Design and fabrication of flexible biodegradable microelectrode array for recording electrocorticography signals

Conventional flexible implantable microelectrode arrays, used for real-time brain activity monitoring, incur minimal tissue damage due to their flexibility; however, these require retrieval surgery, causing trauma to subjects. Implants, fabricated using biodegradable materials, dissolve gradually in body fluid, eliminating the necessity for retrieval surgery. This work reports designing and developing a 10-channel flexible biodegradable microelectrode array to acquire electrocorticography signals from rats brains. The array was fabricated using tungsten, a transient metal, and PLLA:PCL (80:20), a biodegradable composite polymer. The subdural implantation of the array on the somatosensory cortex of rats (n=3) facilitated electrical biopotentials acquisition using OpenBCI Cyton Boards. The baseline activities, the induced epileptic discharges after peripheral electrical stimulation, and the recovered baseline activities after antiepileptic drug administration were recorded from sedated rats. The chronic baselines and evoked activities were also acquired from awake rats. The gradual decline of chronic baselines was evident, suggesting a possible dissolution of electrodes. Furthermore, the time-frequency analyses demonstrate the differences between baselines and induced epileptic activities. The signals recorded from microelectrode arrays demonstrate their potential to monitor brain activities in a chronic study. Histology of the harvested vital organs from the euthanized rats confirmed minimal tissue damage due to implantation.