Table 10.

Summary of key characteristics, advantages and disadvantages of SFF scaffolding techniques

Technique	Layer thickness ($\mathbf{\mu }$m)	Resolution ($\mathbf{\mu }$m)	Typical accuracy ($\mathbf{\mu }$m)		Porosity (%) and pore size ($\mathbf{\mu }$m)		Advantages	Disadvantages		Ref.
Photopolymerisation-based processing
Stereolithography (SLA)	25–150	14–150	<50		<90 20–1,000		Good surface finish; possibly build transparent parts; excellent accuracy; anatomically shaped structures	Expensive machinery; support structure needed; the limited choice of resin available; use of mostly toxic resins; shrinkage during polymerisation		(Melchels et al. 2012; Dalton et al. 2009; Gurr and Mülhaupt 2012; Mota et al. 2012; Swift and Booker 2013)
Micro-stereolithography (μSLA)	<1	0.5–10	0.2		– 100–300		Similar to SLS; the highest resolution with micrometre scale	Similar to SLA		(Choi et al. 2009; Seol et al. 2013; Mota et al. 2012)
Two-photon polymerisation (TPP)	<5	0.1–4	0.2		–		Similar to SLS; low laser intensity; very fine lateral resolutions; fast processing	Similar to SLA		(Melchels et al. 2010; Weiss et al. 2009; Weiss et al. 2011; Mota et al. 2012)
Digital light processing (DLP)	15-70	40	<0.4		<90 500		Similar to SLS; no use of laser; higher resolution; higher build speed	Similar to SLA		(Felzmann et al. 2012; Tesavibul et al. 2012)
Powder-based processing
Selective laser sintering (SLS)	75-150	50-1000	50-100		<40 30–2,500		Solvent free; no need for support material; fast processing	Expensive machinery; difficulty removing trapped powder; high temperatures in the chamber; powdery surface finish		(Melchels et al. 2012; Leong et al. 2003; Dalton et al. 2009; Gurr and Mülhaupt 2012; Mota et al. 2012; Swift and Booker 2013)
Surface selective laser sintering (SSLS)	200	150-200	<20		–		Similar to SLS; reduction of heat operating temperature; possible incorporation of bioactive agents	Similar to SLS		(Antonov et al. 2005; Kanczler et al. 2009)
Three-dimensional printing (3DP)	50-150	50-300	50-100		<45–60 45–1,600		Easy process; low cost; low heat effect on raw powder; no need for support material; fast processing	Poor surface finish, accuracy and mechanical properties; difficulty removing trapped powder; powdery surface finish		(Melchels et al. 2012; Leong et al. 2003; Dalton et al. 2009; Gurr and Mülhaupt 2012; Mota et al. 2012; Swift and Booker 2013)
Extrusion-based processing
Fused deposition modelling (FDM)	50–750	100–500		100	<80 100–2,000	Solvent free; no materials trapped in the scaffolds; good mechanical strength; wide range of materials; versatile in lay-down pattern; low costs			Needs filament preparation; limited choice of filament materials; high heat effect on material; difficult fabrication for scaffolds with small pore sizes; medium accuracy	(Melchels et al. 2012; Leong et al. 2003; Dalton et al. 2009; Mota et al. 2012; Swift and Booker 2013)
Multi-head deposition system (MHDS)	200	several tens of microns		several tens of microns	~70 600	Enhanced range of material use and pore architecture; high resolution			High heat effect on material	(Kim and Cho 2009)
Low-temperature deposition manufacturing (LDM) and (M-LDM)	150	300-500			~88 200–500	Enhanced range of material use; ability to incorporate biomolecules			Solvent use; requires freeze drying	(Yeong et al. 2004; Xiong et al. 2002; Li et al. 2011; Liu et al. 2009; Mota et al. 2012)
Precision extruding deposition (PED)	250	100–500		100	<70 200–500	No requirement of filament preparation			High heat effect on material; rigid filament	(Melchels et al. 2012; Yeong et al. 2004; Shor et al. 2009; Arafat et al. 2011; Mota et al. 2012)
Pressure-assisted microsyringe (PAM)/(PAM2)	150–200	10–1000		5–10	70 10-600	Enhanced range of material use; ability to incorporate biomolecules; very fine resolution			Small nozzle inhibits incorporation of particles; narrow range of printable viscosities; solvent use	(Yeong et al. 2004; Tartarisco et al. 2009; Vozzi and Ahluwalia 2007; Heo et al. 2009; Mota et al. 2012)
Robocasting (direct-write assembly)	250	100–450		few microns	<90 5–100	Enhanced range of material use; possible fabrication of highly concentrated suspension; no need of support material; excellent resolution			Expensive machinery; precise control of ink properties is crucial	(Melchels et al. 2012; Yeong et al. 2004; Serra et al. 2013; Mota et al. 2012)
3D-Bioplotter®	50–300	100–500		100	– 200–400	Enhanced range of material use and conditions; ability to incorporate biomolecules, proteins and cells			Low strength; smooth surface; low accuracy; slow processing; calibration for new material; suitability for soft-tissue area	(Yeong et al. 2004; Landers et al. 2002; Gurr and Mülhaupt 2012; Mota et al. 2012)