Liquid bridge inspired 3D mesh-like nanocellulose aerogel cross-linked by “spot welding”

In recent years, aerogels based on cellulose nanofibers have attracted much attention. Cellulose nanofibers are prone to be tightly packed by the growth of large ice crystals during the general freezing process, which undoubtedly weakens the nanoscale effects. The original three-dimensional (3 D) mesh-like arrangement of nanofibers could be effectively retained by rapid freezing at ultra-low temperature. However, mesh-like aerogel exhibits poor structural stability due to the weaker interaction between the fibers. Inspired by the liquid bridge, a spot-welded cross-linked 3 D mesh-like bacterial cellulose (BC) aerogel is reported in this study. Polysiloxane particles are applied to construct spot-welded crosslinks at key stress points such as contact points or intersections of fibers. The flowing polysiloxane particles are able to wet and adhere the BC nanofiber bundles, emerging a contact angle of approximately 33°. The force analysis shows that the polysiloxane particles could spontaneously move to the contact points or the intersections between the nanofibers. And the shape of the welding spots varies with the number of fiber bundles and the intersection angle, thus building a variety of liquid bridges with varying shapes. Compared with the traditional honeycomb-like aerogel, the 3 D mesh-like BC aerogel delivers a higher specific surface area and more prominent hydrophilicity. And benefited from the uneven distribution of cross-linked sites, the size effect of the nanofibers and the surface chemistry of cellulose is preserved to a greater extent. Compared with the traditional honeycomb aerogel, the spot-welded cross-linked 3 D mesh-like BC aerogel exhibited more promising prospects in the fields of dye adsorption, emulsion separation and thermal insulation.