Neural probe arrays are expected to significantly benefit the lives of amputees and people affected by spinal cord injuries or severe neuromotor diseases. By providing a direct route of communication between the brain and artificial limbs, these arrays record and stimulate neurons in the cerebral cortex. Researchers have developed a three-dimensional probe array for chronic and long-term implantation in the brain. This array is compact enough to freely float along with the brain when implanted on the cortex.

The compact neural probe array consists of a three-dimensional probe array, a custom 100-channel neural recording chip, and a flexible polyimide polymer cable. (© 2014 A*STAR Institute of Microelectronics)

The two-dimensional probes were inserted them into a thin slotted silicon platform for assembly. To produce a three-dimensional probe array, the assembly was joined to the recording chip. Instead of being aligned, however, the contacts of the probe electrodes and recording chip were orthogonally arranged with respect to each other, resulting in mismatched planes. To solve this issue, a silicon-based connector, or interposer, was developed that electrically linked these components.

Compared with commercial neural probes, the new array exhibited competitive electrical properties, including electrode impedance. Moreover, biocompatibility tests showed that the presence of array components did not rupture cell membranes or suppress cell growth.