Fig. 2

Model validation, design and synthesis of the self-assembled architectures. a Scanning electron microscopy (SEM) images of polyvinylidene fluoride (PVDF) self-assembled architectures on the flat collector with a concave zone. Scale bar at the left of (a), 10 μm. Scale bars at the right of (a), 1 μm. b SEM images of PVDF self-assembled architectures across concaves with different widths. The concave widths in (b) (from left to right) are 3, 5 and 10 μm. Scale bars in (b), 2 μm. Scale bars in the insets of (b), 500 nm. c Relative permittivity of the collectors including polyacrylonitrile (PAN) fiber membranes with different electrospinning durations, nonwoven fabric and paper. PAN-X, X is the spinning duration (min). d Charge density (e/m), jet and droplet thresholds of the fluids ejected from the PVDF solution and received using various collectors in (c) during the direct electronetting process. Error bars in (c, d) represent s.d. e Typical SEM images of PVDF self-assembled architectures collected using different collectors. Top images in (e) (from left to right): aluminum (Al) foil, nonporous paper, copper (Cu) mesh, nonwoven fabric. Bottom images in (e) PAN fiber membranes with various structures (from left to right): untreated 10 min, untreated 30 min, untreated 240 min and compacted 30 min. The insets are the corresponding high-magnification images of the self-assembled architectures. Scale bars in (e), 1 μm. Scale bars in the insets of (e), 500 nm