MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI Medical Instrument Analysis and Machine Intelligence

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI Quick presentation of “Results of micro-electrodes survey” Salam R. Gabran May 11 th 2005

MIAMI Research Group Electrical and Computer Eng. Dept. Signals of interest 2 methods of signal detection :  EEG (electroencephalogram)  MEG (magneto encephalogram) MIAMI MEMS and Bio-Sensors Team

MIAMI Research Group Electrical and Computer Eng. Dept. MEG (magneto encephalogram):  Detection using SQUID (super conducting quantum interface device) magnetometers  SQUIDs are super conductors and require cryogenic temperatures  The skull is more transparent to the magnetic fields emitted by the brain  “MEG and EEG record electric activity of the brain in a similar way” [Jaakko Malmivuo] MIAMI MEMS and Bio-Sensors Team

MIAMI Research Group Electrical and Computer Eng. Dept. Conclusion on MEG:  SQUIDs (Josephson junction) are nano devices and the design can include quantum transistor amplifiers.  This technology is still evolving and requires further research  The Cryogenic nature of super conductors is a major drawback for our targeted device  This requires further survey MIAMI MEMS and Bio-Sensors Team

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI MEMS and Bio-Sensors Team EEG (electroencephalogram): Types of electrodes: WetDry  These are the ordinary electrodes to be replaced by our electrodes  Size limitation by electrical and mechanical constraints (large in size)  Require conducting gel  Long setup and cleaning time  An array of micro pins stick to the scalp  Do not require conducting gel  Fast setup and cleaning time  Improve mechanical contact  Improve conductivity and signal pick up (since they penetrate into the skin)

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI MEMS and Bio-Sensors Team Conclusion: Dry EEG electrode is the targeted device

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI MEMS and Bio-Sensors Team EEG (electroencephalogram): Stages of dry electrode design: Stage 1: Electrode design and Micro-fabrication Electrode design: Design the shape of the pin array Electrode material: Non-toxic and compatible with the fabrication technology

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI MEMS and Bio-Sensors Team EEG (electroencephalogram): Stage 2: Circuit design Pre-amplifier circuit: Electrode-preamp distance affects artifacts Filters: Including 60Hz notch filters Bio-amplifier: High CMRR (common mode rejection ratio) and high SNR (signal to noise ratio) to suppress artifact effects Usually designed using instrumentation amps

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI MEMS and Bio-Sensors Team EMI Calibration and variable gain adjustment Faulty placement detection method 1: high impedance or open circuit detection method 2: signal strength window Micro-wires Required for connection between electrodes and other device elements Circuits and electrodes will be designed to share the same substrate or chip

MIAMI Research Group Electrical and Computer Eng. Dept. MIAMI MEMS and Bio-Sensors Team Related papers “An active micro fabricated scalp electrode array for EEG recording” “Characterization of micro machined spiked bio- potential electrodes” “Characterization of a micro machined planar patch clamp for cellular electrophysiology” There are other papers discussing intracranial (brain penetrating) electrodes