Table 1. Summary of 3D printing technology with respect to soft robots.

Mechanism	Robot part	State of starting material	Layer creation technique	Materials	Size	Advantage	Disadvantage	Application	Sub-Heading number	Reference
Stereolithography (SLA)	Bio-bot arrays		Layer by layer	Poly(ethylene glycol)		Less resin material, large build volume, Precise control, Rapid polymerization	Post-curing, warping, brittle parts with a tacky surface, support required, little choice of material, unused material is toxic	Miniaturized Walking	I	[59]
				Diacrylate (PEGDA)
								Biological Machines
	Multi-material cantilevers		Layer by layer	Poly(ethylene glycol) diacrylate (PEGDA) and acrylic-PEG-collagen (PC) mixtures	2 × 2 × 4 mm					[60]
	Actuator		Bottom up approach	Elastomeric precursor; Spot-E resin, Spot-A	40.0 × 71.1 mm2			Octopus Tentacles		[61]
Inkjet Printing	Bellows actuators, gear pumps, soft grippers and a hexapod Robot,	Liquid	Multi-material layer by layer printing	Tangoblack+	14 × 9 × 7 cm			Hydraulically actuated robots	Ii	[62]
	Complete robot		Multi-material UV-curable printing	Urethane and epoxy	80 × 5 × 5 mm			Tri-legged soft bot with spider Mimicry		[63]
	Mould			ABS and silicon rubber				Caterpillar-inspired soft-bodied rolling robot		[64]
Selective laser sintering (SLS)	Bellow actuators		Top-Down	Elastic silicone material		No support required		Soft robotic hand	Iii	[65]
	Flexure hinges			Polyamide (PA 12, Nylon)	0.1 mm × 0.5 mm			Soft Robot Kinematics of snake		[66]
DIW	Extensible sensing skin			Silicone elastomer, hydrogel elastomers, polyacrylamide etc.	3.75 × 3.75 cm		Unable to fabricate continuous fibre-reinforced composites	Tactile Machines with kinesthetic sense	Iv	[69]
SDM	Cockroach Limbs			Viscoelastic polyurethane	120 mm × 120 mm × 50 mm			Biomimetic Components	V	[70]
	Small robot limbs			Viscoelastic polyurethane	–			Biomimetic Robotic Mechanisms		[71]
	Fingers of robot			Two-part industrial polyurethanes				Robust compliant grasper		[73]
	Hexapedal Robots			Viscoelastic polyurethane, polyester fibres and low melting temperature wax	16 cm			Performance and locomotion Dynamics of insects		[72]
	Fingers of Grasper			Polyurethane elastomer	116 cm3			Soft, Atraumatic and Deployable surgical grasper		[74]
Fused deposition modelling (FDM)	Actuator		Layer by layer	Silicone elastomer	50 × 20 × 40 mm			Soft robot prototypes	Vi	[75]
	3D structures		Layer by layer	Nafion	5 mm × 10 mm × 0.5 mm			Macro-scale soft robotic systems		[76]
	Actuator modules			Silicon rubber elastomer	–			Soft snake		[77]
	Flexible Fingers			Poly(vinyl chloride) (PVC) sheets	–			Soft prosthetic Finger		[78]
	Soft pneumatic actuators			Thermoplastic elastomer filament ninjaflex (ninjatek, PA)	150 mm × 25 mm × 11 mm			Soft Robotic applications		[79]
3D Printing				Fugitive (Pluronic F127) and catalytic inks				Entirely soft octobot with embedded electronics		[47]
	Moulds			Elastomeric silicon				Pneumatic networks for soft robotics		[48]
	Moulds			ABS	15 cm			Robotic Tentacles		[49]
	Soft Actuators, main frame		Layer by layer	ABS Plastic	30 × 10 mm			Rehabilitation of spinalized rodents		[50]
	Whole body		Multi-material printing	Tangoplus and veroclear	8 cm			Mimicking of caterpillar motion		[51]
	Soft Skin		Multi-material printing	Tangoplus	173 cm3			Safe human-robot interaction		[52]
	Robot Body		Multi-material printing					Combustion-powered robot		[53]
	Outer mould, lid, model core		Layer by layer	Silicon rubber	0.45 m × 0.19 m × 0.13 m			Hydraulic autonomous soft robotic fish		[54]
	Mould, passive wheel, valve holders, tail enclosure			Silicon rubber				Dynamics of a fluidic soft robot		[55]
	Mould			Silicon rubber	2.5 × 2.5 × 11 cm			Soft Robotic Gripper		[56]
	Softworms			Deformable rubber-like Polymer				Bio-inspiration soft robots		[57]