Bio-inspired heterostructured bead-on-string fibers that respond to environmental wetting

Inspired by the geometric structure of ecribellate spider capture silk and its spinning characteristics, we propose a one-step electrohydrodynamic method to fabricate bead-on-string heterostructured fibers (BSHFs). By combining electrospinning and electrospraying strategies using a sprayable outer fluid with low viscosity and a spinnable inner fluid with high viscosity in a coaxial jetting process, hydrophilic poly(ethylene glycol) beads are successfully imprinted on a hydrophobic polystyrene string. It is demonstrated that the BSHFs are capable of intelligently responding to environmental change. With a change in relative humidity, the fibers show a segmented swelling and shrinking behavior in the "bead" parts whereas the "string" parts remain the same. The elastic BSHFs with alternating hydrophilic and hydrophobic surface characteristics represent a type of mesoscale analogues that block copolymers and may bring about new properties and applications. Moreover, the combined electrohydrodynamic approach developed herein should open new routes to multifunctional one-dimensional heterostructured materials.