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An in-depth understanding of the interface between cells and nanostructures is one of the key challenges for coupling electrically excitable cells and electronic devices. Recently, various 3D nanostructures have been introduced to stimulate and record electrical signals emanating from inside of the cell. Even though such approaches are highly sensitive and scalable, it remains an open question how cells couple to 3D structures, in particular how the engulfment-like processes of nanostructures work. Here, we present a profound study of the cell interface with two widely used nanostructure types, cylindrical pillars with and without a cap. While basic functionality was shown for these approaches before, a systematic investigation linking experimental data with membrane properties was not presented so far. The combination of electron microscopy investigations with a theoretical membrane deformation model allows us to predict the optimal shape and dimensions of 3D nanostructures for cell-chip coupling.

We describe the fabrication process and characterization of polymer coated multielectrode array chips featuring 64 planar Ag/AgCl electrodes for electrophysiological and electrochemical measurements of ionic currents. The multielectrode chip consists of platinum feedlines and microelectrodes fabricated on an oxidized silicon substrate. The feed lines are passivated with a polyimide layer. Silver is deposited electrochemically on the platinum electrodes and chlorinated afterwards resulting in stable micro Ag/AgCl reference electrodes that are recessed within picoliter cavities. We envisage the chip as a platform for high-throughput investigation of lipid bilayers. Schematics of a planar reference electrode. The chips are processed on oxidized silicon (blue) and consist of Pt feedlines (yellow), the Ag/AgCl electrode (black) passivated with polyimide (light blue).

Microelectrode arrays (MEAs) are gaining increasing importance for the investigation of signaling processes between electrogenic cells. However, efficient cell–chip coupling for robust and long-term electrophysiological recording and stimulation still remains a challenge. A possible approach for the improvement of the cell–electrode contact is the utilization of three-dimensional structures. In recent years, various 3D electrode geometries have been developed, but we are still lacking a fabrication approach that enables the formation of different 3D structures on a single chip in a controlled manner. This, however, is needed to enable a direct and reliable comparison of the recording capabilities of the different structures. Here, we present a method for a precisely controlled deposition of nanoelectrodes, enabling the fabrication of multiple, well-defined types of structures on our 64 electrode MEAs towards a rapid-prototyping approach to 3D electrodes.

Inkjet printing is an attractive method for cost-effective additive manufacturing of electronic devices. Especially for applications where disposable sensor systems are of interest, it is a promising tool since it enables the production of low-cost and flexible devices. In this work, we report the fabrication of a disposable microelectrode array (MEA) using solely inkjet printing technology. The MEAs were fabricated with two different functional inks, a self-made gold ink to print conductive feedlines and electrodes and a polymer-based ink to add a dielectric layer for insulation of the feedlines. We printed different MEA designs of up to 64 electrodes with a minimum lateral spacing of 200 μm and a minimum electrode diameter of ~31 μm. As a proof-of-concept, extracellular recordings of action potentials from cardiomyocyte-like HL-1 cells were performed using the all-printed devices. Furthermore, we stimulated the cells during the recordings with noradrenaline, which led to an increase in the recorded beating frequency of the cells. The results demonstrate the feasibility of inkjet printing gold MEAs for cell-based bioelectronics.

We investigate the influence of self-assembled alkanethiol monolayers at the surface of platinum microelectrode arrays on the stochastic amperometric detection of citrate-stabilized silver nanoparticles in aqueous solutions. The measurements were performed using a microelectrode array featuring 64 individually addressable electrodes that are recorded in parallel with a sampling rate of 10 kHz for each channel. We show that both the functional end group and the total length of the alkanethiol influence the charge transfer. Three different terminal groups, an amino, a hydroxyl, and a carboxyl, were investigated using two different molecule lengths of 6 and 11 carbon atoms. Finally, we show that a monolayer of alkanethiols with a length of 11 carbon atoms and a carboxyl terminal group can efficiently block the charge transfer of free nanoparticles in an aqueous solution.

The quality of the recording and stimulation capabilities of multielectrode arrays (MEAs) substantially depends on the interface properties and the coupling of the cell with the underlying electrode area. The purpose of this work was the investigation of a three-dimensional nanointerface, enabling simultaneous guidance and recording of electrogenic cells (HL-1) by utilizing nanostructures with a mushroom shape on MEAs.