Table 3.

Results of Literature Search After Application of Comparison Framework

Ref.	Application	Working principle	Dimensions/mm	Materials	Manufacture and assembly	Actuation	Locomotion/positioning	Sensors/feedback	Force exertion	Bending, twisting, elongation	Variable stiffness	Instrument channels
19	MIS (cardiothoracic)	Continuum	320 mm length, 30–10 mm OD	Elastomer	Molding	Cable driven	Manual	Four optical fibers		Reduction of distance error		One channel
20	MIS (cardiothoracic)	Continuum	300 mm length, 9–30 mm OD	Elastomer	Molding	Cable driven	Robotic	Magnetic guidance				One for 5 mm endoscope, one for instrument
21	Endoscopy (support sleeve)	Continuum	400 mm length, 22 mm OD	PET, Latex	Laser cutting, fiber reinforcement, sewing, interweaving, molding	Cable driven, layer jamming	Manual	None	2 N payload	Some elongation		15 mm Channel
22	MIS	Continuum	200 mm length, 23 mm OD	Latex, polyester	Sewing	Cable driven, pneumatic	Manual	None		180° Max bending	2.1875 Times axial stiffening, 106.67–233.34 N/m at 7.5–15 kPa	None
23	MIS	Continuum	32 mm OD, 50 mm length	Elastomer	Multistage molding, fiber reinforcement	Hydraulic	Manual	Hydraulic pressure				One channel
24	Endoscopy	Continuum	15 mm OD, 100 mm length	Elastomer	Multistage molding, fiber reinforcement/extrusion	Hydraulic	Manual	Pressure sensors, image processing		110° Max bending at 50 kPa		Diathermy, biopsy channel, camera
25	Bronchoscopy	Continuum	7 mm OD, 32 mm length	Elastomer	3D printing, molding	Pneumatic	Manual	None		61.5° Twist at 300 kPa, 59° and 35° max bend for respective chamber at 350 kPa		None
26	Endoscopy	Continuum	1.66 mm OD, 12 mm length	Elastomer	Molding	Pneumatic	Manual	Pressure	Low	160° at 280 kPa, 45° at 280 kPa with camera		CMOS camera
27	MIS, prosthetics	Continuum	18 mm OD, 85 mm length	Elastomer	Molding, 3D printing	Pneumatic	Manual	None		270° at 45 kPa, 23° twist at 40 kPa		None
28	MIS	Continuum	6 mm OD	Elastomer	Molding, 3D printing, fiber reinforcement, adhesion	Pneumatic	Manual	Electromagnetic tracking		180° Bend, 5 mm bend radius		One channel
29	MIS	Continuum	13 mm OD, 93 mm length	Elastomer	Molding, fiber reinforcement	Pneumatic	Manual	Electromagnetic tracking	0.96 N max contact force	>150° Omnidirectional		None
30	Optical Biopsy	Continuum	<10 mm Width	Elastomer	Molding, lithography, vacuum ultraviolet-assisted bonding	Pneumatic	Manual	Two waveguides for fluorescence imaging		120° at 120 kPa		None
31	MIS	Continuum	1 mm OD, <20 mm length	Elastomer	Molding, micromachining	Pneumatic	Manual	None		7.14 mm bend radius at 100 kPa	Stiffness changes with increasing pressure	None
32	MIS	Continuum	25 mm OD, 65 mm length	Elastomer	Multistage molding	Pneumatic	Manual	Electromagnetic tracking for testing	4.6 N at 0.3 bar	90° with different working pressures		None
33	MIS	Continuum	84 mm length, 14 mm OD	Elastomer	Multistage molding, adhesion	Pneumatic	Manual	None	9 N at tip	142.4° Max at 85.5 kPa		None
34	Manipulation (microscale)	Continuum	3 × 25 mm rectangle	Elastomer	Multistage spin coating	Pneumatic	Manual	None	Low torque	Up to 210° bending		None
35	MIS	Continuum	70 mm OD semi-circle, 140 mm length	Elastomer, leather	Molding, sewing, 3D printing	Pneumatic, granular jamming (passive)	Manual	None	∼8 N at ∼100 kPa	10 cm Bend radius	∼4k mNm/rad	None
