A high-density carbon fiber neural recording array technology

Objective: Microwire and Utah-style neural recording arrays are the predominant devices used for cortical neural recording, but the implanted electrodes cause a significant adverse biological response and suffer from well-studied performance degradation. Recent work has demonstrated that carbon fiber electrodes do not elicit this same adverse response, but these existing designs are not practically scalable to hundreds or thousands of recording sites. We present technology that overcomes these issues while additionally providing fine electrode pitch for spatial oversampling.Approach: We present a 32-channel carbon fiber monofilament-based intracortical neural recording array fabricated through a combination of bulk silicon microfabrication processing and microassembly. This device represents the first truly two-dimensional carbon fiber neural recording array. The density, channel count, and size scale of this array are enabled by an out-of-plane microassembly technique in which individual fibers are inserted through metallized and isotropically conductive adhesive-filled holes in an oxide-passivated microfabricated silicon substrate.Main results: Five-micron diameter fibers are spaced at a pitch of 38 microns, four times denser than state of the art one-dimensional arrays. The fine diameter of the carbon fibers affords both minimal cross-section and nearly three orders of magnitude greater lateral compliance than standard tungsten microwires. Typical 1 kHz impedances are on the order of hundreds of kiloohms, and successful in vivo recording is demonstrated in the motor cortex of a rat. 22 total units are recorded on 20 channels, with unit SNR ranging from 0.85 to 4.2.Significance: This is the highest density microwire-style electrode array to date, and this fabrication technique is scalable to a larger number of electrodes and allows for the potential future integration of microelectronics. Large-scale carbon fiber neural recording arrays are a promising technology for reducing the inflammatory response and increasing the information density, particularly in neural recording applications where microwire arrays are already used.

Study on the Mechanical Property of Cu-Filled Isotropically Conductive Adhesive/SiO2 Composites

Cu-filled isotropically conductive adhesive/SiO2 composites were prepared by direct-blending modified SiO2 into Cu-filled ICAs. The effects of different contents of SiO2 on the mechanical property were sdudied in this paper. The infrared spectra of the cured product between epoxy resin and imidazole was obtained with FT-IR. The surface morphology of the composite and its fractured surface after tensil test were observed by scanning electron microscope(SEM). In addition, energy dispersive spectrometry(EDS) was applied to analyze the distribution of Si in the adhesive layer. Experimental results showed that a small amount of SiO2 powders could evenly distribute in the Cu-filled ICAs, and as a reslut the mechanical property of Cu-filled ICA/SiO2 increased dramatically with the addition of SiO2. The best shear strength of the composite could reach up to 16.1MPa and 36.4% higher than the ICAs without addition SiO2 when the content of SiO2 was 3%.