Active Matrix EWOD Array Element Circuit with Integrated Impedance Sensing
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Solution Overview
Problem
Existing EWOD devices face limitations in efficiently sensing and controlling the position, size, and constitution of droplets due to the need for external sensor electronics and high voltage requirements, which increase complexity and cost.
Innovation Solution
An active matrix EWOD device with integrated impedance sensing capabilities, utilizing an AC coupled arrangement to write EW drive voltages and sense impedance at each array element, allowing for simultaneous measurement of droplet location, size, and constitution without external connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensor electronics are used for droplet sensing, then measurement capability is provided, but device complexity and cost increase
Solution Approach 1:
The patent combines the sensor drive circuitry, output amplifiers, and impedance sensing capabilities directly into the active matrix array element circuits. This integration eliminates the need for external sensor electronics, reducing device complexity and cost while maintaining droplet sensing capability through on-chip impedance measurement at each array element.
Solution Approach 2:
The array element circuits are designed to perform multiple functions: they can write EW drive voltages to control droplets, sense impedance to detect droplet location and properties, and amplify output signals. This multi-functionality eliminates the need for separate external sensor electronics, resolving the contradiction between measurement capability and device complexity.
2Ease of operation
If high voltages are applied for EWOD operation, then droplet manipulation is achieved, but power consumption and device stress increase
Solution Approach 1:
The patent employs periodic AC coupling to write EW drive voltages to the array elements. This periodic action allows the circuit to charge and discharge capacitors in a controlled manner, enabling droplet manipulation while managing power consumption through pulsed rather than continuous high voltage application.
Solution Approach 2:
The patent changes the voltage parameters dynamically by using AC coupled arrangements that can write different voltage levels to different array elements. This allows precise control of droplet manipulation while optimizing power consumption by applying high voltages only when and where needed for droplet actuation.
3Ease of manufacture
If integrated sensor circuitry is implemented, then manufacturing cost is reduced, but circuit design complexity increases
Solution Approach 1:
The patent segments the sensor functionality into discrete array element circuits that can be independently designed and integrated into the active matrix. Each array element contains dedicated circuitry for voltage writing, impedance sensing, and signal amplification. This segmentation allows for modular design and integration, reducing overall manufacturing cost while managing circuit design complexity through systematic organization.
Solution Approach 2:
The patent implements a nested structure where sensor drive circuitry and output amplifiers are integrated within the array element circuits, which themselves are part of the larger active matrix array. This nesting allows multiple functional layers to coexist in a compact arrangement, reducing manufacturing cost through integration while organizing circuit design complexity in a hierarchical manner.
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 and monitoring of droplets within the array, reducing manufacturing costs and improving reliability by integrating sensor drive circuitry and output amplifiers, allowing for efficient droplet manipulation and chemical/biochemical reaction monitoring.
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, being just that associated with charging and discharging the capacitance of the insulator layer 20.
Implementation Method 2
sense circuitry for sensing an impedance presented at the drive element
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A static random-access memory (SRAM) cell (210) which includes: a sampling switch (212) and a feedback switch (218); and a first inverter (214) and a second inverter (216) connected in series whereby an output of the first inverter (214) is connected to an input of the second inverter (216). An input of the first inverter (214) is connected to a data input ((IN) of the SRAM cell via the sampling switch (212), and to a data output (OUT) of the SRAM cell independent of the feedback switch (218), an output of the second inverter (216) is connected to the input of the first inverter (214) via the feedback switch (218), and first and second clock inputs (CK1,CK2) of the SRAM cell are configured to control the sampling switch (212) and the feedback switch (218), respectively.