Freestanding Ultrathin Graphene Membranes via Direct CVD Growth
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Solution Overview
Problem
Current methods for producing graphene membranes for nanopore-based applications require transfer processes that can degrade the membranes, introduce defects, and lack scalability for large-scale production of intact, ion-impermeable freestanding membranes with precise nanopore introduction.
Innovation Solution
A method for fabricating freestanding, ultrathin graphene membranes directly on sub-micrometer apertures using chemical vapor deposition, avoiding transfer and enabling precise control of membrane thickness and nanopore creation, with stabilization techniques to maintain membrane integrity and ion-impermeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transfer processes are used to produce graphene membranes, then graphene can be obtained on appropriate substrates, but the membrane quality degrades with wrinkles, cracks, and contamination
Solution Approach 1:
The patent removes the transfer step entirely from the graphene membrane production process. Graphene is grown directly on the final substrate (such as silicon nitride or sapphire) using CVD, eliminating the intermediate transfer process that causes wrinkles, cracks, and contamination. This extraction of the harmful transfer step resolves the contradiction between ease of manufacture and membrane quality.
Solution Approach 2:
Instead of growing graphene on a sacrificial layer and then transferring it to the final substrate (conventional approach), the patent inverts the sequence by growing graphene directly on the final substrate from the beginning. This inversion eliminates the transfer process and its associated defects, simultaneously maintaining manufacturing feasibility while improving membrane quality.
2Ease of operation
If transfer-free approach is used on larger apertures, then freestanding graphene membranes can be produced, but ionic permeability studies are limited and scalability remains unaddressed
Solution Approach 1:
The patent develops a universal CVD growth platform that can produce graphene membranes on various substrates (silicon nitride, sapphire, silicon oxide) with different aperture sizes. The same direct-growth methodology scales from single membranes to arrays of membranes, enabling both ease of operation for individual membrane fabrication and high productivity through parallel production of multiple membranes on a single substrate.
Solution Approach 2:
The patent transitions from producing single isolated graphene membranes to growing graphene across two-dimensional arrays of apertures on a single substrate. This dimensional expansion enables simultaneous production of multiple membranes, addressing scalability while maintaining the simplicity of the direct-growth approach for each individual membrane.
3Reliability
If silicon-based membranes are used, then dielectric properties are achieved, but membrane thickness is limited to ~5-10 nm due to structural and chemical susceptibility to damage
Solution Approach 1:
The patent creates composite structures where graphene (a two-dimensional carbon material with exceptional mechanical strength and chemical stability) is grown directly on dielectric substrates such as silicon nitride, sapphire, or silicon oxide. The graphene layer provides the ultrathin, mechanically robust barrier, while the substrate provides dielectric properties. This composite approach enables thicknesses below 5 nm while maintaining both dielectric functionality and resistance to damage during nanopore fabrication and operation.
Solution Approach 2:
The patent applies graphene specifically at the locations where ultrathin, damage-resistant membranes are needed (covering the apertures), while the substrate provides dielectric properties in regions where electrical insulation is required. This localized application of graphene's superior mechanical properties allows the membrane to be thinner than conventional silicon-based membranes while maintaining overall device reliability through the combination of materials with complementary properties.
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 approach yields high-yield, crack-free, and intact graphene membranes with precise nanopore sizes, enhancing their use in DNA sequencing and water desalination by maintaining membrane integrity and ion-impermeability, while allowing for scalable production.
Implementation Method 1
A method for fabricating freestanding, ultrathin graphene membranes directly on sub-micrometer apertures using chemical vapor deposition
Data Source
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AI summary
Devices contain freestanding, ultra thin (< 10 nm thick) membranes and methods of making such devices. Methods of using devices contain freestanding ultra thin membranes for determining the sequence of a polynucleotide and for desalination of aqueous solutions. A device containing: a substrate having an upper surface, a lower surface, and an aperture, the aperture having one or more walls connecting the upper and lower surfaces and forming a well; and a membrane attached to the lower surface of the substrate and forming a floor of the well, the membrane having a thickness of less than 10 nm. The electrical conductance across the membrane is less than 1 nS/?m2.