrators. 
     SUMMARY OF THE DISCLOSURE 
     One aspect of the present disclosure is a system comprising a chemical pre-concentrator, comprising: a housing configured to hold an array of chemical pre-concentrator element cartridges distributed about a central axis; and a top cover and a bottom cover of the housing being configured to move using a sliding caliper mechanism, by way of a linear actuator; each cartridge comprising: a carbide-derived carbon (CDC) foam element; dielectric/thermal insulators; electrodes; and an elastomer seal; wherein the top and the bottom covers slide to open the chemical pre-concentrator during analyte sample collection and to close the chemical pre-concentrator for analyte sample delivery, energizing the electrodes in a cartridge, heats the foam element to desorb the analytes, and each cartridge is controlled independently and is separately sealed during desorption to avoid bleed of analytes to other cartridges. 
     One embodiment of the chemical pre-concentrator is wherein the linear actuator is used to expand the top cover away from the bottom cover to provide for gaps allowing a flow of air, or other gas, to flow past the element cartridges. 
     In certain embodiments, the array comprises four CDC foam element cartridges. 
     Another embodiment of the chemical pre-concentrator is wherein during analyte sample collection a low impedance air flow path is provided so that ambient air can be independently drawn through each element cartridge to enable collection of the chemical analytes. In some cases, the low impedance airflow path enables both high flow and very low fan/blower power consumption during sample collection. 
     Yet another embodiment of the chemical concentrator further comprises fans/blowers to push/pull air flow through the element cartridges. In certain embodiments, the chemical pre-concentrator further comprises inlets for carrier gas delivery lines and outlets for sample delivery lines used when attaching the pre-concentrator to an analyzer. 
     Still yet another embodiment of the chemical pre-concentrator is wherein the element cartridge further comprises a series of springs with pre-loaded adjustments to facilitate pressing spring pressure plates against high temperature insulators on each side of the foam element, to cause a pair of energized electrodes to contact the CDC foam element in a desorption step. 
     Another aspect of the present disclosure is a method of collecting chemical analytes, comprising: providing a chemical pre-concentrator, comprising: a housing configured to hold an array of chemical pre-concentrator element cartridges distributed about a central axis; and a top cover and a bottom cover of the housing being configured to move using a sliding caliper mechanism, by way of a linear actuator; each cartridge comprising: a CDC foam element; dielectric/thermal insulators; electrodes; and an elastomer seal; sliding the top and the bottom covers to open the chemical pre-concentrator; engaging one or more fans/blowers to create an air flow over the element cartridges during analyte sample collection; capturing the analyte sample with the element cartridges; and sliding the top and the bottom covers to close the chemical pre-concentrator. 
     One embodiment of the method of collecting chemical analytes is wherein the array comprises four element cartridges. In some cases, a linear actuator is used to expand the top cover away from the bottom cover to provide for gaps allowing a flow of air, or other gas, to flow past the element cartridges. 
     Another embodiment of the method of collecting chemical analytes is wherein during analyte sample collection a low impedance air flow path is provided so that ambient air can be independently drawn through each element cartridge to enable collection of the chemical analytes. In some cases, the chemical pre-concentrator further comprises fans/blowers to push/pull air flow through the element cartridges. In certain embodiments, the chemical pre-concentrator further comprises inlets for carrier gas delivery lines and outlets for sample delivery lines used when attaching the pre-concentrator to an analyzer. 
     Yet another aspect of the present disclosure is a method of delivering chemical analytes to a chemical analyzer for analysis, comprising: providing a chemical pre-concentrator, comprising: a housing configured to hold an array of chemical pre-concentrator element cartridges distributed about a central axis; inlets for carrier gas delivery lines and outlets for sample delivery; and a top cover and a bottom cover of the housing being configured to move using a sliding caliper mechanism, by way of a linear actuator; each cartridge comprising: a CDC foam element; dielectric/thermal insulators; electrodes; and an elastomer seal; energizing the electrodes in a cartridge; heating the foam element to desorb the analytes, wherein each element cartridge is controlled independently and is separately sealed during desorption to avoid bleed of analytes to other cartridges; switching a switched gas valve to deliver a burst of pressurized carrier gas to drive the analytes towards the chemical analyzer inlet by flowing through the foam element and out the sample delivery line to the chemical analyzer. 
