Dominik Laa (co-first author), Katharina Ehrmann (PI), Michael Göschl (co-first author) (Photo: tuwien.at)

Vienna University of Technology: Variable 3D printing produces materials with complex structures

A team of researchers led by Katharina Ehrmann from Vienna University of Technology (https://www.tuwien.at/) has developed new security codes that can be 3D printed and become visible when heated, but are otherwise hidden in the surrounding material. They also warn of unacceptable temperatures for sensitive goods such as medicines and food. Special inks are applied to a substrate and cured with light. This creates the planned object layer by layer.

Light and wavelengths

What is new about the technology from Vienna is that light with different wavelengths is used to structure the material. Sometimes this turns it into a crystal, sometimes it gives it an amorphous structure, or the molecules line up next to each other so that they look like tiny spaghetti. Depending on the structure that forms, the material is hard and brittle or soft and flexible at this point.

‘The optical properties can also vary greatly, from glass-like transparency to opaque white,’ says researcher Dominik Laa. For example, it changes under the influence of heat and reveals a security code or warning notice that is located under a layer that is normally opaque. Only heating makes it transparent like glass, they say.

The temperature must be right

If you want to make the security code visible, you have to get the temperature just right. If you don’t, the code cannot be made visible for a while – similar to a smartphone that cannot be used for a certain period of time once the wrong code has been entered three times in a row. Possible applications range from data storage and security to biomedical applications.