New-Generation Electrodes to Measure the Electrical Activity of Electrogenic Cells

One of the most exciting scientific advancements of the 21st century will undoubtedly be the further convergence of life sciences with information technology. One prominent example is the recording and stimulation of heart and brain cells using microelectrodes, which is currently used for a multitude of in vivo and in vitro applications such as deep brain stimulation, brain-computer interfaces, cardiac pacemakers, and drug screening and safety pharmacology. In order to obtain high signal-to-noise ratios, much research is being directed at improving the interface between the cell and the electrode.While there is a growing need for soft and three-dimensional interfacing, traditional electrodes for microelectrode array (MEA) applications are still mostly planar and rigid structures. This is because of the inherent two-dimensionality of lithographic processes which make the scalable fabrication of complex and multifunctional surface architectures at sub-millimeter scales notoriously difficult and/or expensive. Using advancements in the latest micro- and nanofabrication techniques, this Ph.D. project explores two novel electrode types which allow more complex cell-electrode interfacing and higher recorded signal amplitudes. Despite the added complexity, all fabrication is done using conventional and cost-effective cleanroom technology.The first new MEA for cell interfacing is based on capillary aggregation of carbon nanotubes (CNTs). It is shown for the first time that 3D well-shaped CNT electrodes offer multiple advantages compared to flat or other microstructured CNT electrodes for recording electrogenic cells. Average spike amplitudes are as much as twofold larger with occasional overshoots up to 425% better than the reference. The second type of platform explored in this research is a first-of-its-kind multielectrode shell chip with self-folding electrodes, capable of wrapping around the cell in 3D. The approach utilizes residual stress-based self-folding: upon dissolution of a sacrificial layer, flexible panels with embedded electrodes self-actuate and capture cells due to intrinsic differential stress in an ultrathin bilayer. The overall design of these multielectrode interfaces allows simultaneous recordings of every folded electrode located on each of the four cardinal points, and thus the possibility to record 3D spatiotemporal electrical signatures from captured cells.

Publication year:2019