Electrowetting Cell Sealing for Thermal Expansion Compensation
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Solution Overview
Problem
Existing electrowetting cell technologies face challenges in sealing and pressure compensation, particularly for large format cells with significant thermal expansion, which can adversely affect optical performance and assembly efficiency, as prior solutions often require moving optical components or limited temperature ranges.
Innovation Solution
The proposed solution involves a sealing chamber assembly with a spacer and sealing gasket that compensates for volumetric thermal expansion by allowing lateral movement, maintaining optical stability and supporting both beam steering and shaping functions within a single cell design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a rubber membrane or O-ring is used to compensate for fluidic thermal expansion, then thermal expansion compensation is achieved, but optical surfaces must move up and down which adversely affects optical capability
Solution Approach 1:
The patent transitions from vertical (up-down) movement to lateral (side-to-side) movement of the optical surface. The flexible circuit board bends laterally to accommodate thermal expansion while keeping the optical surface position stable in the vertical dimension, thus resolving the contradiction between thermal compensation and optical performance.
Solution Approach 2:
The patent introduces a flexible circuit board as an intermediary element between the fluidic chamber and the optical components. This flexible board acts as a mediator that absorbs thermal expansion forces through its flexibility while maintaining a stable mounting surface for optical components, preventing direct transmission of expansion forces to the optics.
2Temperature
If a stainless steel diaphragm is used to compensate for thermal expansion, then thermal expansion is compensated, but the optical window must move which impacts optical performance
Solution Approach 1:
The patent changes the direction of flexibility from vertical (affecting optical window position) to lateral (maintaining optical window position). The flexible circuit board is designed to bend sideways rather than up and down, keeping the optical window stable while still accommodating thermal expansion.
3Temperature
If electrowetting cells are designed for small temperature ranges, then thermal expansion is minimal, but the cells cannot operate over wide temperature ranges
Solution Approach 1:
The patent changes the physical parameter of flexibility in the circuit board to accommodate a wider range of temperature conditions. By designing the circuit board with appropriate flexural properties, the system can adapt to thermal expansion across a broad temperature range rather than being limited to narrow conditions.
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 enables efficient assembly and operation of electrowetting cells over a wide temperature range without compromising optical performance, allowing for versatile applications in variable optics, such as lenses and prisms, while maintaining the stability of optical components.
Implementation Method 1
Electrowetting is a microfluidic phenomenon that modifies the shape of a liquid in relation to a surface by applying an electrical field, e.g. by applying a voltage across two electrodes.
Implementation Method 2
compensate for fluidic thermal expansion
Data Source
AI summary
The examples herein relate to assembly techniques and structures for sealing and lateral pressure compensation techniques that can be utilized in, for example, an electrowetting cell. The electrowetting cell can include a substrate that supports a well filled with a liquid. The electrowetting cell can include a control channel electrode to control the liquid via an electric field and a circuit connection to drive the control channel electrode. A seal is coupled to a spacer to seal the well between the substrate and the transparent cover. An expansion space, exterior to the well, is formed with the coupling of the seal and the spacer. As the liquid or the gas thermally expands or contracts, the seal compensates laterally by deforming sideways in an empty space of the expansion space.