Table 1.

Summary of different design and actuation methods.

Literature	Design principle	DOF	Actuation	Diameter (mm)	Accuracy	Characteristics
[44]	Parallel	5	Rod driven	—	2.3%	Large workspace and high precision
[45]	Backbone	2	SMA driven	5	0.98 mm	Modular; teleoperation
[39]	Backbone	4	Tendon driven	38	<2 mm	Passive structural flexibility
[46]	Backbone	6	Fluid driven	30	—	Variable stiffness
[47]	Concentric tube	12	Motor driven	2.74; 1.92; 1.21	1%	Dual-arm
[48]	Backbone	4	Fluid driven	32	1.3%	Soft and has variable stiffness
[49]	Backbone	6	Magnetic driven	—	<7.86	Combination of soft and hard joints
[50]	Backbone	5	Magnetic driven	2.5	—	Variable stiffness
[51]	Backbone	5	Tendon and magnetic driven	3	10 μm	Large workspace and high precision
[52]	Backbone	5	Fluid and tendon driven	25	—	High load capacity
[53]	Backbone	5	Magnetic driven	20	—	Omnidirectional bending and twisting
[54]	Concentric tube	4	Motor driven	4.36; 2.265	—	3D printed