Movable microprobes for the brain

Neuroscientists have long recognized the significance of using microelectrode arrays for recording extracellular potentials from populations of neurons, and a number of such devices have been developed so far. However, current implantable microelectrode technologies to monitor single neuronal function in-vivo often fail in chronic situations primarily due to mechanical drift in positioning mechanisms, micromotion of brain tissue and gliosis around the implant site. We report here two novel microactuator (electrostatic and electrothermal) and associated microelectrode technologies that enable precise repositioning of microelectrodes after implantation in the event of failure or otherwise. Both microactuator technologies are capable of bi-directional motion of the microelectrodes. The movement resolution of electrostatic microactuators is in the order of 1 μm and that of the thermal microactuators in the order of 9 μm. However, the thermal microactuators are mechanically more robust. Multi-unit data obtained from in vivo animal models using both technologies are reported. This is first successful demonstration of a micromachining approach to the fabrication of movable microprobes. These movable microprobes will potentially lead to better long-term interfaces with single neurons in vivo.