Fig. 6. Validation of closed-loop controller integrated with the two MEMS-based subcomponents—GP microelectrode and electrothermal microactuators.
a A typical trial of the closed-loop controller—the controller moved the electrode using the electrothermal microactuators in steps of 6.5 μm toward a neuron until the electrical impedance of the electrode tip was below the threshold value of 6 MΩ, after which the controller switched to the “penetration and/or tuning” mode to autonomously penetrate the neuron and record intracellular potentials. b Two additional trials demonstrating ability of the controller and microactuators to successfully locate and penetrate two separate neurons. c Comparison of performance of the controller with the conventional microdrive (5 neurons) vs electrothermal microactuators (5 neurons) showed no significant difference in RP, AP, and ΔVp–p between the two systems (p > 0.1 in all cases).