SOI MEMS Parallel Kinematic Stages for Decoupled Motion

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Solution Overview

Problem

Existing micro-electromechanical systems (MEMS) face challenges in achieving high precision and flexibility in positioning due to limitations in actuation technologies and manufacturing processes, particularly in decoupling motion in multi-axis stages and maintaining high structural stiffness while allowing for large motion ranges.

Innovation Solution

The development of micro-positioning stages using Silicon-on-Insulator (SOI) wafers with integrated electrostatic comb drive actuators and parallel kinematic mechanisms, which decouple motion in the XY plane and restrict parasitic rotations, enabling high precision and large motion ranges through the use of flexure hinges and rotary comb drives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If traditional MEMS actuators are used for positioning, then manufacturing is simplified, but motion decoupling and structural stiffness are compromised

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidmotion decoupling precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The positioning stage is divided into multiple independent kinematic chains, each responsible for a specific degree of freedom. This segmentation allows each chain to be optimized independently for its function while maintaining overall system manufacturability through standardized MEMS fabrication processes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from planar MEMS structures to three-dimensional parallel kinematic mechanisms by adding vertical stacking of kinematic chains and utilizing Z-axis motion components, enabling complex 6-DOF positioning while maintaining decoupling through spatial separation of motion paths.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If parallel kinematic mechanisms are implemented, then motion decoupling improves, but device complexity increases

Engineering Contradiction:

Improvemotion decoupling precisionVSAvoidmechanism complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Each kinematic chain is designed as a multi-functional module that simultaneously provides motion transmission, structural support, and positioning control. The standardized chain design allows replication across multiple axes, reducing overall system complexity through modular architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Flexible hinges serve as intermediary elements that couple rigid structural components while enabling controlled rotational motion. These hinges act as compliant joints that simplify the overall mechanism by eliminating the need for complex rigid joint assemblies.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If large motion ranges are enabled, then positioning flexibility improves, but structural stiffness decreases

Engineering Contradiction:

Improvemotion rangeVSAvoidstructural stiffness

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The system employs dynamic stiffness adjustment through active control of the parallel kinematic chains. By coordinating the motion of multiple chains, the system maintains high effective stiffness during operation even when individual components operate through large ranges of motion.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The structure utilizes composite construction combining rigid structural elements with flexible hinge components. This composite approach allows regions requiring stiffness to be highly rigid while regions requiring motion compliance use flexible materials or geometries, achieving both large motion range and high structural stiffness simultaneously.

Inventive Principle:

Principle #40Composite materials

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

These stages achieve high bandwidth, large motion ranges, and nanometer-scale resolutions, suitable for applications like scanning probe microscopy and near-field optic sensing, with the ability to operate at high scan rates and frequencies, such as kHz to MHz, while maintaining stability and precision.

Implementation Method 1

These stages are driven by the force generated by an integrated electrostatic comb drive actuators

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Data Source

PatentUS8310128B2High precision silicon-on-insulator MEMS parallel kinematic stages

Publication Date: 2012.11.13 THE BOARD OF TRUSTEES OF THE UNIV OF ILLINOIS

AI summary

MEMS stages comprising a plurality of comb drive actuators provide micro and up to nano-positioning capability. Flexure hinges and folded springs that operably connect the actuator to a movable end stage provide independent motion from each of the actuators that minimizes unwanted off-axis displacement, particularly for three-dimensional movement of a cantilever. Also provided are methods for using and making MEMS stages. In an aspect, a process provides a unitary MEMS stage made from a silicon-on-insulator wafer that avoids any post-fabrication assembly steps. Further provided are various devices that incorporate any of the stages disclosed herein, such as devices requiring accurate positioning systems in applications including scanning probe microscopy, E-jet printing, near-field optic sensing, cell probing and material characterization.