     One embodiment of the method of delivering chemical analytes to a chemical analyzer for analysis is wherein a high temperature insulator is used around the CDC foam element to keep heat applied to the CDC foam element via an energized electrode from spreading throughout the remainder of the system or to the rest of the device. In some cases, a temperature applied to the CDC foam element for desorption is about 350° C. 
     Another embodiment of the method of delivering chemical analytes to a chemical analyzer for analysis is wherein the element cartridge further comprises a series of springs with pre-load adjustments to facilitate pressing spring pressure plates against high temperature insulators on each side of the foam element, to cause a pair of energized electrodes to contact the CDC foam element in a desorption step. In certain embodiments the chemical pre-concentrator further comprising fans/blowers to push/pull air flow through the element cartridges. In some cases, the array comprises four element cartridges. 
     These aspects of the disclosure are not meant to be exclusive and other features, aspects, and advantages of the present disclosure will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims, and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features, and advantages of the disclosure will be apparent from the following description of particular embodiments of the disclosure, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure. 
         FIG. 1  is a diagram of one embodiment of a carbide-derived carbon (CDC) foam element assembly for a multi-element, ultra-low swap chemical pre-concentrator according to the principles of the present disclosure. 
         FIG. 2  is a diagram of one embodiment of a radial arrangement for a multi-element, ultra-low swap chemical pre-concentrator according to the principles of the present disclosure. 
         FIG. 3  is a cross-sectional view of one embodiment of a multi-element, ultra-low swap chemical pre-concentrator showing a concurrent adsorption step according to the principles of the present disclosure. 
         FIG. 4  is a cross-sectional view of one embodiment of a multi-element, ultra-low swap chemical pre-concentrator showing a sequential desorption step according to the principles of the present disclosure. 
         FIG. 5  is a flow chart of one embodiment of a method according to the principles of the present disclosure. 
         FIG. 6  is a flow chart of another embodiment of a method according to the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     One embodiment of the present disclosure is a device that forms the front-end collection stage for an ultra-low-power chemical analysis capability for the detection and identification of hazardous chemicals, explosives, chemical weapons, narcotics, industrial toxins and pollutants, and the like. The device of the present disclosure utilizes an embodiment of Carbide Derived Carbon or CDC foam element. In certain cases, the CDC foam element is functionalized to target distinct groups of chemical threats. In one embodiment, four elements are arranged in an array of multiple sampling elements. The CDC foam element array is packaged into a low SWaP, multi-element sampling device that enables highly efficient collection and delivery of chemical samples. In some cases, low-SWaP includes a hand-held device. In certain cases, the low-SWaP device is stationary. 
     In one embodiment, the technology used in the device of the present disclosure is Applicant&#39;s open cell foam adsorbent material which allows high volume sampling (e.g., liters per minute) to achieve low detection limits (ppt) using high-volume, low-pressure air sources (i.e. fans or blowers) rather than pumps. The device delivers the sample directly to an analyzer without the need for a typical intermediate cryogenic trapping step. 
     In certain embodiments, top and bottom plates are moved by a linear actuator to provide scaling around a CDC foam element insert through clamping. This approach utilizes static seals which have inherent advantages over dynamic, sliding seals in that energy is not consumed overcoming sliding seal friction. Additionally, lubrication is not required and reduced seal wear enables improved longevity of the sealing rings. This concept also enables a radial arrangement of multiple collection units (four nominally). 
     In one embodiment, each collection unit is sealed from the other collection units to prevent analyte bleed to the other sites. Each collection unit CDC foam element can be triggered independently for collection or desorption. In some cases, top and bottom plates slide vertically to open the pre-concentrator during sampling and close the pre-concentrator during desorption. 
     The device of the present disclosure is both compact and efficient from a power consumption standpoint. It is also scalable to enable a varying quantity of functionalized CDC foam elements. In one embodiment, a single linear actuator is used to selectively place all sensing elements in either an adsorb or a desorb position. This is accomplished without expending energy against the friction associated with sliding seals of conventional samplers. It also enables both low impedance air flow for sampling and high concentration sample bolus delivery to a chemical analyzer. In addition, the packaging concept provides a compliant method for producing electrical contact with the CDC foam element to enable heating which has been shown to extend the life of the element. 
