Magnetic properties of PDMS embedded with strontium ferrite particles cured under different magnetic field configurations

Amanda De Oliveira Barros,Daniel Luna,Wilhelmus J Geerts,Md Nayeem Hasan Kashem,Wei Li,James Yang

doi:10.1063/9.0000338

Amanda De Oliveira Barros, Daniel Luna + Show 4 more

Open Access

https://doi.org/10.1063/9.0000338

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Journal: AIP Advances	Publication Date: Mar 1, 2022
Citations: 8	License type: cc-by

Affiliation: Texas Tech University, Texas State University

Abstract

Flexible materials embedded with hard magnetic particles have recently gained widespread recognition as small-scale actuators due to their capacity to be a rapid and precise shape-shifting material. Strontium ferrite (SrFe12O19) particles have been shown as a great candidate for such applications, since it is an inert hard magnetic material that, in contrast to barium ferrite and neodymium, is also biocompatible. The preparation of such material is done by mixing the magnetic particles into the uncured elastomer (polydimethylsiloxane (PDMS)), in liquid form, and then pouring the mixture in a mold for curing. If the samples are subjected to a magnetic field during the curing process, chains of particles are formed in the direction of the applied field, thus creating an easy axis in this same direction. The magnetic properties of such composite cannot yet be found in literature. In this study, we analyzed three concentrations of strontium ferrite particles in PDMS under three field configurations, resulting in 9 different samples. The concentrations used were 1:1, 2:1, and 4:1 ratios of PDMS to strontium ferrite per weight. All three types of samples were cured either in a zero magnetic field, or over the north pole of a neodymium permanent magnet, or over the side of said magnet. A biaxial vibrating sample magnetometer (VSM) was used to measure hysteresis curves parallel and perpendicular to the curing field. The samples cured in a field show a squareness ratio of up to 0.94 while the samples cured in zero field, only close to 0.5. The samples cured in a field show a magnetic anisotropy with an easy axis parallel to the curing field. Harvesting these modified properties, a mobile robot manufacturing method is proposed that bypasses the need of applying a high intensity magnetic field.

Highlights

Hard-magnetic flexible composites are materials composed of a mixture of hard-magnetic particles that have a large coercivity dispersed in a soft matrix which enables magnetic actuation
The squareness, defined as the ratio between remanent and saturation magnetizations, of the Mx hysteresis curve is much smaller for the curves measured along the hard axis and approaches 1 for the curves measured along the easy axis
Three magnetic field configurations were applied during the curing process of the samples producing significantly different magnetic properties

Summary

Introduction

Hard-magnetic flexible composites are materials composed of a mixture of hard-magnetic particles that have a large coercivity dispersed in a soft matrix which enables magnetic actuation. This upcoming technology has been gaining rapid development in several applications such as microfluidics (Mitsumata et al, 2007) and minimally invasive medical devices (Ren et al, 2019) due to its precise, fast, and repeatable shape-shifting capabilities. In this scenario, characterization of such composites is a critical part of the development of new designs and manufacturing techniques, it is still scarce in literature. On the other hand, has been scitation.org/journal/adv shown to be non-toxic (Kirrane et al, 2006), is chemically stable, and presents a high Curie temperature (Verma et al, 2000)

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