Influence of the Stabilization Process on the Piezotronic Performance of Electrospun Silk Fibroin
© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The ability to provide the energy needed while keeping the product ergonomic, lightweight and non-intrusive, is the ultimate challenge for wearable technologies. In this work, silk fibroin (SF) is electrospun and immersed in liquid methanol (MeOH) over 3 and 48 h. A phase transformation from water-soluble α-helix (silk I) to insoluble β-sheets (silk II) is observed, increasing the protein crystallinity and the membrane stability against aqueous environments. The phase transformation from silk I to silk II leads to a reorganization of the polymer chains inside the protein fibers, which influences the dipolar reorientation of the SF molecules. A cost-effective energy harvester device is built, showing an open-circuit output voltage of 4.5 V, a power density around 1 µmW cm−2, with an efficiency up to 6%, and a mechano-sensitivity of 0.078 ± 0.01 V kPa−1. This work provides new insights into the effect of the stabilization process of the SF membranes and its influence on the electroactive properties of the protein. Overall, the electromechanical and energy harvesting performance of the SF membranes opens new opportunities for applications as wearable self-powered microelectronics, with the potential to be fully integrated inside clothing, with potential applications in personalized healthcare devices and sports training systems.