     Referring to  FIG. 1 , a diagram of a top view of one embodiment of a carbide-derived carbon (CDC) foam element assembly for a multi-element, ultra-low SWaP chemical pre-concentrator according to the principles of the present disclosure is shown. More specifically, a housing high temperature insulator  2  is used around the CDC foam element  4 . In some cases, the insulator is a ceramic ring. This helps to keep any heat applied to the CDC foam element via an energized electrode  12  from spreading throughout the remainder of the system or to the rest of the device. In some embodiments, the temperature applied to the CDC foam element for desorption is about 350° C. 
     Still referring to  FIG. 1 , a series of springs  6  with pre-load adjustments are used to facilitate pressing spring pressure plates  8  against high temperature insulator plates  10  on each side of the CDC foam element insert, to cause a pair of energized electrodes  12  to contact the CDC foam element  4  in a desorption step. In this embodiment, an electrical current is applied to the electrode  12  to generate the heat needed for desorption. Due to the use of a circular array, as shown in  FIG. 2 , the overall pre-concentrator unit volume does not increase as fast as it would with a more linear arrangement of elements. Thus, it is possible to create a smaller form factor and/or use larger CDC foam element inserts. 
     In one case, the main housing wall  15  surrounds the elements and in one example the side wall  14  is about 0.11 inches and the pre-load spring wall  16  is about 0.26 inches as it provides an extra wall thickness to house the interior springs. In some cases, the electrode and insulator layer are about 0.13 inches. In some cases, the foam element dimensions are about 0.53×about 0.53×about 0.30 (thick) inches. A preliminary study focused on the volume of each element and determined that thinning of the foam from 0.3″ to 0.2″ (while maintaining a length and a width at 0.53″×0.53″) saved about 4.2 cm 3 . A further reduction of the foam dimensions to 0.26″×0.26″×0.2″ would increase the savings in volume down to about 125 mL. In one case, a further reduction in the overall volume was achieved (i.e., about 105 mL) by switching from a square packaging to a cylindrical packaging. 
     Referring to  FIG. 2 , a diagram of one embodiment of a radial arrangement for a multi-element, ultra-low SWaP chemical pre-concentrator  34  according to the principles of the present disclosure is shown. More specifically, the pre-concentrator is scalable to any number of foam elements. Here, four elements  22  are used to keep system volume low. As such, this embodiment is a circular array because of a resulting reduction in system volume. Additionally, this embodiment has no sliding seals, independent elements (for sequential desorption), no adjacent bleed, and a reduction in dead volume—less dilution of samples. In certain embodiments, a radial arrangement enables multiple foam units to be used for collection/desorption. 
     Still referring to  FIG. 2 , placement of four sampling elements  22  in a multi-element chemical pre-concentrator housing  20  is shown. Each element  22  is mounted in a cartridge comprising a foam element  4 , dielectric/thermal insulators  2  and an elastomer seal  26 . Each cartridge is installed in a main housing  20  and at the center of the housing there is a passageway  24  that guides motion of the top and the bottom covers (as described in  FIGS. 3 and 4 ). Energized electrodes  28  are used to heat the foam element  4  during a desorption step. Each unit is controlled independently and is separately sealed during desorption to avoid bleed of the analytes to other chambers. The top and bottom plates (visible in  FIG. 3  and  FIG. 4 ) slide vertically to open the pre-concentrator  34  during sampling and close the pre-concentrator  34  during desorption. In this example there is an interface  36  to provide electrical power and control. According to one embodiment, the foam element  4  in each of the sampling elements  22  is the same. In a further embodiment, the foam elements  4  in the sampling elements are different in order to serve a broader spectrum of detection. 
