Three-dimensional (3D) graphene architectures are of great interest as applications in flexible electronics and biointerfaces. In this study, we demonstrate the facile formation of predetermined 3D polymeric microstructures simply by transferring monolayer graphene. The graphene adheres to the surface of polymeric films via noncovalent π−π stacking bonding and induces a sloped internal strain, leading to the self-rolling of 3D microscale architectures. Micropatterns and varied thicknesses of the 2D films prior to the self-rolling allows for control over the resulting 3D geometries. The strain then present on the hexagonal unit cell of the graphene produces a nonlinear electrical conductivity across the device. The driving force behind the self-folding process arises from the reconfiguration of the molecules within the crystalline materials. We believe that this effective and versatile way of realizing a 3D graphene structure is potentially applicable to alternative 2D layered materials as well as other flexible polymeric templates.

Interfaces between single neurons and conductive substrates were investigated using focused ion beam (FIB) milling and subsequent scanning electron microscopy (SEM) observation. The interfaces play an important role in controlling neuronal growth when we fabricate neuron-nanostructure integrated devices. Cross sectional images of cultivated neurons obtained with an FIB/SEM dual system show the clear affinity of the neurons for the substrates. Very few neurons attached themselves to indium tin oxide (ITO) and this repulsion yielded a wide interspace at the neuron-ITO interface. A neuron-gold interface exhibited partial adhesion. On the other hand, a neuron-titanium interface showed good adhesion and small interspaces were observed. These results are consistent with an assessment made using fluorescence microscopy. We expect the much higher spatial resolution of SEM images to provide us with more detailed information. Our study shows that the interface between a single neuron and a substrate offers useful information as regards improving surface properties and establishing neuron-nanostructure integrated devices.

Electrophysiology of 3D neuronal cultures is of rapidly growing importance for revealing cellular communications associated with neurodevelopment and neurological diseases in their brain‐like 3D environment. Despite that the brain also exhibits an inherent modular architecture that is essential for cortical processing, it remains challenging to interface a modular network consisting of multiple 3D neuronal tissues. Here, a self‐folding graphene‐based electrode array is proposed that enables to reconstruct modular 3D neuronal tissue and investigate firing dynamics among moduli. A graphene‐sandwiched parylene‐C film self‐folds into a cylindrical structure within which living cells can be encapsulated. Culture of encapsulated cells inside the folded graphene enables to spontaneously construct 3D cell aggregates and ensure firm contact between the graphene surface and encapsulated cells. As the inner graphene surface can be utilized as an electrode, the reliable cell–electrode contact allows for long‐term electrical recording from multiple 3D aggregates. Additionally, the modular network consisting of multiple 3D aggregates exhibits richer firing patterns than a conventional homogenous 2D network, which demonstrates that the approach enables measurements of firing dynamics in complex 3D neuronal networks. The deformable graphene electrode will be a powerful platform for investigating complex cellular communications in brain‐like 3D cultures.

Three-dimensional (3D) architectures of graphene are of great interest for applications in flexible electronics, supercapacitors, and biointerfaces. Here, we demonstrate that multi-layer graphene (MLG), like single-layer graphene (SLG), can self-fold to form 3D architectures at the interface with a polymeric film. Bilayers composed of graphene and polymeric film tightly adhere to each other and possess a sloped internal strain, which leads to spontaneous rolling to predetermined 3D microscale architectures. The curvature radii of self-folding films can be controlled by changing the thicknesses of the polymeric film and the stacking order. In contrast to single-layer graphene, multi-layer graphene shows no strain in most of the outer graphene layers and linear ohmic current characteristics after self-folding. Throughout the self-folding process, the conductance of MLG decreases but remains higher than that of SLG. This versatile way of forming a 3D multi-layer graphene structure is potentially applicable for fabrication of practical carbon devices without the changes in their conductive properties.

Neuronal patterning is useful for understanding signal propagation between neurons as well as for biosensors and cell-based assays. The patterning of living cells has been made possible by employing surface physicochemical and topographic features. This study investigated neuronal growth on patterned nanopillars. Rat cortical neurons were cultivated on quartz substrates with amorphous silicon (a-Si) and Au pillars 100 and 500 nm in diameter. The neurites grew better with the larger diameter pillars, and the partly-selective neurite growth was observed for a-Si pillars but not for Au pillars. These results reveal the possibility of controlling neuronal growth by using a-Si nanopillars.