Metal-assisted chemical etching for controllable fabrication of silicon nanochannels

Silicon nanochannels possess adjustable structural characteristics and excellent mechanical properties, and have great application potential in nanoelectromechanical systems, seawater desalination, and nanoreactors. However, achieving controllable synthesis and precise structural modulation remains highly challenging. Metal-assisted chemical etching (MACE), with its advantages of simple operation and low cost, has been widely used in the fabrication of silicon nanochannels. This study systematically investigates the morphological regulation mechanism of silicon nanochannels prepared via MACE, with a focus on analyzing the influence of etching solution composition, gold nanoparticle microstructure, and reaction time on the formation of helical structures. By combining thermomechanical molding for replicating nanochannel structures with electron microscopy characterization, comprehensive morphological analysis was achieved. The results indicate that an etching solution ratio of HF:H₂O₂:H₂O = 6:4:5 (v/v/v) yields helical nanochannels with greater length and higher yield. Increasing the HF proportion promotes the formation of helical structures; however, excessively high HF concentration leads to severe lateral etching, inhibiting deep channel propagation. The study further reveals an externally-driven mechanism for helical structure formation: the hydrogen bubbles generated during the reaction and the flow of the etching solution exert thrust on the nanoparticles, causing them to move and carve helical pathways.