Travelling Surface Acoustic Wave Microfluidic Particle Sorting
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Solution Overview
Problem
Existing cell sorting technologies face limitations in robustness and selectivity, particularly with standing surface acoustic waves (SAW) due to inherent constraints on particle displacement and sorting region width, and require complex coupling structures, which affect efficiency and biocompatibility.
Innovation Solution
A microfluidic device utilizing a travelling surface acoustic wave (SAW) with a focused beam generated by an interdigital transducer (IDT) having a tapered end aperture of 4 μm to 150 μm, allowing for highly localized and efficient particle manipulation and sorting without additional coupling structures, using a piezoelectric substrate to produce a confined acoustic field for precise particle translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standing surface acoustic waves are used for particle sorting, then particles can be translated to nodal positions, but the maximum displacement is limited to less than one quarter of the acoustic wavelength and the sorting region width becomes large (150-300 μm)
Solution Approach 1:
The patent inverts the conventional standing wave approach by using traveling surface acoustic waves instead. This inversion allows particles to be translated over much longer distances along the flow direction without being constrained by wavelength limitations, while maintaining a narrow sorting region width through focused beam geometry.
Solution Approach 2:
The patent transitions from one-dimensional standing wave patterns to two-dimensional traveling wave patterns with focused beams. By introducing the dimension of wave propagation direction perpendicular to the flow, the system achieves both precise lateral sorting and extended longitudinal particle translation.
2Manufacturing precision
If standing surface acoustic waves are used, then particles can be sorted, but complex coupling structures are required which reduce efficiency and biocompatibility
Solution Approach 1:
The patent extracts and eliminates the complex coupling structures required by standing wave systems. By using traveling waves that propagate along the channel wall, the system directly couples acoustic energy to the fluid without requiring intermediate coupling elements, thereby simplifying the device architecture.
Solution Approach 2:
The patent introduces the channel wall itself as the intermediary medium for wave propagation. Instead of using separate coupling structures, the acoustic waves travel along the wall to directly interact with particles in the fluid, simplifying the system while maintaining effective particle manipulation.
3Productivity
If conventional FACS is used for cell sorting, then high sorting rates can be achieved, but the systems are large, expensive, and not amenable to portable platforms
Solution Approach 1:
The patent replaces the complex mechanical and electrical systems of conventional FACS (aerosol generation, electrical charging, deflection fields) with a simpler acoustic field-based system. Surface acoustic waves directly manipulate particles in a continuous flow, eliminating the need for bulky mechanical components while maintaining high sorting rates.
Solution Approach 2:
The patent employs periodic acoustic wave generation to achieve continuous particle sorting at high rates. By modulating the acoustic field periodically and coordinating with particle flow, the system maintains high throughput similar to FACS but with a compact, portable form factor.
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 device achieves robust and selective particle sorting with improved displacement capabilities and reduced attenuation, enabling efficient sorting of particles as small as 2 μm, while maintaining biocompatibility and minimizing device complexity.
Implementation Method 1
an acoustic source to generate a travelling surface acoustic wave transverse the flow of the fluid suspension in the channel
Implementation Method 2
the wave generated by the acoustic source manipulates the particles present in the channel when it travels along the channel from the inlet to the outlet
Implementation Method 3
using a piezoelectric substrate to produce a confined acoustic field for precise particle translation
Data Source
AI summary
The present invention relates to the use of acoustic waves for the manipulation and sorting of particles and cells. In an embodiment, there is provided a microfluidic device for manipulating a particle in a fluid suspension, the device comprising: (a) a substrate; (b) a channel defined in the substrate, the channel having an inlet for receiving the fluid suspension and an outlet for discharging the fluid suspension; and (c) an acoustic source configured to deliver a travelling surface acoustic wave transverse the flow of the fluid suspension in the channel, wherein the acoustic source is an interdigital transducer (IDT), the IDT comprises a plurality of concentric circular arcs having a tapered end directed at the channel, and the tapered end has an aperture of between 4 μm and 150 μm. In an alternative embodiment, the device comprises a second channel disposed intermediate the first channel and the acoustic source wherein the first and second channels are connected by a pumping channel.