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Researchers print, tune graphene sensors to monitor food freshness, safety

Posted By Graphene Council, Friday, June 26, 2020
Researchers dipped their new, printed sensors into tuna broth and watched the readings. It turned out the sensors – printed with high-resolution aerosol jet printers on a flexible polymer film and tuned to test for histamine, an allergen and indicator of spoiled fish and meat – can detect histamine down to 3.41 parts per million.

The U.S. Food and Drug Administration has set histamine guidelines of 50 parts per million in fish, making the sensors more than sensitive enough to track food freshness and safety.

Making the sensor technology possible is graphene, a supermaterial that’s a carbon honeycomb just an atom thick and known for its strength, electrical conductivity, flexibility and biocompatibility. Making graphene practical on a disposable food-safety sensor is a low-cost, aerosol-jet-printing technology that’s precise enough to create the high-resolution electrodes necessary for electrochemical sensors to detect small molecules such as histamine.

“This fine resolution is important,” said Jonathan Claussen, an associate professor of mechanical engineering at Iowa State University and one of the leaders of the research project. “The closer we can print these electrode fingers, in general, the higher the sensitivity of these biosensors.”

Claussen and the other project leaders – Carmen Gomes, an associate professor of mechanical engineering at Iowa State; and Mark Hersam, the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University in Evanston, Illinois – have recently reported their sensor discovery in a paper published online by the journal 2D Materials. (See sidebar for a full listing of co-authors.)

The National Science Foundation, the U.S. Department of Agriculture, the Air Force Research Laboratory and the National Institute of Standards and Technology have supported the project.

The paper describes how graphene electrodes were aerosol jet printed on a flexible polymer and then converted to histamine sensors by chemically binding histamine antibodies to the graphene. The antibodies specifically bind histamine molecules.

The histamine blocks electron transfer and increases electrical resistance, Gomes said. That change in resistance can be measured and recorded by the sensor.

“This histamine sensor is not only for fish,” Gomes said. “Bacteria in food produce histamine. So it can be a good indicator of the shelf life of food.”

The researchers believe the concept will work to detect other kinds of molecules, too.

“Beyond the histamine case study presented here, the (aerosol jet printing) and functionalization process can likely be generalized to a diverse range of sensing applications including environmental toxin detection, foodborne pathogen detection, wearable health monitoring, and health diagnostics,” they wrote in their research paper.

For example, by switching the antibodies bonded to the printed sensors, they could detect salmonella bacteria, or cancers or animal diseases such as avian influenza, the researchers wrote.

Claussen, Hersam and other collaborators (see sidebar) have demonstrated broader application of the technology by modifying the aerosol-jet-printed sensors to detect cytokines, or markers of inflammation. The sensors, as reported in a recent paper published by ACS Applied Materials & Interfaces, can monitor immune system function in cattle and detect deadly and contagious paratuberculosis at early stages.

Claussen, who has been working with printed graphene for years, said the sensors have another characteristic that makes them very useful: They don’t cost a lot of money and can be scaled up for mass production.

“Any food sensor has to be really cheap,” Gomes said. “You have to test a lot of food samples and you can’t add a lot of cost.”

Claussen and Gomes know something about the food industry and how it tests for food safety. Claussen is chief scientific officer and Gomes is chief research officer for NanoSpy Inc., a startup company based in the Iowa State University Research Park that sells biosensors to food processing companies.

They said the company is in the process of licensing this new histamine and cytokine sensor technology.

It, after all, is what they’re looking for in a commercial sensor. “This,” Claussen said, “is a cheap, scalable, biosensor platform.”

Tags:  3D Printing  Biosensor  Carmen Gomes  Graphene  Iowa State University  Jonathan Claussen  Mark Hersam  Northwestern University  Sensors 

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Aerosol-printed graphene unveiled as low cost, faster food toxin sensor

Posted By Graphene Council, Wednesday, June 10, 2020
Researchers in the USA have developed a graphene-based electrochemical sensor capable of detecting histamines (allergens) and toxins in food much faster than standard laboratory tests.

The team used aerosol-jet printing to create the sensor. The ability to change the pattern geometry on demand through software control allowed rapid prototyping and efficient optimization of the sensor layout.

Commenting on the findings, which are published today in the IOP Publishing journal 2D Materials, senior author Professor Mark Hersam, from Northwestern University, said: "We developed an aerosol-jet printable graphene ink to enable efficient exploration of different device designs, which was critical to optimizing the sensor response."

As an additive manufacturing method that only deposits material where it is needed and therefore minimizes waste, aerosol-jet-printed sensors are low-cost, straightforward to make, and portable. This could potentially enable their use in places where continuous on-site monitoring of food samples is needed to determine and maintain the quality of products, as well as other applications.

Senior author Professor Carmen Gomes, from Iowa State University, said: "Aerosol-jet printing was fundamental to the development of this sensor. Carbon nanomaterials like graphene have unique material properties such as high electrical conductivity, surface area, and biocompatibility that can significantly improve the performance of electrochemical sensors.

