Microfluidic Valve Unit Fabrication Without Injection Protrusions
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Solution Overview
Problem
Existing microfluidic devices face manufacturing defects and increased costs due to weld-lines and rough surfaces caused by protrusions in mold designs, which affect the rigidity and smoothness of the devices, and can lead to valve malfunction when energy is applied.
Innovation Solution
A valve unit design without an inlet for injecting a valve material, featuring a first region, a second region deeper than the first, and a third region, with a valve material chamber in the upper substrate that overlaps only part of the first region, allowing the valve material to melt and flow into a non-overlapped portion to control fluid flow, using thermoplastic resin substrates and micro heating particles for energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a protrusion is formed in the mold to create an injection hole, then the valve unit can be manufactured, but weld-lines are formed that deteriorate the rigidity of the microfluidic device
Solution Approach 1:
The patent removes the injection hole (protrusion) from the mold design entirely. Instead of injecting valve material through a protrusion that causes weld-lines, the valve material is supplied externally and introduced into the valve chamber through alternative means that do not require mold protrusions, thereby eliminating weld-line formation and preserving device rigidity
Solution Approach 2:
The patent separates the valve material supply process from the mold injection process. The valve material is supplied externally as a separate step rather than being integrated into the mold injection, allowing the mold to remain simple without protrusions while still enabling valve material placement
2Ease of manufacture
If a protrusion is formed in the mold to create an injection hole, then the valve unit can be manufactured, but the mold surface becomes rough and smoothness deteriorates
Solution Approach 1:
The patent removes the protrusion from the mold design, eliminating the source of surface roughness. By not forming protrusions in the mold, the mold surface maintains its smoothness and can be polished more easily, while the valve material is still successfully placed through external supply methods
3Ease of manufacture
If an injection hole is formed with a draft angle, then the injection product can be easily separated from the mold, but a step difference is formed that causes light diffusion and valve malfunction
Solution Approach 1:
The patent eliminates the injection hole entirely by removing the protrusion from the mold. Without an injection hole, there is no need for draft angles, and consequently no step differences are formed on the inner circumferential surface. This prevents light diffusion and ensures proper valve operation while still allowing easy mold separation
Solution Approach 2:
Instead of forming an injection hole in the mold and then trying to mitigate its negative effects, the patent inverts the approach by supplying the valve material externally and introducing it through methods that do not require mold protrusions or draft angles, thereby eliminating the root cause of the step difference problem
4Reliability
If a process of closing the injection hole is added, then the valve unit can be completed, but the manufacturing costs increase
Solution Approach 1:
The patent removes the injection hole from the design, which eliminates the need for the additional closing process. By not having an injection hole to begin with, the manufacturing process is simplified and costs are reduced while the valve unit is still successfully completed through external material supply
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 design reduces manufacturing costs, eliminates weld-line defects, and prevents fluid leakage, ensuring smooth operation and maintaining device integrity even at high rotational speeds.
Implementation Method 1
when a valve material V is irradiated by laser light L, a plurality of micro heating particles P included in the valve material V are rapidly heated, and thus the phase transition material is rapidly heated
Implementation Method 2
the phase transition material is rapidly heated and is then melted into a liquid state
Implementation Method 3
some of the melted valve material V flows into the non-overlapped portion 103 of the first region 101 by a capillary phenomenon
Data Source
AI summary
Provided are a valve unit, a microfluidic device including the same, and a method of fabricating the valve unit. The method includes: forming a lower substrate including a channel including a first region and a second region which is deeper than the first region and is adjacent to one side of the first region; forming an upper substrate comprising a valve material chamber which extends only partially through the upper substrate; filling the valve material chamber with a valve material and curing the valve material in the valve material chamber; attaching a surface of the upper substrate in which the valve material chamber is formed to a surface of the lower substrate in which the channel is formed, so that the valve material chamber overlaps an overlapped portion of the first region, and does not overlap a non-overlapped portion of the first region; melting the valve material accommodated in the valve material chamber to flow the valve material into the non-overlapped portion of the first region; and curing the valve material flowed into the non-overlapped portion to close the first region.