MEMS Mirror Pendulum Electrode Layout to Prevent Stiction
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Solution Overview
Problem
DMD mirrors suffer from stiction issues due to adhesive forces when reduced in size, leading to stuck mirrors and visible defects in projected images, which restricts the possibility of reducing pixel size.
Innovation Solution
The MEMS devices incorporate a pendulum electrode that is separate and spaced from the mirror, receiving an electrostatic force to rotate the mirror about a tilt axis without physical contact, avoiding stiction by applying rotational torque through the pendulum electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mirror size is reduced to increase resolution, then higher resolution is achieved, but stiction forces increase causing mirrors to stick and become defective
Solution Approach 1:
The patent replaces the traditional mechanical torsion spring hinge with an electrostatic hinge system. The mirror is rotated by applying electrostatic force between control electrodes and the mirror or pendulum electrode, eliminating the need for mechanical contact components that cause stiction. This substitution of mechanical actuation with electrostatic actuation resolves the contradiction by enabling precise mirror control at small scales without adhesive forces preventing movement.
Solution Approach 2:
The patent introduces a pendulum electrode as an intermediary component between the control electrodes and the mirror. The pendulum electrode is coupled to the mirror via a hinge and is spaced from the control electrodes. When electrostatic force is applied to the pendulum electrode, it rotates the mirror through the hinge mechanism. This intermediary approach allows indirect actuation that reduces direct contact and stiction issues while maintaining effective mirror control.
2Ease of operation
If traditional mechanical hinge is used to rotate mirror, then mirror rotation is achieved, but physical contact causes stiction and mirror sticking
Solution Approach 1:
The patent replaces the traditional mechanical torsion spring hinge with an electrostatic hinge system. The mirror is rotated by applying electrostatic force between control electrodes and the mirror or pendulum electrode, eliminating the need for mechanical contact components that cause stiction. This substitution of mechanical actuation with electrostatic actuation resolves the contradiction by enabling precise mirror control at small scales without adhesive forces preventing movement.
Solution Approach 2:
The patent extracts and removes the problematic mechanical contact components (torsion springs) from the hinge system. By eliminating the mechanical elements that cause stiction and replacing them with electrostatic actuation, the harmful adhesive forces are completely removed from the system while mirror rotation functionality is preserved through the electrostatic field.
3Stability of the object's composition
If mirror contact with components is allowed, then structural support is maintained, but adhesive forces cause stiction and visible defects
Solution Approach 1:
The patent introduces a pendulum electrode as an intermediary component between the control electrodes and the mirror. The pendulum electrode is coupled to the mirror via a hinge and is spaced from the control electrodes. When electrostatic force is applied to the pendulum electrode, it rotates the mirror through the hinge mechanism. This intermediary approach allows indirect actuation that reduces direct contact and stiction issues while maintaining effective mirror control.
Solution Approach 2:
The patent replaces the traditional mechanical torsion spring hinge with an electrostatic hinge system. The mirror is rotated by applying electrostatic force between control electrodes and the mirror or pendulum electrode, eliminating the need for mechanical contact components that cause stiction. This substitution of mechanical actuation with electrostatic actuation resolves the contradiction by enabling precise mirror control at small scales without adhesive forces preventing movement.
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 design prevents mirror contact with other components, maintaining mirror mobility and reducing defects in projected images, enabling smaller mirror sizes and higher resolution without stiction-related issues.
Implementation Method 1
a pair of control electrodes spaced from the pendulum electrode. The control electrodes are configured to selectably apply an electrostatic force between electrodes of the pair of control electrodes and the pendulum electrode to thereby rotate the mirror
Data Source
AI summary
A microelectromechanical systems (MEMS) device includes a mirror, and a mirror post having a first end and a second end, the first end coupled to the mirror. Additionally, the MEMS device includes a hinge having a first side and a second side, the first side of the hinge coupled to the second end of the mirror post. Further, the MEMS device includes a pendulum electrode coupled to the second side of the hinge, and a pair of control electrodes spaced from the pendulum electrode.