Fabrication Of 3D Nanostructured Multielectrode Arrays By Using Thermal Nanoimprint Lithography To Improve Cell Coupling For Low Signaling Neurons

Abstract

Event Abstract Back to Event Fabrication Of 3D Nanostructured Multielectrode Arrays By Using Thermal Nanoimprint Lithography To Improve Cell Coupling For Low Signaling Neurons Dominique Decker1*, Sven Ingebrandt1, Holger Rabe1, Karl-Herbert Schäfer1 and Monika Saumer1 1 University of Applied Sciences Kaiserslautern, Department of Informatics and Microsystems Technologie, Germany Motivation Recently a lot of effort was done in optimizing MEA technology in order to enhance signal qualities and to improve the coupling with cells in a culture. Recording performances can be improved by either coating the MEA with artificial or biological polymers or by adding three dimensional nanostructures on top of the sensing pad, thus increasing the surface area and ensuring a tight cell electrode coupling by partly engulfing the nanosized MEA features by the cells [1, 2]. Here we present a fabrication process of nanostructured MEA chips based on nanoimprint lithography (NIL) and electroplating. Compared to other nanostructuring techniques, NIL offers the possibility to fabricate a whole set of nanostructures on several chips at the same time in a fast, simple and inexpensive full wafer process. The nanostructured MEA devices will later be used for action potential measurements and drug testing with neurons with relative weak signals, such as those from the enteric nervous system. Materials and Methods Silicon or glass wafers are vapor-deposited with 20 nm titanium and 200 nm gold layers, followed by a 200 nm thin spin-coated layer of a thermal resist. Nanoimprint lithography is performed (figure 1) with a customized silicon master stamp including a broad range of nanostructures with different geometries, diameters and arrangements. After removing the residual layer with reactive ion etching the nanostructures are filled with gold by electroplating. Microfabrication techniques including photolithography, wet chemical etching and chemical vapor deposition steps are needed to define the leads, the sensing areas and the contact pads of the MEA chips. Subsequently the wafer is cut. The separated chips are bonded to a PCB, encapsulated and prepared for cell culture experiments. Results and Discussion Different nanostructures like meanders, lines, pillars and tubes with diameters from 50 nm up to 800 nm, different heights up to 500 nm and variable distances between the structures have successfully been fabricated on gold-coated substrates. By means of overelectroplating it is also possible to create mushroom-like or muffin-like structures. AFM and SEM pictures show a good structure transfer during NIL and a high uniformity of the electroplated nanostructures over the whole wafer (figure 2). Electrochemical characterization of the fabricated structures is done with cyclic voltammetry and electrochemical impedance spectroscopy. As expected the measurements show an increase of the electrochemical active surface area and a reduction of the impedance compared to planar electrodes. First biocompatibility tests with P19 cells also show a good cell electrode coupling. Conclusion The presented fabrication process incorporates an alternative, high throughput, time saving and thus cost-efficient method for the integration of nanostructures on MEA chips. Different nanostructures are investigated to find an ideal combination of shape, dimension and arrangement for enhancing the signal-to-noise ratio. Future work will be based on recordings with living cells where we intend to work with neurons from the enteric nervous system. These experiments will explore which nanostructures are best suited for cell electrode coupling and thus signal detection from this particular cell type.