Porous Membrane Fabrication via Mixed Solvent Phase Separation
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Solution Overview
Problem
Current methods for creating porous membranes with regular nanometer-sized pores are limited, as existing techniques like track-etching and self-assembly of block co-polymers face issues with scalability, cost, and long-term stability, while conventional methods like NIPS and TIPS result in dense surface layers with low porosity.
Innovation Solution
A novel method involving mixed solvents phase separation (MSPS) is used, where a solvent and non-solvent form a critical solution temperature system, allowing for the formation of highly porous membranes with interconnected surface and bulk porosity by adjusting temperatures to induce phase separation, enabling the creation of membranes with uniform nanometer-sized pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods like NIPS and TIPS are used to prepare polymeric membranes, then large-scale production is achieved, but the surface layer becomes dense with very low porosity
Solution Approach 1:
The invention changes the temperature parameter during the phase separation process. By controlling the temperature profile (cooling rate, temperature gradients), the method induces spinodal decomposition that creates regular nanometer-sized pores on the surface while maintaining bulk porosity, thereby achieving both high surface porosity and scalability
Solution Approach 2:
The invention utilizes temperature-induced phase separation (TIPS) with spinodal decomposition. By controlling the phase transition of the polymer solution during cooling, regular nanometer pores are formed on the surface through spinodal decomposition, while the bulk maintains high porosity, resolving the contradiction between surface porosity and scalable production
2Manufacturing precision
If track-etching by high-energy particles is used to generate regular surface pores in the nanometer pore size range, then regular nanometer pores are achieved, but surface porosity becomes very low
Solution Approach 1:
The invention replaces the track-etching process with temperature-induced phase separation. By controlling the cooling rate and temperature gradients during phase separation, regular nanometer pores are formed through spinodal decomposition, achieving both manufacturing precision and high surface porosity without the limitations of particle etching
3Manufacturing precision
If self-assembly of block co-polymers is used to produce perpendicular isopores on the membrane surface area, then regular surface pores are achieved, but the cost becomes very expensive
Solution Approach 1:
The invention changes from using expensive block co-polymers to using conventional homopolymers. By adjusting the temperature parameters during phase separation, regular nanometer pores are formed through spinodal decomposition, achieving the same manufacturing precision at much lower material cost
Solution Approach 2:
The invention replaces expensive block co-polymers with conventional, inexpensive homopolymers. The phase separation process creates the desired pore structure without requiring specialized expensive materials, making the process economically viable for large-scale applications
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 MSPS method produces membranes with high water permeance and efficient molecular sieving capabilities, overcoming the limitations of existing techniques by achieving high porosity and uniform pore sizes, and can be applied to various polymers, including PVDF and cellulose acetate, enhancing membrane flux and anti-fouling performance.
Implementation Method 1
adjusting the temperature to a second temperature sufficient to induce phase separation of the solvent and non-solvent and form a porous membrane
Data Source
AI summary
Embodiments of the present disclosure describe a method of making a membrane comprising contacting one or more membrane materials, a solvent, and a non-solvent at a first temperature sufficient to form a homogenous solution; casting the homogenous solution at about the first temperature; and adjusting the temperature to a second temperature sufficient to induce phase separation of the solvent and non-solvent and form a porous membrane.