*4.5. Other Applications*

MRE can be adopted in many other applications. According to Hu et al. [31], the silicone elastomer that consists hard magnetic neodymium-iron-boron (NdFeB) microparticles of 5 μm size was able to act as magneto-elastic soft milimetre-scale robot. This soft robot can move around on surface of liquid, walk and roll on solid surfaces, and crawl in narrow tunnels. The fabrication of small-scale continuum robots with materials of silicone and magnetic particle (NdFeB) enables to navigate through constrained and complex environment for medical applications [153]. In addition, the origami-inspired rapid prototype robot has been fabricated for self-folding, reconfigurable shape, and controllable motility with poly (ethylene glycol) diacrylate and magnetite particles [154].

MRE is also viable for micro-fluid actuation applications. The manipulation of micro-fluid is crucial in biological analysis, optics, chemical synthesis, and information technology. The micro-fluid actuation was achieved using artificial cilia and iron particle with polymer matrix [155]. Another actuated artificial cilia was made using polybutylacrylate and paramagnetic magnetite nano particles to simulate the cilia motion [156]. The MRE has also been used in biomedical application in such a way as active scaffolds for drug and cell delivery. The new active porous scaffold that can be controlled by a magnetic field to transfer different biological agents using alginate hydrogel and magnetite particles [157]. The formation of biofilm on medical device causes serious infections. Hence the engineered tunable active surface topographies with micron-sized pillars was developed using magnetite particles, which was controlled by electromagnetic field [158]. In addition, the MRE could be also applicable in shape-programmable magnetic soft matter, generating new time-varying shapes of soft matter with magnetization profile and actuating field, using ferromagnetic and aluminum particles [159].

Finally, MRE can be used in acoustic metamaterials. The transformation of 3D phase of magnetoactive lattice structures from 2D phase by magnetic field allows to switching signs of constitutive parameters repeatedly. It opens new potential of MRE in acoustic transportation, imaging and refraction [160].
