Nanotube-Embedded Membranes for Selective Permeability
Solution Overview
Problem
Conventional reverse osmosis membranes using the solution-diffusion mechanism have low flux and high salt rejection, but modifications to increase flux often compromise purity, and traditional nanotube-based membranes are limited by alignment requirements and high production costs.
Innovation Solution
A membrane is fabricated by embedding nanotubes in a polymeric matrix through interfacial polymerization of polymerizable species in liquid phases, allowing selective molecular passage without alignment constraints, enhancing both selectivity and permeability, and suitable for large-scale, cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nanotubes are aligned vertically on a silicon chip surface, then molecular transport selectivity is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
Instead of aligning nanotubes vertically on a flat surface as in prior art, this invention embeds nanotubes in random orientations within a three-dimensional porous polymeric matrix. The continuous barrier layer surrounds and seals the nanotubes, allowing molecular selection through size exclusion regardless of nanotube orientation. This inversion of the traditional approach eliminates the need for precise alignment while maintaining selectivity.
Solution Approach 2:
The invention creates a composite structure combining nanotubes embedded in a polymeric matrix with a continuous barrier layer. This composite material approach allows the nanotubes to provide selective transport pathways while the polymeric matrix provides structural support and random orientation accommodation, eliminating the need for complex alignment processes required in pure nanotube membranes.
2Ease of manufacture
If nanotubes are embedded in a polymeric matrix through interfacial polymerization, then production cost and scalability are improved, but control over nanotube orientation is lost
Solution Approach 1:
The invention changes the critical parameter from nanotube orientation to nanotube density and size distribution. By using interfacial polymerization to form a continuous barrier layer around randomly oriented nanotubes, the system achieves selective permeability through controlled nanotube inner diameters rather than through orientation control. This parameter shift enables scalable, cost-effective production while maintaining molecular weight cutoff control through nanotube size selection.
3Productivity
If conventional solution-diffusion membranes are used, then salt rejection is high, but water flux is low and purity is compromised when flux is increased
Solution Approach 1:
The invention replaces the dense polymeric structure of solution-diffusion membranes with a porous structure containing nanotube channels. These nanotubes provide well-defined pore sizes that enable size-exclusion-based separation, allowing water molecules to pass through at high rates while blocking larger salt ions. The porous nanotube network maintains high salt rejection while enabling significantly higher water flux compared to conventional dense membranes.
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 membrane achieves improved selectivity and permeability for reverse osmosis, desalination, and other filtration applications, with controlled molecular weight cutoff and reduced production costs, enabling high-throughput and high-volume use.
Implementation Method 1
nanotube channels themselves offer selectivity in molecular transport. Water molecules, for example, pass through nanotube channels at a significantly faster rate than salt ions or other species whose molecular size exceeds that of water
Implementation Method 2
a membrane containing nanotubes embedded in a polymeric matrix such that molecular species selectively pass through the nanotubes on a size-exclusion basis can be fabricated by polymerizing monomers or prepolymers, i.e., polymerizable species in general, from liquid media in which open-ended nanotubes are suspended
Implementation Method 3
The most common reverse osmosis membranes are those utilizing a solution-diffusion mechanism in which the species of interest (water in the case of desalination) both dissolves in and diffuses through the membrane material at a faster rate than other species in the feed fluid
Implementation Method 4
This invention resides in the field of membranes for reverse osmosis, with particular interest in the desalination of water
Data Source
AI summary
Membranes for filtration by size exclusion are formed from open-ended nanotubes embedded in a polymeric matrix. The matrix forms a layer whose thickness is substantially less than the average length of the nanotubes, allowing the nanotubes to be randomly oriented throughout the matrix while providing channels extending through the layer for the selective passage of molecular species or particles based on size.