How To Make Direct-written 3D Structures

Many complex 3D nanofibrous structures with high aspect ratio have been built based on NFES. Lee and Kim proposed a method to fabricate a freestanding nanowall (Fig. 9.20C) with direct-written nanofibers. To control the whipping instability of the electrical nanojets, a conductive microline on the insulating plate was used as the grounded collector to focus the electrical field. In this way, a jet with 180 nm diameter and 30 mm/s velocity can be used to construct a nanowall of 4.5 mm height and 220 mm length. Han et al. applied electrohydrodynamic printing for 3D microstructures. A droplet will print on the top of the previous droplet once the nozzle is fixed at a certain location, which results in a high aspect ratio of pillars. A circular tube with a height of 40-60 mm and wall thickness of 6 mm was printed, as shown in Fig. 9.20D. Compared with traditional 3D printing, the resolution was improved by 1 or 2 orders of magnitude.