Microelectrode technologies for neuroengineered systems

Many neuroengineered systems, such as neural recording and neural stimulation devices, make use of microelectrodes to establish direct neural-electronic interfaces. The design of microelectrodes used in neural-electronic interfaces varies considerably from application to application in order to meet a wide range of different performance specifications (electrical, mechanical, chemical, biological, thermal, magnetic, and optical). Desirable characteristics of chronically implanted devices used to record activity in the cortex include stable high-impedance electrodes, high electrode count, and 3-D electrode arrangement. Desirable characteristics of chronically implanted prosthetic devices used to stimulate activity in the retina or auditory nerve include low-impedance electrodes, high electrode density, 1-D or 2-D electrode arrangement, flexible substrate, and long electrode lifetime. Microelectrodes can also be used to quantify the concentration of specific chemicals if properly prepared with ion-selective thin-film coatings. A variety of microelectrode applications, technologies, and performance specifications will be compared and discussed.