EWOD Sensing Apparatus Differential Current Measurement
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Solution Overview
Problem
Current microfluidic devices using Electro-wetting on Dielectric (EWOD) technology face limitations in accurately sensing the electrical properties of fluid packages within the device, particularly due to interference from parasitic capacitance and electromagnetic interference, which affects the precision of measurements in biochemical and chemical workflows.
Innovation Solution
The implementation of a differential current sensor system within the EWOD device, which includes multiple electrodes and a guard electrode, allows for the sensing of current differences between fluid packages, thereby isolating and minimizing the impact of interfering signals and enhancing the signal-to-noise ratio for precise electrical property measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-ended current sensing is used in EWOD devices, then the device structure remains simple, but measurement precision deteriorates due to parasitic capacitance and electromagnetic interference
Solution Approach 1:
The patent implements a differential sensing system by creating a copy of the sensing electrode (second sensing electrode) and using it in conjunction with the first sensing electrode. This copy approach allows the system to measure current differences between two paths, thereby eliminating parasitic capacitance and electromagnetic interference effects that would affect a single-ended measurement, thus improving measurement precision without requiring complex external shielding or isolation systems.
Solution Approach 2:
The patent introduces a reference electrode as an intermediary element between the two sensing electrodes. This reference electrode serves as a common reference point that allows the differential current sensor to measure the difference in current flow between the first and second sensing electrodes, effectively isolating the measurement from parasitic capacitance and electromagnetic interference while maintaining a relatively simple device structure.
2Reliability
If differential current sensing with multiple electrodes is implemented, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The patent segments the sensing function by dividing the sensing electrode into two separate sensing electrodes (first sensing electrode and second sensing electrode) that can independently detect current flow. This segmentation allows the differential current sensor to measure the difference between the two electrodes, thereby rejecting common-mode noise and parasitic capacitance effects, improving reliability while maintaining a modular and manageable electrode configuration.
Solution Approach 2:
The patent uses a reference electrode to establish a common equipotential reference for both sensing electrodes. By maintaining the reference electrode at a stable potential, the system eliminates potential differences that would arise from parasitic capacitance and electromagnetic interference, allowing the differential sensor to accurately measure current differences while keeping the device structure relatively simple.
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 significantly improves the accuracy of electrical property measurements by reducing noise interference, enabling more reliable monitoring of reactions and fluid composition changes within the microfluidic device, particularly in the context of biochemical and chemical analyses.
Implementation Method 1
a current sensor for sensing a difference between (1) a first current flowing between the first electrode and one of the second electrodes via a first fluid package in the fluid chamber of the EWOD device and (2) a second current flowing between the first electrode and another of the second electrodes via a second fluid package in the fluid chamber of the EWOD device
Implementation Method 2
Electro-wetting on dielectric (EWOD) is a well-known technique for manipulating discrete droplets of fluid by application of an electric field
Data Source
AI summary
An electro-wetting on dielectric (EWOD) device, includes first and second substrates defining a fluid chamber therebetween, a plurality of electro-wetting electrodes on the first substrate, and at least one first electrode and at least two second electrodes on the second substrate. The device further includes a current sensor or sensing a difference between (1) a first current flowing between the first electrode and one of the second electrodes via a first fluid package in the fluid chamber of the EWOD device and (2) a second current flowing between the first electrode and another of the second electrodes via a second fluid package in the fluid chamber of the EWOD device.