Robust Anticorrosive Polymer Thin Film for Reliable Protection of Ingestible Devices

Ingestible devices (ID) provide a safe and noninvasive method for monitoring, diagnosing, and delivering drugs to specific sites in the human body, particularly within the gastrointestinal (GI) tract. However, the GI environment is highly acidic and humid, which can cause IDs to fail, and their corrosion in the acidic environment can cause leaching of toxic metal ions, thereby substantially limiting their long-term use. Thus, an efficient method is required to protect IDs, especially in the chemically and mechanically harsh GI environment. However, an anticorrosive polymer coating that can safeguard IDs in the GI environment without delamination or performance degradation has not been developed to date. The protective layer must satisfy several critical requirements, e.g., high biocompatibility, mechanical durability, and superior anticorrosion performance. This paper reports a highly cross-linked but submicron-thick siloxane-based anticorrosive polymer thin film that can be deposited directly onto IDs without damaging them. The 500 nm-thick cross-linked polymer coating demonstrates exceptional corrosion resistance and chemical and mechanical stability in the GI environment without cytotoxicity. A printed circuit board (PCB) coated with the developed ultrathin protective film sustained performance after exposure to a pH 1.00 phosphate buffered saline solution at 37 °C for 72 h without leaching of metal ions. The ID continued to operate effectively under such challenging conditions; thus, the developed film is suitable for applications that require prolonged functionality, e.g., diagnostics, drug delivery, and continuous health monitoring in the GI tract.