Active Matrix Electrowetting Sensor Circuitry for Droplet Impedance Detection
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Solution Overview
Problem
Existing Active Matrix Electrowetting-On-Dielectric (AM-EWOD) devices face challenges in efficiently manipulating droplets and sensing impedance changes, particularly in detecting small capacitance changes due to bio-molecule adsorption on hydrophobic surfaces, which affects the accuracy and sensitivity of droplet manipulation and chemical reactions.
Innovation Solution
The AM-EWOD device incorporates an array element circuit with dual-mode sensor circuitry that includes an active capacitor, allowing operation in different sensitivity ranges by adjusting the voltage level of the row select line, enabling precise detection of droplets and changes in hydrophobic surface properties without additional circuit components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single fixed sensitivity range is used in sensor circuitry, then the device structure remains simple, but the ability to detect both large and small capacitance changes accurately is compromised
Solution Approach 1:
The sensor circuitry dynamically switches between a first sensitivity range and a second sensitivity range based on operating conditions. The sensitivity range is adjusted by changing the capacitance value of the active capacitor through voltage control, allowing the system to adapt to different measurement requirements without requiring multiple fixed circuit configurations
Solution Approach 2:
The capacitance value of the active capacitor is changed by adjusting the voltage applied to it, which directly changes the sensitivity range of the sensor circuitry. This parameter change allows the same physical circuit to operate in different sensitivity modes, resolving the contradiction between measurement precision and device complexity
2Measurement precision
If multiple separate sensor circuits are used for different sensitivity ranges, then detection accuracy across different ranges is improved, but the device area and component count increase
Solution Approach 1:
A single sensor circuit is designed to perform multiple functions by operating in different sensitivity ranges. The same sensor circuitry detects both large capacitance changes (droplet presence) and small capacitance changes (bio-molecule adsorption) by adjusting the active capacitor voltage, eliminating the need for separate dedicated circuits for each detection task
Solution Approach 2:
The patent merges the functionality of multiple sensitivity ranges into a single integrated sensor circuit. By combining the first and second sensitivity ranges in one circuit configuration and controlling them through voltage adjustment of the active capacitor, the design achieves multi-range detection capability without requiring separate physical circuits
3Measurement precision
If high sensitivity detection of small capacitance changes is implemented, then detection of bio-molecule adsorption is improved, but the device becomes more complex and less reliable
Solution Approach 1:
The system dynamically selects appropriate sensitivity ranges based on the detection task. For bio-molecule adsorption detection, the circuit switches to the second (higher) sensitivity range by adjusting the active capacitor voltage. This dynamic adaptation allows high sensitivity detection when needed while maintaining system simplicity and reliability through a single versatile circuit design
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 enhances the sensitivity and accuracy of droplet manipulation and chemical sensing, allowing for effective detection of bio-fouling and bio-molecule binding, while maintaining a compact and reliable device design suitable for lab-on-a-chip applications.
Implementation Method 1
sensor circuitry configured to sense an impedance present at the corresponding array element
Implementation Method 2
Electrowetting-On-Dielectric (EWOD) is a well known technique for manipulating droplets of fluid by application of an electric field
Data Source
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AI summary
An active matrix electrowetting on dielectric (AM-EWOD) device includes a plurality of array elements (38) configured to manipulate one or more droplets of fluid on an array (42), each of the array elements including a corresponding array element circuit (84). Each array element circuit includes write circuitry (120) configured to write data to the corresponding array element for controlling the manipulation of the droplets of fluid, and sensor circuitry (40/58) configured to sense an impedance present at the corresponding array element. The sensor circuitry is configured to operate in one of a normal mode of sensitivity for detection of a droplet, or a high mode of sensitivity to detect an electric property of an array element hydrophobic surface. The sensor circuitry includes an active element (58), such as an active capacitor or active transistor, and a capacitance across the active element is different in the normal sensitivity mode as compared to the high sensitivity mode.