Laminate Melt Flow Index Gradient for Microfluidic Ink Protection
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Solution Overview
Problem
In microfluidic devices, the heat seal polymer flow distorts and breaks conductive ink patterns, leading to circuit failure, while insufficient bonding occurs when the heat seal polymer does not flow, due to existing heat seal materials and methods.
Innovation Solution
A laminate with a first thermoplastic polymer layer having a lower melt flow index, adjacent to a second thermoplastic polymer layer with a higher melt flow index, both made of the same polymer, such as polyethylene, is used, where the ink pattern is applied on the first layer, allowing for bonding without ink distortion during heat sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat seal polymer flows to bond layers together, then bonding strength is improved, but ink pattern distorts and breaks
Solution Approach 1:
The heat seal polymer layer is divided into two segments with different melt flow indices: a lower MFI portion that remains stable to protect the ink pattern, and a higher MFI portion that provides sufficient flow for bonding. This segmentation allows each portion to fulfill its specific function without compromising the other.
Solution Approach 2:
Different portions of the heat seal polymer layer are assigned different local qualities (melt flow indices) to perform different functions. The lower MFI region provides stability where the ink pattern is located, while the higher MFI region provides flow capability for bonding, creating localized functional zones within the same layer.
2Manufacturing precision
If heat seal polymer does not flow to protect ink pattern, then ink pattern integrity is improved, but bonding strength becomes insufficient
Solution Approach 1:
The heat seal polymer layer is segmented into regions with different melt flow indices, allowing the lower MFI portion to protect the ink pattern while the higher MFI portion ensures adequate bonding, resolving the contradiction between protection and bonding.
Solution Approach 2:
The heat seal polymer layer functions as a composite material system with different portions having different melt flow characteristics, combining the benefits of both low MFI (stability) and high MFI (flow capability) polymers within a single layer.
3Ease of manufacture
If single melt flow index is used for heat seal polymer, then manufacturing simplicity is improved, but cannot simultaneously achieve bonding and ink pattern protection
Solution Approach 1:
Different portions of the same heat seal polymer layer are assigned different melt flow indices to perform different functions, allowing the layer to simultaneously provide both ink pattern protection and bonding capability without requiring multiple separate layers or complex manufacturing processes.
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 approach ensures efficient heat sealing without distorting or breaking the ink pattern, providing strong bonding between layers while maintaining the integrity of the ink pattern, especially for conductive electrodes in microfluidic devices.
Implementation Method 1
Upon application of a suitable temperature, the layer of polymer will become tacky and form a seal
Implementation Method 2
bonded together, upon application of the suitable temperature and pressure
Data Source
AI summary
The present invention relates to laminate comprising a first thermoplastic polymer layer with a first melt flow index, adjacent a thermoplastic polymer second layer with a second melt flow index, the first and second layer comprising the same thermoplastic polymer, characterized in that the first melt flow index is lower than the second melt flow index. The invention also relates to a microfluidic device comprising the laminate and a method for incorporating an ink pattern in the laminate.