Hydrogel microphone
A device includes a capacitive sensor having a hydrogel structure that includes a first surface and a second surface. A first electrode is provided at the first surface of the hydrogel structure, the first electrode including a network of conductive nanoparticles extending into the hydrogel structure. A second electrode is provided at the second surface of the hydrogel structure.
1. A device comprising:
a capacitive sensor comprising:
a hydrogel structure comprising a first surface and a second surface;
a first electrode at the first surface of the hydrogel structure, the first electrode comprising a network of metal nanoparticles extending into the hydrogel structure; and
a second electrode at the second surface of the hydrogel structure;
wherein the network of metal nanoparticles extends from the first electrode toward the second electrode but does not contact the second electrode.
2. The device of claim 1 , wherein the hydrogel structure comprises a cross-linked and hydrophilic polymer.
3. The device of claim 1 in which the network of metal nanoparticles is deformable in response to changes in the hydrogel structure.
4. The device of claim 1 in which the network of metal nanoparticles comprises at least one of tree-like or dentritic structures that have branches, and electric double layers are formed between the branches.
5. The device of claim 4 in which the capacitive sensor has electric double layer capacitances that change as the network of metal nanoparticles is deformed due to a change in the hydrogel structure.
6. The device of claim 1 , wherein the first surface and the second surface of the hydrogel structure define a thickness between 0.1 mm and 5 mm.
7. The device of claim 1 , wherein the first electrode comprises a terminal positioned on and extending along the first surface of the hydrogel structure, the terminal being electrically coupled to the network of metal nanoparticles.
8. The device of claim 7 , wherein the terminal comprises copper.
9. The device of claim 1 , wherein the network of metal nanoparticles extends from the first surface into the hydrogel structure a depth of 2 to 3 micrometers.
10. The device of claim 1 , wherein the network of metal nanoparticles extends toward the second electrode away from the first surface.
11. The device of claim 1 , wherein the network of metal nanoparticles comprises a metal ion selected from the group consisting of Ag+, Ni2+, Au+, and Pd+.
12. The device of claim 1 , wherein the second electrode comprises a conductive material selected from the group consisting of aluminum, indium tin oxide, and graphene.
13. The device of claim 1 , wherein the capacitive sensor comprises a static compressive load sensitivity of at least 0.1 nF/kPa in air or at least 217 nF/kPa in water.
14. The device of claim 1 , wherein the capacitive sensor has a response magnitude to an acoustic signal between 20 Hz to 60 Hz of at least −150 dB.
15. The device of claim 1 in which the hydrogel structure comprises at least 50% water content by volume.
16. The device of claim 1 , comprising an array of the capacitive sensors configured to detect a contour of a shaped contact.
17. The device of claim 16 in which the array of capacitive sensors share a common hydrogel structure, and different capacitive sensors comprise different first electrodes that are disposed at different regions of the first surface of the hydrogel structure.
18. The device of claim 1 , comprising a hydrogel microphone that comprises:
the capacitive sensor;
a voltage source configured to provide a bias voltage to the first and second electrodes of the capacitive sensor; and
output nodes configured to generate an output signal that varies in response to changes in a capacitance of the capacitive sensor.
19. The device of claim 1 in which the capacitive sensor comprises a static compressive load sensitivity of at least 217 nF/kPa in water.
20. The device of claim 1 in which the capacitive sensor is configured such that a capacitance of the capacitive sensor varies in response to variations in a pressure applied to the first surface of the hydrogel structure.
21. The device of claim 1 in which the first electrode comprises a cathode, the second electrode comprises an anode.
22. The device of claim 1 in which the network of metal nanoparticles comprises at least one of deformable tree-like or deformable dentritic structures that have branches formed of metal nanoparticles, and electric double layers are formed between the branches of the metal nanoparticles.
23. A hydrogel microphone comprising:
a capacitive sensor comprising:
a hydrogel structure comprising a first surface and a second surface;
a first electrode at the first surface of the hydrogel structure, the first electrode comprising a network of conductive particles extending into the hydrogel structure; and
a second electrode at the second surface of the hydrogel structure;
wherein the network of conductive particles extends from the first electrode toward the second electrode but does not contact the second electrode;
a voltage source configured to provide a bias voltage to the first and second electrodes of the capacitive sensor; and
output nodes configured to generate an output signal that varies in response to changes in a capacitance of the capacitive sensor.
24. The hydrogel microphone of claim 23 in which the bias voltage is a DC voltage.
25. The hydrogel microphone of claim 23 in which the network of conductive particles comprises a network of metal nanoparticles.
26. The hydrogel microphone of claim 25 in which the network of metal nanoparticles comprises metal ions selected from the group consisting of Ag+ ions, Ni2+ ions, Au+ ions, and Pd+ ions.
27. The hydrogel microphone of claim 23 in which the capacitive sensor has a capacitance across the first electrode and the second electrode, and the capacitive sensor is configured such that the capacitance varies in response to variations in a pressure applied to the first surface of the hydrogel structure.
28. The hydrogel microphone of claim 23 in which the network of conductive particles comprises at least one of deformable tree-like or deformable dentritic structures that have branches, and electric double layers are formed between the branches, and
wherein the at least one of deformable tree-like or deformable dentritic structures are configured to increase a capacitance of the capacitive sensor such that the capacitive sensor having the at least one of deformable tree-like or deformable dentritic structures has a larger capacitance that if the capacitive sensor does not have the at least one of deformable tree-like or deformable dentritic structures.
29. The hydrogel microphone of claim 28 in which the network of conductive particles comprises at least one of deformable tree-like or deformable dentritic structures that have branches formed of metal nanoparticles, and electric double layers are formed between the branches of the metal nanoparticles.
30. The hydrogel microphone of claim 23 in which the network of conductive particles comprises at least one of deformable tree-like or deformable dentritic structures that have stems and branches, each stem having a first end connected to the first electrode and a second end connected to two or more branches, and each branch has a first end connected to a corresponding stem and a second end extending into the hydrogel.
31. The hydrogel microphone of claim 23 in which the capacitive sensor has electric double layer capacitances that change as the network of conductive nanoparticles is deformed due to a change in the hydrogel structure.
32. The hydrogel microphone of claim 23 in which the capacitive sensor comprises a static compressive load sensitivity of at least 217 nF/kPa in water.
33. The hydrogel microphone of claim 23 in which the capacitive sensor has a response magnitude to an acoustic signal between 20 Hz to 60 Hz of at least −150 dB.
34. The hydrogel microphone of claim 23 , comprising an array of the capacitive sensors configured to detect a contour of a shaped contact.
35. An apparatus comprising:
a capacitive sensor comprising:
a hydrogel structure;
a cathode comprising a network of metal nanoparticles extending into the hydrogel structure, in which the network of metal nanoparticles is formed by introducing ionic precursors into the hydrogel and causing metal ions in the ionic precursors to form the network of metal nanoparticles; and
an anode that contacts the hydrogel structure, in which the network of metal nanoparticles extends from the cathode toward the anode but does not contact the anode.
36. The apparatus of claim 35 in which the network of metal nanoparticles comprises at least one of deformable tree-like or deformable dentritic structures that have stems and branches formed of metal nanoparticles.
37. The apparatus of claim 35 , comprising an array of the capacitive sensors configured to detect a contour of a shaped contact, in which the array of capacitive sensors share a common hydrogel structure, and different capacitive sensors comprise different first electrodes that are disposed at different regions of the first surface of the hydrogel structure.