A desktop printer loaded with a silver salt solution and vitamin C has been used to produce electronic circuits. The UK researchers behind the feat say their experimental device could pave the way for safer and cheaper electronics manufacturing.
Being able to print out electronic components and whole circuit boards could provide an alternative to current manufacturing techniques, which are energy intensive and environmentally unfriendly.
Printing conductive polymer ink (see Goodbye wires and silicon, hello plastic chips), or pastes containing graphite or metal particles are two existing options. But researchers at Leeds University in the UK wanted to avoid the solvents needed for these processes.
Advertisement
PhD student Seyed Bidoki loaded a standard Hewlett Packard ink-jet printer with a solution of metal salts and water. After a pattern is printed using the solution, a chemical known as a reducing agent is then printed over the top to make solid silver form.
鈥淲e wanted to be able to use a totally water-soluble base,鈥� explains team member and chemist Matthew Clark. 鈥淭hat allows for much more environmentally friendly processes.鈥�
Metal ink
Bidoki loaded two separate chambers in the printer鈥檚 cartridge, which normally contain different ink, with the metal solution and the reducing agent. Using silver nitrate solution as the 鈥渕etal ink鈥� and ascorbic acid (vitamin C) as the reducing agent proved the most successful combination.
He then programmed the printer to produce a variety of circuits and radio antennas on different surfaces including paper, cotton and acetate, all of which were placed in the printer like a normal sheet of paper.
鈥淥ne test involved patterning an antenna like that used in a mobile phone on transparent film,鈥� says Clark. 鈥淚t was possible to bend it almost in half without any loss of conductivity.鈥�
After a circuit is printed using silver nitrate, vitamin C is overlaid a few minutes later. Water can then be used to wash away other products, leaving the silver behind. Scanning electron microscope images reveal a rough surface of silver nanoparticles.
Join the dots
Printing the same pattern two or three times improves conductivity because it increases the number of contacts between silver nanoparticles. Desktop printers make images from tiny dots of ink that do not overlap, but bleed slightly into each other, explains Clark: 鈥淚n future, we鈥檇 like to use an industrial jet printer that can so we鈥檒l need fewer passes.鈥�
Graham Martin at the University of Cambridge, UK, agrees that ink-jet technology could make new kinds of devices possible. But he says competing with existing technology could be difficult: 鈥淭his concept are often simple but there are many challenges to meet. Creating a low enough resistance to match current standards is one of them.鈥�
But ink-jet printing definitely has a future, he adds. Currently, circuit boards and other components are made by etching the desired design out from a layer of metal, which is an energy intensive process. 鈥淧rinting is an additive, not subtractive process, making it more environmentally effective,鈥� says Martin.
Journal reference: Journal of Micromechanics and Microengineering ()
