Floating Rocker MEMS Mirror for High Contrast Displays
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Solution Overview
Problem
MEMS devices designed as cantilevers face variations in restoring force due to width, thickness, and adhesion, which affect switching properties and are sensitive to processing parameters, making it difficult to achieve high packing density and optimal reflectivity in display applications.
Innovation Solution
A free floating rocker design is used in MEMS devices, where adhesion forces hold the rocker in stable positions, eliminating the need for a spring-like restoring arm, allowing for faster switching and improved control over color and grayscale, and enabling smaller pixels with higher density displays without temperature susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring-like restoring arm is used to hold the rocker in position, then the rocker can be held in stable positions, but the restoring force varies due to width, thickness, and adhesion variations, affecting switching properties and making the device sensitive to processing parameters
Solution Approach 1:
The patent removes the spring-like restoring arm entirely from the rocker structure. Instead of using a mechanical spring element that requires precise fabrication, the invention extracts this component and replaces it with adhesion-based positioning, eliminating the source of restoring force variation caused by width, thickness, and adhesion variations in the spring arm itself.
Solution Approach 2:
The patent replaces the mechanical spring-like restoring arm with an adhesion-based holding mechanism. The rocker is held in stable positions through adhesion forces between the rocker and the substrate, rather than through elastic restoration from a mechanical spring element. This substitution eliminates the sensitivity to processing parameters that affect spring arm dimensions.
2Reliability
If the mirror is attached to the substrate with a via, then the mirror can be held in position, but the attachment area reduces the available reflection area
Solution Approach 1:
The patent removes the via attachment structure from the mirror design. Instead of drilling or etching holes through the mirror to attach it to the substrate, the invention extracts this mechanical attachment method and replaces it with adhesion-based positioning, allowing the mirror to be held in position without sacrificing reflection area.
Solution Approach 2:
The patent makes the mirror surface multi-functional by allowing it to serve both as the reflective surface and as the attachment surface. The entire mirror area can be used for reflection while simultaneously providing adhesion to the substrate, eliminating the need for separate attachment structures that would reduce the reflective area.
3Ease of operation
If the spring arm is made thin to be compliant, then it can flex properly, but it cannot be made at the same time as the reflective pixel material which needs to be optimized for high reflectivity
Solution Approach 1:
The patent removes the spring arm component entirely from the device structure. By extracting this separate compliant element, the invention eliminates the conflict between fabricating a thin, compliant spring arm and fabricating a high-reflectivity mirror in the same process. The compliance function is replaced by the adhesion-based mechanism that does not require a separate structural element.
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
The free floating rocker design enables faster switching with reduced power consumption, improved contrast ratio, and higher packing density due to the absence of light scatter from supporting contacts, and allows for mechanical latching based on stiction, enhancing memory efficiency and optical performance.
Implementation Method 1
the floating rocker is only held in any stable position by adhesion forces
Implementation Method 2
The floating rocker can be switched using any force, from inertial, magnetic and electrostatic
Implementation Method 3
Because the mirror is now not attached, more of the area can be used for reflection
Data Source
AI summary
The current disclosure shows how to make a fast switching array of mirrors for projection displays. Because the mirror does not have a via in the middle connecting to the underlying spring support, there is an improved contrast ratio that results from not having light scatter off the legs or vias like existing technologies. Because there are no supporting contacts, the mirror can be made smaller making smaller pixels that can be used to make higher density displays. In addition, because there is not restoring force from any supporting spring support, the mirror stays in place facing one or other direction due to adhesion. This means there is no need to use a voltage to hold the mirror in position. This means that less power is required to run the display.