MEMS Diaphragm Collapse Prevention via Dual Dielectric Force Balancing
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Solution Overview
Problem
Conventional MEMS devices face challenges with diaphragm collapse under high shock or acoustic loads due to increased mechanical stiffness caused by higher bias voltages, which also reduce mechanical compliance and sensitivity.
Innovation Solution
A dual dielectric motor system is employed, where two opposed dielectric motors balance electrostatic forces, maintaining overall compliance independent of applied voltage, and preventing diaphragm collapse by maintaining a net zero or controlled electrostatic force between electrodes and dielectric.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher bias voltage is applied to capacitive MEMS devices, then output and operation performance improve, but mechanical stiffness increases and mechanical compliance decreases
Solution Approach 1:
The patent employs a dual dielectric motor system with two opposed dielectric motors that generate equal and opposite electrostatic forces. These counteracting forces balance each other out, resulting in a net zero electrostatic force on the diaphragm. This allows high bias voltages to be applied for improved output performance without the forces translating into increased mechanical stiffness, as the opposing forces cancel each other's stiffening effect.
Solution Approach 2:
The patent uses asymmetric electrode and dielectric configurations where the two dielectric motors are positioned on opposite sides of the diaphragm with different geometries and material properties. This asymmetry in configuration allows each motor to generate different individual forces while still producing equal and opposite net forces, enabling independent optimization of each motor's characteristics while maintaining overall force balance.
2Power
If higher bias voltage is applied to capacitive MEMS devices, then output performance improves, but mechanical compliance decreases
Solution Approach 1:
The dual dielectric motor system generates counteracting electrostatic forces that balance each other, preventing the voltage-dependent stiffening that would otherwise reduce mechanical compliance. This force balancing allows the diaphragm to maintain its natural compliance characteristics even at high bias voltages, preserving sensitivity and mechanical adaptability while achieving improved output performance.
3Power
If higher bias voltage is applied to capacitive MEMS devices, then output performance improves, but diaphragm collapse tendency increases
Solution Approach 1:
The two opposed dielectric motors generate equal and opposite electrostatic forces that cancel each other out, resulting in no net electrostatic force acting on the diaphragm. This force balance prevents the diaphragm from experiencing the excessive attractive forces that cause collapse at high bias voltages, thereby maintaining diaphragm stability and reliability while enabling high voltage operation for improved output performance.
Solution Approach 2:
The dual dielectric motor system proactively applies counteracting forces before diaphragm collapse can occur. By maintaining balanced opposing forces throughout operation, the system prevents the conditions that lead to collapse rather than merely responding to collapse after it begins, ensuring continuous stable operation at high bias voltages.
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 approach allows for increased bias voltages without diaphragm stiffening, maintaining sensitivity and mechanical compliance, thereby stabilizing the MEMS device under varying loads.
Implementation Method 1
The resulting electrostatic force operates to pull the dielectric and electrodes so that the dielectric covers as much of the electrodes as possible thereby maximizing the capacitance between them. The force is proportional to the change in capacitance with displacement and with the square of the voltage.
Implementation Method 2
The energy in a capacitor is E=1/2 CV2. Moving the dielectric into a gap between the electrodes increases the capacitance.
Data Source
AI summary
A MEMS device can include a solid dielectric including a plurality of apertures, the solid dielectric having a first side and a second side. The MEMS device can include a first plurality of electrodes extending completely through a first subset of the plurality of apertures, a second plurality of electrodes extending partially through a second subset of the plurality of apertures, a third plurality of electrodes extending partially into a third subset of the plurality of apertures. The MEMS device can include a first diaphragm coupled to the first plurality and to the third plurality of electrodes, the first diaphragm facing the first side of the solid dielectric. The MEMS device can include a second diaphragm coupled to the first plurality and to the second plurality of electrodes the second diaphragm facing the second side of the solid dielectric.