Journal of Vacuum Science & Technology B emphasizes processing, measurement and phenomena associated with micrometer and nanometer structures and devices. Processing may include vacuum processing, plasma processing and microlithography among others, while measurement refers to a wide range of materials and device characterization methods for understanding the physics and chemistry of submicron and nanometer structures and devices.
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Commercial microelectrode arrays (MEAs) for in vitro neuroelectrophysiology studies rely on conventional two dimensional (2D) neuronal cultures that are seeded on the planar surface of such MEAs and thus form a random neuronal network. The cells attaching on these types of surfaces grow in 2D and lose their native morphology, which may also influence their neuroelectrical behavior. Besides, a random neuronal network formed on this planar surface in vitro also lacks comparison to the in vivo state of brain tissue. In order to improve the present MEA platform with the above mentioned concerns, in this paper, the authors introduce a three dimensional platform for neuronal cell culturing, where a linear nanoscaffold is patterned on a microsieve array by displacement Talbot lithography (DTL) and reactive ion etching. Good pattern uniformity is achieved by the DTL method on the topographically prepatterned nonflat surface of the microsieve array. Primary cortical cells cultured on the nanopatterned microsieve array show an organized network due to the contact guidance provided by the nanoscaffold, presenting 47% of the total outgrowths aligning with the nanogrooves in the observed view of field. Hence, the authors state that this nanopatterned microsieve array can be further integrated into microsieve-based microelectrode arrays to realize an advanced Brain-on-Chip model that allows us to investigate the neurophysiology of cultured neuronal networks with specifically organized architectures.
The authors present the fabrication and characterization of corrugated graphene sheets on polydimethylsiloxane (PDMS) substrates for flexible and stretchable electrodes. The graphene sheets were grown on imprinted Cu foil via atmospheric pressure chemical vapor deposition. The grown graphene sheets with both corrugated and flat surfaces were then transferred from the Cu foil to PDMS substrates using a novel, direct transfer method, where PDMS was directly casted and cured on the graphene sheets followed by removal of Cu via wet etching. This process largely eliminated the formation of cracks in the graphene caused by traditional transfer processes. The corrugated graphene sheets were characterized using Raman spectroscopy and conductivity measurements under the application of lateral strain parallel and perpendicular to the graphene corrugation on the PDMS substrates, demonstrating a smaller shift of the two dimensional Raman peak for the corrugated graphene electrodes as compared to the flat graphene. It was shown that the maximum achievable strain prior to a change in electrode resistance increased from 8% for the flat graphene sheet to 15% for the corrugated graphene electrode. Preliminary results also showed that the corrugated graphene sheet maintained its material integrity and electrical conductivity under multiple cycles of high strains.