Electrostatic MEMS Micromirror Actuation for Large Tip-Tilt Angles
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Solution Overview
Problem
Current MEMS micromirrors lack the capability for large angle deflections (>90°) with high fill-factor, particularly in electrostatic designs, which are essential for broadband steering and imaging applications.
Innovation Solution
A multi-staged electrostatic MEMS actuation system utilizing bimorph designs with materials having inherent residual stress and differing coefficients of thermal expansion (CTE) to achieve large out-of-plane deflections, enabling tip/tilt angles of ±45 degrees and piston motion, with a high fill-factor (>90%) and scalable to large aperture sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If electrostatic designs are used for MEMS micromirrors, then large tip/tilt angles can be achieved, but high fill-factor (>90%) cannot be obtained
Solution Approach 1:
The micromirror array is divided into individually addressable elements with simplified support structures. Each element can be independently controlled to achieve large tip/tilt angles while maintaining high fill-factor through the segmented architecture that eliminates complex mechanical interconnections.
Solution Approach 2:
Traditional mechanical gimbal systems are replaced with electrostatic actuation mechanisms. The electrostatic designs use electric fields to induce large angular deflections without mechanical moving parts, enabling both large tip/tilt angles and high fill-factor by eliminating mechanical support structures that would occupy space.
2Shape
If large tip/tilt angles (>10°) are achieved, then beamsteering capability is improved, but fill-factor decreases below 90%
Solution Approach 1:
The micromirror elements are designed with dynamic electrostatic actuation capabilities that enable large angular deflections. The elements can be rapidly switched between different angular positions using electrostatic forces, achieving >10° tip/tilt angles while maintaining high fill-factor through optimized electrode geometries and actuation sequences.
Solution Approach 2:
The design optimizes electrostatic field distribution and electrode parameters to achieve large deflection angles. By carefully controlling voltage parameters and electrode geometry, the system achieves >10° tip/tilt angles while maintaining compact structures that preserve high fill-factor.
3Area of stationary object
If high fill-factor designs are used, then area utilization is improved, but tip/tilt angle is limited to less than 5°
Solution Approach 1:
The design transitions from planar mechanical rotation to three-dimensional electrostatic field-based actuation. By utilizing the electric field dimension, the system achieves large tip/tilt angles through field-induced deformation rather than mechanical rotation, enabling both high fill-factor and >5° deflection angles simultaneously.
Solution Approach 2:
The micromirror elements incorporate composite structures with tailored mechanical and electrical properties. The composite design enables large angular deflections while maintaining compact footprints, achieving both high fill-factor and sufficient tip/tilt angles through optimized material combinations and structural configurations.
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 system enables fast scanning speeds and multi-beam steering capabilities, replacing gimbal systems with conformal, adaptable, and scalable devices suitable for EO/IR beamsteering, medical endoscopy, imaging, and laser communications.
Implementation Method 1
The second portion of the metallic layer is prestressed causing the distal end to deform away from the substrate
Implementation Method 2
applying a voltage potential between the first and second metallic layers creates an electrostatic field drawing the distal end toward the substrate
Data Source
AI summary
An actuator element of a MEMS device on a substrate able to create large, out-of-plane deflection includes two separated metallic layers contacting the substrate. The second metallic layer has a first portion contacting the substrate and a second portion having cantilevered over the substrate and first metallic layer. A first insulating layer contacts the cantilevered metallic layer on a bottom contacting surface and a second insulating layer contacting the cantilevered metallic layer on a portion of a top contacting surface. The second, cantilevered portion of the metallic layer is prestressed causing the distal end to deform away from the substrate. Applying a voltage potential between the first and second metallic layers creates an electrostatic field drawing the distal end toward the substrate.