Fig. 1

Technical history and principal description of the technologies developed to achieve cell encapsulation, by year. a Micromolding was used in a variety of fields, but not for cell encapsulation until the early 1980s. Lithography based on micromolding was founded by Broers et al. [92] whereas techniques using replica [93] and capillary molding [94] were developed in 1996, and MSC encapsulation began in 2002. b Nawab and Mason suggested liquid droplets under electrostatic fields, which formed the principle of electrostatic droplet extrusion in 1958 [95]. For cell encapsulation using this technology, Goosen et al. proposed cell immobilization within a semipermeable membrane [96]. Moreover, Bugarski et al. proved the mechanism of polymer droplet formation with electrostatic droplet extrusion in 1994 [42]. Finally, MSC encapsulation was conducted in the late 2000s [97, 98]. c Schmidt et al. introduced a microfluidic device in 1990 [99], and the cell encapsulation was studied by Sugiura in 2005 [100]. Zhang et al. generated microgel particles with a capsular structure [101]. Microfluidic emulsification, achieved by Edd et al., offered enhanced controls over a number of encapsulated cells [102]. In 2010, MSC encapsulation was beginning to be studied. d The 3D printer was invented by Charles W. Hull in 1983 [103]. The inkjet 3D printing-based hard tissue scaffold was developed by Gima et al. in the early 1990s [104], which was an earlier step for application into soft tissue engineering [105]. Cell-laden and MSC-encapsulated 3D bioprinting was attempted form the 2000s onward after the development of the cell-free printed scaffold [74]. Finally, 4D bioprinting was developed as an advanced bioprinting technique for next-generation technology in the biomedical fields [106]