Paraffin Closure for Fluidic Actuator Shelf Life
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Solution Overview
Problem
Microfluidic systems face challenges with the evaporation of electrolytes used in electrochemical actuators, which limits their shelf life due to high water vapor permeability in common materials, and the need for a balance between maintaining large gas volume and ensuring the actuator function is not compromised.
Innovation Solution
A fluidic actuator design featuring a deformable closure assembly with a paraffin-containing film or layer, which has low water vapor permeability and high extensibility, allowing for pressure changes to deform and control the actuator effectively while minimizing evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick or dense film is used to seal the electrolyte, then evaporation is reduced and shelf life is extended, but the gas volume generated by electrolysis is reduced and actuator function is compromised
Solution Approach 1:
The patent employs a thin, flexible paraffin-based film as the closure assembly that seals the electrolyte while allowing significant deformation. This thin film structure prevents evaporation (maintaining shelf life) while its flexibility allows it to deform substantially under gas pressure, preserving the actuator's ability to generate large volume changes despite the reduced thickness compared to traditional thick membranes.
Solution Approach 2:
The closure assembly is constructed from composite materials including paraffin, olefin, and elastomer in specific weight ratios (paraffin: 5-50 wt%, olefin: 50-95 wt%, elastomer: 0.1-10 wt%). This composite structure combines the low water vapor permeability of paraffin with the elasticity and deformability of elastomers, achieving both evaporation prevention and sufficient mechanical compliance for actuator function.
2Adaptability or versatility
If common elastomer or plastic films are used for the closure assembly, then high elongation and elasticity are achieved, but water vapor permeability is high causing rapid evaporation
Solution Approach 1:
The closure assembly combines materials with complementary properties: paraffin provides low water vapor permeability (reducing evaporation), while elastomers provide high elongation and elasticity. The specific composition range (paraffin 5-50 wt%, elastomer 0.1-10 wt%) optimizes both the barrier function against water vapor and the mechanical deformability required for actuator operation.
Solution Approach 2:
The closure assembly has non-uniform composition with different material concentrations in different regions. The paraffin content varies (5-50 wt%) and elastomer content varies (0.1-10 wt%) to create local properties that balance evaporation resistance in some areas with flexibility and elasticity in others, allowing the film to simultaneously prevent water vapor loss and deform under pressure.
3Loss of substance
If metallization is applied to reduce water vapor permeability, then evaporation is reduced, but cracks form during deformation and barrier function is compromised
Solution Approach 1:
Instead of using metallization, the patent changes the material parameters by employing organic polymer materials (paraffin and olefin) with inherently low water vapor permeability. These materials maintain their barrier function during deformation because they are flexible and crack-free, unlike rigid metallized layers. The compositional parameters (weight ratios of paraffin, olefin, and elastomer) are optimized to achieve both low permeability and high deformability without cracking.
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
The use of paraffin in the closure assembly reduces water vapor permeability and maintains the actuator's ability to generate large gas volumes, enhancing the shelf life and functionality of microfluidic systems by ensuring the actuator remains liquid-tight and gas-tight.
Implementation Method 1
a gas is generated in a liquid (e.g. water) via an electrochemical reaction
Implementation Method 2
a material or a combination of materials which consists at least partially of paraffin. Paraffin has a low water vapor permeation coefficient
Implementation Method 3
The deformable closure assembly is designed to be deformed upon activation of the activatable substance due to the change in pressure of the activatable substance
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
The invention relates to a fluidic actuator comprising a base arrangement (1, 10) having at least one cavity (6) formed therein, an activatable substance (20) inside the cavity (6), and a deformable closure arrangement. The activatable substance, for example, an electrolyte, can be at least partially converted by suitable activation and at the same time cause a pressure change in the cavity (6). The deformable closure arrangement (30; 4) serves to close the cavity (6). The deformable closure arrangement comprises a paraffin-containing element (30; 40) and upon activation of the activatable substance (20) can be deformed owing to the pressure change of the activatable substance. A corresponding production method comprises the following steps: preparing the base arrangement (1, 10); forming a cavity (6) open on at least one side in the base arrangement (1, 10); and closing the cavity with the deformable closure arrangement (30; 4) that comprises a paraffin-containing element (30; 40).