Chemical preconcentrator
First Claim
1. A chemical preconcentrator apparatus, comprising:
- (a) a substrate having a suspended membrane formed thereon;
(b) a resistive heating element disposed on a surface of the membrane; and
(c) a sorptive material disposed on at least one surface of the membrane to sorb and concentrate at least one chemical species of interest from a vapor over time, with the chemical species being releasable from the sorptive material upon heating of the sorptive material by the resistive heating element.
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Accused Products
Abstract
A chemical preconcentrator is disclosed with applications to chemical sensing and analysis. The preconcentrator can be formed by depositing a resistive heating element (e.g. platinum) over a membrane (e.g. silicon nitride) suspended above a substrate. A coating of a sorptive material (e.g. a microporous hydrophobic sol-gel coating or a polymer coating) is formed on the suspended membrane proximate to the heating element to selective sorb one or more chemical species of interest over a time period, thereby concentrating the chemical species in the sorptive material. Upon heating the sorptive material with the resistive heating element, the sorbed chemical species are released for detection and analysis in a relatively high concentration and over a relatively short time period. The sorptive material can be made to selectively sorb particular chemical species of interest while not substantially sorbing other chemical species not of interest. The present invention has applications for use in forming high-sensitivity, rapid-response miniaturized chemical analysis systems (e.g. a “chem lab on a chip”).
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Citations
38 Claims
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1. A chemical preconcentrator apparatus, comprising:
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(a) a substrate having a suspended membrane formed thereon;
(b) a resistive heating element disposed on a surface of the membrane; and
(c) a sorptive material disposed on at least one surface of the membrane to sorb and concentrate at least one chemical species of interest from a vapor over time, with the chemical species being releasable from the sorptive material upon heating of the sorptive material by the resistive heating element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for forming a chemical preconcentrator apparatus for sorbing a chemical species of interest from a vapor over time and releasing the chemical species of interest upon demand, comprising steps for:
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(a) forming a suspended membrane on a substrate;
(b) forming a resistive heating element on a surface of the suspended membrane; and
(c) coating at least one surface of the suspended membrane with a sorptive material capable of sorbing the chemical species of interest. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
depositing a sacrificial layer over the substrate;
depositing a film over the sacrificial layer;
forming a plurality of openings through the film to expose the sacrificial layer; and
removing, at least in part, the sacrificial layer through the openings formed in the film.
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20. The method of claim 19 wherein the film is selected from the group consisting of silicon nitride, polycrystalline silicon, silicon oxynitride and silicon carbide;
- and the sacrificial layer is selected from the group consisting of silicon dioxide, silicate glasses and polymers.
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21. The method of claim 20 wherein the step for removing the portion of the sacrificial layer comprises etching the sacrificial layer with a wet etchant comprising hydrofluoric acid.
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22. The method of claim 20 wherein the step for removing the portion of the sacrificial layer comprises dissolving the sacrificial layer using a solvent.
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23. The method of claim 13 wherein the step for forming the resistive heating element comprises depositing a metal layer and patterning the metal layer to form a circuitous metal trace.
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24. The method of claim 23 wherein the metal layer comprises a metal selected from the group consisting of platinum, molybdenum, titanium, chromium, palladium, gold, tungsten and combinations thereof.
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25. The method of claim 23 further including a step for annealing the circuitous metal trace for relieving any stress therein.
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26. The method of claim 13 wherein the step for coating the surface of the suspended membrane comprises depositing a sorptive material selected from the group consisting of polymers, microporous materials, and sol-gel oxides.
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27. The method of claim 26 further including a step for curing the deposited sorptive material by heating.
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28. A method for forming a chemical preconcentrator apparatus for sorbing a chemical species of interest from a vapor over time and releasing the chemical species of interest upon demand, comprising steps for:
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(a) depositing a film over a top surface of a substrate;
(b) forming a resistive heating element on a portion of the film;
(c) removing material from the substrate underneath the portion of the film and thereby forming a suspended membrane from the film; and
(d) coating at least one surface of the suspended membrane with a sorptive material capable of sorbing the chemical species of interest. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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Specification