Cascaded Electrostatic Actuator for MEMS Travel and Force
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Solution Overview
Problem
Microelectromechanical systems (MEMS) actuators, such as comb drives and gap-closing actuators, have limitations in terms of travel and force capability, which restrict their application in devices like miniature cameras for focus, zoom, and optical image stabilization.
Innovation Solution
The development of cascaded electrostatic actuators with alternating layers that contract when charged, allowing for enhanced travel and force capabilities by configuring the layers to move linearly or rotationally, and using MEMS fabrication techniques to create these actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional MEMS actuators (comb drives, gap-closing actuators) are used, then the device structure is simple, but the travel and force capability are limited
Solution Approach 1:
The actuator is divided into multiple alternating layers (first layers and second layers) that can be independently charged. Each layer pair acts as an independent electrostatic actuation unit, and their combined effect produces substantial force while maintaining manageable structural complexity through modular design
Solution Approach 2:
The alternating layers are nested within a single actuator structure, with first layers and second layers interleaved in a cascaded configuration. This nesting allows multiple actuation stages to be integrated in a compact form factor, achieving high force output without proportionally increasing overall device size
2Length of moving object
If conventional MEMS actuators are used, then the manufacturing process is simple, but the travel capability is limited
Solution Approach 1:
The actuator transitions from planar movement to three-dimensional cascaded layer contraction. By stacking multiple layer pairs in the vertical dimension and charging them sequentially or simultaneously, the actuator achieves travel distances that exceed the width of a single gap, effectively utilizing the third dimension to multiply displacement output
Solution Approach 2:
The layers are pre-configured with gaps during fabrication, and the electrostatic charges are applied in a controlled sequence to achieve progressive contraction. This preliminary structural preparation enables the actuator to achieve enhanced travel through coordinated layer-by-layer collapse rather than requiring a single large-displacement mechanism
3Power
If charges are placed on alternating layers, then substantial force is generated, but the control complexity increases
Solution Approach 1:
The control system applies charges to the alternating layers in periodic sequences or patterns. By controlling which layers are charged at any given time, the system can modulate the force output and achieve precise positional control while maintaining relatively simple control logic based on sequential or alternating charge application
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 cascaded electrostatic actuators provide increased travel and force capabilities, enabling effective actuation of shutters and lenses in miniature cameras for focus, zoom, and optical image stabilization, with the ability to move beyond the width of a single gap and generate substantial forces, such as 10 grams of force from a 1 mm wide actuator.
Implementation Method 1
placing charges of opposite polarities upon the first layers and the second layers causes the stack to contract
Data Source
AI summary
A cascaded electrostatic actuator can be formed from a substantially planar substrate. The cascaded electrostatic actuator can be formed in a plane of the substrate. Various embodiments are described.