David Savastano, Editor10.25.17
Electrochromic inks and films are an intriguing technology for printed electronics applications. In one well-known example, rear-view mirrorsin vehicles use this technology, which shifts color due to a tiny electric current.
There is a critical drawback to electrochromic inks and films, as they are traditionally a solvent-based technology. They are flammable, and the odors that the solvents emit are a major problem for printing and spraying machinery.
Researchers for Dr. John Reynolds’ team at Georgia Institute of Technology recently announced that they have developed water-based electrochromic film inks. Aside from being safer in terms of handling volatile organic chemicals (VOCs), eliminating certain protective equipment would also offer cost savings. The team published its findings in the journal ACS Central Science on Aug. 16, 2017.
Brian Schmatz of Georgia Tech Schools of Chemistry and Biochemistry and Material Science and Engineering, the study’s first author, said that concerns over the use of solvents such as chlorobenzene, sustainability and industry readiness led to Georgia Tech’s researchers coming up with the new technology for water-based electrochromic inks. Georgia Tech’s Zhibo Yuan, Augustus Lang, Jeff Hernandez and Elsa Reichmanis co-authored the study.
“Within this field, a majority of research labs use chlorinated and/or aromatic solvents as the carrier within their electronic inks,” Schmatz continued. “These solvents are not the safest to work with, but are usually accepted, as fundamental concepts are being explored and the scope is often limited to university research labs.
“However, as the field has matured and the potential for market adoption has greatly increased, replacing these dangerous solvents with something safer has become a major focus,” he added. “A key advantage of the entire printed electronics field is the ability to scale manufacturing through roll-to-roll processing, but industrial printers do not want to scale a printing process based on inks that are toxic and flammable. With this in mind, we wanted to move to a solvent system that would be environmentally benign and safe for people to work with on a typical roll-to-roll printing line.”
Schmatz noted that the advantages are centered around the safety of water as a solvent, beginning with the lack of noxious odors.
“We all know what water is, interact with it on a daily basis, and generally feel safe working with it,” he said. “It also has no odor, something I would have not considered a major advantage until speaking with employees at printing facilities, who identified odor as a problem they have with solvents they work around all day.
Aside from the benefit to the employees and the environment, safer inks also provide economic advantages.
“Raw material and waste disposal costs are lower, but the biggest savings come from lower overhead costs,” Schmatz added. “Water-based inks can be used in the type of open environments seen in many graphics printing facilities, and so they don’t require specialized and expensive chemical enclosures. This also means there is potential for these inks to be used in existing or retrofitted graphics printing facilities, severely lowering the initial capital investment to get this technology off the ground.”
There were numerous challenges in developing water-based electrochromic inks, beginning with dissolving electroactive polymers in water.
“The first hurdle was achieving water solubility,” Schmatz observed. “These materials, electroactive polymers, do not inherently dissolve in water. In fact, they don’t inherently dissolve into any solvent, but over the past 30 years, design motifs have been developed to achieve solubility in organic solvents so that inks could be made. We had to rethink these designs to achieve water solubility.
Once dissolved, the electroactive polymers needed to retain their electronic properties after being printed from water
“A common route to making polymers water soluble is to incorporate ionic species into the design, and many research labs, ours included, have used this method to make water soluble electroactive polymers in the past,” Schmatz said. “The problem is that ionic species are charged, and can therefore interfere with the electronic processes taking place in device applications. They can also serve as molecular sites for degradation, decreasing their shelf-life.
“In our new materials, we still use ionic species to obtain water solubility, but now incorporate a molecular trigger that allows us to remove it after the printing step is complete,” Schmatz concluded. “We are now able to print these polymers from water, then irradiate the films with UV light to activate the trigger and remove the ionic species. This process provides retention of the electronic properties we sought, and also has the added benefit of rendering the material insoluble to all solvents, organic or aqueous. This makes the material robust and applicable to both dry and wet applications.”
Schmatz noted that Georgia Tech has a world-class research community with state-of-the-art facilities and instrumentation, so everything the team needed to develop, characterize, and test for this technology is right on campus.
