Abstract
Low impedance at the interface between tissue and conducting electrodes is of utmost importance for the electrical recording or stimulation of heart and brain tissue. A common way to improve the cell-metal interface and thus the signal-to-noise ratio of recordings, as well as the charge transfer for stimulation applications, is to increase the electrochemically active electrode surface area. In this paper, we propose a method to decrease the impedance of microelectrodes by the introduction of carbon nanotubes (CNTs), offering an extremely rough surface. In a multistage process, an array of multiple microelectrodes covered with high quality, tightly bound CNTs was realized. It is shown by impedance spectroscopy and cardiac myocyte recordings that the transducer properties of the carbon nanotube electrodes are superior to conventional gold and titanium nitride electrodes. These findings will be favorable for any kind of implantable heart electrodes and electrophysiology in cardiac myocyte cultures.
Highlights
Microelectrode arrays (MEAs) have been applied for in vivo and in vitro recording and stimulating of electrogenic cells, namely neurons and cardiac myocytes
An array of multiple microelectrodes covered with high quality, tightly bound carbon nanotubes (CNTs) was realized
These findings will be favorable for any kind of implantable heart electrodes and electrophysiology in cardiac myocyte cultures
Summary
Microelectrode arrays (MEAs) have been applied for in vivo and in vitro recording and stimulating of electrogenic cells, namely neurons and cardiac myocytes. The extracellular recording technique with MEAs permits a minimum of adverse effects on the cells, making long-term applications such as brain or heart tissue implants possible. Biocompatibility and good electrical coupling at the interface between the solid-state devices and cardiac tissue are important issues for this kind of electrode. Low impedance allows for low noise, implicating an improved signalto-noise ratio (SNR) essential for the detection of very small amplitudes of action potentials in a noisy background. This low impedance is obtained with a large surface area. With the constraint to conserve the lateral dimensions of the microelectrodes, conventional noble metal electrodes are often coated with rough titanium nitride (TiN) or platinum black to increase the surface roughness. Rough TiN is the state of the art coating for microelectrode array chips [5] with good adhesion properties
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