New error compensation method for precise 3D printing

Two-photon polymerisation (TPP) 3D printing is an important manufacturing technique that enables advancements in the development and manufacture of small and intricate structures like miniature optical components. However, in the field of micro-optics, errors in the nanometre range can have significant consequences — it is therefore important to compensate for the systemic errors in the printing process.

Research published in the Journal of Optical Microsystems has explored the challenge of correcting tilt and curvature errors in TPP printing. These errors stem from inherent imperfections in the optomechanics of any printer. Conventionally, the established method for error correction involves using costly surface metrology tools, such as confocal microscopes or scanning electron microscopes. While effective, these techniques can be expensive for some laboratories.

Researchers from Bonn-Rhein-Sieg University of Applied Sciences in Germany have introduced a simplified optical setup for measuring tilt and curvature errors. The core idea was to print an optical structure without compensating for the errors, subsequently observing the effect of such imperfections on the image produced when illuminating the structure with a laser. A computer algorithm was then used to reconstruct the errors, enabling compensation in subsequent prints. A similar method is already used to verify dimensions of small structures in semiconductor manufacturing.

One of the researchers, Elias Ellingen, said the team tested the functionality of the method with structures deliberately engineered to exhibit defined errors. “We also conducted a compensation procedure on one of our print sets and compared the image of optical elements printed with compensation to that of the uncompensated system,” Ellingen said.

The researchers also conducted a compensation procedure on one of the print sets and compared the image of optical elements printed with compensation to that of the uncompensated system. The test showed a reconstruction of tilt and curvature errors is possible. The associated uncertainties are lower than the expected errors for the researchers’ print set, with a precision of 1.1 mRad for tilt errors. When the researchers compared the images of the uncompensated print to those of the compensated print, they observed a reduction in noise, further emphasising the improvement their approach brings to the quality of printed microstructures.

The research findings have introduced a cost-effective method for correcting tilt and curvature errors in TPP printing. The method offers a practical solution for labs and facilities that may find traditional error correction methods prohibitively expensive.

Image credit: iStock.com/Grafner