Variable Wettability Layers for Surfactant-Free Digital Microfluidics

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Solution Overview

Problem

Digital microfluidic devices face limitations in performing massive parallel assays and reactions due to the limited number of electrodes in passive matrix devices, and the addition of surfactants to adjust droplet wetting properties can damage biological molecules, making it challenging to accommodate variability in droplet formulations.

Innovation Solution

A digital microfluidic device with a spatially variable wettability layer covering the dielectric layer, comprising regions with different contact angles or a contact angle gradient, allowing for programmable droplet manipulation and actuation without the need for surfactants, utilizing thin-film transistors and a controller to provide driving voltage to the electrodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If surfactants are added to adjust droplet wetting properties, then contact angle variability is accommodated, but biological molecules are damaged

Engineering Contradiction:

Improvecontact angle variability accommodationVSAvoidbiological molecule damage

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating spatially variable wettability regions on the substrate surface with different contact angles (e.g., 20°, 40°, 60°, 80°, 100° regions). Each region is tailored to accommodate specific droplet formulations without requiring surfactants, thus preserving biological molecule integrity while providing adaptability across diverse droplet compositions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the surface energy parameter of the substrate by applying treatments (such as plasma treatment, chemical coating, or physical modification) to create regions with different contact angles. This parameter change allows the surface to adapt to various droplet formulations intrinsically, eliminating the need for surfactant addition and preventing biological molecule damage.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If passive matrix devices with limited electrodes are used, then device fabrication is simplified, but massive parallel assays cannot be performed

Engineering Contradiction:

Improvedevice fabrication simplicityVSAvoidmassive parallel assay capability

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent segments the substrate surface into multiple spatially variable wettability regions, each capable of independently manipulating droplets. This segmentation allows a single substrate to perform multiple parallel operations simultaneously, enabling massive parallel assays while maintaining the simplicity of passive matrix device fabrication without requiring complex active matrix electrode structures.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If uniform wettability surface is used, then device structure is simple, but droplet manipulation for different formulations is limited

Engineering Contradiction:

Improvesurface structure simplicityVSAvoiddroplet formulation accommodation

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent introduces local quality variations on the substrate surface by creating regions with different wettability characteristics (different contact angles). This allows the surface to accommodate diverse droplet formulations with varying wetting properties while maintaining overall structural simplicity. Each local region is optimized for specific droplet types, providing versatility without complex device architecture.

Inventive Principle:

Principle #3Local quality

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

Enables efficient and reliable droplet manipulation and actuation across a wide range of droplet formulations, allowing for simultaneous analytical processes and improved droplet migration control, while avoiding surfactant-related damage to biological molecules.

Implementation Method 1

a spatially variable wettability layer covering the dielectric layer. In one embodiment, the spatially variable wettability layer comprises a first portion having a first contact angle, and a second portion having a second contact angle

Methodology Applied

Scientific EffectWetting: Wetting

Implementation Method 2

A droplet is placed on the hydrophobic layer, and the stack, once actuated, can cause the droplet to deform and wet or de-wet from the surface depending on the applied voltage

Methodology Applied

Scientific EffectElectrowetting: Electrowetting

Data Source

PatentUS11927740B2Spatially variable hydrophobic layers for digital microfluidics

Publication Date: 2024.03.12 NUCLERA LTD

AI summary

An active matrix electrowetting on dielectric (AM-EWoD) device including a substrate with thin-film transistors (TFT), a dielectric layer, and a spatially variable wettability layer covering the dielectric layer. As depicted herein, the spatially variable wettability layer may include a plurality of portions having different contact angles, one or more contact angle gradients, or both.