Ultra high aspect ratio penetrating metal microelectrodes for biomedical applications

Studying the functioning of the brain through the use of penetrating microelectrodes has revolutionized our understanding of the brain and has the potential to treat physical conditions such as the aftermath of a stroke, disease or other neural problems. Cochlear implant electrodes have transformed the lives of people who were suffering from cochlear auditory disorders. However, limitations of manufacturing procedures restrict the choice of work materials to mostly silicon based materials, and biocompatibility issues have constrained the extensive use of these devices. Metal microelectrodes can absolve this limitation and enable extensive study of the neural centers. In this paper we report the fabrication of tungsten penetrating microelectrodes using electrochemical machining. Ultra high aspect ratio penetrating metal microelectrodes with diameters 10 mu m and below, with surface roughness (Ra) values in the range of 300-500 nm, have been fabricated by electrochemical machining process. Details regarding the fabrication process and a mathematical model developed for the electrochemical machining process are discussed in this paper.