Table 5.

Comparison among 3D fabrication technologies.

Gas foaming method	Mechanism	Gas bubbles generated in situ either via a chemical reaction or solubility difference of CO2 in ethanol and water and depressurization of subcritical CO2 fluid
	Advantages	Increase the pore size and porosity of scaffold; Promote cell infiltration migration, proliferation, and angiogenesis
	Disadvantages	Most scaffolds are restricted of weak mechanical strength; Imprecise thickness control and cause inflammatory; response in vivo; Hard to be used as a carrier of drugs or factors
	Applications	Nerve regeneration; Hemostasis; Wound healing; In vitro tissue models
	Ref	[[31], [32], [33], [34], [35], [36], [37], [38]]
Direct electrospinning	Mechanism	Collect scaffold directly with a special 3D shaped device; Use a thumbtack as collector producing 3D silica fibrous scaffold via self-assembly; Use the sol-gel solution to produce a bioactive 3D scaffold
	Advantages	Promote biomineralization and cell infiltration; Reduce bulk density
	Disadvantages	Uncontrolled shape; Weak mechanical property
	Applications	Bone regeneration; Oils absorption
	Ref	[26,[41], [42], [43]]
Short nanofibers assembling into 3D aerogels/scaffolds	Mechanism	Cut the nanofibrous membrane into small pieces, and then uniformly disperse the small pieces in the medium using a homogenizer. In general, short fibers are introduced into aerogels/scaffolds to enhance their structural stability or serve as an ECM template to provide a suitable microenvironment for cell growth and proliferation.
	Advantages	Possess various excellent properties such as elastic resilience, energy absorption, shape memory, superabsorbent, and high-pressure sensitivity
	Disadvantages	Some scaffolds are non-biodegradable, hydrophobic and use toxic cross-linking agents; Complex preparation process
	Applications	Osteoporotic; Bone regeneration; Cartilage regeneration; Cranial bone regeneration; Thermal insulation; Sound absorption; Emulsion separation
	Ref	[[44], [45], [46], [47], [48], [49], [50], [51]]
3D printing	Mechanism	Print 3D scaffolds with short fiber ink enabling the scaffold surface with fibrous structures; Use stable jet electrospinning (SJES) to produce aligned ultrafine fibers via strengthening the control of jet instability
	Advantages	Controlled shape; Promote cell proliferation, infiltration, adhesion and migration
	Disadvantages	Complex preparation process; Various parameters need to be controlled
	Applications	Cartilage regeneration; Anisotropic tissue regeneration
	Ref	[[52], [53], [54], [55]]
Electrospray	Mechanism	Homogenize electrospun nanofiber mats to generate nanofiber segments and electrospray the crosslinker containing nanofiber segment solution into liquid nitrogen to obtained microspheres.
	Advantages	Fabricate NMs from any material feasible for electrospinning
	Disadvantages	Complex preparation process; Crosslinking agent toxicity
	Applications	Biomimetic and injectable carrier; Osteogenesis; Angiogenesis; Tissue filling; Cell and drug delivery
	Ref	[56,57]
Origami and cell sheet engineering	Mechanism	Cells were seeded on both two sides of the electrospun nanofiber film and use the co-cultured membrane to fabricate bio-tubular scaffolds or nanofiber boxes via origami.
	Advantages	Cell infiltration; Intricate architectures
	Disadvantages	Complex preparation process; High requirements for operators
	Applications	3D tissue construction; Vascular grafts regeneration
	Ref	[[58], [59], [60]]
Centrifugal electrospinning	Mechanism	Use an electrospun rotating spinneret and obtain nanofiber from a conductive iron circular collector surrounding the spinneret.
	Advantages	Promote production rates; High orientation
	Disadvantages	Require special equipment; Few types of the fiber structure
	Applications	Mass production of electrospun fibers; Drug release
	Ref	[61]