Research Of Flexible And Bioresorbable ECoG Girds

In recent years,with the in-depth study of neuronal signal transmission mechanism and the continuous exploration of clinical solutions to brain diseases,higher requirements for neuronal signals detection are put forward in medicine field.The development of bioelectrode with high sensitivity,high resolution,high biocompatibility,low damage and low cost has become an urgent demand in electroencephalogram research.The traditional intracortical brain electrodes have high signal-to-noise ratio.However,the acute and chronic inflammatory reactions induced by implantation not only cause irreversible damage to the brain but also lead to electrode failure.The non-implantable signal detection methods such as fMRI,EEG,MEG,etc.,cause no damage to the brain,but their low resolution make them difficult to meet the requirements of accurate detection of brain waves,disease diagnosis and disease treatment for clinical applications.The ECoG electrode,a non-penetrating and implantable electrode for cortical signal collection,can detect high-resolution signals with limited brain damage and therefore has a promising application in brain science.In this paper,two novel ECoG electrodes,flexible ECoG electrode and bioresorbable ECoG electrode,were proposed.These two kinds of electrodes were fabricated by micro/nano processing technology.The flexible ECoG electrode adheres closely to the cortical surface to detect clear ECoG signals.The bioresorbable ECoG electrode degrades naturally in biofluids after work in certain amount of time,which avoid potential infection during the electrode removal surgery.Both the in vitro and in vivo test methods were used to verify the excellent performance of the electrode in this paper.Both flexible and bioresorbable electrodes can detect ECoG signal with high signal-to-noise ratio,which proves them suitable for clinical experiments and practical applications,especially for epilepsy diagnosis and detection.The details and achievements of the research are as follows:1.Stable and repeatable fabrication process of flexible ECoG electrode was obtained.Based on the micro-nano processing platform,flexible ECoG electrode array with high intensive channels of 32 that have stable performances were fabricated.The metal layer has good binding force with the substrate.The in vitro electrochemical impedance tests showed that the impedance of all 32 channels were less than 120 kΩ,as a result that the flexible ECoG electrode array prepared by this process is suitable for in vivo implantation.The flexible ECoG electrode array enabled to acquire distinct waveforms at different sites after implantation,demonstrating that the electrode’s flexibility allows it to adhere closely to the cortical surface for clear ECoG signals,and that the high density of the electrode sites ensured accurate collection of brain waves in all positions within the electrode coverage.2,Biodegradable ECoG electrodes were prepared.According to the characteristics of biodegradable polymer materials,for example fragile to high temperature,poor flexibility,and soluble in organic solvent,we provided a typical fabrication process for bioresorbable electronic sensor.Three different bioresorbable materials,gelatin,PLGA and PCL/PLLA,as optional substrate and encapsulation materials were studied to determine their influence on the final electrode.PCL/PLLA was proved to be the best choice for substrate and encapsulation materials among these three materials,due to its good flexibility,malleability,and temperature resistance.To verify that the process protocol for biodegradable electronic devices in this study was equally applicable for the preparation of other bioelectronic devices,an intracranial pressure sensor was designed on the end of abioresorbable ECoG electrode array.3.Degradation process of bioresobable ECoG electrodes was investigated.The results showed that the electrode would work stably for about five days before its loss of efficacy,which fully meet the requirements for various clinical applications.The sleep model and epilepsy model of rats in vivo proved the result that the electrode is capable of both physiological and pathological signal detection.