MEMS Electrode Stiction Separation via Electrostatic Bow Effect
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Inertial Micro-Electro-Mechanical Systems (MEMS) devices face the challenge of stiction between conductive electrodes, which leads to operational failures due to strong surface adhesion forces exceeding mechanical restoring forces, and existing solutions like increasing spring stiffness or using anti-stiction coatings are not sufficiently effective or cost-efficient.
Innovation Solution
Applying a predetermined voltage between electrodes to generate an electrostatic force that displaces the mobile mass in the direction of stiction, creating a 'bow effect' to separate the stuck electrodes, relying on classical means within MEMS devices and being simple to implement and cost-effective.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If spring stiffness is increased to reduce stiction, then restoring force is improved, but device compactness and sensitivity are worsened
Solution Approach 1:
The patent changes the physical state of the electrode surfaces by applying a predetermined voltage to generate electrostatic forces, which temporarily modifies the adhesion characteristics. This allows the system to overcome stiction without changing the mechanical spring stiffness or device geometry, thus maintaining compactness while improving restoring force capability.
Solution Approach 2:
The patent replaces the mechanical approach of increasing spring stiffness with an electrostatic field-based solution. By applying voltage to generate electrostatic forces, the system achieves the goal of overcoming stiction without the mechanical consequences of heavier springs, thereby maintaining device compactness and sensitivity.
2Force
If anti-stiction coating is applied to reduce stiction forces, then surface adhesion is improved, but manufacturing complexity and cost are worsened
Solution Approach 1:
The patent substitutes the chemical/physical approach of anti-stiction coatings with an electrostatic field-based solution. By applying a predetermined voltage to generate electrostatic forces, the system overcomes stiction without requiring additional surface treatment processes, thus maintaining manufacturing simplicity and reducing cost.
Solution Approach 2:
The patent employs a self-service approach where the MEMS device uses its own operational elements (electrodes and voltage supply) to overcome stiction. The predetermined voltage applied during operation generates electrostatic forces that automatically separate stuck electrodes, eliminating the need for external anti-stiction coatings or additional manufacturing processes.
3Force
If mechanical shock is applied to overcome stiction, then electrode separation is improved, but device complexity and cost are worsened
Solution Approach 1:
The patent replaces the mechanical shock approach with an electrostatic field-based solution. By applying a predetermined voltage to generate electrostatic forces, the system achieves electrode separation without requiring external mechanical shock mechanisms, vibration systems, or additional actators, thus reducing device complexity and cost.
Solution Approach 2:
The patent makes the existing electrode structure multi-functional by using it both for its primary sensing function and for generating separation forces through applied voltage. This eliminates the need for separate mechanical shock devices, vibration systems, or additional actators, thereby reducing overall device complexity while maintaining separation capability.
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
Effectively reduces the probability of electrode stiction by generating restoring forces that overcome adhesion, ensuring separation of stuck electrodes and improving the operational reliability of MEMS devices without increasing complexity or cost.
Implementation Method 1
Applying a predetermined voltage between electrodes to generate an electrostatic force that displaces the mobile mass in the direction of stiction
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
An anti-stiction method is proposed in an inertial micro-electro-mechanical device comprising: - a mobile mass (150), suspended to an armature via spring means (115), comprising at least one mobile electrode; and - at least one fixed electrode rigidly attached to the armature, each fixed electrode cooperating with one of said at least one mobile electrode to form a pair of electrodes. The anti-stiction method is such that it carries out a step of detecting, for at least one stuck pair of electrodes, a stiction associated to a stiction force and at least one separating step, comprising a step of applying, during a predetermined time period, a predetermined voltage between the electrodes of at least one of said pair or pairs of electrodes, to create an electrostatic force.