Soft And Skin-Like Stretchable Silk-Based Epidermal Organic Bioelectronics For Comprehensive Human Physiological Signal Monitoring

Skin-like epidermal bioelectronics, which emerged as a unique and transformative technology, offers highly imperceptible and wearable, soft digital health units mechanically akin to human skin for continuous and real-time health monitoring. These innovations, stemming from advancements in novel material synthesis and fabrication techniques, offer unparalleled features such as conformability, miniature footprint, and elasticity, where such unique features not only enhance the precision of health data recording but also promote patient adoption due to their comfort and unobtrusiveness. However, existing solutions still lack desirable properties, such as self-adhesivity, breathability, biodegradability, and transparency, and fail to offer a streamlined and scalable fabrication process. This thesis addresses the shortcomings in the current state-of-the-art by presenting protein-based silk-based skin-like epidermal bioelectronics, exploiting all the desirable material features of silk as a substrate, which have been individually present in existing devices but never combined into a single embodiment. As a significant advancement, the all-in-one solution presented in this thesis demonstrates excellent self-adhesiveness (300 N/m), high breathability (1263 g.h-1.m-2), and rapid biodegradability in soil within a mere two days. Additionally, possessing an elastic modulus of ~ 5 kPa and surpassing 600% in stretchability, the silk-based, biodegradable soft electronics seamlessly replicate the mechanics of the epidermis and form a conformal skin/electrode interface. Therefore, precisely inkjet-patterned with silver nanoparticle inks and coupled with a flexible readout circuitry, silk epidermal bioelectronics is capable of real-time and non-invasive recording of electrophysiological signals, including cardiac (ECG), neural (EEG), muscular (EMG), and ocular (EOG) biopotentials, in durations reaching up to 12 hours with superior performance in par with Ag/AgCl gold standard, “wet” electrodes.