Active Matrix Microfluidic Device for EWOD and DEP Control
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Solution Overview
Problem
Existing passive matrix architectures for EWOD and DEP are limited by the need for separate electrical connections to each electrode, making large arrays impractical due to the number of individually controllable elements being restricted by the number of electrical inputs.
Innovation Solution
An active matrix microfluidic device with thin film electronics that provides drive signals to top substrate and drive electrodes, allowing for either DC or low frequency AC voltage for EWOD or high frequency AC voltage for DEP, enabling manipulation of droplets and particles within a droplet, and is reconfigurable to switch between EWOD and DEP actuation mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive matrix architecture is used for EWOD and DEP, then device structure is simpler, but the number of individually controllable elements is limited by the number of electrical inputs
Solution Approach 1:
The patent divides the control function into two independent sets of electrodes: row electrodes and column electrodes. Each electrode can be independently controlled through active matrix TFT circuits, enabling individual control of array elements without requiring separate electrical connections to each electrode. This segmentation resolves the contradiction by maintaining simple device structure while dramatically increasing the number of controllable elements.
Solution Approach 2:
The patent transitions from one-dimensional control (single set of electrodes) to two-dimensional control (row and column electrode intersections). By applying voltages to both row and column electrodes simultaneously, the system creates a matrix of controllable elements where each intersection point can be independently addressed, exponentially increasing control capacity without proportionally increasing electrical connections.
2Ease of operation
If high voltage is applied for EWOD actuation, then droplet manipulation is achieved, but device degradation and insulator reliability issues occur
Solution Approach 1:
The patent modifies the electrical parameters by using AC voltage signals instead of DC, and by carefully controlling voltage amplitude and frequency. The active matrix circuitry generates appropriate AC drive signals that provide sufficient voltage for droplet manipulation while preventing DC bias accumulation that would degrade the insulator. This parameter optimization resolves the contradiction between achieving droplet manipulation and maintaining insulator reliability.
3Reliability
If AC drive scheme is used for EWOD, then device reliability is improved, but additional inversion circuitry is required
Solution Approach 1:
The patent combines the voltage inversion function with the existing active matrix TFT switching circuitry. The same TFTs that control electrode selection also perform the inversion function by switching between different voltage rails. This merging eliminates the need for separate inversion circuits, resolving the contradiction between improved reliability and reduced device complexity.
Solution Approach 2:
The active matrix TFT circuits are designed to perform multiple functions: electrode selection, voltage level control, and signal inversion. By making the drive circuitry universal and multi-functional, the system achieves AC drive reliability benefits without adding dedicated inversion circuitry, thus resolving the contradiction between reliability improvement and complexity increase.
4Device complexity
If DC voltage is applied to liquid crystal displays, then voltage inversion is not needed, but deleterious effects occur on the LC material
Solution Approach 1:
The patent changes the temporal characteristics of the voltage signal from static DC to time-varying AC. By periodically reversing the voltage polarity, the system eliminates DC bias accumulation that causes LC material degradation while maintaining effective droplet control. This parameter change resolves the contradiction between voltage control simplicity and LC material protection.
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 the creation of large format, reconfigurable devices capable of performing complex digital microfluidic operations, allowing independent control of liquid droplets and particles, facilitating applications like particle concentration and sorting, while reducing the number of electronic components and power consumption.
Implementation Method 1
selectively provide the drive signals to the top substrate and drive electrodes of the one or more array elements in order to maintain either a DC or relatively low frequency AC voltage wave form across the one or more liquid droplets for manipulating the one or more droplets by electro-wetting-on-dielectric (EWOD)
Implementation Method 2
provide a relatively high frequency AC voltage waveform for manipulating the one or more droplets by dielectrophoresis (DEP)
Data Source
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AI summary
A microfluidic device includes a plurality of array elements (43) configured to manipulate one or more droplets of fluid (4) on an array (42), each of the array elements (43) including a top substrate electrode (28) and a drive electrode (38) between which the one or more droplets (4) may be positioned, the top substrate electrode (28) being formed on a top substrate (36), and the drive electrode (38) being formed on a lower substrate (72); and active matrix drive circuitry (76,78,84,86) arranged to provide drive signals to the top substrate and drive electrodes (28,38) of the plurality of array elements (43) to manipulate the one or more droplets (4) among the plurality of array elements (43). With respect to one or more of the array elements (43) the active matrix drive circuitry (76,78,84,86) is configured to provide the drive signals to the top substrate and drive electrodes (28,38) to selectively manipulate the one or more droplets (4) within the array element both by Electro-wetting-on-Dielectric (EWOD) and by Dielectrophoresis (DEP).