Peeling off the 2D ionogel membrane. Photo: The University of Texas at Austin/Cockrell School of Engineering.
Peeling off the 2D ionogel membrane. Photo: The University of Texas at Austin/Cockrell School of Engineering.

A common chemical reaction that most people have seen first-hand has inspired a new way to make a flexible gel film that could lead to innovations in sensors, batteries, robotics and more.

A research team led by engineers at the University of Texas at Austin has developed what they call a ‘dip-and-peel’ strategy for the simple and rapid fabrication of two-dimensional (2D) ionogel membranes. This involves dipping sustainable biomass materials into certain solvents, which causes the molecules making up the materials to arrange themselves into functional thin films at the edge of the material. These thin films can easily be removed using a simple set of tweezers.

According to the researchers, this strategy was inspired by what happens to milk at elevated temperatures. “In the milk-skin effect, a film forms at the outer layer of milk when it is heated,” said Guihua Yu, a professor in the Cockrell School of Engineering’s Walker Department of Mechanical Engineering and Texas Materials Institute who focuses on materials science. "We were inspired by this phenomena and explored it in different materials to produce multifunctional gel membranes that are easy to separate." Yu and his team report this work in a paper in Nature Synthesis.

These gels are made up of a polymer network surrounded by ionic liquid. They are similar to hydrogels in structure, where water is the liquid element. But ionogels feature a less rigid structure, giving the ions more room to move around.

Because of this, ionogels are highly conductive and very sensitive. They show great potential as sensors, possibly as part of wearable electronics that could more accurately track motion, monitor heartbeat and perform other aspects of health monitoring. They could even serve as the electrolyte in solid-state batteries, shuttling ions back and forth to facilitate charging and discharging.

The major innovation in this research is the novel fabrication process, and it can work on many different materials. The process can be reproduced hundreds or thousands of times at high speed and low cost. And the films can be easily manipulated to be as thick or thin as needed, as well as shaped or coated onto other materials.

“This simple yet effective solvent-induced self-assembly method really allows rapid and scalable production of 2D functional polymer films from different sustainable biomass materials, including cellulose, chitosan, silk fibroin, guar gum and more," said Nancy (Youhong) Guo, a former graduate student in Yu's lab and now a postdoctoral researcher at Massachusetts Institute of Technology (MIT), and one of the lead authors of the paper.

Yu said he hopes other researchers will pick up this technique and run with it for various technologies. Going forward, the research team will work to further optimize the mechanical properties of these films for more applications and advanced functionalities for next-generation technologies such as wearable electronics, smart robotics and artificial intelligence.

This story is adapted from material from the University of Texas at Austin, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.