ABSTRACT
A 8-channel neural signal′s simultaneous transducer detection micro system was developed to research the neural loop located at the brain hippocampus zone. The components of the system contained the neural probe manufactured with the Micro-electro-mechanical-systems (MEMS) technique based on silicon-on-insulator (SOI) substrate, biological low noise chopper-stabilization amplifier, low noise and intermediate speed SAR-ADC converter, reduced and low power ASK/FSK modulation radio transmitter. The micro system was applicable with the characters of small volume, interferences free, neural electrophysiology and neurotransmitter simultaneous detection, high sensitivity, high linearity, etc. The electrode resistance was optimized to 35.0 kΩ after depositing nanometer platinum black on the 4 electrophysiological sites on the Pt electrode. With the modification enzyme technique, nanomaterial enzyme membrane (Pt-mPD-GluOx) was directly fixed on the glutamate detection locus for selectively detecting special neural neurotransmitter matter. In addition, the electrochemistry measurement results indicated that the linear range of glutamate was 6-35 μmol/L with correlation coefficient of 0.97, the sensitivity was 0.0069 pA/(μmol/L). The current response error was less than 3.0 pA, which showed that the neural needle satisfied differential selection. Also, the logic/analog mixed signal 180-nm Application specific integrated circuit (ASIC ) technique (SmicRF180 nm 1Poly6M) was used to manufacture the transducer back-end disposing IC chip, and the test results provided some key parameters such as chopper-stabilization amplifier (equivalent in putting noise voltage ≤0.7 μV rms@1 kHz, gain of 71-82 dB, CMRR/PSRR>100 dB), SAR-ADC (ENOB is 12 bits, power consumption is 1.2 mW when maxmium conversion speed is 1 Msps, signal-noise-ratio is 60.9 dB, etc), and ASK/FSK modulation radio transmitter (the PA′s outputting power of 4-5 dBm, the radiation range of 10 meters). The micro neural transducer integrated system was convenient and wireless wearable for the research of brain hippocampus region.