AM-EWOD Array Circuit with Memory Capacitor for Droplet Impedance Sensing
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Solution Overview
Problem
Existing Active Matrix Electro-wetting on Dielectric (AM-EWOD) devices require complex circuitry and high voltage transistors to manage actuation and impedance sensing, limiting their scalability and optical transparency for applications like lab-on-a-chip systems.
Innovation Solution
A method and circuit design for AM-EWOD devices that uses a 2-Transistor array element circuit with a memory function, allowing for AC electro-wetting by switching between +VEW and −VEW voltages, and incorporating a minimal number of transistors and capacitors to simplify the array element circuit, enabling smaller droplet manipulation and larger array formats with improved optical transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex circuitry with high voltage transistors is used to manage actuation and impedance sensing, then reliable droplet manipulation is achieved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent divides the array element circuit into distinct functional blocks: a first transistor for actuation control, a second transistor for impedance sensing, and associated capacitors. This segmentation allows each component to perform its specific function efficiently, reducing overall circuit complexity while maintaining reliable droplet manipulation through dedicated control paths for actuation and sensing operations.
Solution Approach 2:
The patent implements a multi-functional array element circuit where the same circuit structure handles both actuation and impedance sensing operations. The first and second transistors work together to provide both droplet actuation through voltage application and impedance measurement for droplet detection, eliminating the need for separate dedicated circuits and reducing overall device complexity.
2Ease of operation
If more transistors and capacitors are used in the array element circuit, then better actuation and sensing control is achieved, but optical transparency and array scalability are reduced
Solution Approach 1:
The patent extracts and eliminates unnecessary circuit components from the array element design, retaining only the essential first and second transistors along with their associated capacitors. This minimal component configuration maintains adequate actuation and sensing control while maximizing optical transparency by removing excess materials that would block light, thereby enabling better scalability to larger array formats.
Solution Approach 2:
The patent optimizes the electrical parameters of the minimal transistor-capacitor circuit to achieve effective actuation and sensing control. By carefully selecting transistor dimensions, capacitance values, and operating voltages, the circuit provides sufficient control capability with fewer components, thus maintaining optical transparency and enabling larger array formats without compromising functionality.
3Force
If high voltage transistors are used for actuation management, then sufficient electro-wetting force is achieved, but manufacturing yield and device scalability are limited
Solution Approach 1:
The patent employs dynamic voltage switching using the first transistor to apply appropriate voltages to the droplet for actuation. The circuit dynamically transitions between different voltage states (including high voltage for actuation and low voltage for sensing) through controlled transistor switching, achieving sufficient electro-wetting force while using standard voltage transistors that are compatible with conventional manufacturing processes, thereby improving manufacturing yield and scalability.
Solution Approach 2:
The patent implements periodic actuation cycles where high voltage is applied temporarily to generate the necessary electro-wetting force for droplet manipulation, followed by return to lower voltage states for sensing and stable positioning. This periodic application of high voltage achieves effective droplet control while limiting the time exposure to high voltage conditions, reducing stress on transistors and improving overall device reliability and manufacturing yield.
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 approach reduces the complexity and size of the array elements, facilitating the manipulation of smaller droplets, achieving high manufacturing yield, and enhancing optical transparency, which is crucial for chemical tests that involve optical property changes.
Implementation Method 1
Active Matrix EWOD (AM-EWOD) refers to implementation of EWOD in an active matrix array incorporating transistors
Implementation Method 2
an impedance sensor circuit configured to sense impedance at the array element electrode to determine a droplet property at the array element
Data Source
AI summary
An active matrix electro-wetting on dielectric (AM-EWOD) device includes a plurality of array elements arranged in an array, each array element including array element circuitry, an element electrode, and a reference electrode. The array element circuitry includes an actuation circuit configured to apply actuation voltages to the electrodes, and an impedance sensor circuit configured to sense impedance at the array element electrode to determine a droplet property. The actuation circuitry includes a memory capacitor for storing voltage data corresponding to either an actuated state or an unactuated state of the array element, and an input applied to the memory capacitor operates to effect an operation of the impedance sensor circuit. Such input may isolate the array element from the actuation voltage during operation of the impedance sensor circuit, and the memory capacitor may operate as part of the impedance sensor circuit as a reference capacitor for determining the droplet property.