A magnetic poly(dimethylesiloxane) composite membrane incorporated with uniformly dispersed, coated iron oxide nanoparticles

Abstract

We report a new magnetic polymer membrane for MEMS application. The polymeric magnetic composite has coated iron oxide nanoparticles incorporated in a polydimethylsiloxane (PDMS) matrix. Existing magnetic polymeric materials have particle agglomeration problems, which result in rough surfaces and uneven mechanical and optical properties. We show that the use of iron oxide nanoparticles (10 nm in diameter) with fatty acid and hydrophobic coatings inhibits aggregation of particles in the PDMS polymer matrix. Agglomerated particle sizes in thin-film PDMS composites incorporated with uncoated and coated particles are 51 ± 24 μm and 1.6 ± 0.25 μm, respectively. The PDMS composites exhibit saturation magnetization of 22.8 to 23.94 emu g −1 . Stress-strain curves of the composites are characterized by tensile tests. Free-standing magnetic PDMS membranes are fabricated in different sizes from 4 mm to 7 mm in diameter and with the thickness of 35.5 ± 1.5 μm. The membrane of 7 mm diameter achieves deflection of 625 μm in a 0.417 T magnetic field. The magnetic PDMS membranes may be used in micro-pumps and lab-on-a-chip applications.

Characterization of Ferrofluid-Based Stimuli-Responsive Elastomers

“…These data suggested that the increase of MNPs caused a significant increase of small aggregates -formed by two or three MNPs -which do not hamper the overall behavior of the M-SRE since their distribution is homogeneous in the material, as it can be seen at the insets of Figure 2. From these data, it can be confirmed that the PDMS matrix can host up to four times more FF volumes than those previously presented (Pirmoradi et al, 2010;Balasoiu et al, 2011) without having large aggregates. In turn, this higher FF concentration will assure a higher actuation in response to a magnetic stimulus, as it will be discussed in the following sections.…”

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.…”

“…11,12,[21][22][23][24][25] Therefore, this class of magnetic materials opened new opportunities for their utilization in various applications where soft actuators are required such as microfluidic systems or micropumps. 12,21 Indeed, the low elastic modulus of the polymeric matrix allows a direct transfer to the polymeric chains of the forces acting on the magnetic particles under the external field, thus resulting in rapid actuation of flat membranes.…”

“…under an external magnetic field of 417 mT, a deflection of 125 µm is observed for a film of 4 mm in diameter) 11 or high diameters should be employed (e.g. 125 µm deflection under 18 mT magnetic field for a film of 50 mm in diameter).…”