     Referring to  FIG. 3 , a cross-sectional view of one embodiment of a multi-element, ultra-low SWaP chemical pre-concentrator  40  showing a concurrent adsorption step according to the principles of the present disclosure is shown. More specifically, in one embodiment, multiple CDC foam elements are packaged in a radial array configuration (See, e.g.,  FIG. 2 ). The top and bottom surfaces of the array are selectively capped or opened by use of a sliding caliper mechanism, by way of an actuator  54 . This mechanism allows the CDC foam element array to be shifted between a sample collection (adsorb) (See,  FIG. 3 ) and sample delivery (desorb) (See,  FIG. 4 ) operational modes by use of a single linear actuator  54 . In the adsorb position a low impedance air flow path input  72  and output  74  are provided so that ambient air can be independently drawn through each CDC element  66  to enable collection of the chemical sample. This low impedance airflow path enables both high flow and very low fan power consumption during sample collection. 
     Still referring to  FIG. 3 , a cross section of multi-element, ultra-low SWaP chemical concentrator  40  is shown with a linear actuator  54  used to expand a top cover  42  away from a bottom cover  44  to provide for gaps allowing a flow of air, or other gas,  72  and  74  to flow past the CDC foam element inserts  66 . Here, fans or blowers  68  are used to push/pull the flow through the CDC foam element inserts. In this figure,  46  and  50  represent two of the connections to be used when attaching the pre-concentrator to an analyzer and  48  and  52  represent switched gas lines (not in use during adsorb stage). 
       FIG. 3  represents the multi-element chemical pre-concentrator  40  positioned in the adsorb position. Linear actuator  54  is driven to extend its lead screw which is guided in column  58  and retained to the top cover  42  by retaining nut  56 . Journal bearing  60  slides within the chamber I s  and guides the motion of the top cover  42  while coil spring  62  maintains equal travel of the bottom cover  44  by pulling the journal bearing  60  against the center housing. With the covers  42 ,  44  extended, low impedance air paths  72  and  74  are created for fans  68  which when energized draw air through the CDC foam elements  66  to enable sampling of the ambient air. CDC foam element thermal and electrical insulator  64  retains the foam element  66  in to the center housing. Both carrier gas delivery lines  48  and  52  and sample delivery lines  46  and  50  are deactivated during the sampling/adsorbing mode of operation. 
     Referring to  FIG. 4 , a cross-sectional view of one embodiment of a multi-element, ultra-low SWaP chemical pre-concentrator showing a sequential desorption step according to the principles of the present disclosure is shown. More specifically, in the desorb mode the CDC element  66  is placed in a position having minimum dead volume where the chemical sample is released by heating of the CDC foam element through direct application of electric current. The minimal dead volume that is achieved during desorb serves to maximize the concentration of the sample bolus that is delivered to the chemical analyzer. Once the sample is desorbed, a switched gas valve ( 48 ,  52 ) delivers a burst of pressurized carrier gas to drive the sample towards the chemical analyzer inlet ( 46 ,  50 ). 
       FIG. 4  represents the multi-element chemical pre-concentrator positioned in the desorb position. Linear actuator  54  is driven to retract its lead screw which is guided in column  58  and retained to the top cover  42  by retaining nut  56 . Journal bearing  60  slides within the chamber O s  and guides the motion of the top cover  42  while coil spring  62  is compressed to enable closure of the bottom cover  44 . Both the top and bottom covers  42 ,  40  form an air tight seal against the center housing by clamping against elastomer seals  70 . With the top and bottom covers now sealed, the CDC foam elements  66  can be selectively heated by applying electric current while insulator  64  simultaneously minimizes the energy required for heating and directs electric current only through the foam element  66  via the opposing electrodes. Once the foam  66  is heated, carrier gas port  48  is switched “on” enabling gas containing analytes  80  to flow through the foam element  66  and out the sample delivery line  46  to the chemical analyzer (not shown). 
     In certain embodiments, energy consumption is directly linked to the volume of the foam as a first approximation. Therefore, a foam volume reduction will result in a commensurate energy consumption reduction. Such a volume reduction may induce a lower loading capacity or an earlier analyte breakthrough. Several options are available to compensate for such a potential drawback. For example, the depth of the foam can be increased to generate a longer flow path. Another alternative is to use a foam with a denser porosity, which will increase the overall surface area available for analyte interaction. 
