Two-dimensional sensor arrays
Sensors incorporating piezoresistive materials are described. One class of sensors includes piezoresistive material that is held or otherwise supported adjacent conductive traces on a substrate. Another class of sensors includes conductive traces formed directly on the piezoresistive material. Two-dimensional sensor arrays incorporating piezoresistive materials are also described.
1. A sensor system, comprising:
piezoresistive fabric;
a flexible dielectric substrate having a plurality of conductive trace groups printed in conductive ink on a first side of the flexible dielectric substrate and a plurality of routing traces printed in conductive ink on a second side of the flexible dielectric substrate opposite the first side, the conductive trace groups and the piezoresistive fabric being in contact and forming a sensor array in which each of the conductive trace groups corresponds to a sensor in the sensor array, each of the conductive trace groups including two conductive traces, each of the conductive traces being electrically connected through the flexible dielectric substrate to a corresponding routing trace on the second side of the flexible dielectric substrate; and
sensor circuitry configured to use the routing traces to energize the sensors and receive resulting sensor signals, the sensor circuitry also being configured to use the sensor signals to generate data representing locations and magnitudes of force resulting from objects in contact with a surface of the sensor system.
2. The sensor system of claim 1 , wherein the sensor circuitry is further configured to generate successive frames of the data for the sensor array, and to compare the successive frames of the data to improve reliability of the data.
3. The sensor system of claim 1 , wherein the two conductive traces of each conductive trace group comprise interdigitated extensions.
4. The sensor system of claim 1 , wherein the two conductive traces of each conductive trace group comprise clover and cruciform shapes.
5. The sensor system of claim 1 , wherein the piezoresistive fabric is a calendared material.
6. The sensor system of claim 5 , wherein the piezoresistive material includes polymerized conductive particles.
7. The sensor system of claim 1 , wherein one or more characteristics of the conductive trace groups are configured to achieve a particular dynamic range for the sensor system, the one or more characteristics including one or more of (1) shapes of the conductive traces of each conductive trace group, (2) distances between the conductive traces of each conductive trace group, or (3) conductivity of the conductive traces of each conductive trace group.
8. The sensor system of claim 1 , further comprising one or more of (1) force focusing elements configured to focus the force on the surface of the sensor system toward one or more corresponding sensors of the sensor array, (2) structural elements configured to resist the force on the surface of the sensor system, or (3) cutouts in the piezoresistive fabric that promote physical and electrical isolation of adjacent sensors.
9. The sensor system of claim 1 , wherein the conductive traces of each conductive trace group are electrically connected to the corresponding routing traces using conductive ink vias, conductive paint vias, metal vias, or metal rivets.
10. The sensor system of claim 1 , wherein the piezoresistive fabric is a single substrate for all of the conductive trace groups.
11. The sensor system of claim 10 , further comprising an insulating layer adjacent the piezoresistive fabric, the insulating layer having openings that line up with the conductive trace groups.
12. The sensor system of claim 1 , wherein the piezoresistive fabric is multiple pieces, each piece of piezoresistive fabric corresponding to a different subset of the conductive trace groups.
13. The sensor system of claim 1 , wherein the piezoresistive fabric is coupled to the flexible dielectric substrate.
14. The sensor system of claim 13 , wherein the piezoresistive fabric is laminated to the flexible dielectric substrate.
15. The sensor system of claim 1 , wherein the piezoresistive fabric is held at a distance from the conductive trace groups when pressure is not applied to the surface of the sensor system.
16. The sensor system of claim 1 , further comprising an insulating material printed at locations at which two of the routing traces cross, the insulating material insulating the two routing traces from each other.
17. The sensor system of claim 1 , wherein the sensor circuitry is configured to energize the sensors in a sequence and to receive the sensor signals in the sequence, and wherein the sensor circuitry is further configured to use the sensor signals to determine a speed of motion of a touch event relative to the surface of the sensor system, and a direction of motion of the touch event.
18. The sensor system of claim 1 , wherein the sensor array is one of a linear array, a rectilinear array, a polar array, a hemispherical array, or an irregular two-dimensional array.