WO2020237204A1 - Plateformes, systèmes, procédés et structures de capteurs voltamétriques - Google Patents

Plateformes, systèmes, procédés et structures de capteurs voltamétriques Download PDF

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Publication number
WO2020237204A1
WO2020237204A1 PCT/US2020/034360 US2020034360W WO2020237204A1 WO 2020237204 A1 WO2020237204 A1 WO 2020237204A1 US 2020034360 W US2020034360 W US 2020034360W WO 2020237204 A1 WO2020237204 A1 WO 2020237204A1
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WO
WIPO (PCT)
Prior art keywords
flexible membrane
sensor according
forming
metallic
voltammetric sensor
Prior art date
Application number
PCT/US2020/034360
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English (en)
Inventor
Pierre-Alexandre Gross
Ehsan SADEGHIPOUR
Thomas Jaramillo
Original Assignee
The Board Of Trustees Of The Leland Stanford Junior University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by The Board Of Trustees Of The Leland Stanford Junior University filed Critical The Board Of Trustees Of The Leland Stanford Junior University
Publication of WO2020237204A1 publication Critical patent/WO2020237204A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
    • G01N27/4045—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors for gases other than oxygen

Definitions

  • This disclosure relates generally to chemical sensors and more particularly to voltammetric sensor platforms, systems, methods, and structures for the detection of gaseous phase chemical entities.
  • voltammetric platforms, systems, methods and structures for the sensing and/or detection of gaseous phase chemical entities including - but not limited to - pollutants, greenhouse gases, industrial emissions, agricultural emissions, energy exploration, and/or energetics (explosives).
  • voltammetric platforms, systems, methods and structures according to the present disclosure are: mechanically flexible; insensitive to change(s) in external temperature and/or humidity; and may advantageously detect chemical species and/or molecule(s) in a low-concentration gaseous phase while exhibiting the advantages of being manufacturable and capable of configuring into ultra-low power sensing voltammetric platform, system or networks of such platforms and/or systems.
  • Such voltammetric platforms, systems, and structures according to aspects of the present disclosure include a flexible membrane onto which are printed, electrically conductive metallic electrodes, heating element(s), and temperature sensor(s).
  • This SUMMARY is provided to briefly identify some aspect(s) of the present disclosure that are further described below in the DESCRIPTION. This SUMMARY is not intended to identify key or essential features of the present disclosure nor is it intended to limit the scope of any claims.
  • FIG. 1 shows a schematic diagram depicting a perspective view of an illustrative design, structure, and geometric layout of a voltammetric sensor structure according to an aspect of the present disclosure
  • FIG 2 shows a schematic diagram depicting a top view of an illustrative voltammetric sensor structure mounted on a planar board and connector(s) according to an aspect of the present disclosure
  • FIG 3 shows a schematic diagram depicting a side view of an illustrative voltammetric sensor structure mounted on a planar board and connector(s) according to aspects of the present disclosure
  • FIGs 4(A) and 4(B) are plots showing: FIG. 4(A) the conductivity of Nafion membranes doped with different ionic liquids increases with increasing temperature wherein all conductivities are much larger than the conductivity of undoped hydrated Nafion; and FIG. 4(B) Thermogravimetric Analysis (TGA) of undoped Nafion compared to various doped Nafion membranes showing that doping increases resistance to high temperature treatments;
  • TGA Thermogravimetric Analysis
  • FIG. 5 is a schematic block diagram depicting an illustrative voltammetric sensor structure and electronic computer system configured to operate as an electrochemical sensing system according to aspects of the present disclosure
  • FIG. 6 is a schematic block diagram depicting an illustrative voltammetric sensor network including a plurality of electrochemical sensing systems and structures according to aspects of the present disclosure.
  • any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements which performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function.
  • the invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Applicant thus regards any means which can provide those functionalities as equivalent as those shown herein.
  • voltammetry is one of several electroanalytical methods that may be employed to provide information about an analyte - a chemical constituent of interest in an analytical procedure.
  • the information about the analyte is obtained by measuring electrical current as an electrical potential (voltage) is varied.
  • FIG. 1 there is shown a schematic diagram depicting a perspective view of an illustrative design, structure, and geometric layout of an voltammetric sensor structure 100 according to aspects of the present disclosure.
  • such sensor structure illustratively includes a Nafion® membrane 110 onto which is disposed reference 120, counter 130, and working 140 electrodes, along with temperature sensor 160, and heater 180 structures.
  • the electrodes and temperature sensor structure(s) are shown as specifically positioned on one (top) side of the Nafion membrane while the heater structure(s) is/are positioned on an opposite (bottom) side of the membrane.
  • Nafion is a brand name for a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer exhibiting ionic properties and is a member of a class of synthetic polymers known as ionomers.
  • ionomers generally comprise both electrically neutral repeating units and ionized units covalently bonded to a polymer backbone.
  • useful ionomers exhibit semipermeable membrane properties and are sufficiently flexible.
  • the Nafion membrane may be a primary component of the membrane employed, which may be one of a variety of thicknesses, reinforced with other materials including Teflon® mesh structures, and further doped or otherwise including ionic compositions, i.e., liquids.
  • the electrodes, temperature sensor(s), and heater structure(s) will generally include a conductive, metallic material that is printed onto the membrane and may include such metals as Platinum (Pt), Silver (Ag), Palladium (Pd), Gold (Au), or other metals.
  • Platinum Platinum
  • Silver Silver
  • Palladium Pd
  • Au Gold
  • this disclosure illustratively and preferably describes the use of Platinum and Silver, those skilled in the art will appreciate that our disclosure is not so limited.
  • the printed metals comprising the sensor structure(s) generally require that two metallic inks or pastes be printed or otherwise disposed onto the membrane namely, Pt and Ag.
  • metallic ink printing may be performed by any of a number of techniques including inkjet printing, screen-printing, flexographic printing, or other suitable roll-to-roll processes.
  • the membrane - i.e., Nafion - may also be printed as a dispersion such that a thin film membrane is produced or - alternatively - extruded or cast into a thin film membrane.
  • the membrane e.g., Nafion
  • the membrane is substantialy 250 300 pm thick and as we shall describe in greater detail is pre treated.
  • the working and counter electrodes are Pt while the reference electrode and heater elements are Ag.
