Ultrasonic Flow Path Layout for Efficient Standing Wave Generation
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Solution Overview
Problem
Existing fluid devices that perform acoustic convergence on fine particles in a fluid face inefficiencies due to significant differences in acoustic impedance between the fluid and the flow path substrate, leading to reduced standing wave generation efficiency and increased drive voltage and frequency requirements.
Innovation Solution
A fluid device with a flow path and a first ultrasonic wave transmitter that transmits ultrasonic waves directly to the fluid, positioned to face an antinode region, improving wave generation efficiency by minimizing impedance mismatch and allowing for lower drive voltage and frequency settings, while the flow path dimensions are optimized to prevent standing wave generation in undesirable directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the ultrasonic wave is transmitted from the flow path substrate to the fluid, then the standing wave can be generated in the fluid, but most of the ultrasonic waves are reflected at the boundary due to large acoustic impedance difference, reducing generation efficiency
Solution Approach 1:
An acoustic impedance matching layer is introduced between the flow path substrate and the fluid to serve as an intermediary medium. This matching layer has acoustic impedance between that of the substrate and the fluid, reducing the impedance mismatch and minimizing ultrasonic wave reflection at the boundary, thereby improving energy transmission and standing wave generation efficiency
Solution Approach 2:
The acoustic impedance parameters of the interface between flow path substrate and fluid are modified by introducing a matching layer with specific acoustic impedance characteristics. This parameter change optimizes the acoustic coupling, reducing reflection loss and improving ultrasonic wave transmission into the fluid
2Reliability
If the drive voltage and driving frequency are increased to compensate for low generation efficiency, then the standing wave can be generated, but the device complexity and energy consumption increase
Solution Approach 1:
The acoustic impedance matching layer acts as a mediator that improves ultrasonic wave transmission efficiency, allowing the piezoelectric element to generate effective standing waves at lower drive voltages and frequencies, thereby reducing energy consumption while maintaining reliable particle convergence performance
3Device complexity
If the flow path substrate is used to transmit ultrasonic waves, then the structure is simple, but the acoustic impedance mismatch causes most ultrasonic waves to be reflected
Solution Approach 1:
An acoustic impedance matching layer is introduced as an additional component between the flow path substrate and the fluid. While this increases structural complexity slightly, it dramatically reduces ultrasonic wave reflection loss by providing gradual acoustic impedance transition, improving overall system efficiency
Solution Approach 2:
The flow path substrate structure is enhanced by incorporating a composite matching layer with specific acoustic properties. This composite structure combines the mechanical support function of the substrate with the acoustic coupling function of the matching layer, optimizing both structural integrity and ultrasonic transmission
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
Enhances the generation efficiency of standing waves within the flow path, increasing the volume flow rate that can be treated and improving the propagation efficiency of ultrasonic waves, thereby allowing for a wider standing wave generation area with reduced operational demands.
Implementation Method 1
a piezoelectric element provided at the flow path substrate. An ultrasonic wave generated by the piezoelectric element is transmitted to an inside of the flow path via the flow path substrate
Implementation Method 2
since a difference between an acoustic impedance of the fluid and an acoustic impedance of the flow path substrate is large, when the ultrasonic wave generated by the piezoelectric element is propagated from the flow path substrate to the fluid, most of the ultrasonic waves are reflected at a boundary between the flow path substrate and the fluid
Implementation Method 3
Fine particles in the fluid converge in a predetermined range in the flow path due to a pressure gradient of the fluid formed by the standing wave
Data Source
AI summary
A fluid device includes: a flow path through which a fluid flows; and an ultrasonic wave transmitter configured to transmit an ultrasonic wave to generate a standing wave to the fluid in the flow path along a first direction orthogonal to a flowing direction of the fluid. The ultrasonic wave transmitter is in contact with the fluid and faces an antinode region corresponding to any antinode in the standing wave.