MEMS Piezoelectric Actuator Passivation Layer Design
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Solution Overview
Problem
Current microfluidic devices with piezoelectric actuation suffer from non-uniform deformation of the membrane, leading to a bulge effect that results in increased overpressure during liquid ejection, which is undesirable for precise fluid dispensing in applications like inkjet printing.
Innovation Solution
Incorporating a passivation layer with elongated holes or slits on the membrane surface, which provides rigidity in the longitudinal direction while maintaining flexibility in the transverse direction, reducing the bulge effect and ensuring uniform deformation during actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a piezoelectric actuator is used to deform the membrane for liquid ejection, then the membrane can be actuated to eject liquid, but the membrane deforms non-uniformly causing a bulge effect that increases overpressure
Solution Approach 1:
The passivation layer is segmented by introducing elongated holes or slits that divide the continuous layer into multiple sections. This segmentation allows different regions of the membrane to deform independently and uniformly, preventing the bulge effect while maintaining actuation capability.
Solution Approach 2:
The passivation layer is modified with elongated holes or slits positioned strategically to provide localized rigidity in the longitudinal direction while maintaining flexibility in the transverse direction. This creates non-uniform local properties that compensate for the non-uniform deformation tendency.
2Manufacturing precision
If the membrane is made more rigid to reduce bulge effect, then deformation uniformity improves, but the ability to displace liquid volume may be reduced
Solution Approach 1:
The passivation layer with elongated holes provides localized rigidity enhancement only in the longitudinal direction where bulging occurs, while maintaining flexibility in the transverse direction. This selective reinforcement reduces bulge effect without significantly restricting the overall membrane deformation needed for liquid ejection.
Solution Approach 2:
The structure combines the flexible membrane material with a passivation layer containing elongated holes, creating a composite structure that exhibits both rigidity (to prevent bulging) and flexibility (to maintain liquid displacement 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
The modified microfluidic device achieves uniform deformation in both longitudinal and transverse directions, eliminating bulging and maintaining the ability to displace the same volume of liquid as prior art devices, thus improving the control and efficiency of fluid ejection.
Implementation Method 1
The actuator 14 may be piezoelectric. In this case, it generally comprises two electrodes 16, 17, arranged on top of each other, and an intermediate piezoelectric layer 18
Implementation Method 2
The portion of the thin layer 5 overlying the actuator chamber 12 forms a membrane or diaphragm 13
Data Source
AI summary
A microfluidic MEMS device is formed by a plurality of ejection cells each having a fluid chamber; an actuator chamber; a membrane having a first surface facing the actuator chamber and a second surface facing the fluid chamber; a piezoelectric actuator on the first surface of the membrane; and a passivation layer on the piezoelectric actuator. The membrane has an elongated area defining a longitudinal direction and a transverse direction. The passivation layer has a plurality of holes. The holes extend throughout the thickness of the passivation layer and, in a plan view, have an elongated shape with a greater dimension parallel to the longitudinal direction of the membrane and a smaller dimension parallel to the transverse direction.