64-Channel Carbon Fiber Electrode Arrays for Chronic Electrophysiology

Abstract

A chief goal in neuroscience is to understand how neuronal activity relates to behavior, perception, and cognition. However, monitoring neuronal activity over long periods of time is technically challenging, and limited, in part, by the invasive nature of recording tools. While electrodes allow for recording in freely-behaving animals, they tend to be bulky and stiff, causing damage to the tissue they are implanted in. One solution to this invasiveness problem may be probes that are small enough to fly under the immune system's radar. Carbon fiber (CF) electrodes are thinner and more flexible than typical metal or silicon electrodes, but the arrays described in previous reports had low channel counts and required time-consuming manual assembly. Here we report the design of an expanded-channel-count carbon fiber electrode array (CFEA) as well as a method for fast preparation of the recording sites using acid etching and electroplating with PEDOT-TFB, and demonstrate the ability of the 64-channel CFEA to record from rat visual cortex. We include designs for interfacing the system with micro-drives or flex-PCB cables for recording from multiple brain regions, as well as a facilitated method for coating CFs with the insulator Parylene-C. High-channel-count CFEAs may thus be an alternative to traditional microwire-based electrodes and a practical tool for exploring the neural code.

Construction and Implementation of Carbon Fiber Microelectrode Arrays for Chronic and Acute <em>In Vivo</em> Recordings

“…A number of electroplating times were tested, and 30 s produced superior signal isolation among the recording sites (Figure 5). While it has been well established that PEDOT-pTS 12 , 24 , 25 , 26 and PEDOT-TFB 21 provide reliable options for preparing carbon fiber recording sites, we found that plating with gold, a proven and dependable method for electroplating electrodes for chronic implantation 27 , 28 , increased the ease of implantation and prevented the electrode tips from clumping together. In producing final impedance values of less than 0.2 MΩ on average, this method proves comparable to values achieved using PEDOT-TFB 21 and PEDOT-pTS 26 .…”

Direct laser writing of 3D electrodes on flexible substrates

“…This progressive loss of signal is a major motivation behind our electrode design work, because the only known way to improve signals over the long run is to reduce electrode scale. While carbon fiber electrode arrays have demonstrated stable recordings over long time scales, yield is low and the fabrication process is not scalable [40]. Thin-film silicon carbide ultramicroelectrodes provide a scalable alternative that will be investigated further [41], and polymer electrodes using insertion shuttles show promise for increasing signal longevity [42].…”

Benchtop Carbon Fiber Microelectrode Array Fabrication Toolkit

“…The Maharbiz lab has also developed a higher channel probe that was inserted to depths of 2.5-3 mm [51]. The Cox lab has also developed a carbon fiber bundle probe ~ 1 mm in length [39]. These probe geometries will be of greater use to labs doing chronic work in deeper brain structures.…”

“…Despite the many advantages of carbon fibers, many labs find manual fabrication of these arrays to be arduous. Some groups [39] combine carbon fibers into bundles that collectively result in a larger ( ~ 200 μm) diameter than a traditional microwire [39], [40]. Others have fabricated individuated carbon fiber electrode arrays, though their methods require cleanroom-fabricated carbon fiber guides [41]–[43] and equipment to populate their arrays [35], [42], [43].…”