Fabrication and characterization of an Upside-down CNT MEA

Abstract

Over the last few years the need of new alternatives to traditional disease modelling, drug screening and toxicity tests has boosted the development of a new class of devices called Organ on Chip. These usually consist in a substrate or a well in which cells are cultured with the aim of differentiating them in a particular tissue lineage. With sensors and actuators integrated in the device, a culturing environment, as close as possible to in vivo one, is reproduced. This stimulates both cell differentiation and viability, boosting model reliability in this way. An instance of this class of devices is the Heart on Chip developed by Philips Research in collaboration with TU Delft. This device, also know as Cytostretch device, is a stretchable polydimethylsiloxane (PDMS) membrane embedding a micro-electrode array meant to mea- sure the electrical activity of cardiomyocytes grown on the top of the membrane. Unlike most of previous organ-on-chip designs, the Cytostretch device was developed aiming at fabricating a clean-room compatible product. This should guarantee a large-scale fabrication and a rapid commercialization. Besides this, Philips Research team focused on the mechanical properties of the membrane by opting for a polymer-last approach. These design choices led to the fabrication of multi-electrode array characterized by an electrode-electrolyte impedance too high for the detection of the low-amplitude biopotential signals coming from the cells. In order to solve this problem, the integration of carbon nanotube (CNT) electrodes into the Cytostretch device will be considered; CNT forests have been widely used to coat biopo- tential electrodes since they guarantee intrinsically large surface area as well as low electrode- electrolyte impedance. To the best of authors knowledge, this is the first attempt to embed CNT electrodes in an Organ on Chip. Moreover, this is the first work which aims to produce a CNT multiple electrode array with a large-scale fabrication, a fully clean-room compatible process and a polymer-last approach. This project had three main goals. Firstly, it aimed to characterize Cobalt-grown CNTs as bio-electrode coating. Secondly, it verified the feasibility of a novel fabrication process which allows to embed CNT electrodes in a PDMS membrane without the need to perform critical manual steps and last but not least, it aimed to prove the biocompatibility of CNTs as bio-electrode coating in in vitro tests including human induced pluripotential stem cells.