Bimorph Piezo Actuator Passive Layer Bias Elimination
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Solution Overview
Problem
Bimorph piezo-electric actuators in inkjet print heads require a bias voltage, which leads to stress and reduced lifetime, and dedicated driver electronics that consume energy and generate heat.
Innovation Solution
Incorporating a passive layer on the top electrode side of the piezo-electric actuator, making the membrane more compliant than the passive layer laterally, allowing the actuator to flex towards the passive layer without needing a bias voltage, thus reducing power consumption and increasing the actuator's lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bias voltage is applied to the bimorph piezo-electric actuator, then the actuator maintains a deformed state for droplet ejection, but the actuator experiences increased stress and reduced lifetime
Solution Approach 1:
The patent changes the structural parameters of the actuator by adding a passive layer with different mechanical properties (higher stiffness, lower compliance) than the membrane. This structural modification allows the actuator to achieve the necessary deformation without requiring a bias voltage, thereby eliminating the continuous stress that reduced actuator lifetime.
2Ease of operation
If a bias voltage is applied over dedicated driver electronics, then the actuator can be deformed for operation, but energy is dissipated and heat is generated
Solution Approach 1:
Instead of using a bias voltage to maintain actuator deformation (the conventional approach), the patent inverts the approach by using a passive layer to provide the necessary mechanical constraint. This inversion eliminates the need for continuous electrical power to maintain the actuator's operational state, significantly reducing power consumption.
3Reliability
If the membrane is made more compliant than the passive layer, then the actuator flexes towards the passive layer without bias voltage, but the structural design becomes more complex
Solution Approach 1:
The patent segments the actuator structure into distinct functional layers: a compliant membrane for flexibility and a stiffer passive layer for structural support. This segmentation allows each layer to perform its specific function optimally - the membrane provides compliance for actuator flexing while the passive layer provides the necessary stiffness to enable flexing without bias voltage, resolving the contradiction between reliability and complexity.
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 configuration eliminates the need for a bias voltage, reducing power consumption and extending the lifetime of the actuator by minimizing stress and heat generation, while also enabling cost-effective manufacturing by potentially reducing the number of wafer layers.
Implementation Method 1
an actuator assembly comprising a flexible membrane and a piezo-electric actuator arranged on the flexible membrane such that the flexible membrane flexes when a drive voltage is applied over the piezo-electric actuator
Data Source
Figure 1~2B
Figure 3A~3D
Figure 4A~4C
AI summary
In a print head having a bimorph thin-film piezo actuator, the piezo-electric actuator is arranged on a membrane at a first side of the piezo-electric actuator and a passive layer is arranged on the piezo-electric actuator at a second side of the piezo-electric actuator, wherein the second side is opposite to the first side. The membrane is more compliant, at least in a lateral direction, for contraction than the passive layer. Thus, a bending direction of the actuator is affected. As a consequence, there is no need for a bias voltage on the actuator during a standby state of the print head. Omitting the bias voltage during standby results in an increased lifetime and stability of the actuator assembly.