## 4 Discussion and Future Prospects  
In order to increase applications of single-molecule measurement by nanodevice, further integration of functional nanostructures and improvements and the simplification of analysis methods are required. Some approaches to these issues are described in the following paragraphs. The first approach is the integration of various functional nanostructures on nanodevice sensors. For instance, nanochannels have made great achievements in sample control and transport by electrophoresis in sensor devices [113; 114; 115] and nanopillar structure serve as purification, separation, and transportation [116; 117]. Along with the integration of nanodevices, the development of fabrication techniques for integrated nanodevices is an important issue. In nanodevices, if the shape of the fabricated device can be parallelized with high accuracy, the throughput of measurement can be expected to be dramatically improved. So far, parallelization has been reported for nanopore and nanogap devices [118; 119]. The second approach is to use nanochannel or nanowell structures for optical sensor detection. For example, a single molecule in a nanochannel can be detected by optical microscopy with high sensitivity [120; 121; 122; 123]. There are also zero-mode waveguides using the near-field effect and Raman spectroscopy using the plasmon phenomenon in the nanogap [124; 125; 126; 127; 128]. These nano-optics/electronics hybrid devices would improve the sensing selectivity. The third approach is the development of bioinformatics analysis methods using artificial intelligence (AI). In single-molecule measurements, the data volume is exponentially increased because of the high-speed data acquisition and large number of detected molecular signals in sample solutions, compared to conventional analytical methods. Moreover, the detected signal shape, i.e., electrical current-time profile, become more complex. Therefore, AI-based informatics analysis methods are suitable for sample identifications as the method enables the extraction of characteristic parameters from complex signals. In recent years, AI-based analysis has made it possible to identify target molecules among similar structural molecules [10; 131; 129; 130; 131]. Thus, it can be said that the evolution of bioinformatics analysis is essential for single-molecule measurement by nanodevice. In addition to these developments of nanodevice based technologies and methods, there are several steps that precede real clinical practice use. The first step is the standardization of measurement systems, the nanodevices, and the data-analysis methods. The next step is to obtain medical approval from the government in each country. In the current stage, nanodevice methods are currently taking these steps towards application in the medical field. For example, the Food and Drug Administration (FDA) has issuedguidelines for obtaining medical approval for next-generation sequencing nanodevices such as MinION [132; 133; 134]. Furthermore, the recent COVID-19 pandemic has accelerated the movement to detect viruses (SARS-CoV-2) and virus mutants by nanodevices. It is expected that the application of this technology will expand as this trend becomes more active in the future. In summary, the single-molecule electrical measurement by nanodevices is an interdisciplinary field that is currently undergoing development while incorporating new technologies. I believe that single-molecule measurement methods using nanodevices will greatly develop as a key technology for realizing personal medical care that enables point-of-care, which is considered a dream come true, while expanding the range of its applications. This research was funded by Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (21H01741). Not applicable for studies not involving humans or animals. Not applicable. The authors declare no conflict of interest.