"But, since in-field electrochemical sensors are typically disposable, they need materials that are amenable to low-cost, high-throughput, and scalable manufacturing. Aerosol-jet printing gave us this."

The team created high-resolution interdigitated electrodes (IDEs) on flexible substrates, which they converted into histamine sensors by covalently linking monoclonal antibodies to oxygen moieties created on the graphene surface by a CO2 thermal annealing process.

They then tested the sensors in both a buffering solution (PBS) and fish broth, to see how effective they were at detecting histamines.

Co-author Kshama Parate, from Iowa State University, said: "We found the graphene biosensor could detect histamine in PBS and fish broth over toxicologically-relevant ranges of 6.25 to 100 parts per million (ppm) and 6.25 to 200 ppm, respectively, with similar detection limits of 2.52 ppm and 3.41 ppm, respectively. These sensor results are significant, as histamine levels over 50 ppm in fish can cause adverse health effects including severe allergic reactions - for example, scombroid food poisoning.

"Notably, the sensors also showed a quick response time of 33 minutes, without the need for pre-labelling and pre-treatment of the fish sample. This is a good deal faster than the equivalent laboratory tests."

The researchers also found the biosensor's sensitivity was not significantly affected by the non-specific adsorption of large protein molecules commonly found in food samples and used as blocking agents.

Senior author Dr Jonathan Claussen, from Iowa State University, said: "This type of biosensor could be used in food processing facilities, import and export ports, and supermarkets where continuous on-site monitoring of food samples is needed. This on-site testing will eliminate the need to send food samples for laboratory testing, which requires additional handling steps, increases time and cost to histamine analysis, and consequently increases the risk of foodborne illnesses and food wastage.

"It could also likely be used in other biosensing applications where rapid monitoring of target molecules is needed, as the sample pre-treatment is eliminated using the developed immunosensing protocol. Apart from sensing small allergen molecules such as histamine, it could be used to detect various targets such as cells and protein biomarkers. By switching the antibody immobilized on the sensor platform to one that is specific towards the detection of suitable biological target species, the sensor can further cater to specific applications. Examples include food pathogens (Salmonella spp.), fatal human diseases (cancer, HIV) or animal or plant diseases (avian influenza, Citrus tristeza)."

Tags:  Biosensor  Carmen Gomes  Graphene  Iowa State University  Jonathan Claussen  Kshama Parate  Mark Hersam  Northwestern University  Sensors 

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UV-resistant elastic for N95 masks receives NSF RAPID grant

Posted By Graphene Council, Wednesday, May 20, 2020
Northwestern University’s Mark Hersam has received funding to develop a new elastic material that could enable N95 medical face masks to be disinfected and reused dozens of times.

Last week, the project received a $200,000 rapid response research (RAPID) grant from the National Science Foundation, which has called for immediate proposals that have potential to address the spread of the novel coronavirus (COVID-19).

“The ongoing COVID-19 pandemic has led to a shortage of critical medical equipment, including N95 medical masks. To conserve resources, medical workers have been reusing masks,” said Hersam, a Walter P. Murphy Professor of Materials Science and Engineering in Northwestern’s McCormick School of Engineering. “The problem is that sterilization using ultraviolet light breaks down the elastic in the nose foam and head straps, preventing the masks from fitting properly.”

To disinfect equipment, including N95 masks, medical professionals use ultraviolet germicidal irradiation (UVGI). While the widely used technique is highly effective in killing or inactivating pathogens, such as viruses and bacteria, UVGI also rapidly ages plastics and rubber.

The outcomes of this research not only address the current COVID-19 crisis, but are applicable for general medical use, including in future pandemics.” Mark Hersam, materials scientist.

Hersam’s team is developing a new type of elastic composite based on hydrated graphene oxide (hGO), a material that shows resistance to ultraviolet radiation and has proven intrinsic antimicrobial properties. By incorporating this material into N95 masks, the elastic components could better withstand UVGI and continue to maintain a snug fit even after being reused dozens of time.

A world-renowned graphene expert, Hersam will lead proof-of-concept experiments in his laboratory throughout the summer. He believes that better materials for medical equipment will be important well into the future.

“The outcomes of this research not only address the current COVID-19 crisis,” he said, “but are applicable for general medical use, including in future pandemics.”

The project, “Hydrated graphene oxide elastomeric composites for sterilizable and reusable N95 masks,” is funded by NSF award number 2029058.

Tags:  Graphene  Healthcare  Mark Hersam  Medical  Northwestern University 

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Creating 2D heterostructures for future electronics

Posted By Graphene Council, Thursday, November 7, 2019
Updated: Thursday, November 7, 2019
While many nanomaterials exhibit promising electronic properties, scientists and engineers are still working to best integrate these materials together to eventually create semiconductors and circuits with them.

