Low-cost silicon neural probe: fabrication, electrochemical characterization and in vivo validation

Abstract

This paper presents the fabrication of a silicon neural probe using low-cost microfabrication technologies, such as thin-films deposition, blade dicing, and photolithography. The metal stack that forms the 9 microelectrodes of 50 × 50 µm2 area, the tracks and the pads were made of Ti and Pt, while the passivation stack was SiO2 and Si3N4. The fabricated probe was characterized using electrochemical impedance spectroscopy, before and after deposition of poly(3,4-ethylene-dioxythiophene) (PEDOT) on Pt microelectrodes. The electrochemical deposition of PEDOT, a conductive polymer, reduced the impedance of the Pt microelectrodes. The neural probe with PEDOT was used for in vivo electrophysiological acute recordings in an adult rat. The extracellular recordings were filtered to obtain the spike and local field potential (LFP) data, using Butterworth bandpass filters of 400–6000 Hz and 0.1–300 Hz, respectively. The results obtained with the fabricated neural probe validated its functionality, comparing with the signals acquired with a commercial neural probe, and the viability of the fabrication process, which avoids high–cost and complex etching processes.

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Acknowledgements

ANI supports this work through the Brain-Lighting project by FEDER funds through Portugal 2020, COMPETE 2020 with the reference POCI-01-0247-FEDER-003416. This work is also supported by FCT with CMEMS-UMinho Strategic Project, reference UIDB/04436/2020, the project Infrastructures Micro&NanoFabs@PT, reference NORTE-01-0145-FEDER-022090, POR Norte, Portugal 2020 and by the project OpticalBrain, reference PTDC/CTM-REF/28406/2017, by FEDER funds through the COMPETE 2020 - Programa Operacional Competitividade e Internacionalização (POCI). The authors acknowledge also FCT CEECIND grants, Bial Foundation Grants 207/14 and 037/18 to JO; Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (FEDER) (NORTE-01-0145-FEDER-000013); FEDER Funds, through the Competitiveness Factors Operational Programme (COMPETE), and The National Fund, through the FCT (POCI-01-0145-FEDER-007038). The authors also thank to N. A. P. de Vasconcelos from ICVS-University of Minho for the implementation of the setup for the in vivo recordings.

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The work presented in this paper was a collaboration of all authors. J. A. Rodrigues, S. Pimenta, J. F. Ribeiro, and J. H. Correia conceived and designed the experiments. The fabrication process was performed by S. Pimenta, J. P. Pereira, N. M. Gomes, M. R. Souto, H. C. Fernandes and J. F. Ribeiro. The electrochemical impedance spectroscopy characterization and PEDOT deposition was performed by J. A. Rodrigues. J. A. Rodrigues, S. Pimenta, I. Caetano, C. Soares-Cunha and J. F. Oliveira performed the in vivo electrophysiological acute recordings. J. A. Rodrigues and S. Pimenta analyzed the data. The first draft of the manuscript was written by J. A. Rodrigues and S. Pimenta, and all authors commented on previous versions of the manuscript. J.H.C supervised all the work.

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Correspondence to José A. Rodrigues.

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All procedures performed in studies involving animals were in accordance with the European Regulations (European Union Directive 2010/63/EU). Animal facilities and the people involved in animal procedures were certified by the Portuguese regulatory entity – DGAV (Direção-Geral de Alimentação e Veterinária). All protocols followed the guidelines of Life and Health Sciences Research Institute, the Institutional Animal Care and Use Committee from University of Minho and were approved by the Ethics Committee of the Life and Health Sciences Research Institute.

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Rodrigues, J.A., Pimenta, S., Pereira, J.P. et al. Low-cost silicon neural probe: fabrication, electrochemical characterization and in vivo validation. Microsyst Technol 27, 37–46 (2021). https://doi.org/10.1007/s00542-020-04898-3

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