Microfluidic Wells with Half-Open Chimney Channels for Air-Free Filling
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Solution Overview
Problem
Existing microfluidic devices face challenges with uncontrolled air entrapment during liquid filling, particularly on surfaces with a contact angle below 90°, requiring additional efforts like precise adjustments or pressure application to avoid air bubbles.
Innovation Solution
A microfluidic device design featuring channels and wells with a contact angle less than 90°, utilizing sharp corner transitions and half-open vertical chimney channels to facilitate capillary filling without air entrapment, where the channels and walls have a smaller contact angle than the lid, and are coated with silicon oxide to enhance wetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surfaces with contact angle below 90° are used to enhance wetting, then liquid filling efficiency is improved, but air entrapment occurs during the filling process
Solution Approach 1:
The filling system is segmented into distinct functional zones: a first region with contact angle <90° for efficient wetting and a second region with contact angle >90° for air release. This spatial segmentation allows each zone to perform its specific function optimally without interfering with the other, resolving the contradiction between filling efficiency and air entrapment.
Solution Approach 2:
Different regions of the substrate are assigned different contact angle properties. The first region has hydrophilic properties (contact angle <90°) to enhance liquid uptake, while the second region has hydrophobic properties (contact angle >90°) to facilitate air release. This local differentiation of surface properties allows simultaneous optimization of both filling efficiency and air management.
2Object-generated harmful factors
If pressure is applied to prevent air bubbles, then air entrapment is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The device uses its own structural features (the dual-contact-angle regions) to automatically manage air entrapment without requiring external pressure application mechanisms. The hydrophobic second region passively releases air bubbles as the liquid fills the device, eliminating the need for complex pressure control systems.
Solution Approach 2:
The mechanical approach of applying external pressure to prevent air bubbles is replaced by a surface chemistry approach using contact angle differences. The hydrophobic region creates a natural air release pathway through surface tension effects, substituting mechanical pressure control with a passive surface property-based solution.
3Object-generated harmful factors
If precise adjustments are made to contact angles, then air entrapment is minimized, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the contact angle parameter in a discrete, binary manner rather than requiring precise continuous control. By defining clear thresholds (<90° for first region, >90° for second region), the manufacturing process becomes more tolerant to variations while still achieving the desired functional differentiation. This parameter simplification reduces manufacturing precision requirements.
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 controlled filling of deep structures without air entrapment, suitable for common mass production processes, using only two layers and no additional materials, and compatible with surfaces having contact angles below 90°.
Implementation Method 1
channels and wells with a contact angle less than 90°, utilizing sharp corner transitions and half-open vertical chimney channels to facilitate capillary filling without air entrapment
Implementation Method 2
coated with silicon oxide to enhance wetting
Data Source
AI summary
Structures for supporting the filling of wells, in particular in microfluidic devices and provides a microfluidic device, comprising a substrate with at least a first horizontal channel which continues as a first vertical chimney channel into a first well having a greater depth than the first horizontal channel with respect to an upper surface of the substrate, wherein the first vertical channel is half open to the volume of the first well. A method for filling a well of a microfluidic device using the device is also an object of the disclosure.