DSeeLab employees show the 'fan' that creates 3D images during an innovation competition in Nanjing, Jiangsu province, in July. [Photo by LIU LI/CHINA DAILY]

Zhou, a recent graduate of Southeast University in Jiangsu province, invented the device with some partners when he was in college. It consists of four bars with small LEDs that can create 3D images as they rotate. A glass cover protects people from the spinning bars.

"We call it a 'holographic 3D smart screen' and it's mainly used for advertising," said Zhou. "The 3D graphics can be seen by the naked eye and it is suitable for advertising in many places, such as exhibitions, shopping malls and airports."

Zhou and his partners founded their company, DSee-Lab, in 2016. As of the first half of this year, the company had sold more than 15,000 screens, with total sales surpassing 40 million yuan ($6 million).

He said that some large automobile, retail and cellphone companies have purchased the device or formed long-term partnerships with the company.

Zhou, 25, joined others who had computer and engineering skills in Nanjing in his third year in college. Their inventions included wheel screens for cars and bikes, and a smart light that can turn on or off according to people's living habits.

Developing the holographic 3D screen was not easy. Each bar contains hundreds of LED bulbs that must flash in complicated patterns while rotating.

"Sometimes I felt that no progress was being made, even though a great amount of money had been spent during the invention process," Zhou said. "There's no shortcut, only persistence."

Yan Ke, the product manager at DSeeLab, who is attending the China International Small and Medium Enterprise Fair in Guangzhou, said the products drew great attention.

"We have customers from many countries, such as the US, France and Australia. Our main product, the one going viral on the internet, has been well received since it started mass production in June."

The product, about 50 centimeters long, sells for 3,699 yuan and comes with a remote control and a glass cover. Other models are 65, 100, 120 and 150 centimeters, according to the company's website.

"We are creating screens in larger sizes and in cylindrical shapes to show the 3D effects more clearly," Yan said.

He said that the company is considering producing fans that can show 3D graphics while blowing air. The fans will be mainly exported to other countries.

Guo Jun contributed to this story.