Research On Liquid Metal Flexible Neural Electrode Arrays

As the core component of neuroelectrophysiological signal detection,neural electrodes can accomplish in situ collection and synchronously detection of neuroelectrophysiological signals,which allows the interpretation of brain neural network activities,an important way to discover the pathogenesis of major neurological diseases.However,most of the electrodes used in clinical practice are rigid nerve electrodes made of silicon-based materials.There is a large difference between the mechanical properties of the electrodes and the nerve tissue.The mechanical properties of the nerve electrode-brain tissue interface do not align during the implantation process,which would likely lead to the damage of brain tissue,severe immune inflammation.Therefore,the development of long-term stable and mechanically matched flexible neural electrode-brain tissue interface is an urgent research topic in the current field of neural electrodes.In recent years,new flexible neuroelectrodes developed based on flexible electronics and flexible materials have received much attention.To meet the higher requirements of neuroscience research on the tensile performance of nerve electrodes,a new type of stretchable nerve electrode is developed to solve the problem of tissue damage during the current long-term implantation and to improve the long-term stability of electrophysiological signal detection.Liquid metal materials represented by gallium-indium alloys have received extensive attention from researchers domestically and abroad for their good biocompatibility,high conductivity,and excellent tensile properties.In this thesis,a flexible and stretchable liquid metal neural electrode array is prepared by combining liquid metal and flexible polymer materials through screen printing technology and micro-nano processing technology.The specific research protocols are as follows:Targeting the defects of high fluidity and uneven oxide film surface of liquid metal,micro-nano liquid metal particles were prepared by ultrasonic method.Liquid metal particles were used as screen printing ink.Electrodes were prepared by screen printing technology with a resolution as high as 50 μm line width.The reciprocating tensile test results show that the liquid metal electrode has good tensile properties.While maintaining stable electrical properties,the maximum tensile strength is 108%.At the same time,magnetron sputtering technology is used to wrap the electrode recording site.In vitro experimental results show that magnetron sputtering platinum particles can significantly improve the long-term stability of liquid metal electrodes,and significantly reduce the electrode interface impedance,which established the experimental basis for the signal acquisition of the neurons.To make up for the complex preparation process,high production costs and mismatch with the mechanical properties of neuronal cells associated with traditional commercial multi-channel electrode arrays,a multi-channel liquid metal neural electrode array is prepared using screen-printing technology.In vitro cell experiments show that the multi-channel liquid metal neural electrode array possesses excellent cell compatibility.Hippocampal neuron cells cultured on the surface of the liquid metal electrode reveals normal biological activity.Long-term culture experiments indicate that hippocampal neuronal cells can be cultured on liquid metal electrodes for up to 30 days,which verifies the long-term stability of liquid metal electrodes.Finally,the multi-channel liquid metal neural electrode array exhibits good neural signal acquisition capabilities and achieves synchronous recording of the firing signals of isolated hippocampal neurons.Different types of firing signals of hippocampal neurons are distinguished with a maximum amplitude of 40 μV.This application provides a new technical solution for the development of flexible microelectrode arrays.Targeting the limitations of traditional implantable nerve electrodes such as the mismatched mechanical properties with brain tissue and poor adhesiveness,a flexible and stretchable liquid metal nerve electrode array is fabricated using liquid metal materials combined with flexible PDMS-based materials.The liquid metal nerve electrode array has good tensile stability.After 2000 cycles of tensile testing,the electrochemical impedance remains unchanged.At the same time,the results of longterm in vivo experiments show that the liquid metal nerve electrode has good histocompatibility and great stability.The electrode does not affect the surrounding tissues of the implantation site.Real-time monitoring of the rat epilepsy signal is successfully done by using a liquid metal nerve electrode.Field potential signal of the entire process of the epileptic seizure was recorded,which verified the potential application of the liquid metal nerve electrode array in the field of neuroelectrophysiology.The liquid metal electrode is expected to be applied to fields related to epilepsy diagnosis and disease onset warning in the future.In summary,this thesis greatly improves the priting resolution of the liquid metal electrodes to 50 μm,and combines the PDMS substrates to prepare flexible and stretchable neural electrode arrays,and realizes the real-time monitoring of hippocampal neurons signals and rat epilepsy signals.Stretchable and flexible liquid metal-based neural interfaces provide a good solution for solving the poor mechanical performance of existing rigid electrodes,which have a wide range of applications in the fields of brain-computer interfaces and neurological diagnosis.