Active matrix device and method of driving the same
An active matrix electrowetting on dielectric (AM-EWOD) device includes a plurality of array elements configured to manipulate one or more droplets of fluid on an array, each of the array elements including a corresponding array element circuit. Each array element circuit includes a top substrate electrode and a drive electrode between which the one or more droplets may be positioned, with an insulator layer being interposed between the one or more droplets and the drive electrode; and write circuitry configured to write data to the array element. At least some of the array element circuits include measure circuitry configured to detect a pinhole defect in the insulator layer.
1. An active matrix electrowetting on dielectric (AM-EWOD) device, comprising:
a plurality of array elements configured to manipulate one or more droplets of fluid on an array, each of the array elements including a corresponding array element circuit;
each array element circuit including
a top substrate electrode and a drive electrode between which the one or more droplets may be positioned, with an insulator layer being interposed between the one or more droplets and the drive electrode; and
write circuitry configured to write data to the array element; and
wherein at least some of the array element circuits include measure circuitry configured to detect a pinhole defect in the insulator layer.
2. The device according to claim 1 , wherein the measure circuitry in an array element is configured to measure a resistance of the insulator layer to detect a pinhole defect in the insulator layer.
3. The device according to claim 2 , wherein the measure circuitry relies on presence of the one or more droplets in the array element in order to detect the pinhole defect.
4. The device according to claim 1 , wherein the measure circuitry in an array element circuit is configured to measure a leakage of charge from the drive electrode through the insulator layer in order to detect the pinhole defect.
5. The device according to claim 1 , wherein the measure circuitry in an array element is configured to measure an RC time constant associated with a leakage of charge from the drive electrode through the insulator layer in order to detect the pinhole defect.
6. The device according to claim 1 , wherein the measure circuitry is configured to make multiple measurements of a voltage of the drive electrode at different sampling times following data being written to the array element in order to detect and classify the pinhole defect.
7. The device according to any claim 1 , wherein the write circuitry includes an SRAM circuit for storing the data written to the array element, and a selection circuit for selectively connecting an output of the SRAM circuit to the drive electrode to write the stored data to the drive electrode and subsequently disconnecting the output of the SRAM from the drive electrode in order that leakage of charge from the drive electrode is primarily due to leakage via a pinhole defect in the insulator layer; and
the measure circuitry samples the voltage of the drive electrode following being disconnected from the output of the SRAM in order to detect the pinhole defect in the insulator layer.
8. The device according to claim 7 , wherein the data to be written to the array element is stored in the SRAM circuit via a data line, and an output of the measure circuitry is output from the array element via an output line.
9. The device according to claim 8 , wherein the data line and output line are common to a plurality of the array elements within a same column of the array.
10. The device according to claim 8 , wherein the data line and the output line are the same line.
11. The device according to claim 1 , wherein the write circuitry is configured to develop an AC voltage between the drive electrode and top electrode to actuate electro-wetting manipulation of the one or more droplets, and a DC voltage in order to measure circuitry to detect the pinhole defect in the insulator layer.
12. The device according to claim 11 , wherein the write circuitry is configured to develop the DC voltage in order the measure circuitry to detect the pinhole defect in the insulator layer without necessitating rewriting of write data to the array element.
13. The device according to claim 11 , wherein the write circuitry and the measure circuitry share a common inverter.
14. The device according to claim 1 , wherein the write circuitry and the measure circuitry share a common switch element used to write data from an input/output line to the array element, and to output an output of the measure circuitry from the array element to the same input/output line.
15. The device according to claim 1 , wherein the write circuitry includes a DRAM circuit for writing a voltage to the drive electrode, and
the measure circuitry samples the voltage written to the drive electrode in order to detect the pinhole defect in the insulator layer.
16. The device according to claim 1 , the array elements each further comprising a droplet sensor circuit for sensing a presence of the one or more droplets of fluid.
17. The device according to claim 1 , further comprising a computer controller configured to compute a route for the one or more droplets of fluid to be manipulated on the array accounting for the presence of pinhole defects in the insulator layer as determined via the measure circuitry in the at least some of the array elements.