     In some cases, to address an increase in background analyte levels, the effective loading of the foam is increased. First, increasing the porosity of the foams provides more surface area and therefore more binding sites for background analytes to enable the capture of more analytes. Second, increasing the CDC foam element layer can have similar effect in terms of providing more bonding sites. In some cases, an increase in sampling time is driven by the optimization of the duty cycle of the air sampling fan. The duty cycle can be modified and balanced against the energy consumption. 
     Referring to  FIG. 5 , a flow chart of one embodiment of a method according to the principles of the present disclosure is shown. More specifically, a method of collecting chemical analytes, comprises providing a chemical pre-concentrator, comprising: a housing configured to hold an array of chemical pre-concentrator element cartridges distributed about a central axis  100 . In certain embodiments, the pre-concentrator has a top cover and a bottom cover configured to move using a sliding caliper mechanism, by way of a linear actuator  102 . In certain embodiments, each cartridge comprises a CDC foam element, dielectric/thermal insulators, electrodes, and an elastomer seal  104 . By sliding the top and the bottom covers, the chemical pre-concentrator opens  106 . Engaging one or more fans or blowers to create an air flow over the element cartridges during analyte sample collection  108 , enables capturing the analyte sample with the element cartridges  110 . By sliding the top and the bottom covers of the chemical pre-concentrator, it is closed  112 . 
     Referring to  FIG. 6 , a flow chart of another embodiment of a method according to the principles of the present disclosure is shown. More specifically, a method of delivering chemical analytes to a chemical analyzer for analysis, comprises providing a chemical pre-concentrator, having a housing configured to hold an array of chemical pre-concentrator element cartridges distributed about a central axis  200 . In some embodiments, the pre-concentrator has inlets for carrier gas delivery lines and outlets for sample delivery  202  and a top cover and a bottom cover of the housing being configured to move using a sliding caliper mechanism, by way of a linear actuator  204 . In some embodiments, each cartridge comprises CDC foam element, dielectric/thermal insulators, electrodes, and an elastomer seal  206 . By energizing the electrodes in a cartridge  208  the foam elements are heated to desorb the analytes, wherein each element cartridge is controlled independently and is separately sealed during desorption to avoid bleed of analytes to other cartridges  210 . By switching a switched gas valve to deliver a burst of pressurized carrier gas, the analytes are driven towards the chemical analyzer inlet by flowing through the foam element and out the sample delivery line to the chemical analyzer  212 . 
     It will be appreciated from the above that the invention may be implemented as computer software, which may be supplied on a storage medium or via a transmission medium such as a local-area network or a wide-area network, such as the Internet. It is to be further understood that, because some of the constituent system components and method steps depicted in the accompanying Figures can be implemented in software, the actual connections between the systems components (or the process steps) may differ depending upon the manner in which the present invention is programmed. Given the teachings of the present invention provided herein, one of ordinary skill in the related art will be able to contemplate these and similar implementations or configurations of the present invention. 
     The computer readable medium as described herein can be a data storage device, or unit such as a magnetic disk, magneto-optical disk, an optical disk, or a flash drive. Further, it will be appreciated that the term “memory” herein is intended to include various types of suitable data storage media, whether permanent or temporary, such as transitory electronic memories, non-transitory computer-readable medium and/or computer-writable medium. 
     It is to be understood that the present invention can be implemented in various forms of hardware, software, firmware, special purpose processes, or a combination thereof. In one embodiment, the present invention can be implemented in software as an application program tangible embodied on a computer readable program storage device. The application program can be uploaded to, and executed by, a machine comprising any suitable architecture. 
     While various embodiments of the present invention have been described in detail, it is apparent that various modifications and alterations of those embodiments will occur to and be readily apparent to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the appended claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various other related ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items while only the terms “consisting of” and “consisting only of” are to be construed in a limitative sense. 
     The foregoing description of the embodiments of the present disclosure has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise form disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the present disclosure be limited not by this detailed description, but rather by the claims appended hereto. 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the scope of the disclosure. Although operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. 
     While the principles of the disclosure have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the disclosure. Other embodiments are contemplated within the scope of the present disclosure in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present disclosure.