Active Matrix Electrowetting On Dielectric Drive Circuit
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Solution Overview
Problem
Existing Active Matrix Electrowetting-On-Dielectric (AM-EWOD) devices face challenges with high operating voltages that exceed the maximum voltage rating of thin-film transistors (TFTs), leading to device degradation and high power consumption due to the need for high electrowetting drive voltages.
Innovation Solution
The implementation of an AC drive scheme with time-varying voltage waveforms V1 and V2, where V2 is the logical inverse of V1, and an optional offset voltage Voffset, allows for reduced maximum voltage switching by TFTs, enabling higher electrowetting drive voltages while minimizing dynamic power consumption and enhancing insulator reliability and droplet dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high electrowetting drive voltages are applied to manipulate droplets, then droplet manipulation capability is improved, but TFT voltage rating is exceeded leading to device degradation
Solution Approach 1:
The patent applies periodic AC voltage waveforms instead of DC voltages to the electrowetting electrodes. By using time-varying voltages with frequency components above the droplet response frequency, the system achieves effective droplet manipulation while the average voltage remains within TFT rating limits, preventing device degradation.
Solution Approach 2:
The patent transforms the voltage parameter from static DC levels to dynamic AC waveforms characterized by frequency, amplitude, and duty cycle. This parameter transformation allows the peak voltage to exceed TFT ratings temporarily while the RMS voltage remains within safe operating limits, enabling both high droplet manipulation capability and device reliability.
2Reliability
If high electrowetting drive voltages are used, then droplet manipulation capability is improved, but power consumption increases
Solution Approach 1:
By using AC waveforms with controlled duty cycles and frequencies, the system delivers voltage pulses only when needed for droplet manipulation. The periodic nature allows the droplet to respond to peak voltages while the average power consumption is reduced during the off-periods of the waveform.
Solution Approach 2:
The patent applies reverse polarity voltage phases in the AC waveform that counteract the forward actuation phases. These preliminary anti-actions reduce the net energy consumption by canceling out portions of the voltage application, while still maintaining effective droplet control through the alternating sequence.
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 allows for higher electrowetting drive voltages within the TFT's voltage rating, reducing power consumption and improving device reliability and droplet dynamics, while maintaining the benefits of high-frequency AC drive schemes.
Implementation Method 1
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 which includes a plurality of array elements configured to manipulate one or more droplets of fluid on an array, each of the array elements including a corresponding array element circuit. Each array element circuit includes a top substrate electrode and a drive electrode between which the one or more droplets may be positioned; circuitry configured to write data to the corresponding array element by selectively applying to the drive electrode either: (i) a time-varying voltage waveform V1 of amplitude VB and period to; or (ii) a time-varying voltage waveform V2, the logical inverse of V1, and applying to the top substrate electrode the time-varying voltage waveform V2 + Voffset, where Voffset represents an offset voltage signal which may have AC and/or DC components and may equal zero.