“The collaborative and supportive environment here is essential for innovation, and we have an incredibly strong community in the area of organic and printed electronics,” Schmatz added. “You can synthesize polymers in our organic labs, walk upstairs to get help modeling and understanding new materials, walk one building over to build and test prototype devices, and can even meet with another lab to discuss large scale manufacturing. There is an amazing culture of innovation here, and I think that inspires chemists to push their work beyond the lab and into applied areas.
“I believe the Reynolds lab perfectly embodies this sprit of innovation and collaboration,” he continued. “We have people working in polymer synthesis, electrochemical characterization, and electronic device processing, and they are by no means siloed into those areas. Each researcher has the ability to see their work through from lab to fab, and I think that’s what makes everyone excited to go a bit outside their core discipline. Dr. Reynolds is also a leader in the area of polymer electrochromics, and so in terms of this specific technology, we have so much expertise from many years of research and a large library of electrochromic polymers created by the group.”
The technology can produce virtually any color. Schmatz said that the two major markets for water-based electrochromic inks are window tinting and displays.
“On the tinting side, we have sunglasses and visors, which can be instantly switched from any color to clear, and coatings for windows,” he noted. “For windows, electrochromic coatings can provide both shade and heat management. These coatings can block IR light from generating heat within the building, while visible light can still pass through to provide natural light.
“On the display side, electrochromics have value as low power digital displays, similar to the displays in a Kindle, but with the ability to have any color you want” Schmatz added. “Some examples include digital price tags in stores, with the ability to change price or item through a centralized computer, and also as displays for Internet of Things (IoT) applications. While many IoT applications use sensors to send data to a centralized or cloud-based computer, there are still places where a physical display on the sensor would be beneficial, and you would want to use a very low power display to extend the operating lifetime.
“Aside from electrochromic applications, there are many other markets for water soluble electroactive inks,” noted Schmatz. “Transistors, solar cells, LEDs, and biosensors can all be developed using electroactive polymers, and the ability to print these components from water-based inks benefits the scalability of all of these applications.”
Dr. Reynolds said that consumers may see this technology sooner rather than later.
“My group has developed a full family of electrochromic polymers over many years with a broad patent portfolio developed at the University of Florida and Georgia Tech,” Dr. Reynolds noted. “This new technology adds on top of that. We are working closely with a company in the field of electrochromic polymers and displays who have licensed the bulk of the patent portfolio, and we are working together towards commercialization.”
There is a critical drawback to electrochromic inks and films, as they are traditionally a solvent-based technology. They are flammable, and the odors that the solvents emit are a major problem for printing and spraying machinery.
Researchers for Dr. John Reynolds’ team at Georgia Institute of Technology recently announced that they have developed water-based electrochromic film inks. Aside from being safer in terms of handling volatile organic chemicals (VOCs), eliminating certain protective equipment would also offer cost savings. The team published its findings in the journal ACS Central Science on Aug. 16, 2017.
Brian Schmatz of Georgia Tech Schools of Chemistry and Biochemistry and Material Science and Engineering, the study’s first author, said that concerns over the use of solvents such as chlorobenzene, sustainability and industry readiness led to Georgia Tech’s researchers coming up with the new technology for water-based electrochromic inks. Georgia Tech’s Zhibo Yuan, Augustus Lang, Jeff Hernandez and Elsa Reichmanis co-authored the study.
“Within this field, a majority of research labs use chlorinated and/or aromatic solvents as the carrier within their electronic inks,” Schmatz continued. “These solvents are not the safest to work with, but are usually accepted, as fundamental concepts are being explored and the scope is often limited to university research labs.
“However, as the field has matured and the potential for market adoption has greatly increased, replacing these dangerous solvents with something safer has become a major focus,” he added. “A key advantage of the entire printed electronics field is the ability to scale manufacturing through roll-to-roll processing, but industrial printers do not want to scale a printing process based on inks that are toxic and flammable. With this in mind, we wanted to move to a solvent system that would be environmentally benign and safe for people to work with on a typical roll-to-roll printing line.”
Schmatz noted that the advantages are centered around the safety of water as a solvent, beginning with the lack of noxious odors.
“We all know what water is, interact with it on a daily basis, and generally feel safe working with it,” he said. “It also has no odor, something I would have not considered a major advantage until speaking with employees at printing facilities, who identified odor as a problem they have with solvents they work around all day.
Aside from the benefit to the employees and the environment, safer inks also provide economic advantages.