  • the electrodes and elements are directly printed or otherwise disposed onto the membrane. Following the printing, the metallic elements are sintered which - as those skilled in the art will appreciate - presents numerous difficulties as Pt in particular requires a relatively high (-300 °C) sintering temperature which is problematic for membrane materials such as Nafion that degrades at temperatures above - 120 °C. As we shall show and describe however, such degradation - i.e., burning and shrinking - is substantially overcome according to aspects of the present disclosure.
  • the heater(s) and temperature sensor(s) are printed onto the membrane as well and in the illustrative arrangement shown in the figure the temperature sensor(s) are printed on the same (i.e., front) side of the membrane sufficiently proximate to the electrodes while the heater(s) is/are printed on the reverse (i.e., back) side of the membrane.
  • the presence of a temperature sensor and heater allow the sensor device to be operated at a constant, closed-loop controlled temperature - for example 80 °C.
  • Such constant, closed-loop controlled temperature operation advantageously provides a higher reliability sensor device as cyclic voltammetry is quite sensitive to temperature changes.
  • operation at such elevated temperature provides greater sensitivity as the elevated temperature increases the adsorption rate of molecules of the chemical entities of interest on the surface of the electrodes, as well as the ionic conductivity of the membrane collectively resulting in the sensitivity improvement.
  • These sensitivity improvements are further increased by the greater electrode densities made possible - in part - by the metallic printing described previously.
  • the metallic traces are illustratively designed and configured to exhibit a resistance of 10 W (Ohm) for the heater(s) and 1.0 kQ (kilo Ohm) for the temperature sensor(s) - which advantageously allow the operation of the sensor structure in a closed-loop temperature control while exhibiting a minimal power consumption.
  • resistance characteristics may be varied during fabrication by - for example - changing the shape of the traces in-plane or changing the thickness of metal layers formed on the membrane.
  • FIG 2 shows a schematic diagram depicting a top view of an illustrative voltammetric sensor structure mounted on a planar board and connector(s) according to an aspect of the present disclosure.
  • a sensor structure 210 - such as that previously described including membrane 220, having formed thereon electrodes 230 and temperature sensor 240 - is mounted to the planar board 250 via zero- insertion-force connectors 260 at each end of the sensor structure. Further communication of the sensor structure is made via header connector 270 which permits integration of the sensor structure / board assembly to a larger system such as a computer and / or network of computers / and/or additional sensor structure(s)/assemblies.
  • the sensor structures according to the present disclosure include a flexible membrane and lack a rigid substrate, interconnecting it to larger systems poses problems. Accordingly, a custom assembly such as that illustratively depicted in FIG. 2. is employed. Such assembly - and in particular the use of ZIF socket/connectors - permit the electrical / mechanical connection to sensor leads to both the top and bottom of the structure.
  • the sensor structure is raised above the surface of the supporting planar board thereby thermally isolating the sensor structure from the planar board by a gap amount.
  • such arrangement results in thermal energy produced by operation of the heater(s) heating only the sensor and not the planar board.
  • Nafion membranes are sensitive to relative humidity, which may be affected by humidity in the air, or by changes in temperature. Exposure to moisture contained in the metallic inks used - in addition to successive expansion and retraction experienced during drying and sintering - induce cracks or other defects in the resulting metal layers indicating a need for improved mechanical stability. Such additional stability is not only important during fabrication, but also during operation as the devices are - as previously noted - operated at elevated temperature.
  • FIGs 4(A) and 4(B) are plots showing: FIG.
  • FIG. 4(A) the conductivity of Nafion membranes doped with different ionic liquids increases with increasing temperature wherein all conductivities are much larger than the conductivity of undoped hydrated Nafion; and FIG. 4(B) Thermogravimetric Analysis (TGA) of undoped Nafion compared to various doped Nafion membranes showing that doping increases resistance to high temperature treatments.
  • TGA Thermogravimetric Analysis
  • FIG. 4(B) it may be observed that as PIL doping increases the thermal resistance of the membranes increases as compared to the undoped Nafion membranes.
  • FIG. 4(B) shows further that undoped Nafion begins to degrade at temperatures above 100 3 ⁇ 4 C, whereas various forms of PIL doping retard the onset of thermal degradation to approximately 350-400 3 ⁇ 4 C.
  • PIL doping procedures for Nafion were described in a paper by Lu, F., et al ., which appeared in Soft Matter in 2014, at 10(39), pp. 7819-7825, - the entire contents of which is incorporated by reference herein.
  • Nafion membranes are treated in PILs comprising 1,4-diaminobutane (DBA), Tributylammonium (TBA), or 1-butylamine (BA) and methanesulfonic (MS) acid.
  • DBA 1,4-diaminobutane
  • TSA Tributylammonium
  • BA 1-butylamine
  • MS methanesulfonic
  • the resulting solution is then diluted/mixed with deionized water in a 40% (v/v) proportion, and the Nafion membrane is immersed in this diluted solution for approximately a week and subsequently cleaned via a series of acidic baths resulting in the modified Nafion.
  • the Silver and Platinum metal inks are then printed on the modified Nafion and treated thermally, photonically, or with microwaves to effect the conversion of the printed inks into metals comprising the sensor structures.
  • sensor systems, methods, and structures according to the present disclosure exhibit numerous advantages over the prior art.
  • the sensors may be printed using well understood, high throughput printing techniques that manufacture favorably.
  • the on-chip, closed-loop temperature control permits operation of sensors according to the present disclosure to operate at a range of external temperatures and environmental conditions while the PIL treated/doped membrane allows operation in a variety of humidity and weather conditions while maintaining an advantageous manufacturability.
  • their low power, low maintenance characteristics allow an extended deployment while still providing superior detection / identification of gas phase chemical entities at very low concentrations.
  • Such capability(ies) advantageously facilitate rapid alarming when the detected chemical entity is hazardous.
  • FIG. 5 there is shown a schematic block diagram depicting an illustrative voltammetric sensor module structure and electronic computer module configured to operate as an electrochemical sensing system according to aspects of the present disclosure.
  • computing modules including processor, memory, input/output structures and optional storage devices are well known in the computing and in particular the embedded controller arts.
  • wired and/or wireless networking facilities and structures which advantageously permit the assembly of a number of such voltammetric modules into a powerful network of modules/sy stems that may operate over an extended geographic area - if so desired and configured.
  • FIG. 6 - is a schematic block diagram depicting an illustrative voltammetric sensor network including a plurality of electrochemical sensing systems according to aspects of the present disclosure.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

