nanomembranes

Nanomembranes are ultrathin films, typically a few nanometers to hundreds of nanometers thick, that act as selective barriers. They can be freestanding or supported and are valued for high surface area and unique transport properties that arise from extreme thinness.

Materials range from two-dimensional crystals such as graphene, MoS2, and hexagonal boron nitride to amorphous oxides like silicon oxide or nitrides, and from inorganic to polymeric films. Porous versions incorporate nanopores to enable size-based separation. The combination of material choice, thickness, and porosity determines permeability and selectivity.

Fabrication methods include thinning down bulk films by etching, exfoliating layered materials, and vapor- or solution-based deposition to form ultrathin films. Freestanding nanomembranes are released from substrates, and nanoporous variants are patterned by lithography or drilling. Layering and interfacial assembly further tailor properties.

Transport through nanomembranes is governed by mechanisms such as solution-diffusion, molecular sieving, or Knudsen flow, depending on material and pore structure. They offer high permeance and tunable selectivity, with performance adjustable through chemical functionalization and stacking of multiple layers.

Applications span water purification and desalination, gas separation, energy devices (batteries and supercapacitors), sensing, flexible electronics, and biomedical uses including controlled release and tissue engineering scaffolds. They also enable microfluidics and optoelectronic components.

Challenges include scalable, defect-free manufacturing, uniform thickness control, fouling, and integration with devices, along with cost and long-term stability concerns. Ongoing research aims to expand materials, architectures, and scalable production methods to improve performance and practicality.