Microfluidic Capillary Barriers for Bubble-Free Liquid Interfaces

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Loading microfluidic chips with multiple liquids is challenging due to limited access, channel dimensions, surface forces, and potential fluid loss, especially when creating liquid-to-liquid interfaces with scarce samples like rare cells or DNA.

Innovation Solution

A capillary barrier is used to position a liquid meniscus at a fluid-interface region using capillary forces, with an escape path for the second liquid and a fluid-flow limiter to control volume flow rate, and a gas-outflow port to manage pressure, all without vacuum assistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If vacuum assistance is used to load liquids into microfluidic channels, then loading speed and efficiency are improved, but fluid loss and sample contamination increase

Engineering Contradiction:

Improveloading speedVSAvoidfluid loss

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

The patent replaces the vacuum-based mechanical loading system with a capillary force-based system. The capillary barrier structure utilizes surface tension and capillary pressure to control liquid flow and positioning without requiring vacuum assistance, thereby eliminating the harmful effects of vacuum while maintaining loading efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The capillary barrier acts as an intermediary structure between the liquid reservoir and the microfluidic channel. It mediates the liquid flow by using capillary forces to advance the liquid meniscus precisely to the interface region without direct vacuum contact, preventing fluid loss and contamination.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If multiple liquids are loaded simultaneously from multiple directions, then interface creation is accelerated, but bubble trapping and flow control difficulties increase

Engineering Contradiction:

Improveinterface creation speedVSAvoidbubble-free interface

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent segments the liquid loading process into two distinct phases: first loading the buffer solution to the capillary barrier, then loading the sample liquid. This segmentation prevents bubble trapping by ensuring proper layering and interface formation without simultaneous multi-directional flow conflicts.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The buffer solution is loaded first as a preliminary step before introducing the sample liquid. This preliminary action establishes a stable base layer and proper flow path, enabling subsequent sample liquid introduction without bubble formation and ensuring reliable interface creation.

Inventive Principle:

Principle #10Preliminary action

3Length of moving object

If channel dimensions are reduced to 100 μm for microfluidic applications, then device integration and portability are improved, but surface forces dominate causing liquid advancement difficulties

Engineering Contradiction:

Improvechannel dimensionVSAvoidliquid advancement

Core Design Contradiction:

Length of moving objectVSEase of operation

Solution Approach 1:

The patent utilizes capillary pressure (a form of hydraulic principle) to drive liquid advancement in the micro-scale channels. The capillary barrier structure creates positive capillary pressure that overcomes surface forces and enables reliable liquid meniscus advancement to the interface region without external pressure application.

Inventive Principle:

Principle #29Pneumatics and hydraulics

Solution Approach 2:

The patent changes the surface energy parameters of the capillary barrier structure to optimize capillary forces. By adjusting the wettability and surface properties of the barrier, the system achieves controlled liquid advancement and meniscus positioning despite the small 100 μm channel dimensions.

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 method allows for efficient creation of liquid interfaces in microfluidic channels without fluid loss, enabling high recovery efficiency in nucleic acid purification and analysis, such as DNA extraction from blood samples.

Implementation Method 1

a capillary barrier that positions a meniscus of the first liquid at a fluid-interface region using capillary forces

Methodology Applied

Scientific EffectCapillary forces: Capillary Action

Implementation Method 2

gas pressure is released from the fluid-interface region via a gas-outflow port

Methodology Applied

Scientific EffectPressure release: Depressurisation

Data Source

PatentUS12435329B2Capillary barriers for staged loading of microfluidic devices

Publication Date: 2025.10.07 THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIV

AI summary

Various aspects of the present disclosure are directed toward methods and apparatuses for interacting a first liquid and a second liquid in one or more fluidic channels of a capillary structure. The methods and apparatuses can include providing at least one capillary barrier that positions a meniscus of the first liquid at a fluid-interface region using capillary forces within the capillary structure. Additionally, a path is provided along one of the channels for the second liquid to flow toward the fluid-interface region. Additionally, gas pressure is released, via a gas-outflow port, from the fluid-interface region while flow of the first liquid is arrested. Further, the first liquid and the second liquid contact in the fluid-interface region with the capillary barrier holding the first liquid at the fluid-interface region.