Manufacturing Flexible Electronics and Photovoltaics

Building off of the Cockrell School of Engineering's existing, patented ink-jet technology with Molecular Imprints, researchers believe a revamped manufacturing process, known as ink-jet roll-to-roll nanopatterning, could be the key to producing the large-scale, inexpensive manufacturing tools needed for electronic devices and photovoltaics.

Building off of the Cockrell School of Engineering's existing, patented ink-jet technology with Molecular Imprints, researchers believe a revamped manufacturing process, known as ink-jet roll-to-roll nanopatterning, could be the key to producing the large-scale, inexpensive manufacturing tools needed for electronic devices and photovoltaics.

What if an electronic device could be implanted into patients to monitor their health and treat disease? In a patient with diabetes, the device would know instantly if sugar levels were low and could report the results in real-time to the patient’s doctor, who would wirelessly command the device to release life-saving insulin.

Now imagine a sheet of solar cells, one that can be printed affordably and at large-scale – as simply as printing newspapers. The sheets would be flexible, lightweight and capable of generating so much energy that U.S. troops in remote areas could easily carry and unroll them whenever they needed power for laptops, chargers or batteries.

Scientists and engineers have long dreamed of such scenarios, but transforming them into a reality has been hampered in past decades because of high costs and the inability to manufacture nano-devices at mass-scale – rather than building them one by one as their tiny, complicated structures have traditionally required. The perpetual demand for smaller and more powerful electronics, however, has fueled recent research advancements in the field of nanotechnology and moved the vision of large-scale, flexible electronics and photovoltaics closer to a reality.

Among those spearheading these research advancements are faculty and students at The University of Texas at Austin’s Cockrell School of Engineering. In the past decade, Cockrell School researchers have taken their research from the lab to the market by commercializing a new and higher performing nanotechnology manufacturing process. The process, known as ink jet nanopatterning, spawned the Austin startup company Molecular Imprints, Inc., which now boasts more than 100 employees and serves as a widely recognized model for how top research institutions can partner with industry to bring new technologies to markets.

The Cockrell School has also assembled a multidisciplinary research team made up of experts in materials science, nanomanufacturing, design and devices. Expertise from each of the fields is needed for the challenge they face: to manufacture a process in which materials and devices – 1,000 times smaller than a strand of hair – can be precisely manipulated, controlled and mass produced for cheap.

“Electronic devices have now shrunk to dimensions that are so tiny, and they’re acting differently and new physical phenomena are occurring because of it,” said Sanjay Banerjee, a professor, member of the research team and director of the Microelectronics Research Center at the university’s Pickle Research Campus. “Students ask me all the time if nanotechnology is an area they should get into and whether there’s a long-term career in it. I tell them I’ve not been this excited about the field in a long time because the potential of nanotechnology right now is so enormous.”

Expanding the research team’s role as a game-changer in the field is a recent $1.3 million grant from the National Science Foundation Scalable Nanomanufacturing Program for which Mechanical Engineering Professor S.V. Sreenivasan is the principal investigator, and the installation of new custom-made, state-of-the-art equipment that is the only one of its kind in the world.

The equipment, housed at the Microelectronics Research Center (MRC), is jointly funded by the school and Molecular Imprints, and will enable researchers to create the manufacturing processes required for large-scale roll-to-roll nanopatterning.

“With this equipment, we are at the leading edge of technology,” said Sreenivasan, a mechanical engineering professor, inventor and co-founder of Molecular Imprints. “This is the kind of facility that could keep paying off for years and usher in a new generation of electronics and devices.”

Better control of materials leads to higher performance and versatility

Nanopatterning is used to create the integrated circuits, or microchips, found in almost all modern electronic equipment. The process produces the electronic circuits by fabricating complex exotic patterns at the nano-scale.

“You could have a fairly complicated circuit pattern but the individual elements of these circuits are as small as 30 nanometers, 1,000 times smaller than a human hair,” Sreenivasan said. “So you can’t easily see them and measure them, let alone fabricate them in highly a repeatable manner. We’ve been able to do it on silicon wafers – where it leads to high value devices. But when you want to make flexible electronics and photovoltaics, the process has to be really inexpensive for them to be viable.”

Building off of their existing, patented ink-jet technology with Molecular Imprints, Cockrell School researchers believe a revamped manufacturing process, known as ink-jet roll-to-roll nanopatterning, could be the key to producing the large-scale, inexpensive manufacturing tools needed for electronic devices and photovoltaics.

The ink-jet based process is capable of creating photovoltaics and electronic devices out of a roll of flexible materials, or films. The process also gives researchers more control over where the materials go and how they respond. By having more control, the manufacturing process is higher performing and provides more flexibility and versatility than current manufacturing applications offer.

Demonstrating its uses

In a lab on the first floor of the MRC, Sreenivasan and his students demonstrate how the manufacturing process works for flexible display elements, and are collaborating with engineering faculty, like Associate Dean of Research and Chemical Engineering Professor John Ekerdt, Chemical Engineering Department Chair Roger Bonnecaze, and Mechanical Engineering Professor and graphene pioneer Rodney Ruoff to incorporate novel nanomaterials.

Sreenivasan and his students hold a high quality substrate that, on the surface, looks like nothing more than a small, round glass plate. But on this glass material is a complex, nano-scale pattern that is so small it can only be viewed using high-powered electron microscopes capable of seeing features on the nanometer scale.

The pattern is known as the “master pattern,” because – once inserted into the manufacturing machine – the tool will automatically replicate it over and over again on to flexible film materials that roll throughout the equipment, similarly to how film is fed through a projector.

“The interesting thing about this test bed, compared to most other university experimental facilities, is that this is a manufactured test bed,” Sreenivasan said. “So it really allows you to study processes at a more applied level, and that allows you to innovate on devices and processes.”

The equipment has been on campus for less than a month, but researchers working on the project expect that they could see some early wins in producing flexible, large-scale photovolatics.

Creating flexible electronic devices, like one that could monitor a patient’s health or a flexible display for things like iPads and other devices, could be more complicated, but the potential has never been this great, said Banerjee, an expert on devices and displays.

“To make these devices affordable and easy to produce in volume has been the holy grail of this field for a long time,” Banerjee said. “There are challenges at every level but we are on the cusp of the next phase of nano-electronics and nanotechnology.”