Abstract
Neural prosthesis has helped many patients to restore their physiological functions. To achieve high resolution neural recording/ stimulation, high density microelectrode array (MEA) is necessary for the development of advanced neural prosthesis. As the electrode size shrinking, the impedance of the electrodes which are made of gold, platinum, and silver chloride will increase, thus degrades the signal-to-noise ratio (SNR) of neural recording. Carbon nanotube (CNT) possesses good electrical conductance and material stability. Using CNT-coupled MEA to interface with neurons has been proposed in literatures, and the electrode impedance is greatly improved after CNT coating on the electrode. In this thesis, at first, the high temperature synthesis CNT bundles are employed to fabricate the two types of CNT probes (i-CNT and g- CNT probes). The two types of CNT probes have been proved that can record the neural activity faithfully. Besides, to test the endurance of the CNT probes, the CNT probes are forced to conduct a 500 nA direct current for two hours. The experimental results indicate that this direct current does not degrade the CNT probes’ performance, instead, improves the recording capability of the CNT probes. This improvement is attributed to the permanent (chemical) and non-permanent (physical) mechanisms. Besides, using low temperature (400C) chemical vapor deposition (CVD) method to synthesize the CNTs on the flexible substrate directly has been proposed in this thesis. By combining the designed neural amplifier array, an active, flexible CNT-coupled microelectrode array (cMEA) is formed. The experimental results prove that the proposed active, flexible cMEA can not only reduce the electrode impedance, but also record the neural activities (neural spike of crayfish nerves and ECoG of rat brain) faithfully. In the last part of this thesis, an integrated system for both intracellular and extracellular neural recording is proposed. This chip (6.25 mm2) provides four intracellular and four extracellular neural recording channels. For the designed extracellular neural recording amplifier, the calculated noise efficiency factor (NEF) is 5.04, which is comparable with the state-of-the-art designs. The results of the biological experiments further indicate that the designed extracellular neural amplifier can record the neural activity faithfully. For the intracellular neural recording channel, both the size (0.3 mm2) and power consumption (0.304 mW) are lower than those proposed in literatures. The designed intracellular recording channel is proved that can record the resting potential and the action potential of the LG neurons of crayfish. Besides, the designed current injection circuitry can further inject current pulses into the LG neurons to evoke the action potentials. The experimental results demonstrate that the designed circuitry can achieve intracellular current clamp recording.