Do-it-yourself electronics manufacturing may soon be possible with your desktop printer, say the designers of a new system that directly prints electronic circuits onto ordinary paper.
Jing Liu, of the Chinese Academy of Sciences in Beijing, said his team's advance—published May 9 in the journal Scientific Reports—could be a leap forward in the booming business of printed electronics.
"This brand-new technique offers a vital opportunity to realize rapid fabrication of inexpensive, disposable, conveniently portable circuits and functional components," he said, adding that the process could help "pave the way toward personal printed electronics."
Someday people could use this, and similar technologies, to create their own customized electronic devices including electronic greeting cards, video game controls, touch-sensitive mobile phone cases, or solar cell arrays.
Scientists already print electronic circuits on flexible materials like plastics that can be shaped into functional products—antennas are a common example. But many of the existing electronic inks used to create such circuits have to be printed at very high temperatures—around 750°F (400°C)—or they won't conduct enough electricity to work.
This means they can't be easily printed on paper. But paper is highly desirable for printed electronics because it's cheap, renewable, recyclable, and light, and it can be easily rolled or folded.
A New Formula
So Jing and colleagues developed a new metal-based ink that could work at room temperatures. Their initial formula caused the ink to ball up into droplets, which made it difficult to apply and adhere to the paper.
So the team modified the ink by injecting the liquid metal alloy with oxygen, making it more suitable for printing on the kind of paper used for book covers, labels, and advertising stock. A newly developed brush—like a porous pinhead—was also developed to deliver the slow-flowing ink that would clog more-conventional printers.
While most electronic inks solidify after printing, the one employed by the researchers remains liquid and is encapsulated by a second coating of silicone rubber—this creates a channel to hold the ink.
Bendy
"The fabricated circuits cannot be broken off easily even under frequent bending, showing an attractive and distinguished mechanical flexibility which is a critical advantage in fabricating flexible electronics," the authors write.
Because the electronic inks are encased in rubber they can also be stacked in layers without altering their electrical functionality. This would allow users to build electromechanical functions into the body of 3-D printed objects.
"Most of the currently available 3-D printers are only capable of making mechanical objects without electronics features inside," Jing said, such as custom items like mobile phone cases or jewelry.
Jing's team successfully printed circuits and functional components on paper including conductive wires, inductance coils, and flexible antennas—the building blocks of personalized electronic devices.
Cheap, Green, But Not Easy
Printing electronics on paper, rather than plastics, has proven problematic, but it promises a greener alternative to traditional production.
One of the developing field's big advantages is a smaller environmental footprint, as the process eliminates much of the raw materials, energy, and water now used to make more-conventional electronics.
The machine Jing and his team developed is still expensive for everyday use, but the group is striving to make it affordable for the average desktop.
Their machine could soon join a crowded field; more than 3,000 organizations are already at work on printed electronics.
IDTechEx, a market research consulting group based in Cambridge, England, projects that the paper electronics market—estimated at some $16 billion in 2013—will grow to nearly $77 billion by 2023.
Here are some areas where that fivefold growth could occur...
