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Research Paper

Development of Titanium Needle Probes for Neural Recording and Evaluation of Magnetic Resonance Imaging Artifacts

[+] Author and Article Information
Hargsoon Yoon, Devesh C. Deshpande

Department of Electrical Engineering, Innovative Nano/Bio Devices and Systems Laboratory, University of Arkansas, 700 Research Center Boulevard, Fayetteville, AR 72701

T. H. Kim, Eun-Kee Jeong

Department of Radiology, Utah Center for Advanced Imaging Research, University of Utah, 729 Arapeen Drive, Salt Lake City, UT 84108-1218

Robert E. Harbaugh

Department of Neurosurgery, College of Medicine, Pennsylvania State Hershey Medical Center, 500 University Drive, Hershey, PA 17033

Vijay K. Varadan

Department of Electrical Engineering, Innovative Nano/Bio Devices and Systems Laboratory, University of Arkansas, 700 Research Center Boulevard, Fayetteville, AR 72701; Department of Neurosurgery, College of Medicine, Pennsylvania State Hershey Medical Center, 500 University Drive, Hershey, PA 17033

J. Nanotechnol. Eng. Med 1(1), 011004 (Sep 30, 2009) (8 pages) doi:10.1115/1.4000039 History: Received May 03, 2009; Revised July 24, 2009; Published September 30, 2009

The aim of this research is to develop a mechanically flexible and strong neural probe with microelectrode array for future clinical applications in neural prosthetics and neurological disorder fields. This research specifically focuses on the development of neural recording electrodes with iridium oxide (IrOx) electrodes on a titanium needle probe and discusses the fabrication techniques and their evaluation for physical properties and electrochemical performance. Microfabrication processes, such as inductive coupled plasma etching, were used to deeply etch the Ti needle structures on titanium foils, and microelectrode arrays with iridium oxide films were formed by electrochemical deposition for low impedance neural recording. Mechanical and electrochemical analyses were performed to verify the viability of Ti needle probes in vitro. The final section of this paper addresses the issue of magnetic resonance imaging artifacts of titanium needle probes, and test results are compared with similarly fabricated Si needle probes. The advantages of using a titanium needle probe are discussed in the application of neural probe electrodes, as well.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 2

(a) Image of Ti needle probes and (b) SEM image of a Ti needle and Au electrode array after fabrication

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Figure 3

SEM images of the tip area of a Ti needle probe tip after DRIE process

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Figure 4

SEM images of (a) grass-like defects, (b) clean surface, and (c) measured elements by EDS for the defect and clean areas

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Figure 5

Images of (a) indentation test set up and (b) needle probes (bent and straight) after insertion into gelatin

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Figure 6

(a) Impedance modulus and (b) phase measured with Au and IrOx electrodes in 50 mM PBS at 5 mV ac and 0 V dc potential versus Ag/AgCl reference electrode

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Figure 7

Results of the image artifact test for needle probes (a) photograph of fabricated titanium needles along with a silicon needle embedded in gelatin jelly, (b) and (c) MR images using 3D TSE pulse with different read-out gradient direction: (0.6 mm)3 isotropic spatial resolution—Si is the first probe from the left side, two 200 μm thick Ti is the third and fifth probes from the left side, and two 50 μm thick Ti is the second and forth probes from the left side

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Figure 1

Schematic diagram of core nanoelectrode fabrication processes: (a) lamination of a Ti foil on a glass substrate, (b) PECVD SiO2 deposition, (c) Ti/Au deposition by evaporation and electroplating, (d) first lithography, (e) wet etching of Au and Ti, (f) SiO2 passivation and SU-8 lithography, (g) Ti deep RIE etching, (h) wet cleaning of polymer residue, (i) passivation by SU-8 lithography, (j) thick photoresist coating for front side protection and detaching from lamination, (k) backside etching of the Ti sample, and (l) cleaning and retaining of Ti needles (A is glass, B is gel, C is titanium, D is SiO2, E is Ti/Au, F is SiO2, G is SU-8, and H is AZ4330 photoresist)

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