Transparent high-resistivity layer for electrostatic friction modulation over a capacitive input sensor
A transparent high-conductivity layer for providing electrostatic feedback to a user of an electronic device. The transparent high-conductivity layer is positioned over a capacitive input sensor and has a resistivity sufficiently high to prevent interference with the capacitive input sensor. As one example, the transparent high-conductivity layer can be formed from a layer of geometrically-separated regions of high-conductivity material. The average distance between geometrically-separated regions can substantially define the resistivity of the transparent high-conductivity layer.
1. An electronic device comprising:
an interface surface configured to receive a user input;
a high-resistivity layer at least partially below the interface surface, the high-resistivity layer comprising a number of geometrically-separated regions of high-conductivity material; and
a capacitive input sensor positioned below the interface surface and below the high-resistivity layer; wherein
the capacitive input sensor is configured to detect the user input through the high-resistivity layer; and
the capacitive input sensor is ground-shifted to drive the high-resistivity layer to a high voltage.
2. The electronic device of claim 1 , wherein the high-resistivity layer exhibits optical transmittance greater than 50 % in the wavelength band between, and including, 300 nm and 700 nm.
3. The electronic device of claim 2 , wherein the high-resistivity layer exhibits optical transmittance greater than 80% in the wavelength band between, and including, 300 nm and 700 nm.
4. The electronic device of claim 1 , wherein at least one geometrically-separated region comprises a body having a dome shape.
5. The electronic device of claim 4 , wherein the body is formed from a low-conductivity material and is doped to a selected doping concentration with a high-conductivity material.
6. The electronic device of claim 1 , wherein the high-resistivity layer is formed, at least in part, from a silicon oxide.
7. The electronic device of claim 6 , wherein the high-resistivity layer is formed from a combination of silicon dioxide and tin dioxide.
8. The electronic device of claim 1 , wherein the interface surface is defined by an outer surface of the high-resistivity layer.
9. The electronic device of claim 1 , wherein each geometrically-separated region comprises a body having a flattened dome shape.