Bulk acoustic wave sensor having an overmoded resonating structure
A bulk acoustic wave sensor includes a delay layer. The sensor includes an acoustic mirror and a base resonator. The base resonator includes a piezoelectric layer and two electrodes. One or more delay layers are disposed adjacent to the base resonator. A delay layer may be disposed between the base resonator and the acoustic mirror, a delay layer may be disposed on the base resonator opposite to the acoustic mirror, or both. Each delay section is formed of high quality-factor material. The sensor may define a resonant frequency, and the thickness of each delay section may be an integer multiple of half-wavelengths of the resonant frequency.
1. A bulk acoustic wave sensor comprising an overmoded resonating structure, the resonating structure comprising:
a base resonator comprising a piezoelectric layer, a first electrode disposed on a first surface of the piezoelectric layer, a second electrode disposed on a second surface of the piezoelectric layer opposite to the first side;
an acoustic delay layer adjacent to the base resonator, wherein the acoustic delay layer defines a delay layer thickness configured to provide multiple resonance modes in the resonating structure; and
an acoustic mirror layer adjacent to the base resonator or the acoustic delay layer.
2. The sensor of claim 1 , wherein the acoustic delay layer comprises a high quality-factor material with low acoustic loss.
3. The sensor of claim 1 , wherein the resonating structure defines a base resonator thickness equal to one predetermined wavelength and the delay layer thickness is a non-negative integer multiple of one half-wavelength of the predetermined wavelength.
4. The sensor of claim 3 , wherein the delay layer thickness is one half-wavelength.
5. The sensor of claim 1 , wherein the delay layer thickness is equal to at least 200 half-wavelengths.
6. The sensor of claim 1 , wherein the delay layer thickness provides an Q multiplier factor of at least 3.
7. The sensor of claim 1 , wherein the acoustic delay layer comprises: aluminum oxide, aluminum nitride, zinc oxide, silicon carbide, silicon dioxide, or carbon.
8. The sensor of claim 1 , wherein the acoustic mirror layer comprises alternating layers of material.
9. The sensor of claim 1 , further comprising a substrate disposed adjacent to the acoustic mirror layer opposite to the base resonator.
10. The sensor of claim 9 , wherein the substrate comprises a semiconductor material.
11. The sensor of claim 1 , wherein the acoustic delay layer is disposed between the base resonator and the acoustic mirror layer.
12. The sensor of claim 11 , further comprising another acoustic delay layer disposed on the base resonator opposite to the acoustic mirror layer.
13. The sensor of claim 1 , wherein the acoustic delay layer is disposed on the base resonator opposite to the acoustic mirror layer.
14. A sensing system comprising:
a microfluidic channel configured to receive a sample liquid; and
a bulk acoustic wave sensor having a surface that defines at least a portion of the microfluidic channel, the sensor comprising a resonating structure comprising:
a base resonator comprising a first electrode, a second electrode, and a piezoelectric layer disposed between the electrodes;
an acoustic delay layer disposed adjacent to the base resonator, wherein the acoustic delay layer defines a delay layer thickness configured to provide multiple resonance modes in the resonating structure; and
an acoustic mirror layer disposed adjacent to the base resonator or the acoustic delay layer.
15. The sensing system of claim 14 , wherein the sensor comprises an insulating layer between the microfluidic channel and the second electrode.
16. The sensing system of claim 15 , further comprising a detection platform operatively coupled to the sensor to receive resonator data.
17. The sensing system of claim 16 , wherein the detection platform is removably coupled to the sensor.
18. A thin-film method of making a resonating structure, the method comprising:
providing a substrate;
depositing an acoustic mirror layer on the substrate; and
depositing an acoustic delay layer and a base resonator on the acoustic mirror layer in either order,
wherein the acoustic delay layer is deposited at a thickness configured to provide multiple resonance modes in the resonating structure.
19. The sensing system of claim 15 , comprising functional material disposed on the insulating layer.
20. A bulk acoustic wave sensor comprising an overmoded resonating structure, the resonating structure comprising:
a base resonator comprising a piezoelectric layer, a first electrode disposed on a first surface of the piezoelectric layer, a second electrode disposed on a second surface of the piezoelectric layer opposite to the first side;
an acoustic mirror layer;
a first acoustic delay layer between the base resonator and the acoustic mirror layer; and
a second acoustic delay layer disposed on the base resonator opposite to the acoustic mirror layer.
21. A sensing system comprising:
a microfluidic channel configured to receive a sample liquid; and
a bulk acoustic wave sensor having a surface that defines at least a portion of the microfluidic channel, the sensor comprising a resonating structure comprising:
a base resonator comprising a first electrode, a second electrode, and a piezoelectric layer disposed between the electrodes;
an acoustic mirror layer;
a first acoustic delay layer between the base resonator and the acoustic mirror layer; and
a second acoustic delay layer disposed on the base resonator opposite to the acoustic mirror layer.
22. A thin-film method of making a resonating structure, the method comprising:
providing a substrate;
depositing an acoustic mirror layer on the substrate; and
depositing a first acoustic delay layer on the acoustic mirror layer;
depositing a base resonator on the first acoustic delay layer; and
depositing a second acoustic delay layer on the base resonator.