“Raw material and waste disposal costs are lower, but the biggest savings come from lower overhead costs,” Schmatz added. “Water-based inks can be used in the type of open environments seen in many graphics printing facilities, and so they don’t require specialized and expensive chemical enclosures. This also means there is potential for these inks to be used in existing or retrofitted graphics printing facilities, severely lowering the initial capital investment to get this technology off the ground.”
There were numerous challenges in developing water-based electrochromic inks, beginning with dissolving electroactive polymers in water.
“The first hurdle was achieving water solubility,” Schmatz observed. “These materials, electroactive polymers, do not inherently dissolve in water. In fact, they don’t inherently dissolve into any solvent, but over the past 30 years, design motifs have been developed to achieve solubility in organic solvents so that inks could be made. We had to rethink these designs to achieve water solubility.
Once dissolved, the electroactive polymers needed to retain their electronic properties after being printed from water
“A common route to making polymers water soluble is to incorporate ionic species into the design, and many research labs, ours included, have used this method to make water soluble electroactive polymers in the past,” Schmatz said. “The problem is that ionic species are charged, and can therefore interfere with the electronic processes taking place in device applications. They can also serve as molecular sites for degradation, decreasing their shelf-life.
“In our new materials, we still use ionic species to obtain water solubility, but now incorporate a molecular trigger that allows us to remove it after the printing step is complete,” Schmatz concluded. “We are now able to print these polymers from water, then irradiate the films with UV light to activate the trigger and remove the ionic species. This process provides retention of the electronic properties we sought, and also has the added benefit of rendering the material insoluble to all solvents, organic or aqueous. This makes the material robust and applicable to both dry and wet applications.”
Schmatz noted that Georgia Tech has a world-class research community with state-of-the-art facilities and instrumentation, so everything the team needed to develop, characterize, and test for this technology is right on campus.
“The collaborative and supportive environment here is essential for innovation, and we have an incredibly strong community in the area of organic and printed electronics,” Schmatz added. “You can synthesize polymers in our organic labs, walk upstairs to get help modeling and understanding new materials, walk one building over to build and test prototype devices, and can even meet with another lab to discuss large scale manufacturing. There is an amazing culture of innovation here, and I think that inspires chemists to push their work beyond the lab and into applied areas.
“I believe the Reynolds lab perfectly embodies this sprit of innovation and collaboration,” he continued. “We have people working in polymer synthesis, electrochemical characterization, and electronic device processing, and they are by no means siloed into those areas. Each researcher has the ability to see their work through from lab to fab, and I think that’s what makes everyone excited to go a bit outside their core discipline. Dr. Reynolds is also a leader in the area of polymer electrochromics, and so in terms of this specific technology, we have so much expertise from many years of research and a large library of electrochromic polymers created by the group.”
The technology can produce virtually any color. Schmatz said that the two major markets for water-based electrochromic inks are window tinting and displays.
“On the tinting side, we have sunglasses and visors, which can be instantly switched from any color to clear, and coatings for windows,” he noted. “For windows, electrochromic coatings can provide both shade and heat management. These coatings can block IR light from generating heat within the building, while visible light can still pass through to provide natural light.
“On the display side, electrochromics have value as low power digital displays, similar to the displays in a Kindle, but with the ability to have any color you want” Schmatz added. “Some examples include digital price tags in stores, with the ability to change price or item through a centralized computer, and also as displays for Internet of Things (IoT) applications. While many IoT applications use sensors to send data to a centralized or cloud-based computer, there are still places where a physical display on the sensor would be beneficial, and you would want to use a very low power display to extend the operating lifetime.
“Aside from electrochromic applications, there are many other markets for water soluble electroactive inks,” noted Schmatz. “Transistors, solar cells, LEDs, and biosensors can all be developed using electroactive polymers, and the ability to print these components from water-based inks benefits the scalability of all of these applications.”
Dr. Reynolds said that consumers may see this technology sooner rather than later.
“My group has developed a full family of electrochromic polymers over many years with a broad patent portfolio developed at the University of Florida and Georgia Tech,” Dr. Reynolds noted. “This new technology adds on top of that. We are working closely with a company in the field of electrochromic polymers and displays who have licensed the bulk of the patent portfolio, and we are working together towards commercialization.”