Electrowetting Fluid Control via Downstream Reference Electrode

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Solution Overview

Problem

Microfluidic chips face limitations in controlling fluid flow due to viscous resistance and electrode design, leading to channel length restrictions, which impede the handling of microliter volumes and reproducible flow rates required for medical diagnostics, with prior art ceasing fluid flow within a few millimeters.

Innovation Solution

The placement of at least a portion of the reference electrode abreast or downstream of the working electrode along the flow path reduces the distance between electrodes, preserving the working electrode's ability to alter wettability and enabling fluid control over longer distances, allowing for microliter volume handling and reproducible flow rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the reference electrode is placed upstream of the working electrode, then the electrode setup is simple, but the fluid flow ceases within a few millimeters due to increased distance and viscous resistance

Engineering Contradiction:

Improveelectrode arrangement simplicityVSAvoideffective channel length

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The patent inverts the conventional electrode arrangement by placing the reference electrode downstream of the working electrode instead of upstream. This reversal reduces the distance between electrodes and maintains the electric field strength necessary for effective electrowetting over longer channel lengths, thereby resolving the contradiction between manufacturing simplicity and effective channel length.

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of operation

If capillary driven flow is used, then the system is simple to operate, but variable sample composition and viscosity cause variations in timing, volumes and flow rates

Engineering Contradiction:

Improveflow control simplicityVSAvoidflow rate reproducibility

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces passive capillary-driven flow with active electrowetting-based flow control. By using electric fields to manipulate fluid motion through changes in surface wettability, the system achieves precise and reproducible control over flow rates, timing, and volumes, eliminating the variability inherent in capillary-driven systems while maintaining operational simplicity through electronic control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If electrowetting is used to control fluid flow, then rapid actuation is achieved, but channel length is limited due to viscous resistance

Engineering Contradiction:

Improveactuation speedVSAvoidchannel length

Core Design Contradiction:

SpeedVSLength of stationary object

Solution Approach 1:

The patent changes the configuration parameters of the electrode system, specifically placing the reference electrode downstream to minimize the distance over which the electric field must act. This parameter change reduces viscous resistance effects and allows the rapid electrowetting actuation to be maintained over longer channel lengths, resolving the contradiction between actuation speed and channel length.

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

This configuration allows for the accurate control of fluid flow over centimeter distances, enabling the handling of microliter volumes and achieving the necessary flow velocities and reproducibility for medical diagnostics, overcoming the limitations of prior art by maintaining wettability alteration capacity along the flow path.

Implementation Method 1

A working electrode arranged to contact the fluid sample when the fluid sample moves along the flow path... applying a voltage between the working electrode and the reference electrode... alters the wettability of the working electrode surface and thereby promotes advancement of the fluid front across the working electrode surface

Methodology Applied

Scientific EffectElectrowetting: Electrowetting

Implementation Method 2

A reference electrode arranged to contact the fluid sample when the fluid sample moves along the flow path... applying a voltage between the working electrode and the reference electrode

Methodology Applied

Scientific EffectElectrochemical contact: Conduction (electrical)

Data Source

PatentUS10309926B2On chip control of fluids using electrodes

Publication Date: 2019.06.04 BICO GRP AB

AI summary

The present invention relates to a device for controlling movement of a fluid sample along a flow path and a corresponding method. The device comprises a working electrode (2) arranged to contact the fluid sample when the fluid sample moves along the flow path, and a reference electrode (3) arranged to contact the fluid sample when the fluid sample moves along the flow path. At least a portion of the reference electrode is arranged abreast of or downstream at least a portion of the working electrode. The present invention is advantageous in that it provides a device wherein a fluid sample may be transported and accurately controlled, with respect to e.g. timing, volumes and flow rates, over greater distances compared to prior art.