ODOR SENSORS
Odor sensors and methods for their preparation and use are described. In some examples, an odor sensor may include a convex quartz crystal resonator having a first surface and a second surface, a pair of first electrodes disposed on the first surface, a second electrode disposed on the second surface, and at least one odor-sensitive material disposed on the second electrode.
1 . An odor sensor, comprising:
at least one convex quartz crystal resonator having a first surface and a second surface;
a pair of first electrodes disposed on the first surface;
a second electrode disposed on the second surface; and
at least one odor-sensitive material disposed on the second electrode.
2 . The odor sensor of claim 1 , wherein the at least one convex quartz crystal resonator includes a plano-convex quartz crystal resonator, the first surface is a convex-shaped surface, and the second surface is a substantially planar surface.
3 . The odor sensor of claim 1 , wherein the pair of first electrodes and the second electrode are made of gold.
4 . The odor sensor of claim 1 , wherein the pair of first electrodes and the second electrode are aligned with a convex-shaped portion of the at least one convex quartz crystal resonator.
5 . The odor sensor of claim 1 , wherein the at least one odor-sensitive material has a selective affinity for a chemical to be detected.
6 . The odor sensor of claim 1 , wherein the at least one odor-sensitive material comprises at least one of polycaprolactone, polystyrene, cycloolefin, or acrylic resin.
7 . The odor sensor of claim 1 , wherein the at least one convex quartz crystal resonator includes an AT-cut convex quartz crystal resonator.
8 . (canceled)
9 . A method to fabricate an odor sensor, the method comprising:
providing a quartz crystal substrate;
forming a convex portion in the quartz crystal substrate;
forming a pair of first electrodes on a first surface of the convex portion;
forming a second electrode on a second surface of the convex portion; and
applying at least one odor-sensitive material on the second electrode.
10 . The method of claim 9 , wherein the forming of the convex portion comprises:
applying a photoresist on a surface of the quartz crystal substrate;
patterning the photoresist on the surface of the quartz crystal substrate;
curing the patterned photoresist; and
etching the quartz crystal substrate and the patterned photoresist to form the convex portion.
11 . The method of claim 10 , wherein the forming of the convex portion further comprises determining a sectional profile of the convex portion, and
wherein the patterning of the photoresist is performed based at least in part on the determined sectional profile of the convex portion.
12 . The method of claim 10 , wherein the curing of the patterned photoresist comprises heating the patterned photoresist.
13 . The method of claim 10 , wherein the etching is performed by reactive ion etching (RIE).
14 . The method of claim 10 , wherein the etching comprises etching the quartz crystal substrate and the patterned photoresist at different etching rates.
15 . The method of claim 9 , wherein the forming of the pair of first electrodes comprises:
sputtering gold on the first surface of the convex portion; and
patterning the sputtered gold to form the pair of first electrodes.
16 . The method of claim 9 , wherein the forming of the second electrode comprises:
sputtering gold on the second surface of the convex portion; and
patterning the sputtered gold to form the second electrode.
17 . The method of claim 9 , wherein the at least one odor-sensitive material has a selective affinity for a chemical to be detected.
18 . The method of claim 9 , wherein the at least one odor-sensitive material comprises at least one of polycaprolactone, polystyrene, cycloolefin, and acrylic resin.
19 . The method of claim 9 , wherein the applying of the at least one odor-sensitive material comprises:
applying on the second electrode a solution including the at least one odor-sensitive material.
20 . The method of claim 19 , wherein the solution comprises an organic solvent that dissolves the at least one odor-sensitive material.
21 . The method of claim 20 , wherein the organic solvent includes at least one of acetone, trichloroethylene, and alcohol.
22 . The method of claim 9 , further comprising:
selecting the at least one odor-sensitive material to be applied based at least in part on a chemical to be detected.
23 . The method of claim 9 , further comprising:
selecting an amount of the at least one odor-sensitive material to be applied on the second electrode.
24 . The method of claim 9 , further comprising:
selecting an area of the second electrode on which the at least one odor-sensitive material to be applied.
25 - 26 . (canceled)
27 . A method to detect odor using an odor sensor, the method comprising:
exposing at least one odor sensitive material that is disposed on a first electrode to a chemical, the first electrode disposed on a first surface of at least one convex quartz crystal resonator;
measuring a change in a resonating frequency of the at least one convex quartz crystal resonator; and
detecting the chemical based at least in part on the measured change in the resonating frequency of the at least one convex quartz crystal resonator.
28 . The method of claim 27 , wherein the at least one convex quartz crystal resonator has a second surface, a pair of second electrodes are disposed on the second surface.
29 . The method of claim 27 , wherein the at least one odor-sensitive material has a selective affinity for the associated chemical.