Miniature components from 3D printer.

Although the ancient Greek “nano” means “dwarf”, in the nano sector the dwarf would be a giant. In the technical realm, “nano” means ten to the power of negative nine, or one billionth. In addition, parts even smaller than this are possible, for example, the intricate shapes that come out of the NanoOne 3D printer from UpNano. To produce these, light particles are fired at the starting material. This is a process that plays out over a range of thousandths of a millimetre. So that the substrate can be precisely aligned here, three compact, high-performance motors from FAULHABER ensure the correct position.

The structures that UpNano produces in the 3D printer are so small that they are recognisable neither with the naked eye nor with a strong optical microscope. Only under a scanning electron microscope do the smallest printed structures become visible. They are a sort of “tiny sphere” or dust particle with a total diameter of just a fraction of a millimetre. The bars that make up the construct are 100 times thinner than a human hair. These structures are used, for example, in medical experiments as, among other things, a framework for living cells or as microfilters, microneedles or microlenses.

A castle on the tip of a pencil

UpNano is a spin-off of the Vienna University of Technology. Before the founders switched to free economy more than five years ago, they conducted research at the university in the field of 3D printing with high resolution. To demonstrate what is possible, they printed the model of a castle complete with multiple levels, oriels, ledges, archways, two spires and elegant columns – on the tip of a pencil. The columns were just 950

nanometres thick. The printer, which UpNano has since developed to market readiness and sells worldwide, goes even a step further: Structures smaller than 200 nanometres can be realised horizontally and smaller than 550 nanometres vertically.

The production of such miniaturised objects is possible thanks to so-called 2-photon lithography, which is based on a quantum effect between two light particles. They thereby trigger the solidification of the material, resulting in the formation of stable chains in the plastic molecules. “To get the decisive photon pairs across the finish line, we need to fire a massive number of light particles,” explains Peter Gruber, co-founder and CTO of UpNano. “This is because we need an enormous photon density with respect to both time and space to bring about the controlled polymerisation.”

An accurate laser makes it possible

The laser that supplies the photons operates with extremely short, high-intensity pulses. Moreover, the method allows for high accuracy, as Peter Gruber explains: “With other light-based 3D-printing methods, polymerisation is triggered along the entire beam path. As a result, production can only be performed in layers. With 2-photon lithography, we can focus them on a tiny point. This point can be moved freely through the material by our printer’s high-performance optics. This allows us to produce nearly any geometric structure.”

In addition to channels and other elements for microfluidics, such structures can also be used to create lenses that are printed on the end of individual glass fibres. Printing can even take place in existing microfluidic chips to add additional structures there. A special additional module also enables printing with biomaterial, which contains living cells. Polymerisation of the three-dimensional structures transpires only at the intended locations; the cells in the spaces in between remain intact. The constructs can be formed like a cell cluster in human tissue. In such an arrangement, they are used today for pharmaceutical tests without animal experiments.

Micro-endoscopes and artificial insemination

The customers of UpNano are, however, generally reticent to answer the question of exactly what they are producing with the devices. Many use them under strict secrecy. “We are aware of only a few concrete applications, such as in in-vitro fertilisation, where work is performed with individual egg cells, or for lenses in micro-endoscopes,” reports Peter Gruber. “Our customers are mainly in medical technology, the pharmaceutical industry and telecommunication. There are also more and more industries that are discovering the possibilities of miniaturised 3D printing for their own uses.”

The size scale of the objects that can be produced with a Nano One printer spans from less than 150 nanometres to more than 40 millimetres. Four lenses with different resolutions ensure maximum flexibility. The throughput of more than 450 cubic millimetres per hour is the basis for high productivity. Precision of the printing process is ensured not only by the high-quality laser optics but also by the precise alignment of the substrate. This is secured on a moveable support.

FAULHABER drives in the NanoOne devices

The name “Automatic Tilt Correction Insert” describes the function of this support: It corrects the tipping that is nearly impossible to avoid when inserting the print substrate in the printer. The alignment of the substrate can be changed on three axes (x, y and z) and thereby optimally positioned. “We achieve a flatness in the sub-micrometre range,” emphasises Peter Gruber. “This ensures that the precision of the laser optics actually finds its way into the print material. Furthermore, the relevant components are decoupled from the surrounding technology and the housing. As a result, the printer can simply stand on any stable table.”

The mechanical force for the precise positioning of the support is supplied by three precious metal-commutated DC gear motors with an integrated encoder of the 1512 … SR IE2-8 series from Faulhaber. The uniquely flat winding technology with three flat, self-supporting copper windings enables an extremely compact design with a diameter of 15 millimetres and a length of just 14.3 millimetres. Thanks to the high-performance rare earth magnets, the motor delivers an especially high drive torque.

In addition to the gearhead, an optical encoder is also integrated in the drive. “We selected the gearmotors as the optimum solution for our needs,” recalls Peter Gruber. “The suggestion to select the version with an encoder came from FAULHABER. Alignment thereby functions even more precisely and more smoothly. In relation to its small dimensions, the drive delivers enormous power. With its high precision, it contributes to the quality of the printing process of our NanoOne devices at a key point.”