Despite Hong Kong's status as a key research centre for the nation, the city's scientists are still barred from many projects deemed sensitive by Beijing, mainland officials say.
Collaboration between Hong Kong and mainland research groups has increased since the handover, largely through a system known as State Key Laboratories. The scheme comprises university and private laboratories which receive administrative and financial support from the central government, including lucrative state contracts.
Hong Kong had 16 such laboratories last year, up from two in 2005, out of a total of about 200 across the nation.
The Hong Kong laboratories must partner with an institute on the mainland, some of which are involved in defence research projects. The arrangement raises questions about whether Hong Kong scientists are contributing to the advancement of the nation's military technology.
Cao Guoying , deputy director of fundamental research at the Ministry of Science and Technology, said that was not the case.
Most of the laboratories' funding came from the Hong Kong government, according to local scientists. Cao said the central government provided about 140 million yuan (HK$179 million) last year for work on several research projects.
"All these technologies are for civilian purposes," Cao said.
He said Beijing was interested in making Hong Kong a key national research and development centre, alongside Beijing and Shanghai. The central government was aware of the sensitivity of the work and would not allow the city's research labs to be directly involved in non-civilian technical research, Cao added.
In some areas that involved multiple fields, such as materials science and communications, it is difficult to determine whether a project is for civilian or military use.
In 2008, People's Daily reported that technology developed by Hong Kong scientists had been used in the Beidou satellite navigation system, which has both civilian and military applications.
Wang Yan , deputy director of the ministry's science and technology exchange centre, said she hoped that restrictions could be relaxed in the future. "There is still a gap between what we want to do and what we have done," she said of cross-border collaboration.
Hong Kong scientists were cautious about defence-related research, which would put the city at risk of tighter restrictions on hi-tech imports.
At present, the city, as part of China, is among 20 regions and countries, including Afghanistan, Palestine and Venezuela, that the United States bars from receiving defence-related articles and technical data.
Yung Kai-leung, a Polytechnic University professor whose camera pointing system is used aboard the Chang'e-3 lunar probe, said his device was not developed for military use.
"We have not been involved in any military-related research for any country and have no intention of doing so in the future."
Yung said it was inevitable that some civilian technologies were used by armies. "The common switches that you use at home for switching on or off appliances are extensively used in military installations."
One Hong Kong-based researcher working in a State Key Laboratory on sensitive technology said funding for his research came from the Hong Kong government. He added that he would not take part in military research on the mainland.
"We only do academic research. We publish all findings in academic papers," he said, declining to be named due to the sensitivity of the issue.
"Hong Kong must keep its distance from the mainland's military programmes or there will be big trouble. If some countries get suspicious, we might face worse import restrictions and be unable to get certain devices for our lab."
Professor Dou Wenbin , deputy director with the State Key Laboratory of Millimeter Waves at Southeast University, said his laboratory had a partnership with the State Key Laboratory of Millimeter Waves at City University in Hong Kong, but that, in practice, the two laboratories had little co-operation.
"They have their research and we have ours. We never work on the same subject," he said.