High density multifunctional neural probes for parallel read-out and control

V. Lanzio, M. West, S. Sassolini, S. Dhuey, A. Koshelev, H. Adesnik, G. Telian, R. Witharm, P. Denes, F. Martinez Mc-kinney, S. Ito, S. Cabrini
Lawrence Berkeley National Laboratory,
United States

Keywords: neural probe


In order to advance neuroscience in vivo experiments, it is necessary to interface neural networks at a single cell level and be able to simultaneously use different techniques such as electro physiological recordings, pharmacological manipulation, and optogenetic intervention, while minimizing brain tissue damage. A neural probe capable of perform simultaneously all these types of recordings with, at the same time, a high density of components and small shank dimensions is therefore needed to gain a deeper knowledge on the brain. In this work we present electrical and optical neural probes having different features fabricated on the same type of substrates and with dimensions of 45 um width and 15 um thickness [1]. Many examples of high density neural probes [2][3] or of multifunction integration [4] exist. Ideally, shank dimensions as low as 50 microns wide and 15 microns thick are required. The need for small dimensions is to be achieved in order to minimize brain damage during insertion. [5] High density electrical probes have been fabricated with 64 pads. Interconnections to deliver the signal 120 nm wide and the pads are 5 X 12 um. Starting with a silicon wafer, electrical connections are fabricated using electron beam lithography and lift off techniques. A 75 nm passivation layer is then deposited by ALD, after that shanks are thinned by KOH etching. Probes are then attached to the PCB, wire bonded and encapsulated. Probes with same shank dimensions with silicon dioxide and silicon nitride ridge monomode waveguides have also been fabricated. The wave guides cross section is 350 nm x 160 nm. Ring resonators select different wavelengths which are then delivered to neurons by creating 1 micron diameter spots . The actual probes present two output focusing gratings on the shank. Since the fabrication process is the same for electrical and optical probes, both aspects can be integrated on the same device. Acknowledgments Work at the LBNL Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02- 05CH11231. References [1]: Gyorgy Buzsaki et Al. Tools for Probing Local Circuits: High-Density Silicon Probes Combined with Optogenetics [2]: Gustavo Rios et Al. Nanofabricated Neural Probes for Dense 3-D recordings of Brain Activity [3]: Jorg Scholvin et Al., Close-Packed Silicon Microelectrodes for Scalable Spatially Oversampled Neural Recording [4]: Wu F. et Al., An implantable neural probe with monolithically integrated dielectric waveguide and recording electrodes for optogenetics applications [5]: Zoltan Feteke Recent advances in silicon-based neural microelectrodes and microsystems