36	Endoscopy	Continuum	—	Elastomer	3D printing, molding	Pneumatic, SMA	Manual	None				One channel
37	Catheterization	Continuum	170 mm Long, 4 mm OD	Elastomer	Molding, CNC machining	SMA	Manual	None		270° Twist at 1.25 A		None
38	MIS	Continuum (modular)	20 mm OD, 83.5 mm length	Thermoplastic elastomer	3D printing	Cable driven	Manual	Electromagnetic tracking for testing	1.5 N generated force	∼100° Asymmetric bending and twisting		Manipulator on tip
39	MIS	Continuum (modular)	23 mm Ø, 47 mm length	Elastomer, PET	Molding	Cable driven, pneumatic	Manual	Pressure and tension			Stiffness change of up to 94%, from 130 to 250 N/m	One channel, large
40	Catheterization	Continuum (modular)	3 mm OD, 10 mm valve length, 25 mm length	Elastomer, polymer	Microstereolithography, molding	Hydraulic	Manual	Pressure, no bending angle sensing		170° Max		0.5 mm Channel
41	MIS	Continuum (modular)	14.5 mm OD, 50 mm length	Elastomer	Molding, 3D printing, fiber reinforcement	Pneumatic, granular jamming	Manual	Electromagnetic tracking for testing		171° at 1.5 bar		3 mm Channel
42	MIS	Continuum (modular)	14.3 mm OD, 60 mm length	Elastomer	Molding, 3D printing, fiber reinforcement	Pneumatic, granular jamming	Robotic	Electromagnetic tracking				4 mm Channel
43	MIS	Continuum (modular)	10 mm OD, 30 mm length	Elastomer	Multistage molding	Pneumatic/hydraulic	Manual	Electromagnetic tracking for testing				One channel
44	MIS	Continuum (modular)	14.5 mm OD, 50 mm length	Elastomer	Molding, fiber reinforcement	Pneumatic, granular jamming	Robotic	None				One channel
45	Endoscopy	Continuum (modular)	32 mm Ø, 50 mm length	Elastomer, PET	Multistage molding, fiber reinforcement	Pneumatic, granular jamming	Manual	None	47.1 N max		46% Stiff variation	Two channels
46	Endoscopy	Continuum, peristaltic	35 mm max Ø, 500 mm length	PET	Heat crimping, 3D printing	Cable driven	Self-propelled	Hall sensors for tendon length		90° Max, 25 mm length change		6 mm Camera
47	Endoscopy	Continuum, peristaltic	OD 5.5 mm, 45 mm length	Elastomer, steel, polymer	Multistage assembly	SMA	Self-propelled	None		90° Max, 19 mm radius		CCD image sensor
48	Manipulation (microscale)	Gripper	3–5 mm Width	Elastomer	Molding, 3D printing	Pneumatic	Manual	None				None
49	Drug delivery, manipulation (microscale)	Mobile gripper	3.7 mm Length, 1.5 mm width, 0.185 mm height	Elastomer, neodymium-iron-boron micro particles	Molding, laser cutting, magnetization	Magnetic	Magnetic positioning	None				None
50	Manipulation (microscale)	Mobile gripper	5 mm Ø	Hydrogel	Photolithography	Magnetic, thermal	Magnetic positioning	Haptic assistance—camera		10 s Open/close transition		None
51	Insertion aid (colon)	Peristaltic	16 mm OD, 700 mm length	Elastomer	Injection molding	Pneumatic	Manual	None				N/A
52	Endoscopy	Peristaltic	3 mm OD, 250 mm length	Elastomer/PVC resin	Molding/extrusion	Pneumatic	Self-propelled	None	Low			One channel
53	Endoscopy	Peristaltic (modular)	8 mm OD, 7 mm ID	Elastomer	Molding, 3D printing, fiber reinforcement	Pneumatic	Self-propelled	None		Extension, expansion, twist		Instrument on tip

Ø, Diameter; 3D, three dimensional; ID, inner diameter; OD, outer diameter; PET, polyethylene terephthalate; SMA, shape memory alloy.