Direct Printing of 3D and Curvilinear Micrometer‐Sized Architectures into Solid Substrates with Sub‐micrometer Resolution

Micropatterned hydrogel stamps carrying etchant solutions are used to microstructure glass and silicon with complex 3D architectures (see figure and inside cover). A two-way reaction–diffusion mechanism initiated from the stamp enables direct printing of entire microdevices (left to right: two-level microfluidic channels, curvilinear microlenses in glass, nanostructured silicon) into solid substrates with resolution down to 300 nm.