Surface Acoustic Wave Particle Manipulation in Microfluidic Droplets

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Solution Overview

Problem

Capillary-based microfluidic systems face difficulties in collecting concentrated particles due to the challenge of removing fluid and concentrated material from capillaries.

Innovation Solution

A microfluidic system utilizing an elongate piezoelectric substrate with interdigital electrodes and RF excitation generates surface acoustic waves, allowing for the dispersion or concentration of particles within fluid droplets through azimuthal recirculation, facilitated by varying the wave distribution using oblique reflection surfaces or damping material, enabling efficient collection of concentrated particles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If capillary-based microfluidic systems are used for particle concentration, then particle concentration is achieved, but fluid and concentrated material cannot be easily removed from capillaries

Engineering Contradiction:

Improveparticle concentrationVSAvoidfluid removal

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The patent replaces the mechanical capillary-based system with an acoustic field-based system. Surface acoustic waves generated by interdigital electrodes on a piezoelectric substrate create acoustic radiation pressure that manipulates particles and fluid without physical confinement, enabling easy fluid removal while maintaining particle concentration capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces surface acoustic waves as an intermediary mechanism to achieve particle concentration. The acoustic waves mediate the interaction between the system and particles/fluid, creating acoustic radiation pressure that concentrates particles without requiring fluid to remain confined in capillaries, thus solving the removal problem

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If surface acoustic waves are used for particle manipulation, then particles can be dispersed or concentrated, but system complexity increases

Engineering Contradiction:

Improveparticle manipulation capabilityVSAvoidsystem structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent designs a multi-functional system where the same surface acoustic wave generation mechanism (interdigital electrodes on piezoelectric substrate) can both disperse and concentrate particles by varying operational parameters. The acoustic field serves multiple functions including particle manipulation, fluid rotation, and concentration, reducing the need for separate mechanisms

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent achieves different particle manipulation outcomes (dispersion vs. concentration) by changing acoustic wave parameters such as frequency, power, and duration. By varying these parameters, the system can switch between different operational modes without structural modification, managing complexity through parameter control rather than structural complexity

Inventive Principle:

Principle #35Parameter changes

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 system effectively disperses or concentrates particles within fluid droplets, overcoming the collection challenges of capillary-based systems and allowing for efficient particle collection.

Implementation Method 1

an elongate piezoelectric substrate having opposing ends thereof; a wave generation means for generating a surface acoustic wave in the surface of the piezoelectric substrate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The SAW excitation of the substrate surface acts to displace or manipulate one or more fluid droplets located on that surface

Methodology Applied

Scientific EffectAcoustic radiation pressure: Acoustic Radiation Pressure

Implementation Method 3

facilitate rotation of the fluid within said droplet of fluid located in the path of the surface acoustic wave such that the suspended particles are either dispersed within the droplet or concentrated in an area within the droplet as a result of azimuthal recirculation induced within the droplet

Methodology Applied

Scientific EffectAcoustic streaming:

Data Source

PatentEP2013604B1Concentration and dispersion of small particles in small fluid volumes using acousting energy

Publication Date: 2019.12.18 ROYAL MELBOURNE INST OF TECH

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AI summary

A method of manipulating particles suspended within a fluid droplet using a microfluidic system including a piezoelectric substrate (1) and a wave generation means (3) for generating a wave within the piezoelectric substrate (1), and a working surface (2) through which the wave can be distributed and upon which fluid droplets (9) can be located, the method including locating one or more droplets of fluid on the working surface (2), varying the power applied to the wave generation means (3) or varying the distribution of the wave across the working surface (2), such that particles (1 1) suspended within the fluid droplet (9) are either dispersed within the droplet or concentrated in an area within the droplet in dependence on the power or wave distribution applied by the wave generation means (3) to the piezoelectric substrate (1), or to facilitate rotation of the fluid within said fluid droplets (9) located jn the path of the wave.