Figure 2
From: Implantable Biofuel Cells Operating In Vivo—Potential Power Sources for Bioelectronic Devices
The timeline of development of implanted biofuel cells/biosensors operating in vivo in living organisms. Note that in the early devices the catalytic electrodes were based on inorganic materials, while later enzyme-based electrodes became available for the in vivo operation. (The scheme is adopted from reference (56) with permission.)