3D Printed Microstructures Made Easy

Frederik Mayer’s invention is smaller than a 1-cent coin – and that’s exactly what makes it so interesting. It is a round, stainless steel chamber that’s 1 cm in diameter and 100 micrometers high, which equates to a hundredth of a centimeter. Mayer is a PhD student at the Institute of Applied Physics at Karlsruhe Institute of Technology (KIT). In collaboration with ZEISS, he has developed a special so-called microfluidic chamber. It can handle different liquids in an extremely small space and can be integrated into a 3D laser lithography system. This printer produces the finest 3D structures in the micro- and nanometer range. It’s suitable for producing optical microlenses that are built into the smallest of medical devices, as well as for artificial scaffolds for cell structures. Mayer uses it to print fluorescent structures in several colors, which are then used as security features on banknotes, documents and branded products like spare parts for cars and even jewelry, to prevent counterfeiting. The structures will either be printed on the product itself, or on a security label.

At the KIT optics lab, you can hear the sound of ventilators humming; the windows have been darkened and the room is bathed in yellow light. Sensitive materials like the photoresists used here must not be exposed to white light. Mayer shows us a cover glass featuring printed structures; it’s balanced on the tip of his index finger. But, the fine lines cannot be seen with the naked eye. Every structure is around 50 micrometers high and has a side length of approximately 100 micrometers. “Its height is roughly equal to the thickness of a human hair,” he says. Mayer, who’s casually dressed in a light-blue shirt and a pair of jeans, is very good at explaining things. His explanations are purposely not peppered with jargon as he believes it’s essential for people who aren’t seasoned physicists to be able to understand his research.

The laser lithography system for which Mayer designed the chamber was produced by Nanoscribe, a KIT spin-off. ZEISS offered the startup its technology and advice from day one and acquired shares in the new company in September 2008. The apparatus that conveys the liquids to the chamber consists of an electronic pressure regulator, seven tubes for the different photoresists and development fluids, and a star-shaped selection valve. All the components are connected to each other via tubes and cables, and the processes are controlled by software. “The tubes containing the photoresist are overpressurized,” says Mayer. The selection valve is only opened for one photoresist, which is conveyed to the chamber. Then the laser comes into play: “The photoresist causes the laser focus to move in three dimensions, and it hardens at the laser’s focal point.”