Biodegradable and Antibacterial Ag/PPy/Zein Ultrafine Fibers for Electromagnetic Interference Shielding and Joule Heating

The rapid progress in electronics has exacerbated electromagnetic pollution, escalating the demand for electromagnetic interference (EMI) shielding materials. Whereas the abandonment of conventional nonbiodegradable EMI materials further provoked environmental pollution. Consequently, there is a growing emphasis on the biodegradability of EMI materials, in addition to qualities such as strong absorption, lightweight, flexibility, and breathability. In this study, biodegradable ultrafine fibrous EMI shielding mats were developed from epoxy-modified corn protein zein (ZE) with single- or double-layer coatings of polypyrrole (PPy) and silver (Ag). The epoxy modification endowed the base ZE fibers with adequate mechanical properties and morphological stability in wet conditions, ensuring high air permeability. The PPy/ZE mats achieved an EMI shielding effectiveness (SE) of 26.69 dB within the 8.2 to 12.4 GHz frequency range, which was further boosted to 86.00 dB by the Ag/PPy/ZE mats. Even after 5000 bends, 86.5% and 79.3% of the SE values could be retained. The Ag/PPy/ZE mats demonstrated antibacterial properties and adjustable joule heating performance. Biodegradation was evident after 40 days of soil burial, characterized by near-linear weight loss and alterations in mechanical properties. This study positions the Ag/PPy/ZE mats as a promising option for short-term EMI shielding in electronic devices or biomedical applications, both in vitro and in vivo, thereby stimulating the advancement of biobased EMI shielding materials.