How Small Can Manufacturing Go? Inside the World of Nano-Scale 3D Printing

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

The production of such miniaturized objects is possible thanks to 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 polymerization."

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, polymerization 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 fibers. 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.

Polymerization 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.

"We achieve a flatness in the sub-micrometer range," emphasizes 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-gearmotors with 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 millimeters and a length of just 14.3 millimeters. 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 the 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."

Where Nano-Scale Printing Is Being Used

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 fertilization, 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 in telecommunication. There are also more and more industries that are discovering the possibilities of miniaturized 3D printing for their own uses."