Field-induced deformation of ferromagnetic soft nanocomposites

Abstract

Uniaxial ferromagnetic Ni nanorods were prepared by the anodic aluminum oxide (AAO) template method. Reversible magnetization changes, measured perpendicular to the texture axis, were analyzed in terms of the Stoner–Wohlfarth model (SW). Using empirical model parameters, a quantitative and consistent description of the orientation- and field-dependent magnetic torque per particle was achieved. The model was extended (eSW) to take into account the local rotation of the magnetic nanorods in a soft-elastic matrix. The nanorods were characterized regarding their size, using transmission electron microscopy (TEM), their magnetic moment and colloidal volume fraction, determined from static field-dependent optical transmission (SFOT) measurements, and their rotational shape factor, obtained from oscillating field-dependent optical transmission (OFOT). The eSW-model was used in the simulation of simple bending and torsion of thin composite filaments. These simulations were compared with experimental results with the focus on the effect of finite magnetic anisotropy and local elastic rotation on the field-induced deformation of soft nanocomposites. The high sensitivity of thin filaments enabled the investigation of torque-induced deformation at nanorod volume density as low as 10−4 at which particle-particle interactions were negligible. In addition, reprogramming of the magnetic texture by magnetization reversal and the resulting modification in the deformation pattern was investigated.

Variations in the thermal conductivity of magnetosensitive elastomers by magnetically induced internal restructuring

“…The vector T v contains all temperatures of the inner cells. The entries of the matrices A vv and A vc are extracted from the coefficients in equation (23). In fact, they constitute the negative discretized Laplacian operator for a graph with weighted edges [55].…”

“…In fact, they constitute the negative discretized Laplacian operator for a graph with weighted edges [55]. We then calculate the temperature of each cell by solving equation (24) for T v , In equation (23), the thermal conductivity λ ij is set to λ silicone by default. It is only altered to λ m , when both cells i and j hold magnetized beads that are virtually in contact.…”

“…Both types of reaction illustrate how the materials sense magnetic variations in their environment. Possible applications therefore comprise tunable damping devices [18][19][20] and soft actuators [21][22][23], which are capable of a wider range of motion, such as jumping, walking, and rolling. Highly elastic magnetosensitive elastomers therefore are promising materials in soft robotics [20].…”

Shape-programmable cantilever made of a magnetoactive elastomer of mixed content

“…The magnetostatic potential is approximated quadratically, whereas for the displacement vector a linear approximation is used. The FEM scheme implemented with the aid of FEniCS is used to minimise the energy equation (20), i.e. to solve the quasistatic magnetoelastic problem, where the elastic and magnetic energy densities are rendered by equations ( 8) and ( 16), respectively.…”

“…By now, the main amount of knowledge has been accumulated on the cantilevers made of MAEs-MS, they were the first to become a focus of interest. One may find detailed experimental data [12][13][14][15][16][17][18][19][20][21] together with numerous publications on the theory and numerical simulation [17,18,22,23]. The given references are just examples, the full list is far too long.…”