Self-healing and printable elastomer with excellent shear stiffening and magnetorheological properties

This work reports a novel kind of hybrid magnetorheological elastomer (HMRE) that possesses multi-functions including excellent shear stiffening and magnetorheological (MR) effects, as well as self-healing and printable abilities. The HMRE materials are prepared by embedding carbonyl iron particles (CIPs) into a blend of silicon rubber (SR) and low cross-linking gel-like polyurethane (PU). The relative shear stiffening effect of HMRE-3:1 (the mass ratio of PU and SR is 3:1, and 50 wt% CIPs) is 6095% as the shear frequency increases from 0.1 Hz to 100 Hz, which is about 150 times that of SR based magnetorheological elastomer (MRE). With the magnetic flux density from 0 to 1T, MR effect of isotropic HMRE-3:1 is as high as 266%, which is 3.5 times that of SR based MRE. Notably, HMRE obtains extraordinary mechanical and electrical healing capabilities. HMRE with a destructive cut-through injury can sustain an extensibility of 425% (the initial extensibility ≈ 650%) after healing. Meanwhile, possible mechanisms are proposed to explain the shear stiffening properties, MR effect, and self-healing performance of HMRE. Moreover, the extruded modeling 3D printing of flexible HMRE actuators can be achieved due to the plasticine property of pre-polymerized HMRE, which bestows HMRE with magnetic particle distribution programmability and shape designability. This work may provide a new way for the next-generation multifunctional materials with exceptional shear stiffening behavior, magnetically mechanical properties, self-healabilities, and printable performance.