Photothermal Welding,Melting, and Patterned Expansion of Nonwoven Mats of Polymer Nanofibers for Biomedical and Printing Applications

We report a simple method for the photothermal welding of nonwoven mats of electrospun nanofibers by introducing a near‐infrared (NIR) dye such as indocyanine green. By leveraging the strong photothermal effect of the dye, the nanofibers can be readily welded at their cross points or even over‐welded (i.e., melted and/or fused together) to transform the porous mat into a solid film upon exposure to a NIR laser. While welding at the cross points greatly improves the mechanical strength of a nonwoven mat of nanofibers, melting and fusion of the nanofibers can be employed to fabricate a novel class of photothermal papers for laser writing or printing without chemicals or toner particles. By using a photomask, we can integrate photothermal welding with the gas foaming technique to pattern and then expand nonwoven mats into 3D scaffolds with well‐defined structures. This method can be applied to different combinations of polymers and dyes, if they can be co‐dissolved in a suitable solvent for electrospinning.