In this section, we focus on international collaboration characteristic of three emerging technologies among 20 countries.

Developing countries (China, India, Russia and Brazil) have strong SHII and SHIA and weak SHAI, which shows that the control ability of patent ownership in developing countries is rather weak; the inventors in these countries are in a migrant worker position and a large proportion of patent ownership is controlled by developed countries. The reason is as follows: It is very common that researchers from a developing country have fewer intelligent local colleagues in emerging technology fields and need to look abroad for collaboration [ 43 ]. Furthermore, internationalization of research and development (R&D) activities of multinational companies is very active in the domestic regions of the developing countries. Once they start international cooperation, however, developed countries will hold patent ownership in the end, since they provide a great amount of human and financial resources. On the other hand, developing countries set up fewer R&D institutions abroad, as they lack capital and qualifications.

From the perspective of countries, as reported in Table 1 , there is a striking heterogeneity among the 20 countries studied. First, the SHII indicators of the United States and Germany are at the intermediate position, indicating that they have moderate levels of cooperation, while their levels of SHAI are obviously higher than that of SHIA, showing that these countries’ emerging technology innovation capability is significantly higher than that of other countries. On the other hand, very few inventions of Japan and South Korea are controlled by foreign firms or invented in co-operation with foreign researchers. It has long been recognized that Japan has little cooperation with other countries in emerging technology fields. So does South Korea. Amongst the developed countries, the Netherlands and Australia are characterized by a relatively high degree of international collaboration, with ratios of nearly 50%. Other developed countries (the United Kingdom, Switzerland) are less highly internationalized.

Network relationship analysis

Network relationship can reflect the international collaboration patterns of emerging technologies on the other side [44]. In Figs 1–3, the larger the node (one node = one country), the greater is the number of co-patents associated with that country. Thicker lines between two nodes demonstrate that the two countries have closer cooperation. In addition, in order to better understand Figs 1–3, we calculated the centrality indicators as an auxiliary interpretation which is listed in Tables A-C in S1 File.

In the field of 3D printing (Fig 1), combining the analysis of centrality indicators (Table A in S1 File), we find that the United States and Germany have an obvious advantage: the two countries lie in the centricity, which indicates that they have a larger influence on the international cooperation network. It is important to note, though, that the US ranks first in the degree centrality indicator, and the betweenness centrality of Germany is the biggest. Japan and China are the other two main collaboration countries in 3D printing technology. The relationships between China and the other countries are tighter than those of Japan and the other countries. China is characterized by high degree centrality and low closeness centrality. The network illustrates the characteristics of “balanced collaboration,” which means that most countries exhibit cooperation though not a close cooperation.

Fig 2 presents that, in the field of big data, the United States is the core of the radial network, which shows that nearly every country has technology cooperation with the United States. South Korea, Russia, and Denmark are the isolated points, which means these three countries have no collaboration with other countries. Combining the analysis of centrality indicators (Table B in S1 File), the United Kingdom has strong betweenness centricity in the international big data cooperative network. Though the United Kingdom was not the core country, it maintained a strong mediation centricity role, which embodies the United Kingdom acting as the intermediary and in a bridge role in the international cooperative network. The degree centrality of China and Japan are strong in big data, but the betweenness centrality of each shows weakly.

In the carbon nanotubes and graphene technology field, the network relationship shows characteristics of a “small world”, which refers to having higher clustering coefficients and shorter average path length [45] (Fig 3). A small-world network is widely considered to stimulate creativity and improve overall global performance [46]. There is high interaction between India, South Korea and Japan in this field and they form a significant and strong leading group in terms of their domestic volume and international collaboration. Canada has a mutually collaborative relationship with France. As one of the Brazil, Russia, India and China (BRICs) economies, the most obvious upward trend is seen in China, which plays a more and more important role in the international collaboration network of emerging technologies. Combining the analysis of centrality indicators (Table C in S1 File), the degree centrality of China is the second biggest in this field. The other obvious upward trend is seen in India. And from the Table C in S1 File, it also shows the betweenness centrality of India is quite strong, indicating that India acts as an intermediary in the carbon nanotubes and graphene technology cooperative network.

All in all, the capacity of collaboration depends not only on the capability and quality of the national research base but also on the existing volume of activity. If there is little activity, thus leading to a limited output, then the opportunity for collaboration is naturally constrained. China is a good example: it holds a large number of patents, so its international collaboration level is higher than that of other developing countries. So the developing countries should improve both the volume of activity and the quality of their national research. Furthermore, it is advisable that China, India, Russia and Brazil increase their betweenness centrality and improve their control ability. Only in this way can they boost their collaboration ability and control ability.