Magnetic field gradient and sample size effect on magneto-mechanical response for magnetic elastomers

Significance Statement

At present, there exists several magnetically responsive composites whose physical properties can be controlled by a magnetic stimulus. Magnetic soft materials, mainly consisting of soft polymeric matrices and magnetic particles, tend to exhibit considerable change in elastic modulus when a magnetic field is applied. The field can only be applied either by using permanent magnets or by use of an electromagnet. The former tends to produce a weak magneto-mechanical response due to the inhomogeneity of its magnetic field. Consequently, the size correlation of magnetic elastomer and permanent magnet is quite important for the magneto-mechanical response. Previous studies have incisively emphasized on this. More so, magnetic elastomers with significant magneto-mechanical response tend to exhibit anomalous deformation under the magnetic field. Such works have directed that the magneto-mechanical response clearly levels off when the diameter of magnetic elastomers exceeds that of permanent magnets. This in turn insinuates that the distribution of magnetic fields at the fringe dominates the magneto-mechanical response.

Researchers led by professor Tetsu Mitsumata at Niigata University in Japan investigated the size effect of disk-shaped magnetic elastomers, placed on a permanent magnet, on their magneto-mechanical response for the permanent magnet. They hoped to further study the size-dependent magneto-mechanical response of magnetic elastomers. Their work is published in the research journal, Reactive and Functional Polymers.

The research team initiated their experimental procedure by synthesizing the magnetic elastomers. Unidirectional compression measurements were then undertaken using permanent magnets having different diameters, magnetic elastomers with various volume fractions of magnetic particle and permanent magnets with various geometrical shapes. Eventually, they carried out magnetic field analysis by measuring the magnetic field strength in both horizontal and vertical direction.

The authors observed that the size-dependent magneto-mechanical response was strongly associated with the characteristic distribution of magnetic fields generated by permanent magnets. Moreover, they noted that the magnetic field measurements and numerical simulation revealed that the magnetic field gradient appears at the fringe of permanent magnets not only in the horizontal direction but also in the vertical one. After undertaking image analyses, the research team observed that the bottom of the magnetic elastomers was restricted to deform by the compression. The restricted deformation was seen to be due to the steep gradient of magnetic fields at the fringe of permanent magnet, probably the field gradient in the vertical direction.

Professor Tetsu Mitsumata and colleagues successfully presented a report on the magneto-mechanical response of magnetic elastomers with various diameters by using permanent magnets of different diameters. Based on the unidirectional compression measurements, it has been seen that a considerable magneto-mechanical response is achieved when the diameter of the magnetic elastomer is equal to that of the permanent magnet. Therefore, we firmly believe that the present results provide a smart design for fabricating devices with variable elasticity consisting of magnetic elastomers and permanent magnets.

Magnetic field gradient and sample size effect on magneto-mechanical response for magnetic elastomers. Advances in Engineering

About the author

Tsubasa Oguro

He received a bachelor degree in 2015 from Faculty of Engineering, and a master degree in 2017 from Graduate School of Science and Technology, Niigata University with a study on magnetic-field responsive elastomers, especially, sample size effect on magnetomechanical response.

About the author

Hiroyuki Endo

He received a bachelor degree in 2016 from Faculty of Engineering, Niigata University. He investigates currently magnetic elastomers with variable vibration absorption at Graduate School of Science and Technology, Niigata University.

About the author

Takehito Kikuchi

He is a Associate Professor of Faculty of Engineering, Oita University. He obtained his B.S., M.S. and Ph.D. degrees in mechanical engineering at Osaka University (Japan) in 2001, 2003, and 2006, respectively. He has focused on rehabilitation robotics, mechatronics, virtual reality and application of functional fluids for them. He has developed several types of brakes, clutches and other mechatronics devices by using Electro-Rheological Fluids (ERF) and Magneto-Rheological Fluid (MRF). He is a member of the Japan Society of Mechanical Engineers, the Robotics Society of Japan, the IEEE, and so on.

About the author

Mika Kawai

She has studied polymer science at Profs. Yoshihito Osada and Jian Ping Gong laboratory in Hokkaido University. She works currently at the Graduate School of Science and Technology, Niigata University as a researcher since 2014. She has published more than 20 scientific papers dedicated to soft materials, especially polysaccharides and biopolymers.

About the author

Tetsu Mitsumata

He received his PhD degree in Polymer Science from Hokkaido University in 1999 under the supervision of Profs. Yoshihito Osada and Jian Ping Gong. In this year, he moved to Graduate School of Science and Engineering, Yamagata University as an assistant professor. In 2002, he joined the laboratory of Dr. Patrick De Kepper of CRPP Bordeaux in France. He works currently at Graduate School of Science and Technology, Niigata University as a research professor since 2016. He has published more than 110 scientific papers (including reviews and books) and 11 patents dedicated to soft materials, especially magnetic responsive gels or elastomers.

Reference

Tsubasa Oguro, Hiroyuki Endo, Takehito Kikuchi, Mika Kawai, Tetsu Mitsumata. Magnetic field gradient and sample size effect on magneto-mechanical response for magnetic elastomers. Reactive and Functional Polymers volume 117 (2017) pages 25–33.

 

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