Passive capacitive-based wireless force sensor
A preferred embodiment provides a deformable passive force sensor that induces a change in an interrogation RF signal present on a conductive connection to produce a changed reflective signal and an ID circuit that responds with an ID and the changed reflective signal.
1 . A wireless force sensor comprising a deformable passive force sensor that induces a change in an interrogation RF (radio frequency) signal present on a conductive wire, trace or circuit interconnect to produce a changed reflective signal and an ID (identification) circuit that responds with an ID and the changed reflective signal, wherein the deformable sensor comprises a deformable passive capacitive force sensor comprising a deformable dielectric layer sandwiched between two conductive layers, the ID circuit comprises a digital ID circuit, and the changed reflective signal comprises a phase changed reflective signal on the wire, trace or circuit interconnect.
2 . The wireless force sensor of claim 1 , wherein the deformable dielectric layer comprises one of a polymer layer, an elastomer layer, a carbon filled rubber layer.
3 . The wireless force sensor of claim 1 , formed as a tag applied to an object.
4 . The wireless force sensor of claim 1 , having no battery or power source.
5 . A wireless force sensor comprising a deformable passive force sensor that induces a change in an interrogation RF (radio frequency) signal present on a first conductive wire, trace or circuit interconnect to produce a changed reflective signal and an ID (identification) circuit that responds with an ID and the changed reflective signal,
wherein the deformable sensor comprises a deformable passive capacitive force sensor, the ID circuit comprises a digital ID circuit, and the changed reflective signal comprises a phase changed reflective signal,
wherein the deformable passive capacitive force sensor comprises:
a substrate supporting the conductive wire, trace or circuit interconnect;
a bottom capacitor conductive layer in contact with the conductive wire, trace or circuit interconnect;
a deformable dielectric separating the bottom capacitor conductive layer from a top capacitor conductive layer; and
a second conductive wire, trace or circuit interconnect between the top and bottom capacitor conductive layers and in contact with the top capacitor conductive layer, the second conductive wire, trace or circuit interconnect being grounded to a ground contact of the substrate.
6 . The wireless force sensor of claim 5 , wherein one or both of the first and second conductive wire, trace or circuit interconnect comprises tungsten.
7 . The wireless force sensor of claim 6 , wherein the tungsten comprises a wire that has a diameter ≤15 μm.
8 . The wireless force sensor of claim 5 , wherein one or both of the first and second conductive wire, trace or circuit interconnect has a diameter of ~5 μm.
9 . The wireless force sensor of claim 5 , wherein the deformable dielectric comprises a polymer layer.
10 . The wireless force sensor of claim 9 , wherein the polymer layer comprises an elastomer.
11 . The wireless force sensor of claim 5 , wherein the deformable dielectric comprises a carbon filled rubber layer.
12 . The wireless force sensor of claim 5 , wherein the deformable dielectric comprises a carbon filled silicone rubber layer.
13 . The wireless force sensor of claim 5 , wherein the deformable dielectric comprises a carbon filled neoprene layer.
14 . The wireless force sensor of claim 5 , wherein the top and bottom capacitor conductive layers comprise copper.
15 . The wireless force sensor of claim 5 , comprising an RFID circuit on the substrate.
16 . The wireless force sensor of claim 15 , wherein a capacitor formed by the bottom capacitor conductive layer, the deformable dielectric, the top capacitor conductive layer, and the first and second conductive wire, trace or circuit interconnect is interfaced in parallel to both of an antenna and an IC of the RFID circuit.
17 . A system including the wireless force sensor of claim 5 , and a wireless reader, the reader comprising hardware to emit an excitation signal and receive a reflected signal and correlate the reflected signal to an amount of force on the deformable sensor.
18 . The wireless force sensor of claim 5 , wherein the substrate comprises a flexible substrate.
19 . The wireless force sensor of claim 18 , packaged in a biocompatible material.
20 . A wireless force sensor comprising:
a substrate;
an RF (radio frequency) signal wire, trace or circuit interconnect supported by the substrate;
a bottom capacitor conductive layer in contact with the RF signal wire, trace or circuit interconnect;
a deformable dielectric separating the bottom capacitor conductive layer from a top capacitor conductive layer; and
a ground wire, trace or circuit interconnect between the top and bottom capacitor conductive layers and in contact with the top capacitor conductive layer, the ground wire, trace or circuit interconnect being grounded to a ground contact of the substrate.
21 . A wireless force sensor, comprising:
a substrate;
an RF connection to an antenna supported by the substrate;
a parallel plate capacitor with a deformable dielectric separating top and bottom conductive layers, the deformable dielectric being sandwiched between the top and bottom conductive layers; and
the top and bottom layers interfaced with an antenna's signal and ground ports via a respective RF wire, trace or circuit interconnect on the substrate and a respective ground wire, trace or circuit interconnect on the substrate.