Figure 2. (a) (b) (c) The picture of manufactured microsystem
b) Wirelessly Powered Microsystem
Recording through subcutaneously wired Multi-electrode array(MEA) has revealed a plenty of knowledge about brain and neural signal decoding for a decade. However, subcutaneous connections impose limitation to behavior of subjects and raise great risks of infections.
In order to overcome those limits, a lot of research teams have tried to develop microsystem which is able to record and process neural signals and small enough to be implanted underneath skull. In this microsystem, it is crucial to transfer stable and enough power wirelessly avoiding excessive tissue heating.
Figure 3. Realized microsystem powered by RF
c) Micro-Electrode Array(MEA) in BMI system
In order to record brain signal, researchers have used non-invasive electrode such as EEG, fMRI or MEG that do not need delicate surgery. However, non-invasive method is insufficiency to get accuracy signal from brain. For the reason, researchers start to take invasive method even it needs to open the skull for penetrating electrode to brain. To minimize the risk of invasive electrode, many researcher teams consider to design micro-size, shape and thin probe, flexible substance and 3D array to get multi signal from variety points. Furthermore, the material of electrode should be bio-compatibility and non-toxic as electrode penetrates to brain. Material and design of electrode are main focus to study, some teams are studying integrated micro-electrode array with optics
Figure 4. Schematics of micro-electorde array (MEA) and optical MEA