Graphitic Carbon Electrodes on Flexible Substrate for Neural Applications Entirely Fabricated Using Infrared Nanosecond Laser Technology

Abstract

Neural interfaces for neuroscientific research are nowadays mainly manufactured using standard microsystems engineering technologies which are incompatible with the integration of carbon as electrode material. In this work, we investigate a new method to fabricate graphitic carbon electrode arrays on flexible substrates. The devices were manufactured using infrared nanosecond laser technology for both patterning all components and carbonizing the electrode sites. Two laser pulse repetition frequencies were used for carbonization with the aim of finding the optimum. Prototypes of the devices were evaluated in vitro in 30 mM hydrogen peroxide to mimic the post-surgery oxidative environment. The electrodes were subjected to 10 million biphasic pulses (39.5 μC/cm2) to measure their stability under electrical stress. Their biosensing capabilities were evaluated in different concentrations of dopamine in phosphate buffered saline solution. Raman spectroscopy and x-ray photoelectron spectroscopy analysis show that the atomic percentage of graphitic carbon in the manufactured electrodes reaches the remarkable value of 75%. Results prove that the infrared nanosecond laser yields activated graphite electrodes that are conductive, non-cytotoxic and electrochemically inert. Their comprehensive assessment indicates that our laser-induced carbon electrodes are suitable for future transfer into in vivo studies, including neural recordings, stimulation and neurotransmitters detection.

Analysis of Carbon-Based Microelectrodes for Neurochemical Sensing

“…The characteristics of carbon fiber microelectrodes (CFMs) based biosensors for measuring extracellular concentrations of neurochemicals and other biological analytes, in real-time and with high accuracy, have been of continuous scientific interest for the past few decades [1,2,3,4,5,6,7,8,9]. A variety of electrochemical recording techniques have employed such sensors, including constant-potential amperometry and fast-scan cyclic voltammetry (FSCV) [10,11,12,13,14,15].…”

“…A variety of electrochemical recording techniques have employed such sensors, including constant-potential amperometry and fast-scan cyclic voltammetry (FSCV) [10,11,12,13,14,15]. Since sensitivity in monitoring changes in neurochemical concentrations, in vitro and in vivo , strongly depends on the microelectrode material, on its design, and on its fabrication processes, a large body of research has been directed towards such considerations [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Carbon-based materials, such as pyrolytic graphite, carbon fibers (CFs), glassy carbon (GC), pitch-based graphitic foams, nanographite ribbons, fullerenes, carbon nanotubes (CNT), and doped diamond are still considered to be the most suitable candidates because of their biocompatible, conductive, and mechanical properties [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15].…”

Highly Porous Platinum Electrodes for Dry Ear-EEG Measurements

“…The electrode array for the otoplastics ( Figure 1A) was prepared using a fast laser-aided manufacturing process to gain highest design flexibility. The method used multi-layer processing to achieve the personalized design and was based on previously published processes [18,19]. It entailed the spin coating of a 70 µm thick MED1000 silicone layer (NuSil, Carpinteria, USA) on a flat carrier substrate.…”

Flexible Bioelectronic Devices Based on Micropatterned Monolithic Carbon Fiber Mats

“…Other device components still rely on thin metal films, leading to a compromised interface durability and work‐function differences . Few studies report on laser‐induced carbonization of different polymers in order to achieve flexible structures . This serial process shows large variation in material composition depending on process and material parameters .…”