Adaptive materials have long been the subject of research. Materials that change their shape or structure based on the type of external stimuli applied. Using this idea, scientists in Germany have developed an ultra-thin form of paper that can adjust its firmness in response to an electric current, which would be the external stimuli in this case. The research was published in the journal Nature Communications.
The material can transition between a firm state and a soft state via an electric switch. This kind of material could be used for a number of things, especially shock dampeners, adaptive damping material that hardens when a heavy load is applied to them.
This material was developed in Germany, by scientists at Johannes Gutenberg University Mainz and the University of Freiburg. They used cellulose nanofibrils as the starting point for their research. These nanofibrils can be extracted from the cell walls of trees. The characteristic of these nanofibrils is that they are finer than regular microfibers that are used to make regular paper. Thus, making it possible to create a transparent sheet of glass like paper, that is also firm and strong.
At a molecular level, the material consists of cross-linking points that can break apart when subject to heat. This is where the electric switch comes into play. By subjecting the wafer to an electric current, the cross-links break apart. The more they break, the softer the material becomes. This process reverses when the material cools or if the electric supply is cut off.
The research team is led by Professor Andreas Walther, who said that “All the materials around us are not very changeable, they do not easily switch from stiff to elastic and vice versa. Here, with the help of electricity, we can do that in a simple and elegant way”. He further details his plans of internalizing the electric current supply so the material does not depend on external equipment and manual intervention.
Walther said that “Now we still have to flip the switch ourselves, but our dream would be for the material system to be able to accomplish this on its own”.