Microfluidic Fluid Input Structure for Bubble-Free Loading

Solution Overview

Problem

Microfluidic devices, particularly EWOD devices, face challenges in efficiently loading and maintaining fluid volumes due to issues like air bubbles forming upon heating and filler fluid evaporation, which can lead to inaccurate fluid measurements and contamination.

Innovation Solution

A microfluidic device design with a fluid input structure featuring a fluid well with distinct portions to prevent air entrapment and a housing that accommodates filler fluid to prevent evaporation, along with array element control to guide fluid loading and prevent accidental extraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional fluid loading method is used, then fluid can be introduced into the device, but air bubbles are trapped and filler fluid evaporates during heating

Engineering Contradiction:

Improvefluid loading accuracyVSAvoidair bubbles and evaporation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The fluid well is divided into three distinct portions: a first portion that forms a reservoir for filler fluid, a second portion configured to sealingly engage the fluid applicator, and a third portion that communicates with the fluid exit. This segmentation prevents air entrapment by ensuring the applicator tip remains below the filler fluid surface during engagement, while the sealed second portion prevents filler fluid evaporation during heating operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The filler fluid is pre-loaded into the first portion of the fluid well to establish a reservoir before the working fluid is introduced. This preliminary action ensures that when the fluid applicator is inserted, its tip is automatically positioned below the filler fluid surface, preventing air bubble formation. The pre-positioned filler fluid also serves as a seal during subsequent heating to prevent evaporation.

Inventive Principle:

Principle #10Preliminary action

2Loss of substance

If the fluid well is sealed to prevent evaporation, then filler fluid is retained, but air bubbles form during loading

Engineering Contradiction:

Improvefiller fluid retentionVSAvoidair bubble formation

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The fluid well is divided into three distinct portions: a first portion that forms a reservoir for filler fluid, a second portion configured to sealingly engage the fluid applicator, and a third portion that communicates with the fluid exit. This segmentation prevents air entrapment by ensuring the applicator tip remains below the filler fluid surface during engagement, while the sealed second portion prevents filler fluid evaporation during heating operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The filler fluid in the first portion acts as an intermediary medium that fills the space between the environment and the working fluid. By maintaining a reservoir of filler fluid that extends into the second portion during applicator engagement, it serves as both a seal against evaporation and a barrier preventing air bubble formation, allowing the system to be sealed without trapping air.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If the fluid applicator is inserted deeply to prevent air entry, then air bubbles are prevented, but the device complexity increases

Engineering Contradiction:

Improveair bubble preventionVSAvoidfluid input structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The fluid well is divided into three distinct portions: a first portion that forms a reservoir for filler fluid, a second portion configured to sealingly engage the fluid applicator, and a third portion that communicates with the fluid exit. This segmentation prevents air entrapment by ensuring the applicator tip remains below the filler fluid surface during engagement, while the sealed second portion prevents filler fluid evaporation during heating operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fluid well structure automatically positions the fluid applicator tip below the filler fluid surface through its geometric design. The tapered configuration and sealing engagement in the second portion cause the applicator to self-align and self-position at the correct depth, eliminating the need for complex external positioning mechanisms or deep manual insertion while still preventing air bubble formation.

Inventive Principle:

Principle #25Self-service

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

Ensures accurate and reliable loading of working fluids into microfluidic devices, minimizing air bubbles and fluid loss, and preventing contamination by ensuring the filler fluid remains effective and preventing air from entering the device.

Implementation Method 1

A liquid droplet 14, including a polar material (which is commonly also aqueous and/or ionic), is constrained in a plane between the lower substrate 10 and a top substrate 16... A suitable gap or channel between the two substrates may be realized by means of a spacer 18, and a nonpolar filler fluid or surround fluid 20 (e.g. an oil such as a silicone oil) may be used to occupy the volume not occupied by the liquid droplet 14

Methodology Applied

Scientific EffectSurface tension: Surface Tension

Implementation Method 2

Electro-wetting on dielectric (EWOD) is a well-known technique for manipulating discrete droplets of fluid by application of an electric field... The function of the filler fluid is to reduce the surface tension at the surfaces of the polar droplets, and to increase the electro-wetting force

Methodology Applied

Scientific EffectElectro-wetting: Electrowetting

Implementation Method 3

In operation, voltages termed the EW drive voltages, (e.g. VT, V0 and V00 in FIG. 1) may be externally applied to different electrodes (e.g. reference electrode 30, element electrodes 12, 12A and 12B, respectively). The resulting electrical forces that are set up effectively control the hydrophobicity of the hydrophobic coating 24

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Data Source

PatentUS11577244B2Microfluidic device and a method of loading fluid therein

Publication Date: 2023.02.14 SHARP LIFE SCI EU LTD

AI summary

A microfluidic device comprises upper and lower spaced apart substrates defining a fluid chamber therebetween; an aperture for introducing fluid into the fluid chamber; and a fluid input structure disposed over the upper substrate and having a fluid well for receiving fluid from a fluid applicator inserted into the fluid well. The fluid well communicates with a fluid exit provided in a base of the fluid input structure, the fluid exit being adjacent the aperture. The fluid well comprises first, second and third portions, with the first portion of the well forming a reservoir for a filler fluid; and the second portion of the well being configured to sealingly engage against an outer surface of a fluid applicator inserted into the fluid well. The third portion of the well communicates with the fluid exit and has a diameter at the interface between the third portion and the second portion that is greater than the diameter of the second portion at the interface between the third portion and the second portion.