While soft/partially soft-bodied robots have extensive applications, robust actuation system, efficient locomotion gait, and simple manufacture process are the main challenging problems. To address these challenges, this article proposes a novel magnetorheological fluid (MRF)-filled soft crawling robot with magnetic actuation in congested spaces as a transport function. In this new soft robot, MRF is innovatively applied to establishing a robust actuation system owing to its characteristics of millisecond magnetization, zero magnetic coercivity, and flexible integration. Because the crawling locomotion of the robot is generated by the anisotropic magnetic torque, when the magnetic field is closed neither components of the proposed robot will magnetically interfere with each other. Thus, an efficient locomotion gait can be realized. Lastly, 3-D printing 3-DP has been employed to manufacture the soft robot, which will make the manufacture process simple and costless. Both numerical and experimental evaluations were performed to analyze the dynamics of the newly designed MRF crawling robot with single-step and continuous locomotion conditions. The experimental test result was basically consistent with the simulation, which indicates good movement feasibility of the proposed crawling robot.

Magnetorheological fluid (MRF) is a kind of smart materials with rheological behavior change by means of external magnetic field application, which has been widely adopted in many complex systems of different technical fields. In this work, the state-of-the-art MRF based devices are reviewed according to structural configurations reported from 2018 to 2020. Based on the rheological characteristic, the MRF has a variety of operational modes, such as flow mode, shear mode, squeeze mode and pinch mode, and has unique advantages in some special practical applications. With reference to these operational modes, improved engineering mechanical devices with MRF are summarized, including brakes, clutches, dampers, and mounts proposed over these 3 years. Furthermore, some new medical devices using the MRF are also investigated, such as surgical assistive devices and artificial limbs. In particular, some outstanding advances on the structural innovations and application superiority of these devices are introduced in detail. Finally, an overview of the significant issues that occur in the MRF based devices is reported, and the developing trends for the devices using the MRF are discussed.