# A Study on Technology Competition of Graphene Biomedical Technology Based on Patent Analysis
## 4 Analysis
### _Patent Roadmap_  
#### 4.2.1 Country Level Patent Roadmap  
In order to investigate the distribution of patent application in different countries, especially the distribution of high value patents, it is necessary to build a country level patent roadmap and identify the key country holding high value patents in different technological fields. A citation is a document cited by an applicant, third party or a patent office examiner as well as a reference to a previous work. Forward citations are more likely to be a basic patent in specific technological fields and considered as a commonly used indicator of patent value [51]. Therefore, we define patents which have higher number of forward citations as high value patents based on Price's Law [107]. We define Nmax as the maximum value of the number of forward citation and M as the starting point of high value patents that can provide total number of patents. Thus, M-Nmax is high value patents [108]. From 2004 to 2018, the maximum number of forward citations of graphene biomedical technology is 89. M = 0.749 \(\times\)\(\sqrt{N\max}\) = 0.749 \(\times\)\(\sqrt{89}\) = 7.066 After rounding, the number of forward citations that greater than or equal to 8 times is regarded as high value patents. By integrating high value patents in different countries with patent hotspots and fronts, the country level patent roadmap can be seen in Figure 4.  
The process of patent roadmap is displayed as the following stages. First, we decide the horizontal axis and vertical axis. Specifically, the horizontal axis represents the time-line. We separate the period from 2007 to 2018 into five three-year periods because the patent application among the high value patents begins at the period from 2007 to 2009; and the vertical axis indicates the specific technological field, representing MC (a unique patent classification code indicating the novel technical aspects of the invention, and its commercial applications) which enabled stakeholders to investigate the evolution trend of a target technical area. Second, nodes indicate countries holding high value patents. Third, we employ arrows to link nodes that belong to the same country. Fourth, nodes are marked. We used different colors to display different countries holding high value patents. The red color represents patentees from China, purple from the U.S., green from Korea, blue from the U.K, orange from Germany, pink from France, black from Japan, and yellow from Singapore. Figure 4 shows the distribution of high value patents in different countries. First, regarding the time stage, patent activities come from the U.S.'s and Germany's assignees in the initial stage (2007-2009) of the technology development; High value patents mainly come from the period of 2010-2012 and 2013-2015. Compared to assignees from European countries, Korea, and Japan, assignees from the U.S. and China have obvious advantages in holding the number of high value patents; although the number of high value patents from 2016 to 2018 is few, it will increase over time. Second, in terms of assignees, Harvard University and University of California from the U.S., Chinese Academy of Sciences and Zhejiang University, and from China, Swansea University from the U.K, University of Freiburg from Germany, Nanosense Inc from France, Kyung Hee University from Korea, and Hitachi, Ltd. From Japan are major assignees holding high value patents in graphene biomedical technology. Third, regarding the technological field, the top three technological field with the largest amount of high value patents are D05-H09 (Testing and detection (Except Bacteria, Fungi, Viruses), B11-C12 (Nanotechnology (General)), and B04-E01 (Nucleic acid general and other), holding 31, 25, and 24 high value patents respectively.