## 4 Electroceticals--Intelligent Environments
### Artificial Retina
With all the above desirable considerations, the Boston team has developed the implantable artificial retina; the retinal implant concept is shown in illustrated Figure 5 [106; 107; 108]. The retinal implant components are located outside the eye and are attached to the eye's outermost layer, the sclera. The implanted electronic chip is placed behind the conjunctiva, the thin membrane attached to the eyelids that overlay the sclera. The electrode array is inserted in the sub-retinal space, between the retina and the choroid, delivering stimulus current to the retinal nerve. To sustain the device under intelligent, intellectual, biological atmospheric conditions, the device must be isolated by a biologically compatible and electromagnetic field-compatible sophisticated functional material. Therefore, the Boston team used metallic isolation over the telemetry system chip, a safe isolation material against electromagnetic interference, and is hermetic [106; 107; 108]. Although metallic shielding is immune to electromagnetic interference, researchers and biomedical engineers are thinking biocearamics utilization, probably due to an advanced hermeticity. However, room temperature processability and frequency respective functional properties limit their usage. We hope the advancement in the biocearamics field will help use biocearamics in the packaging of biomedical implants soon. Initially, the Boston team introduced a first-generation retinal implant, shown in Figure 2 of [108]. Later, they introduced a second-generation device with miniaturized, integrated, and more advanced electronic components in a compact design under safety regulations to increase the resolution of artificial vision. The second-generation device concept is illustrated in Figure 1 of [106]. The new second-generation design overcame the three limitations outlined earlier with the first-generation device. The first one is the coil design, which is designed in such a way that the coil surrounds the cornea under the conjunctiva comfortably and efficiently coupled with the transmitted coil antennae. The second one is the hermite metallic sealing of the entire bionic chip, excluding the wirelessly connected coil and the electrodes. The third one is an advanced superior electrode array design to provide efficient stimulations into subretinal space [106; 107; 108]. Diseases of the retina, for example, retinitis \(-\) pigmentosa: abnormality in photoreceptors function are the leading cause of blindness in most cases. To restore vision, alternative approaches are stimulating the photoreceptors' function or replacing the function of the photoreceptors [109; 110; 111]. Recently, [PERSON] et al. demonstrated an on-chip inductive coil-based power transfer system for electrically controlled, optically addressed retinal prosthesis [112]. The device consists of a group of vertical Silicon nanowire photodiodes connected by a transparent conductor and topped by a sputtered iridian oxide electrode. Light is the energy source to induce current from the nanowire-microelectrode-array and is controlled by the inductively coupled power. The electrode-based system is implanted in sub-retinal space since currents as an output of each electrode are proportional to both incident light energy and applied voltage. This is how the system generates the specific shape/timing of biphasic stimulating current to the neurons to f  
Figure 5: Boston bionic implant: concept of Boston bionic implant [106; 107; 108]. system is also feasible for producing a range of stimulating currents depending on the wavelengths of incident light [112]. The optical energy-based addressing retinal prosthesis with electrically activated electrode array operating principle is depicted in Figure 3 of [112]. The [PERSON] et al. group reported a similar implantable retinal prosthesis device with an integrated silicon nanowire-based photodetection circuit to activate the retinal neurons with light energy [113].