A highly tunable silicone-based magnetic elastomer with nanoscale homogeneity

Abstract

Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material which is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (γ-Fe203) nanoparticles 7–10 nm in diameter. The material is homogenous at very small length scales (< 100 nm) and can be crosslinked to form a flexible, magnetic material which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 – 50% wt. without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings.

Structural control of elastic moduli in ferrogels and the importance of non-affine deformations

“…They consist of superparamagnetic or ferromagnetic particles of nano-or micrometer size embedded in a crosslinked polymer matrix [6]. In this way, they combine the properties of ferrofluids and magnetorheological fluids [7][8][9][10][11][12][13][14][15][16] with those of conventional polymers and rubbers [17]: we obtain elastic solids, the shape and mechanical properties of which can be changed reversibly from outside by applying external magnetic fields [6,[18][19][20][21][22][23][24][25].…”

Bridging from particle to macroscopic scales in uniaxial magnetic gels

“…(27) can be consistently mapped onto the energetic changes obtained on the mesoscopic level in Eq. (26) by choosing an appropriate value of the coefficient D 2 in Eq. (29).…”

“…For example, by an external magnetic field the elastic moduli of magnetic gels can be reversibly adjusted from outside. 1,[23][24][25][26][27] Consequently, the possibility of constructing externally tunable damping devices 28 or vibration absorbers 23 has been outlined. Also, the deformations of the materials in external magnetic fields have been investigated [29][30][31][32][33][34] and their use as soft actuators 1,35 and as magnetic sensors [36][37][38] has been pointed out.…”

Thin Polymer Layers with Superparamagnetic Properties

“…Great potential is assigned to the superparamagnetic polymers for the application in sensors or actuators [12,13]. Contrary to the medical applications these are high-volume technical applications.…”

“…Usually an in situ preparation and immediate incorporation of the particles tailored to the polymer system is carried out. As an example, the synthesis of magnetite particles of iron (III) chloride for the incorporation into silicone elastomers was considered by Evans et al [13]. Especially for the PVC polymer system the only described method is the preparation and incorporation of a ferrofluid with DOP (dioctyl phthalate) as the carrier liquid was described by Yáñez-Flores et al [14] and Rodríguez-Fernández et al [15].…”