MEMS Optical Comb Electrode Layout to Prevent Finger Sticking
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Solution Overview
Problem
In optical devices with MEMS technology, the movable portion tends to move perpendicular to the intended direction, causing sticking between comb fingers, which disrupts the intended movement along the predetermined direction.
Innovation Solution
Incorporating a torsion bar and lever in the elastic support portion, with the second comb electrode positioned on the optical function side of the torsion bar, and arranging first and second comb fingers to face each other in the direction of highest external force resistance, reducing electrostatic forces and preventing sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the elastic support portion is configured to allow large movement of the movable portion along the predetermined direction, then the movement range is improved, but the movable portion easily moves in the perpendicular direction causing sticking between comb fingers
Solution Approach 1:
The patent applies local quality by differentiating the external force resistance in different directions. The elastic support portion is designed to have higher external force resistance in the direction perpendicular to the movement direction (second direction) compared to the movement direction itself. This allows large movement along the predetermined direction while suppressing unintended perpendicular movement that causes sticking between comb fingers.
Solution Approach 2:
The patent changes the parameter of external force resistance by configuring the elastic support portion with specific structural features (such as the arrangement and dimensions of elastic beams) that create anisotropic mechanical properties. The elastic support portion is designed so that its external force resistance in the second direction (perpendicular to movement) is higher than in the first direction (movement direction), enabling differential control of movement in different directions.
2Reliability
If the comb fingers are arranged to face each other in the direction of highest external force resistance, then sticking is suppressed, but the device complexity increases
Solution Approach 1:
The elastic support portion serves multiple functions simultaneously: it supports the movable portion, provides the required external force resistance characteristics in different directions, and positions the comb fingers to prevent sticking. By integrating these functions into a single component structure, the patent avoids the need for separate elements for each function, thereby reducing overall device complexity while achieving reliable sticking suppression.
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 configuration allows for large-scale movement of the movable portion along the intended direction while minimizing sticking, enabling efficient operation with a simpler configuration and reduced electrostatic forces.
Implementation Method 1
the elastic support portion includes a torsion bar extending along a second direction perpendicular to the first direction and a lever connected to the torsion bar
Data Source
AI summary
An optical device includes: a base; a movable portion including an optical function portion; an elastic support portion supporting the movable portion so that the movable portion is movable along a first direction; a first comb electrode provided to the base and including a plurality of first comb fingers; and a second comb electrode including a plurality of second comb fingers. The elastic support portion includes a torsion bar extending along a second direction perpendicular to the first direction and a lever. The second comb electrode is provided to a portion of at least one of the movable portion and the elastic support portion, the portion being located on the optical function portion side with respect to the torsion bar. The first comb finger and the second comb finger adjacent to each other face each other in a direction in which the movable portion has higher external force resistance, of the second direction and a third direction perpendicular to the first direction and the second direction.