Flexural Vibrator Fluid Device for Efficient Standing-Wave Coupling
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Solution Overview
Problem
Existing fluid devices face low transmission efficiency of ultrasonic waves due to significant impedance mismatch between the flow path substrate and fluid, leading to increased drive voltage and frequency requirements.
Innovation Solution
A fluid device design with a vibrator having a fluid contact surface and a piezoelectric element that generates flexural vibrations, where the thickness of the vibrator is optimized to satisfy specific relationships with sound velocities and flow path dimensions, ensuring direct ultrasonic wave transmission to the fluid and minimizing longitudinal wave generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ultrasonic wave transmission is performed from flow path substrate to fluid, then standing wave generation is achieved, but transmission efficiency is lowered due to acoustic impedance mismatch
Solution Approach 1:
A matching layer is introduced between the flow path substrate and the fluid to serve as an acoustic impedance intermediary. This matching layer has acoustic impedance between that of the substrate and the fluid, enabling gradual acoustic impedance transition and reducing reflection at the interface, thereby improving ultrasonic wave transmission efficiency while maintaining standing wave generation.
Solution Approach 2:
The acoustic impedance parameters of the interface between flow path substrate and fluid are modified by introducing the matching layer with intermediate acoustic impedance characteristics. This parameter change enables better acoustic coupling and reduces the impedance mismatch problem, allowing efficient ultrasonic energy transfer into the fluid for reliable standing wave generation.
2Reliability
If drive voltage and frequency are increased to compensate for low transmission efficiency, then standing wave generation is improved, but energy consumption increases
Solution Approach 1:
The matching layer acts as an intermediary that improves ultrasonic energy transfer efficiency, reducing the amount of energy lost to reflection. This allows the piezoelectric element to generate the required standing wave with lower drive voltage and frequency, thereby reducing overall energy consumption while maintaining reliable particle convergence.
3Productivity
If flow path width is increased to handle higher volume flow rates, then processing capacity is improved, but ultrasonic wave transmission efficiency decreases
Solution Approach 1:
The matching layer ensures efficient ultrasonic energy coupling at the substrate-fluid interface regardless of flow path width. This enables the system to handle wider flow paths and higher volume flow rates without sacrificing transmission efficiency, as the matching layer optimizes acoustic energy transfer into the expanded fluid volume.
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
Improves ultrasonic wave propagation efficiency, reduces drive voltage and frequency needs, and allows for wider flow path widths, increasing the volume flow rate while preventing vibrator damage.
Implementation Method 1
a piezoelectric element that is provided at the vibrator and that is configured to generate flexural vibration to the vibrator
Implementation Method 2
configured to transmit an ultrasonic wave to the fluid to generate a standing wave in the fluid in the flow path
Implementation Method 3
Fine particles in the fluid converge in a predetermined range in the flow path due to a pressure gradient formed by the standing wave
Data Source
AI summary
A fluid device includes a flow path through which a fluid flows, and an ultrasonic element that transmits an ultrasonic wave to the fluid to generate a standing wave in the fluid in the flow path along a first direction orthogonal to a flowing direction of the fluid. The ultrasonic element includes a vibrator having a fluid contact surface that comes into contact with the fluid, and a piezoelectric element that is provided at the vibrator and that flexurally vibrates the vibrator in a normal direction of the fluid contact surface. When a thickness of the vibrator in the normal direction is t, a sound velocity of a medium of the fluid is C, an average sound velocity of a longitudinal wave transmitted in the vibrator is C′, a dimension of the flow path in the first direction is L, and a mode order of the standing wave is n, the following expression is satisfied.t<C′C×L2n