Abstract
Multi-electrode arrays find application in electrophysiological recordings. The quality of the captured signals depends on the interfacial contact between electrogenic cells and the electronic system. Therefore, it requires reliable low-impedance electrodes. Low-temperature cofired ceramic technology offers a suitable platform for rapid prototyping of biological reactors and can provide both stable fluid supply and integrated bio-hardware interfaces for recordings in electrogenic cell cultures. The 3D assembly of thick film gold electrodes in in vitro bio-reactors has been demonstrated for neuronal recordings. However, especially when dimensions become small, their performance varies strongly. This work investigates the influence of different coatings on thick film gold electrodes with regard to their influence on impedance behavior. PEDOT:PSS layer, titanium oxynitride and laminin coatings are deposited on LTCC gold electrodes using different 2D and 3D MEA chip designs. Their impedance characteristics are compared and discussed. Titanium oxynitride layers emerged as suitable functionalization. Small 86-µm-electrodes have a serial resistance Rs of 32 kOhm and serial capacitance Cs of 4.1 pF at 1 kHz. Thick film gold electrodes with such coatings are thus qualified for signal recording in 3-dimensional in vitro cell cultures.
Highlights
Brain-on-a-chip fluid systems must provide an adequate environment to support the growth of neuronal cells in three-dimensional hydrogels [1]
The layout of the landing pads is compatible with the pad design of commercial recording systems (MEA2100, multichannel systems MSC GmbH, Reutlingen, Germany)
Uncoated thick film gold electrodes with varying size between 86 μm and 215 μm are arranged on these chips
Summary
Brain-on-a-chip fluid systems must provide an adequate environment to support the growth of neuronal cells in three-dimensional hydrogels [1]. This encompasses a reliable fluid supply, provision of a nutrient supply at a constant temperature, and the reliable removal of metabolic products. Modern microfabrication offers a wide range of technologies, which enables the design of bio-microreactors [2]. Low-temperature cofired ceramic technology (LTCC) is suitable for the rapid prototyping of microreactors with integrated electronics [3,4,5].
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