Abstract

L'invention concerne des plateformes, des systèmes, des procédés et des structures de capteurs voltamétriques améliorées, permettant de détecter/d'identifier des entités chimiques en phase gazeuse et des molécules comprenant des polluants et/ou des sources d'énergie. Les systèmes et les structures de capteurs voltamétriques de la présente invention peuvent avantageusement présenter des capacités de détection supérieures dues en partie à leurs températures de fonctionnement et à leur densité d'intégration supérieures et peuvent en outre être configurés en tant que partie d'un réseau de capteurs plus grand.
PCT/US2020/034360 2019-05-22 2020-05-22 Plateformes, systèmes, procédés et structures de capteurs voltamétriques WO2020237204A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201962851200P 2019-05-22 2019-05-22
US62/851,200 2019-05-22

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WO2020237204A1 true WO2020237204A1 (fr) 2020-11-26

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120187000A1 (en) * 2010-12-16 2012-07-26 Sensor Innovation, Inc. A Delaware Corporation Electrochemical sensors
US20150027887A1 (en) * 2012-01-25 2015-01-29 Senova Systems, Inc. Analyte sensor
US20150346144A1 (en) * 2012-12-27 2015-12-03 Senova Systems, Inc. Ph meter
WO2018059717A1 (fr) * 2016-09-30 2018-04-05 Honeywell International Inc. Procédé et appareil de mesure de concentration d'électrolyte

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120187000A1 (en) * 2010-12-16 2012-07-26 Sensor Innovation, Inc. A Delaware Corporation Electrochemical sensors
US20150027887A1 (en) * 2012-01-25 2015-01-29 Senova Systems, Inc. Analyte sensor
US20150346144A1 (en) * 2012-12-27 2015-12-03 Senova Systems, Inc. Ph meter
WO2018059717A1 (fr) * 2016-09-30 2018-04-05 Honeywell International Inc. Procédé et appareil de mesure de concentration d'électrolyte

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