Active Matrix Electrowetting Device Impedance Sensing Circuit
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Solution Overview
Problem
Existing active matrix electrowetting-on-dielectric (EWOD) devices face limitations in efficiently sensing the location, size, and constitution of droplets due to the need for external sensor electronics and limited connectivity, which increases cost and complexity.
Innovation Solution
Integration of an AC coupled impedance sensor capability into the AM-EWOD device, allowing for simultaneous measurement of impedance at multiple array elements with reduced circuit components and connections, enabling efficient droplet monitoring and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensor electronics are used to sense droplet impedance at array elements, then measurement capability is provided, but device complexity and number of connections increase
Solution Approach 1:
The patent combines the sensor functionality with the existing active matrix EWOD drive circuitry by integrating impedance sensing capabilities into the pixel circuit itself. The pixel circuit is modified to include a sensor function that can measure impedance at the array element level, eliminating the need for separate external sensor electronics and reducing overall device complexity while maintaining measurement capability.
2Measurement precision
If impedance sensing is integrated into array element circuits, then measurement capability is provided, but circuit component count increases
Solution Approach 1:
The pixel circuit is designed to perform multiple functions: it serves as both the electrowetting drive circuit and the impedance sensing circuit. By making the pixel circuit universal, the patent avoids adding dedicated sensor components and instead enables the existing circuit to perform both driving and sensing functions, thereby minimizing the increase in circuit component count.
Solution Approach 2:
The pixel circuit senses impedance using its own integrated components without requiring external sensor electronics. The circuit serves itself by utilizing its internal capacitance and switching elements to perform impedance measurements, reducing the need for additional specialized sensor components.
3Reliability
If AC coupled arrangement is used for writing EW drive voltage and sensing impedance, then high voltage compatibility is maintained, but circuit design complexity increases
Solution Approach 1:
The patent introduces a coupling capacitor as an intermediary element in the pixel circuit that allows AC-coupled signal transmission while isolating different voltage domains. This intermediary component enables the circuit to handle both high voltage EWOD drive signals and low voltage sensing signals simultaneously, maintaining high voltage compatibility while enabling integrated impedance sensing functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise droplet positioning, sizing, and constitution analysis within the AM-EWOD device, improving reliability and manufacturability by reducing the number of external connections and maintaining high voltage compatibility, while minimizing cost and layout footprint.
Implementation Method 1
Electrowetting-On-Dielectric (EWOD) is a known technique for manipulating droplets of fluid on an array. Active Matrix EWOD (AM-EWOD) refers to implementation of EWOD in an active matrix array
Implementation Method 2
Integration of an AC coupled impedance sensor capability into the AM-EWOD device, allowing for simultaneous measurement of impedance at multiple array elements
Data Source
AI summary
An active-matrix device is provided which includes a plurality of array element circuits arranged in rows and columns; a plurality of source addressing lines each shared between the array element circuits in corresponding same columns; a plurality of gate addressing lines each shared between the array element circuits in corresponding same rows; a plurality of sensor row select lines each shared between the array element circuits in corresponding same rows, wherein each of the plurality of array element circuits includes: an array element which is controlled by application of a drive voltage by a drive element; writing circuitry for writing the drive voltage to the drive element, the writing circuitry being coupled to a corresponding source addressing line and gate addressing line among the plurality of source addressing lines and gate addressing lines; and sense circuitry for sensing an impedance presented at the drive element, the sense circuitry being coupled to a corresponding sensor row select line; and a row driver and a column driver.