With the help of LightFab GmbH, Bartels Mikrotechnik GmbH, and Miltenyi Biotec GmbH, engineers at Fraunhofer Institute for Laser Technology ILT are currently building a 3D printer that combines DLP (digital light processor) and MPP (multiphoton polymerization) 3D printing technologies. The project is called HoPro-3D, short for “High Productivity and Detail in Additive Manufacturing through the Combination of UV Polymerization and Multi-Photon Polymerization.”
The HoPro-3D project, which is funded by the European Union and the state of North Rhine-Westphalia, seeks to bridge the gap between fast 3D printing and ultra-precise 3D printing. The biggest drawback to MPP 3D printers with submicron resolution is their speed; because they use pulses from a low-power laser to generate a single UV photon, they cure only a voxel (the 3D equivalent of a pixel) of material at a time, limiting their maximum build rate to about 10 μm³ (cubic microns) per second. DLP, on the other hand, is one of the fastest methods of 3D printing with build rates in excess of 1 mm³, even while maintaining a resolution of 10 μm. For comparison, the resolution of MPP 3D printing is 100 nm (nanometers), 1,000 times higher than the 10 μm of DLP 3D printing.
Putting both of those technologies into a 3D printer would allow it to quickly fabricate larger solids that have submicron details. For instance, implantable biomedical devices with micromechanical and microfluidic systems could be 3D printed. Even optical function elements like lens and prisms could be integrated into objects. By combining this technology with the 3D printed microstructures controlled by light, light-based circuits could be 3D printed onto bigger components.
“The advantage lies in the interplay between the two procedures: Depending on the need, we intend to switch between the exposure systems in the process,” explains Dr. Martin Wehner, HoPro-3D project manager at Fraunhofer ILT. “The challenge we face is in process control. The concept has been developed, currently an appropriate machine is being built.” They’re developing control software that will independently decide which printing module to use based on the size of the feature being 3D printed, freely swapping back and forth between macro and micro 3D printing.
Their system is equipped with high-performance LEDs emitting at 365 nm wavelength and a DLP chip with HD resolution for lithography; the MPP module uses a femtosecond laser with a fast scanner and microscope optics. It is a ‘best of both worlds’ 3D printer. The HoPro-3D project will run for three years, having begun in November of 2018, by which time it’s likely they’ll have a marketable machine.