Film-type solid polymer ionomer sensor and sensor cell
View Patent ↗A miniaturized gas sensor including film type electrodes, and a solid ionomer electrolyte, for the detection of toxic gases, i.e., carbon monoxide, and other oxidizable or reducible gases and vapors is described. The all-solid planar sensor cell has two or more film type electrodes arranged on a non-conductive planar surface of a supportive material. The electrodes are discrete and in intimate contact with the same solid polymer ionomer membrane. The sensor cell contains no liquid electrolyte and is operated in a potentiostatic or potentiodynamic mode. The unique feature of the sensor cell is that high sensitivity to a select gas or vapor is achieved by a novel three-phase contact area design for a sensing electrode which is easily accessible to the gas sample via small diffusion openings or holes that penetrate through the solid polymer ionomer membrane layer above the sensing electrode. A significant signal to background noise enhancement is achieved for these film type sensor cells by processes that increase the three-phase contact area.
1. A sensor cell, comprising:
a substrate having a surface for depositing a plurality of electrodes thereon;
at least one electrode in contact with said surface;
an ionomer membrane in contact with said substrate;
an opening in said membrane proximate to at least one electrode, wherein said opening is of circular shape and about 1.0 mm in diameter for defining a passage for a gas to pass freely to contact said plurality of electrodes electrode within said opening;
wherein a plurality of electrode particles are dispersed throughout the ionomer membrane to increase contact between the gas, electrode particles, and ionomer membrane.
2. The sensor cell of claim 1 , further including a three-way contact point in said opening between said electrode, said gas, and said ionomer membrane.
3. The sensor cell of claim 1 , further comprising openings in said membrane proximate to said electrode which facilitate contact in said open three-phase area.
4. The sensor cell of claim 3 , wherein said openings in said membrane contain a particulate catalyst which electrically contacts said sensing electrode.
5. The sensor cell of claim 1 , wherein said electrode is a sensing electrode and further comprising a counter electrode and a reference in contact with said substrate.
6. The sensor cell of claim 5 , wherein said sensing, counter, and reference electrodes are formed by deposition on said membrane.
7. The sensor cell of claim 5 , wherein said sensing, counter, and reference electrodes are formed by deposition on said substrate.
8. The sensor cell apparatus of claim 5 , wherein said sensing, counter, and reference electrodes comprise a material selected from the group consisting of Pt, Au, C, platinized Pt, and platinized Au.
9. The sensor cell of claim 2 , wherein said electrode is coated with a thin proton exchange film layer which acts to increase said three-way contact points.
10. The sensor cell of claim 1 , wherein said ionomer membrane is comprised of dispersed metallic particles which act to increase said three-way contact points and to enhance signal response and stability.
11. The sensor cell of claim 1 , wherein said ionomer membrane is humidified by aqueous material.
12. The sensor cell of claim 1 , further comprising a microprocessor for real time data readout, data storage and retrieval, and remote data transmission.
13. The sensor cell of claim 1 incorporated into a gas sensing instrument.
14. A sensor cell, comprising:
a substrate having a surface for depositing a plurality of electrodes thereon;
at least one electrode in contact with said surface of said substrate;
an ionomer membrane in contact with said substrate;
an opening in said membrane proximate to at least one electrode for defining a passage;
said opening is of circular shape and about 1.0 mm in diameter for defining a passage; and
a gas in said opening and simultaneously contacting said plurality of electrodes and said ionomer membrane for providing a three-way contact between said gas, said plurality of electrode, and said ionomer membrane within said opening, whereby a plurality of electrode particles are dispersed throughout the ionomer membrane.
15. The sensor cell of claim 14 , comprising:
a plurality of electrode particles dispersed throughout said ionomer membrane;
wherein said opening defines a passage for a gas to pass from said first location to said second location and contact said electrode within said opening; and
wherein said plurality of electrode particles increase contact between the gas, electrode particles, and ionomer membrane.
16. The sensor cell of claim 15 , wherein said plurality of electrode particles are selected from the group consisting essentially of platinum, gold, RuO 2 , metal oxides, and combinations thereof.
17. The sensor cell of claim 15 , wherein said opening provides a concentration gradient from said first location to said second location resulting in a generally steady state flux of gas.