Figure 3.

(a) Three typical processes of inkjet printing. Left: Thermal inkjet printing. Middle: Piezoelectric inkjet printing. Right: Continuous inkjet printing. Reproduced from [46], with permission from Annual Reviews, 2010; (b) Left: The process of extrusion printing technology. Right: Printing cylinder structure with the extrusion printing and the fabricated various structures. Reproduced from [48], with permission from Wiley, 2017; (c) Process of spray printing: ink spraying onto the substrate, sprayed layer self-assembling with a hydrogen bonding force. Reproduced from [50], with permission from Wiley, 2009.