Hybrid film type sensor
View Patent ↗A miniaturized gas sensor comprised of thick- or thin-film type electrodes, on a non-conductive supportive substrate, and in contact with 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 substrate. 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 constant-voltage, potentiostatic or potentiodynamic mode. A high sensitivity to a select gas or vapor is achieved by a novel three-phase contact area design for a sensing electrode which provides contact with the solid ionomer electrolyte, as well as the gas sample via diffusion openings or holes that penetrate through the supportive substrate.
1. A sensor cell for detecting gases comprising:
a substrate having a first surface and an opposite second surface;
a sensing electrode; said sensing electrode in contact with said second surface;
an opening extending from said first surface to said second surface proximate to said sensing electrode for controlling a gas flow; and
a gas diffusion membrane in contact with and extending from said first surface to said sensing electrode, wherein said gas diffusion membrane has a thickness less than said substrate at said opening.
2. The sensor cell of claim 1 whereby said gas diffusion membrane is humidified by an aqueous material.
3. The sensor cell of claim 1 incorporated into a gas sensing instrument.
4. The sensor cell of claim 1 , further including a counter electrode.
5. The sensor cell of claim 4 wherein said sensor cell is electronically controlled in a 2 electrode sensor configuration.
6. The sensor cell of claim 4 , further including a reference electrode.
7. The sensor cell of claim 6 whereby at least one of said sensing, counter, or reference electrodes contains a fluorocarbon-bonded particulate catalyst which is bonded to an ionomer membrane.
8. The sensor cell of claim 7 whereby said fluorocarbonbonded particulate catalyst is coated with said gas diffusion membrane where said gas diffusion membrane is polymeric.
9. The sensor cell of claim 6 whereby at least one of said sensing, counter, or reference electrodes contains an ionomer-bonded particulate catalyst which is bonded to an ionomer membrane.
10. The sensor cell of claim 9 whereby said ionomer-bonded particulate catalyst is coated with said gas diffusion membrane where said gas diffusion membrane is polymeric.
11. The sensor cell of claim 6 wherein said sensing, counter, and reference electrodes comprise a material selected from the group consisting of Pt, Au, C, platinized Pt, and platinized Au.
12. The sensor cell of claim 6 wherein said sensor cell is electronically controlled in a 3 electrode sensor configuration.
13. The sensor cell of claim 6 wherein said sensor cell is electronically controlled by a potentiostatic circuit connected to said sensing, counter and reference electrodes.
14. The sensor cell of claim 6 wherein said sensor cell is electronically controlled by a potentiodynamic circuit connected to said sensing, counter and reference electrodes.
15. The sensor cell of claim 1 wherein said sensor cell is electronically controlled by a constant voltage source connected to said sensing electrode and an electrochemically reversible counter electrode also acting as a reference electrode.
16. The sensor cell of claim 1 further comprising a microprocessor for real time data readout, data storage and retrieval, and remote data transmission.
17. A sensor cell for detecting gases comprising:
a substrate having a first surface and an opposite second surface;
a sensing electrode; said sensing electrode in contact with said second surface;
an opening extending from said first surface to said second surface proximate to said sensing electrode for controlling a gas flow; and
a gas diffusion membrane being of polymeric material in contact with and extending from first surface to said sensing electrode, wherein said gas diffusion membrane has a thickness less than said substrate at said opening.
18. The sensor cell in claim 17 , wherein said gas diffusion membrane is a non-electrolytic material.
19. The sensor cell of claim 17 , wherein said gas diffusion membrane is made of polyethylene.