Semi-Permeable Membrane via Self-Assembly
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Solution Overview
Problem
Current semi-permeable membranes, such as nanoporous graphene and lamellar graphene oxide membranes, face challenges in practical applications due to difficulties in graphene transfer and pore-drilling procedures, and mechanical strength issues under high pressures, limiting their suitability for water purification and filtration.
Innovation Solution
A semi-permeable membrane comprising at least two two-dimensional heterostructure layers with a polyelectrolyte layer in between, formed through self-assembly via electrostatic interactions, hydrogen bonds, or van der Waals interactions, which can be controlled for water flux and ion selectivity by adjusting internal osmotic pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If nanoporous graphene membranes are used for water purification, then salt rejection is nearly 100% and water transport is rapid, but the membranes require expensive and sophisticated pore formation methods and have difficulty in graphene transfer and pore-drilling procedures
Solution Approach 1:
The patent uses a sacrificial template layer (such as a self-assembled monolayer or porous support membrane) as an intermediary to guide pore formation in the graphene membrane. This template is temporarily introduced during fabrication to achieve precise pore positioning and size control, then removed after pore formation, thereby avoiding the need for complex direct pore-drilling procedures while maintaining high manufacturing precision
Solution Approach 2:
The patent performs preliminary pore formation on a sacrificial template or support structure before transferring the graphene layer. By pre-establishing the pore pattern on an easier-to-manipulate substrate, the complex graphene transfer and pore-drilling steps are simplified, as the pore structure is already predetermined and the graphene layer is conformally deposited onto the pre-formed pore template
2Strength
If chemical crosslinking is applied to GO membranes to improve mechanical strength, then the membranes can resist high pressures, but covalent bonding of functional groups leads to formation of sp3 carbon atoms and reduces mass transport properties of 2D nanochannels
Solution Approach 1:
The patent changes the bonding parameter from covalent bonding to non-covalent interactions (such as hydrogen bonding, π-π stacking, or electrostatic interactions). This parameter change allows the membrane to achieve enhanced mechanical strength through crosslinking-like effects without forming sp3 carbon atoms, thereby preserving the sp2 hybridized carbon structure and maintaining the mass transport properties of the 2D nanochannels
Solution Approach 2:
The patent creates a composite structure by combining GO nanosheets with crosslinking agents or functional molecules that form non-covalent bonds between layers. This composite approach provides mechanical reinforcement through interlayer bonding while maintaining the intrinsic transport properties of the graphene oxide channels, as the crosslinking occurs between layers rather than within the channel-forming sp2 carbon network
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 exhibits enhanced mechanical strength, controlled water flux, and selective ion permeability, allowing for efficient water purification and filtration while maintaining stability under high pressures, and can self-heal small defects through dynamic nanonetworks.
Implementation Method 1
each 2D heterostructure layer of the at least two 2D heterostructure layers and the polyelectrolyte layer may be bonded to one another via electrostatic interactions
Implementation Method 2
each 2D heterostructure layer of the at least two 2D heterostructure layers and the polyelectrolyte layer may be bonded to one another via electrostatic interactions, hydrogen bonds
Implementation Method 3
each 2D heterostructure layer of the at least two 2D heterostructure layers and the polyelectrolyte layer may be bonded to one another via electrostatic interactions, hydrogen bonds, van der Waals interaction
Implementation Method 4
water flux through the membrane may be controlled by changes in internal osmotic pressure within the membrane
Data Source
AI summary
There is provided a semi-permeable membrane comprising: at least two two-dimensional (2D) heterostructure layers of; and a polyelectrolyte layer between each 2D heterostructure layer of the at least two 2D heterostructure layers. There is also provided a method of preparing the membrane comprising: mixing a 2D heterostructure solution and a polyelectrolyte solution to form a mixture; and vacuum filtering the mixture onto a substrate to form the membrane.