From precisely dimensioned spare parts to custom products, additive manufacturing methods are highly versatile – and at times virtually invisible. Even complex three-dimensional micro- and nano-structures can be fabricated using multi-photon polymerization (MPP). This high-resolution stereo lithography technology is based on photosensitive materials, such as photoresist varnishes, which are hardened by exposure to laser beams. The usable scale extends into the submicron range.

A well-known example: to celebrate the 25th anniversary of the fall of the Berlin Wall, scientists at Nanoscribe, a spinoff of the Karlsruhe Institute of Technology (KIT) , printed a model of the Brandenburg Gate at a scale of 1:26,000 – precisely 1 mm high and 2.5 mm long.

The printer is put to plenty of more practical uses for research and industry, in areas such as optics, medical technology and microsystem engineering (MEMS). It can produce not only tiny parts such as gear wheels or artificial substrates for cell growth, but also large objects with special properties.

By no means superficial

It used to take several steps to create surface properties such as high adhesion (gecko effect) or water shedding (lotus effect). Now, instead of applying special coatings after fabrication to obtain the necessary structures, they can be printed directly, in a single step and with greater precision, by means of multi-photon lithography. One goal is to develop medical implants with better compatibility. It currently takes a relatively long time to generate these fractal surfaces, but German and Spanish researchers are working on a faster method.

The Fraunhofer Institute IWS and TU Dresden are also jointly researching new methods for additive manufacturing, including selective laser beam melting, electron beam melting and 3D printing .

An extra touch for materials

For now, objects made entirely with 3D printing cannot provide all the desired properties, such as thermal strength or conductivity, due to the limitations of the powder and wire materials currently used. Mixing nanoparticles into the base materials could expand the range of materials suitable for photonic machining. According to a study by the University of Duisburg-Essen , this approach can be used to give objects specific magnetic or optical properties. The researchers claim that metals, ceramics and polymers can all be enriched with nanoparticles.

A broader selection of base materials would automatically open up new application areas. Functional lightweight construction, which is still struggling with high material and process costs, is one field that could benefit. Experts such as Martin Hillebrecht (Head of the Competence Center for Lightweight Structures, Materials and Technologies at Edag) see opportunities for high-volume production with additive manufacturing methods: "The degree of freedom offered by the development of toolless manufacturing will make this technology a hot future topic."

What are the practical applications of the various 3D printing methods? Visit the Digital Factory at HANNOVER MESSE to find out. The full spectrum of surface technology awaits you at SurfaceTechnology. Join experts from the scientific and research community to get a glimpse of the future at Research & Technology .