Composite elastic magnet films with hard magnetic feature

Abstract

Hard magnetic materials with high remnant magnetic moment, Mr, have unique advantages that can achieve bi-directional (push–pull) movement in an external magnetic field. This paper presents the results on the fabrication and testing of novel composite elastic permanent magnet films. The microsize hard barium ferrite powder, NdFeB powder, and different silicone elastomers have been used to fabricate various large elongation hard magnetic films. Three different fabrication methods, screen-coating processing, moulding processing and squeegee-coating processing, have been investigated, and the squeegee-coating process was proven to be the most successful method. The uniform composite elastic permanent magnet films range from 40 µm to 216 µm in thickness have been successfully fabricated. These films were then magnetized in the thickness direction after fabrication. They exhibited permanent magnet behaviour; for instance, the film (0.640 mm3 in volume) made of polydimethyl siloxane (PDMS) and hard barium ferrite powders is measured to give a coercive force, Hc, of 3.24 × 105 A m−1 and Mr of 1.023 × 10−5 A m2, and the film (0.504 mm3 in volume) made of PDMS and NdFeB powders gives 1.55 × 105 A m−1 Hc and 8.081 × 10−5 A m2 Mr. These composite elastic permanent magnet films' mechanical properties, like Young's modulus and deflection force, have been evaluated. To validate the films' Young's modulus, a finite-element computer simulation (ANSYS®) is used and one film is chosen whose Young's modulus (16.60 MPa) is confirmed by the simulation results with ANSYS®. The large elongation composite elastic permanent magnet film provides an excellent diaphragm material, which plays an important role in the micropump or valve. The movement of the 126 µm thick film with 4.5 mm diameter made of PDMS and NdFeB powders has been tested in a 0.21 Tesla external magnetic field. It was proven to have large deflection of 125 µm.

Current micropump technologies and their biomedical applications

“…Ferrite/polyimide, ferrite/PDMS, NdFeB/PDMS composite membranes were reported in the previous papers (Lagorce and Allen 1997;Wang et al 2004). This kind of magnetic composite has several advantages: first, bulk permanent magnets or Permalloy pieces do not have to be positioned within the pre-polymer or integrated into the membrane.…”

Design and fabrication of microfluidic mixer from carbonyl iron–PDMS composite membrane

“…The magnetic elastomer's merits, which include high elasticity, a remarkable deformational effect imparted by its low Young's modulus, a quick response to magnetic fields and potential actuation without on-chip power sources, have drawn much attention for the purposes of magnetic elastomer membrane applications in micro valves, pumps, actuators (Khoo and Liu 2001;Wang et al 2004;Fahrni et al 2009a;Pirmoradi et al 2010), and mixers (Huh et al 2007). In fact, many researchers have investigated this novel material and its applications.…”

Highly Magneto-Responsive Elastomeric Films Created by a Two-Step Fabrication Process

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] For these purposes, various actuation principles have been adopted including electrostatic, 2,3,6 thermal 4,14 or piezoelectric. 1,7 However, these methods present diverse limitations, making difficult their direct utilization in the final devices.…”

“…9,11,13 The first magnetic polymeric actuators, made from a mixture of magnetic particles with rigid polymeric matrices, were mainly 3 used as permanent magnets, magnetic cores or connecting elements. 20 These classical actuators presented low flexibility and their size or shape remained unaffected under the effect of the magnetic field, limiting their range of applications.…”

“…9,27 Such microparticles present exceptional magnetic properties 27,28 and can be permanently magnetized. Alternatively, the magnetic response of the polymeric magnetic films can be sufficiently improved arranging the particles in a preferential direction throughout the volume of the polymeric matrix.…”