Anaheim, Calif. — Mukerrem Cakmak took Antec attendees into his world of research of roll-to-roll production of electrically conductive films, which are needed for many emerging flexible electronics products like thin batteries, displays and solar cells, and wearable — or even implantable — sensors.
In his plenary speech at Antec on May 8, he even showed a slide of rooms in a house that can change color at the flick of a switch.
"You can actually match your clothes to your house," he quipped.
Other new-age applications are skylights that can be turned on and off and flexible heaters embedded in the windshields on electric cars — since they don't get heat from the engine to run a defroster.
Figuring out how to make roll-to-roll film is a key to future large-scale production of electrically conductive films.
"It's one of my passions, said Cakmak, a professor of materials engineering and mechanical engineering at Purdue University. He started at Purdue last August, after working at the University of Akron. Much of his plenary speech, and a later technical paper presentation at Antec, outlined work in roll-to-roll production done at Akron.
At Purdue, Cakmak and his students will use a new machine that he said will use melt-processing for the first time in this process, to make a web of film six inches wide.
"This actually has an extruder that will deliver molten sheet onto a heated platform," he said. The electric field gets applied while the material is still hot. The line also can use laser heating.
"This is going to be operational sometime this summer," Cakmak said at the Society of Plastics Engineers' conference.
But Cakmak's passion comes with big challenges.
"The objective is to develop these multifunctional materials that are transparent, electrically conductive and formable," he said.
One problem is the film can take a small curvature, but when you bend it too sharply or do it too many times, the film can lose electrical conductivity, Cakmak said. You can get delamination, he said.
Cakmak described research that attempts to embed nanofibers into the solution that is passing through the cast-film line.
"It's essentially creating a partially embedded, conductive nanofiber network. And that's the whole idea," he said.
Another method is electrospinning the fibers, using special nozzles.
Cakmak said the network of embedded nanofibers makes up the conductive element. When hit with electricity or magnetic force, they orient, or line up in the same direction — which gives maximum conductivity, the professor said.
"Because it's embedded, there's no connected interface for potential delamination if you undergo bending or stretching," he said.
University researchers using an electro-optical measurement system to determine how far you can stretch the materials, for example, through thermoforming, and still maintain conductivity, he said.
Cakmak compared the nano-wires to chicken wire. He projected on the screen an image showing "a forest of trees of nano-columns," all precisely oriented.