Magnetostrictive and Electroconductive Stress-Sensitive Functional Spider Silk

Electronics and soft robotics demand the development of a new generation of hybrid materials featuring novel properties. Among these, remarkable mechanical properties are required to sustain mechanical stresses, and electrical and magnetic properties are essential to design the devices' interface. In this work, a hybrid material is presented, consisting of a spider silk thread, providing mechanical robustness, coated with a layer of a magnetostrictive FeCo alloy, which ensures both electrical conductivity and stress-sensitive magnetic properties. The durability and the homogeneity of the composite are validated, as well as its ability to respond to magnetic and mechanical stimuli. Despite the coating, the soft nature of the silk and its mechanical performances are preserved. The magnetic study reveals that the magnetic behavior of the film is strongly affected by the silk thread-FeCo layer interaction, especially under mechanical stresses. Indeed, when the composite is subjected to tensile strain, the magnetic signal changes accordingly, indicating that the layer-silk interaction is maintained and can be exploited to reveal the tensional state of the sample even under severe cycles. Therefore, the presented hybrid material is a flexible fiber with properties that are suitable for magneto-electronics applications, e.g., magnetic actuators as well as strain/stress sensors.