Percutaneous gas diffusion device suitable for use with a subcutaneous implant

Percutaneous gas diffusion device. In one embodiment, the percutaneous gas diffusion device includes a core layer, an outer layer, and an intermediate layer. The core layer may be cylindrical and may include a gas-permeable, liquid-impermeable material. The outer layer may peripherally surround the core layer and may include a tissue-integrating material. The intermediate layer may peripherally surround the core layer and may be peripherally surrounded by the outer layer. The intermediate layer may include a barrier that prevents infiltration of tissue from the outer layer into the core layer and that additionally reduces diffusion of gas from the core layer into the outer layer. The percutaneous gas diffusion device may be coupled to a subcutaneous implant device, such as a subcutaneous container holding implanted cells and/or tissue, a subcutaneous electrochemical oxygen concentrator, or a water electrolyzer.