# Fabrication of Free-Standing Gelatin Thin Films via the Gelation and Drying of Liquid Foam Films

## TL;DR

Researchers developed stable, ultrathin gelatin films using a simple drying and gelation process, suitable for nanoseparation applications.

## Contribution

A novel method for fabricating mechanically stable, free-standing gelatin thin films via liquid foam film gelation and drying.

## Key findings

- Gelatin thin films with thicknesses from nanometers to micrometers were successfully fabricated.
- Cross-linked gelatin films achieved 100% rejection of 5 and 2 nm gold colloids and specific dyes.
- The films are more mechanically stable than surfactant films and suitable for nanoseparation membranes.

## Abstract

Ultrathin foam films
can be prepared from numerous compounds under
a wide range of conditions but have a narrow application scope because
of their small size, susceptibility to rupture, and other drawbacks
arising from low mechanical stability of the bilayer structure. To
address this gap, we herein prepared ultrathin foam films of gelatin
using a facile method via drying thin liquid films of aqueous gelatin
solutions and the gelation. Their thickness ranges between nanometers
to micrometers in response to changes in process parameters. The effects
of various process parameters, including the solution concentration,
frame size, drying temperature, and humidity, were systematically
investigated. In addition to surface tension affecting the initial
formation of the liquid film, the high viscosity of the solutions
stabilized the film and caused gelation. The key formation factor
of the dried foam films was explained by the sol–gel behavior
of aqueous gelatin solutions. The prepared films are mechanically
more stable than surfactant films and therefore have a wide range
of potential applications as separation membranes. Glutaraldehyde
cross-linking makes these films water-insoluble and therefore suitable
for use as a nanoseparation membrane. Fully cross-linked gelatin thin
films showed a rejection performance of 100% for 5 and 2 nm gold colloids,
Direct Yellow 1, and potassium ferricyanide.