This ink has it all: nanometer thin gold threads are the secret that you can build flexible displays, which do not break down even after 450 bending operations. Saarbrücken researchers have developed the technology for that with flexible touch screens the conductivity caused by the mechanical stress does not suffer.
The effect is amazing. The glass is perfectly transparent. Tiny light is lit all of a sudden right: LEDs made of a transparent material. They are supplied with current flowing through lives also invisible traces. The manufacturers only on a rigid surface like window glass to create this feat. Now succeeds on flexible surfaces. Even invisible electronic circuits are possible.
Nanometer-thin Nano-Technology gold thread
First researchers succeeded at the Leibniz Institute for new materials (INM) in Saarbrücken, to leave traces to nanometer-thin gold thread on flexible materials. Because they are extremely thin with less than a thousandth of a millimeter, you can’t see them. It managed a team led by Tobias Kraus with a self-organizing Nano ink and a stamp printing process.
In the first step, the surface is coated with ink throughout. A stamp that has the desired structure, brings the gold thread and the ligands surrounding them, ensuring their mobility in the form. “The Nano threads follow the structures of the stamp, because they are so thin and agile,” Kraus says.
Nano threads are very good conductors of electricity
“Drying the each thread through self-organization form larger, defined bundles that are interwoven and form the future grid”, so the INM scientists. The ligand is driven out by light heating. The threads are very good conductors of electricity. Their structure can be influenced by changing the quantities of gold thread.
The Saarbrücker researchers see especially touch-sensitive flexible displays, so touch screens as field of application for their process. Tests have shown that the structured traces much better are bending tests made of gold threads as indium tin oxide (ITO), a today use semiconductor, which is completely transparent in visible light. After 450 bending tests, the conductivity of nano threads of gold had decreased to just 5.6%.
Search for cheaper metal threads
“With our results we have demonstrated that the combination of self-organization of gold opens up new procedures for transparent, conductive materials with stamp. We want to transfer this basic principle with further investigations also on other metals”, says Kraus. Even if the amount of gold in the transparent conductors are tiny, the procedure for the use of less valuable metals may get cheaper still is.
Other scientists working on displays of the future need not touch to the program control. Instead it is sufficient in close to the surface, to tap into the air or wipe. The Touchless screen, so the contact-free-to-use monitor that is feasible.