In this study, a novel flexible conductive sodium alginate/chitosan (SA/CS) foam with double-network structure based on dual-coated magnetic particles (MPs) was prepared by a biological crosslinking process of natural biopolymers. The structural characterization, response deformation and magnetic-field-dependent electric performance for different foams were investigated, and they were significantly dependent on the mass ratio of SA/CS, the contents of glycerol and MPs. By increasing SA and CS, the electrostatic interactions of double-network enhanced, leading to an increase in its binding force with the MPs, so the magnetic-responsive performance was strongly improved. Meanwhile, the resistance displayed a remarkable variation under the magnetic fields. For instance, the resistance of the sample with a mass ratio of 3:3 decreased with the magnetic flux densities (0.10-0.40 T) and it ranged from 14.8-6.83 kΩ, which reduced by about 53.9%. Moreover, the periodic measurements were applied so as to verify its recoverability and repeatability. Furthermore, a possible mechanism was provided to explain the magnetic-responsive behavior of the samples. Because of the superior magnetic controllability and preeminent mechanical performance, the conductive porous foam is promising in the fields of artificial electric skins, soft sensors and actuators.

This work reports a novel conductive composite matrix based on magnetically sensitive flexible sponges containing a porous polymeric matrix and bidisperse magnetic microspheres dual-coated with gelatin (GE) and multiwalled carbon nanotubes (MWCNTs). In comparison to the conventional continuous phase, the porous polymeric matrix herein is mainly constructed by sodium alginate (SA) and GE, which displays high flexibility, excellent deformability, and strong stability. The structural characterization, magneto-induced deformation, and magnetic− electric properties of the conductive composite matrix were investigated and they were significantly influenced by the contents of GE and magnetic microspheres. On increasing the GE contents, the electrostatic interactions increased owing to the increased entanglement points and cross-linking degree between polymer molecules, thus reducing the resistance performance of the samples. Meanwhile, the resistances of samples 12; 10 wt % and 12; 40 wt % are 6.83 and 3.94 kΩ under a 400 mT magnetic field, respectively, exhibiting a decreasing trend with the increase of magnetic microspheres. Additionally, the effects of MWCNTs on the electric conductivity were also illustrated. Furthermore, a potential mechanism was proposed to investigate the magnetic-fielddependent electrical properties of the products. Specifically, the iterative loading−unloading of the magnetic field was applied to verify the repeatability and recoverability of the conductive composite matrix. It was found that the electrical resistance and deformation could be synchronously and reversibly changed by the applied magnetic field, which provides a new idea for a new generation of intelligent sensors toward an artificial electric skin and micro-electromechanical system.

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