A number of implantable biomedical devices that are in clinical use or in active development involve the direct integration of solid inorganic metallic or semiconducting electrodes with living tissue. Examples include cardiac pacemakers, cortical microelectrodes, cochlear implants, retinal implants, and glucose sensors. In all of these devices it is important to establish and maintain effective communication between the soft, wet, ionically conducting cells and the hard, dry, electrically conducting engineered device.