Thermal Pin Joining for Microfluidic Cartridge Integrity
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Solution Overview
Problem
Existing joining techniques for microfluidic cartridges, such as ultrasound welding and adhesive bonding, face challenges like mechanical stress, material compatibility issues, and increased costs, which can damage biosensors and affect the fluidic properties of the cartridges.
Innovation Solution
A process involving a film with an adhesive layer, preferably made of ethylene-vinyl acetate copolymer, is laminated onto a plate-shaped substrate with pins that engage with corresponding bores on another substrate, using a thermode to form a frictional and interlocking connection without melting, ensuring a strong, material-saving, and stress-free bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ultrasound welding is used to join microfluidic components, then strong bonding is achieved, but mechanical vibrations damage biosensors and filter membranes
Solution Approach 1:
The patent replaces ultrasound welding (mechanical vibration-based) with a thermal bonding process using a thermode that applies localized heat and pressure. This substitution eliminates the harmful mechanical vibrations that damage biosensors and filter membranes while achieving strong bonding between microfluidic components through controlled thermal fusion of thermoplastic materials.
Solution Approach 2:
The patent changes the bonding mechanism from mechanical (ultrasound) to thermal (heat application). By controlling temperature, pressure, and bonding time parameters of the thermode, strong bonds are formed without introducing damaging vibrations. The process parameters are optimized to achieve adequate bonding strength while preventing damage to sensitive components.
2Strength
If adhesive films are used for joining, then bonding is achieved, but additional material costs and processing complexity increase
Solution Approach 1:
The patent extracts and eliminates the adhesive film layer from the joining process. Instead of using separate adhesive materials, the bonding capability is integrated directly into the microfluidic components themselves through thermoplastic materials that can be thermally bonded. This removal of the adhesive layer simplifies processing and reduces material costs while maintaining bonding strength.
Solution Approach 2:
The patent uses homogeneous thermoplastic materials for the microfluidic components that enable direct thermal bonding without requiring separate adhesive layers. This homogeneity in material composition allows the components to bond directly to each other through controlled heating, eliminating the need for complex adhesive application and processing steps.
3Adaptability or versatility
If different plastic materials are welded or adhesively bonded, then joining of diverse components is achieved, but poor adhesive properties and welding characteristics occur
Solution Approach 1:
The patent optimizes the thermal bonding parameters (temperature, pressure, time) to achieve strong bonds between different thermoplastic materials. By carefully controlling these parameters, the process accommodates material compatibility requirements while achieving adequate bonding strength across diverse component materials.
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 provides a reliable, cost-effective, and stress-free connection that maintains the fluidic properties of microfluidic cartridges, ensuring the integrity of biosensors and reducing the risk of mechanical damage during the joining process.
Implementation Method 1
a suitable pressing tool, particularly a thermode, in the heated state is pressed on to the ends of the pins... the pin material being heated above its glass transition temperature and beginning to flow
Implementation Method 2
it is pressed against the wall of the bore by the ram pressure of the tool so that a frictional connection is formed between the pin and the wall of the bore
Data Source
AI summary
A cartridge includes a fluidically conductive floor element, a cover, and a film disposed between the elements. The cover or the floor element and the film include a filling opening for filling microfluidic channels in one of the elements having sample fluid. Pins engage in corresponding holes in the film and the associated element. By way of deforming a pin, a friction fit is produced with the wall of a hole, and a head contacting the associated substrate in a form-fitting manner is formed. A press tool is placed on a head end of a pin at a predetermined pressure, and heat transfer into the pin takes place during a weld time. The pin material is brought to above the glass transition temperature and/or the melting point, and a friction fit between the pin and the wall of the hole is formed by flowing the pin material in the hole.