Printed transparent heaters using embedded micro-wires
A transparent heater includes a plurality of high aspect ratio micro-wires. A plurality of channels is formed into the surface of a transparent substrate within an active heater region. The channels have a width of between 4 microns and 9 microns to insure that they are invisible to the naked eye, and a depth that is at least 1.5 times the width. Spacing between the channels is preferably at least 100 μm. Micro-wires are formed by at least partially filling the channels with a conductive material. Power source connections are provided to connect to an electrical power source to supply a current through the plurality of micro-wires. An average optical transmittance of the transparent heater within the active heater region is greater than 50 percent.
1. A transparent heater having high aspect ratio micro-wires, comprising:
a substrate that is at least partially transparent;
a plurality of channels extending into a surface of the substrate within an active heater region, wherein the channels have a width of between 4 microns and 9 microns and a depth that is at least 1.5 times the width;
a plurality of micro-wires formed by at least partially filling the channels with a conductive material, wherein the micro-wires have a micro-wire width of greater than 4 microns and no more than 9 microns and a micro-wire thickness that is at least 1.5 times the micro-wire width; and
power source connections adapted to connect to an electrical power source to supply a current through the plurality of micro-wires;
wherein an average optical transmittance of the transparent heater within the active heater region is greater than 50 percent; and
wherein the resistance per unit length of the individual micro-wires is no more than 2000 Ω/m.
2. The transparent heater of claim 1 , wherein a spacing between adjacent channels is at least 100 microns.
3. The transparent heater of claim 1 , wherein the average optical transmittance of the transparent heater within the active heater region is greater than 70 percent.
4. The transparent heater of claim 1 , wherein the substrate is flexible.
5. The transparent heater of claim 1 , wherein the substrate is a glass substrate or a polymer substrate.
6. The transparent heater of claim 1 , wherein the substrate includes a photocurable layer, and wherein the channels are formed in the photocurable layer.
7. The transparent heater of claim 1 , wherein the channels are formed using hot embossing or photolithography.
8. The transparent heater of claim 1 , wherein the conductive material is an ink containing silver nano-particles.
9. The transparent heater of claim 1 , wherein the depth of the channels is less than 30 microns.
10. The transparent heater of claim 1 , wherein the plurality of micro-wires follow parallel paths.
11. The transparent heater of claim 10 , wherein the paths are linear paths, zig-zag paths, curved paths, serpentine paths or spiral ring paths.
12. The transparent heater of claim 1 , further including intermediate connections formed between adjacent micro-wires.
13. The transparent heater of claim 1 , wherein the transparent heater is overlaid on a surface of a display.
14. The transparent heater of claim 1 , wherein the micro-wires are not visible to the naked eye of a human observer.