Microtubes with Complex Cross Section Fabricated by C-Shaped Bessel Laser Beam for Mimicking Stomata That Opens and Closes Rapidly

This article presents a new method for fabricating complex cross-sectional microtubes with a high aspect ratio at micro/nanoscale. The microtubes are directly written in a photoresist using a femtosecond pulsed laser combined with a spatial light modulator (SLM). A new method for generating a C-shaped Bessel beam by modifying the Bessel beams with a SLM is reported for the first time. Using this gap-ring-shaped light field, microtubes with special cross section (trefoil-shaped, clover-shaped, spiral, etc.) have been first achieved through two-photo polymerization rapidly. The microtube wall can reach about 800 nm and the diameter of the gap-ring structure is only a few micrometers. As a demonstration, artificial stomata were manufactured with the same size as actual plants stomata consisting of gap-ring microtubes. This artificial stomata can mimic the function of the real stomata with rapid opening and closing, demonstrating its ability to trap and release microparticles regulated by rinse solvent.