Top photos show photographs of single fibres fabricated by melt electropinning, with collector speeds of a) 0.4 m min−1, b) 0.8 m min-1, c) 1 m min-1. Lower photo shows a 3D structure of NWPU (for Northwestern Polytechnical University, Xi'an, where this work took place) which was prepared in a direct-writing way using thirty layers of melt electrospinning. Image taken from Feng-Li He et al 2017 J. Phys. D: Appl. Phys. 50 425601, © IOP Publishing, All Rights Reserved.