## 4 Conclusions  
The real-time photorheometry study revealed the higher rate of photocross-linking of pure acrylated epoxidized soybean oil than that of its mixture with vanillin dimethacrylate or vanillin diacrylate without a photoinitiator and solvent. Novel plant-derived photocross-linked polymers were synthesized from acrylate epoxidized soybean oil and its mixtures with vanillin dimethacrylate. It was determined that the addition of vanillin dimethacrylate reduced the rate of photocross-linking and the values of the glass transition temperature, thermal decomposition temperature and compressive modulus. The formation of more linear and/or branched macromolecules considered the vanillin dimethacrylate effect as a plasticizer for acrylate epoxidized soybean oil in photocross-linking without  
Figure 7: The SEM images of RB and 3D microporous woodpile structures: (**a**) a side view of RB at the angle of 45 degrees and 1800 magnification. The applied power \(P\) to produce bridges was 0.6 mW (2 TW/cm\({}^{2}\)), scan velocity \(v\) varied from 0.1 mm/s to 0.5 mm/s every 0.1 mm/s; (**b**) a top view of the other RB at 4000 magnification. \(P=0.6\) mW (2 TW/cm\({}^{2}\)), \(v=\) 2–6 mm/s every 1 mm/s; (**c**) \(75\times 75\) μm woodpile structures with a 30 μm period, \(v=5\) mm/s, the scale at the top of the image demonstrates the applied \(I\); (**d**) a 1065 \(\times\) 1065 μm woodpile with a 75 μm period, \(v=5\) mm/s, \(P=0.4\) mW (1.3 TW/cm\({}^{2}\)). (**a**–d) The structures were fabricated out of the resin AESO/VDMI; (**e**) \(75\times 75\) μm woodpile structures with a 30 μm period, \(v=5\) mm/s. Scale on the left of image shows the distance \(d_{xy}\) between neighboring scans; (**f**) a 1095 \(\times\) 1095 μm woodpile with 120 μm period, \(v=5\) mm/s, \(P=0.6\) mW (2 TW/cm\({}^{2}\)). (**e**,**f**) structures were fabricated out of AESO.  
a photoinitiator. It was experimentally demonstrated that the homopolymer of acrylated epoxidized soybean oil and the copolymer of acrylated epoxidized soybean oil and vanillin dimethacrylate are suitable materials for rapid 3D microstructuring by the direct laser writing lithography technique. Spatial features of 1 \(\upmu\)m and a 6900 voxels/second throughput was achieved. Since the 3D cross-linking of the plant-derived materials was initiated using ultrafast laser inducing multiphoton absorption and avalanche ionization, it does not require the usage of any photoinitiator and opens a new pathway for green 3D \(\upmu\)-printing as a flexible tool for rapid prototyping or advanced additive manufacturing.  
[PERSON] and [PERSON] conceived and designed the experiments, analyzed the data; [PERSON] performed all experiments and characterizations except the E.S. part; [PERSON] performed the direct laser writing 3D lithography experiments and characterization of microstructures; both [PERSON] and [PERSON] conceived the experimental plan and did the interpretation of the laser 3D printing results; all of the Authors contributed to writing the manuscript.  
Financial support from the Research Council of Lithuania (project No. S-LAT-17-2) and EU ERDF, through the INTERREG BSR Programme, (ECOLABNET project (#R077)) are gratefully acknowledged.  
The authors declare no conflict of interest.