Aiming to realize the integration of signal processing with the human body, wearable and implantable radio frequency (RF)/microwave devices are rapidly developed. However, the insufficiency in skin commonality and biocompatibility brings up challenges in making such devices. In this study, an ultra-flexible and biocompatible CoFeB/silk film is developed potentially for on-skin and implantable RF/microwave applications. Moreover, the CoFeB/silk films present controllable dissolvability in aqueous solutions and exhibit great potentials in applications for environmentally friendly disposable devices. A strain-tunable bandstop filter based on the CoFeB/silk film was fabricated, which exhibited a large frequency tunability of 3 GHz and ability in monitoring the finger-joints' motions. This concept and method of combining ferromagnetic materials with the biocompatible substrate offers a novel pathway for wearable/implantable applications.
Keywords: RF/microwave; ferromagnetic resonance; magnetic thin films; magnetostriction; silk fibroin.