Do the laser-printed 3D-structures withstand the X-ray synchrotron radiation beam?

Abstract

The radiation stability of polymer objects fabricated by direct laser writing is studied. Two groups of 6 cubes ($50\times 50\times 50\mu$m${}^3$) were printed on a common silicon substrate, with laser power and slicing step uniformly varied from cube to cube in both groups. One group was X-rayed in the synchrotron radiation beam (12 keV, $10^{10}$ photons/mm${}^2$/s, $10^{13}$ photons per each cube), another kept non-irradiated for the reference. The air kerma ($\sim$2000 kGy) near cubes and the radiation dose absorbed in each cube ($\sim$1.4 kGy) were calculated. The latter was verified using thermoluminescent detectors. The radiation effects were observed with a scanning electron microscope and with an optical 3D surface profilometer, also evaluated by Raman spectroscopy. An enhanced cross-linking in the polymer is the primary effect which may draw together the neighboring printed layers thus distorting the laser-printed object; distortions can be avoided by making objects with proper laser power and slicing step.