The ion distribution and physical behavior induced by applying an electric field to a nano-interfacial space are very important for investigating electric double layers (EDLs) in very confined spaces. We perform direct measurements of an EDL in a nanochannel by electrical impedance spectroscopy to experimentally evaluate the EDL thickness dependence on the ion density and the channel width. To this end, we developed a nanofluidic device consisting of a pair of sensing electrodes with a nanochannel between them. The measurement electrodes are completely embedded in a substrate to generate a uniform electric field and to provide a flat surface that can easily be used to seal the nanochannel. Using this device, we found that the EDL on one electrode expands with decreasing ion concentration and eventually merges with the EDL on the opposite electrode so that the nanochannel becomes completely filled with the EDL. The trend observed for the EDL width agrees well with that predicted by theory for the Debye length. These results provide valuable insight into the physical ionic structure in nanochannels, which will improve impedance-based electrical sensing and electrokinetic applications.

Our living sphere is constantly exposed to a wide range of pathogenic viruses, which can be either known, or of novel origin. Currently, there is no methodology for continuously monitoring the environment for viruses in general, much less a methodology that allows the rapid and sensitive identification of a wide variety of viruses responsible for communicable diseases. Traditional approaches, based on PCR and immunodetection systems, only detect known or specifically targeted viruses. We here describe a simple device that can potentially detect any virus between nanogap electrodes using nonlinear impedance spectroscopy. Three test viruses, differing in shape and size, were used to demonstrate the general applicability of this approach: baculovirus, tobacco mosaic virus (TMV), and influenza virus. We show that each of the virus types responded differently in the nanogap to changes in the electric field strength, and the impedance of the virus solutions differed depending both on virus type and virus concentration. These preliminary results show that the three virus types can be distinguished and their approximate concentrations determined. Although further studies are required, the proposed nonlinear impedance spectroscopy method may achieve a sensitivity comparable to that of more traditional, but less versatile, virus detection systems.

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Etchants used for metal etching are generally harmful to the environment. We propose an environmentally friendly method that uses ozone water to etch metals. We measured the dependencies of ozone water etching on the temperature and ozone concentration for several metals and evaluated the surface roughness of the etched surfaces. The etching rate was proportional to the dissolved ozone concentration, and the temperature and the surfaces were smoothed by etching.

N6‐methyladenosine (m6A) is an abundant internal modification in eukaryotic mRNA and plays regulatory roles in mRNA metabolism. However, methods to precisely locate the m6A modification remain limited. We present here a photo‐crosslinking‐assisted m6A sequencing strategy (PA‐m6A‐seq) to more accurately define sites with m6A modification. Using this strategy, we obtained a high‐resolution map of m6A in a human transcriptome. The map resembles the general distribution pattern observed previously, and reveals new m6A sites at base resolution. Our results provide insight into the relationship between the methylation regions and the binding sites of RNA‐binding proteins.