Integrated Impedance Sensor for AM-EWOD Array Elements
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Solution Overview
Problem
Existing EWOD devices face limitations in simultaneously controlling droplet movement and sensing droplet position, size, and constitution due to the need for external sensor electronics and limited impedance sensing capabilities, which restricts their application in complex fluidic operations and Lab-on-a-Chip technologies.
Innovation Solution
An Active Matrix EWOD device with an integrated impedance sensor that uses an AC coupled arrangement to write EW drive voltage and sense impedance at each array element, allowing for simultaneous droplet manipulation and impedance measurement, thereby enhancing droplet control and fluidic protocol verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensor electronics are used for impedance sensing, then droplet position and size can be measured, but device complexity increases and manufacturing costs rise
Solution Approach 1:
The patent combines the impedance sensing function with the existing EWOD drive electronics by integrating sense circuitry into the array element circuit. The sense circuitry shares common electrodes and circuit elements with the drive circuitry, merging two functions (droplet manipulation and impedance sensing) into a single integrated system, thereby reducing device complexity and manufacturing costs while maintaining measurement precision
Solution Approach 2:
The electrodes and circuit elements in the array element are designed to serve multiple functions: they act as both drive elements for electrowetting and as sensing elements for impedance measurement. This multi-functionality eliminates the need for separate sensor electronics, reducing overall device complexity while enabling precise droplet position and size measurement
2Ease of manufacture
If impedance sensing is integrated into EWOD drive electronics, then manufacturing costs are reduced, but the ability to simultaneously control droplet movement and sense impedance is limited
Solution Approach 1:
The patent implements dynamic time-division multiplexing where the array element circuit alternates between drive mode (for droplet manipulation) and sense mode (for impedance measurement). The circuit can dynamically switch between these functions based on operational requirements, enabling simultaneous droplet manipulation and sensing capabilities across different time periods while maintaining cost-effective integrated manufacturing
Solution Approach 2:
The integrated circuit employs periodic alternating cycles of drive operations and sense operations. During each cycle, the circuit performs droplet manipulation tasks, then periodically switches to perform impedance sensing tasks. This periodic action allows the system to maintain both droplet control and sensing capabilities using the same integrated circuitry, enhancing versatility without increasing manufacturing complexity
3Adaptability or versatility
If AC coupled arrangement is used to write EW drive voltage and sense impedance, then simultaneous droplet manipulation and impedance measurement is enabled, but circuit design complexity increases
Solution Approach 1:
The patent introduces an AC coupling capacitor as an intermediary element between the drive voltage source and the impedance sensing circuit. This capacitor blocks DC components while allowing AC sensing signals to pass through, enabling simultaneous drive and sense operations without direct electrical conflict. The intermediary component simplifies the overall circuit design by providing clear signal separation while maintaining simultaneous operational capability
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
Enables precise control over droplet movement and size measurement, improves the reliability of fluidic operations, and reduces manufacturing costs by integrating impedance sensing into the EWOD drive electronics, facilitating advanced applications in Lab-on-a-Chip technologies.
Implementation Method 1
By applying a voltage V to the conductive electrode 22, the contact angle θ 6 can be adjusted. An advantage of manipulating contact angle θ 6 by means of EWOD is that the power consumed is low
Implementation Method 2
sense circuitry for sensing an impedance presented at the drive element; wherein the sense circuitry is configured to sense a result of the perturbation of the drive voltage written to the drive element, the result of the perturbation being dependent upon the impedance presented at the drive element
Data Source
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AI summary
An AM-EWOD device having an array element circuit with an integrated impedance sensor is provided. The array element circuit (85) includes an array element (154) which is controlled by application of a drive voltage by a drive element (152); writing circuitry (58,62,64,68) for writing the drive voltage to the drive element; and sense circuitry (94,104,106,146) for sensing an impedance presented at the drive element.