Investigation into a Conductive Composite Matrix Based on Magnetically Sensitive Flexible Sponges

Abstract

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-field-dependent 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.