Fig. 2: Schematic depiction of the different fabrication methods for freestanding or solid-supported BTX-gels.

a Method 1: Light-induced polymerization with 455 nm light results in the formation of a homogeneous gel. b Method 2: Curing the polymer with 365 nm light, which is absorbed by the BTX-MA monomer, induces a density gradient through the thickness of the gel with a higher degree of polymerization on the side closer to the light source. Cutting these gels into shapes with different aspect ratios gives rise to various 3D shapes. c Method 3: Polymerization with 455 nm light, but using a substrate functionalized with 3-MPS enables the covalent attachment of the gel to the substrate. Depending on the method used, chemical oxidation of the gels with CAN results either in isotropic swelling (a), uncurling or unwinding of 3D shapes (b) or swelling mostly in the direction perpendicular to the substrate (c).