Mechanically Robust and Anti-Biofouling Hybrid Encapsulation via Layered Organic-Liquid Interfaces for Implantable Devices

Abstract

Implantable bioelectronic devices, due to their prolonged contact with biological tissues, face persistent challenges including moisture permeation, mechanical deformation, and biofouling. Traditional encapsulation strategies using either inorganic or organic materials face trade-offs between moisture barrier performance and mechanical flexibility. Inorganic materials provide excellent moisture resistance but are brittle, whereas organic polymers are flexible but inherently permeable. Here, we developed a Multi-layered Organic-based Liquid Encapsulation (MOLE) specifically tailored for implantable bioelectronics. MOLE consists of a layer-by-layer assembly of amine-functionalized silicone elastomer and Parylene-C, forming chemically bonded and conformal interfaces with enhanced interfacial adhesion. The outermost silicone layer, infused with silicone oil, minimizes protein adsorption (<1%), resists biofilm formation (sliding angle <10°), and prevents adhesion of inflammatory cells and proteins, thereby reducing acute inflammation. This hybrid architecture achieves an 86-fold improvement in adhesion strength compared to conventional Parylene-C coatings and significantly enhances mechanical robustness under dynamic deformation. In addition, MOLE provides superior moisture and ion barrier properties. Accelerated aging tests at 85°C demonstrated a 160-fold increase in insulation lifetime over Parylene-C, equivalent to approximately 445 h at physiological temperature (37°C). Furthermore, in vivo studies using a degradable magnesium antenna demonstrated stable encapsulation, minimal interfacial disruption, and strong resistance to biological degradation over time.