Magnetic filaments for anisotropic composite polymers

Laurence Ourry,Vincent Salles,Damien Le Roy,Samir Mekkaoui,Thierry Douillard,Anne-Laure Deman

doi:10.1088/1361-6528/ab9b46

Abstract

The use of contactless magnetic forces meets numerous needs in microelectromechanical systems (MEMS) or microfluidic devices. In this view, heterogeneous materials integrating magnetic nanostructures within a non-magnetic matrix such as polymer can produce local variations of magnetic field, at the sub-micrometer scale. Here we report on the synthesis of magnetic composites using electrospun nanofilaments and a polydimethylsiloxane (PDMS) matrix. Varying the precursor nature and heat treatment conditions, we obtained single phase filaments of Fe, FeNi, and MFe2O4 (M = Co, Fe, Ni). Thanks to a fine investigation of their structure and morphology, it was possible to measure from magnetically-soft (µ0HC ⩽ 5 mT) to relatively hard (µ0HC up to 93 mT, MR/MS up to 0.5) behaviors. The common one-dimensional shape of these filaments leads to an anisotropic magnetic response. This can be exploited to achieve self-organization of the filaments in arrays within the non-magnetic matrix. We show the first step towards the development of magnetically anisotropic membranes of PDMS with 0.23 wt% Fe filaments. These composite materials are promising for implementing magnetic functions in microsystems while circumventing complex micro-fabrication steps.

Highlights

Magnetic composite polymers are part of new multifunctional materials that aroused considerable interest over the past two decades
Magnetic multifunctional materials address numerous applications such as microelectromechanical systems (MEMS) for sensors and actuators [2,3,4,5] controlled drug delivery based on thermoresponsive materials or magnetic guidance [1], bioinspired microstructures [6,7], microfluidics functions such as micro-object trapping [8][9] or fluidics components [10][11]
Marchi et al reported that the deflection of a composite polymeric membrane is increased when particles are aligned in the matrix and the magnetic field is applied along the chains, compared to disordered composite[15]

Summary

Introduction

Magnetic composite polymers are part of new multifunctional materials that aroused considerable interest over the past two decades. The development of composite materials with anisotropic magnetic properties opens up many perspectives This magnetic anisotropy can be achieved through the creation of chains of magnetic particles or the use of magnetic nano- or micro-filaments. Magnetic composite at relatively low concentration (up to 10 wt%), can form arrays of isolated and well-defined chains of magnetic particles homogeneously distributed within the polymer matrix. Magnetic composite polymers based on magnetic fillers with a cylindrical shape are reported in the literature,[4,21,22] , with fillers obtained using a porous and sacrificial template This fabrication process presents a low production rate and is suitable for only a few materials. Taking into account this guideline, a final composite was prepared by filling a PDMS matrix with aligned Fe nanofibers in order to assess the interest of such composites for microfluidic devices

Methods

Results

Conclusion