Northwestern Engineering researchers have created two-dimensional (2D) heterostructures from two of these materials, graphene and borophene, taking an important step toward creating intergrated circuits from these nanomaterials.

"If you were to crack open an integrated circuit inside a smartphone, you'd see many different materials integrated together," said Mark Hersam, Walter P. Murphy Professor of Materials Science and Engineering, who led the research. "However, we've reached the limits of many of those traditional materials. By integrating nanomaterials like borophene and graphene together, we are opening up new possibilities in nanoelectronics."

Supported by the Office for Naval Research and the National Science Foundation, the results were published October 11 in the journal Science Advances. In addition to Hersam, applied physics PhD student Xiaolong Liu co-authored this work.

Creating a new kind of heterostructure

Any integrated circuit contains many materials that perform different functions, like conducting electricity or keeping components electrically isolated. But while transistors within circuits have become smaller and smaller -- thanks to advances in materials and manufacturing -- they are close to reaching the limit of how small they can get.

Ultrathin 2D materials like graphene have the potential to bypass that problem, but integrating 2D materials together is difficult. These materials are only one atom thick, so if the two materials' atoms do not line up perfectly, the integration is unlikely to be successful. Unfortunately, most 2D materials do not match up at the atomic scale, presenting challenges for 2D integrated circuits.

Borophene, the 2D version of boron that Hersam and coworkers first synthesized in 2015, is polymorphic, meaning it can take on many different structures and adapt itself to its environment. That makes it an ideal candidate to combine with other 2D materials, like graphene.

To test whether it was possible to integrate the two materials into a single heterostructure, Hersam's lab grew both graphene and borophene on the same substrate. They grew the graphene first, since it grows at a higher temperature, then deposited boron on the same substrate and let it grow in regions where there was no graphene. This process resulted in lateral interfaces where, because of borophene's accommodating nature, the two materials stitched together at the atomic scale.

Measuring electronic transitions

The lab characterized the 2D heterostructure using a scanning tunneling microscope and found that the electronic transition across the interface was exceptionally abrupt -- which means it could be ideal for creating tiny electronic devices.

"These results suggest that we can create ultrahigh density devices down the road," Hersam said. Ultimately, Hersam hopes to achieve increasingly complex 2D structures that lead to novel electronic devices and circuits. He and his team are working on creating additional heterostructures with borophene, combining it with an increasing number of the hundreds of known 2D materials.

"In the last 20 years, new materials have enabled miniaturization and correspondingly improved performance in transistor technology," he said. "Two-dimensional materials have the potential to make the next leap."

Tags:  2D materials  Graphene  Mark Hersam  nanoelectronics  nanomaterials  Northwestern University  Xiaolong Liu 

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Argonne-led center receives award for pivotal discovery in battery technology

Posted By Graphene Council, Monday, August 5, 2019
This year marks the tenth anniversary of the U.S. Department of Energy's (DOE's) Energy Frontier Research Centers (EFRCs). The DOE Office of Basic Energy Sciences launched forty-six such centers in 2009 to bring together teams of scientists to perform basic research beyond what is possible for individuals or small groups. To celebrate the ten-year milestone, DOE selected ten awardees to recognize their having made a major impact on scientific ideas, technologies and tools, and people. Hence, the award name is "Ten at Ten."

"This award is the consequence of the long-range vision, established at the very start of CEES in 2009, that a robust fundamental understanding of the electrode processes in lithium-ion batteries would have broad benefits." -- Paul Fenter, CEES director

One of the Ten at Ten Awards has gone to three researchers in the Center for Electrochemical Energy Science (CEES), a multi-organizational EFRC led by Argonne National Laboratory in partnership with Northwestern University, University of Illinois and Purdue University. The CEES mission is to explore the fundamental chemistry and materials underlying batteries and energy storage by means of state-of-the-art materials synthesis and characterization.

"This award is the consequence of the long-range vision, established at the very start of CEES in 2009, that a robust fundamental understanding of the electrode processes in lithium-ion batteries would have broad benefits," said Paul Fenter, CEES director and senior physicist in the Chemical Sciences and Engineering division. Such batteries could power electric vehicles and drones as well as provide energy storage for the grid.

The Ten at Ten Award recipients are two former CEES members, Harold Kung and Cary Hayner, and a current CEES member, Mark Hersam. Both Kung and Hersam are professors at Northwestern University, and Hayner is chief technical officer and co-founder of NanoGraf Corp. (formerly SiNode Systems).

"The interdisciplinary collaborative environment within CEES provides a breeding ground not only for fundamental discoveries but also for disruptive thinking that spawns new technologies," said Hersam.  "The EFRC program is a poignant example of how government investment in research ultimately fuels the innovation that underlies economic growth."

The Ten at Ten Award recognizes two new electrode technologies for next-generation lithium-ion batteries that were developed based on research that was initiated in CEES. Both technologies use "graphene," carbon layers just one atom thick, to coat the active materials within the battery electrode to create a "composite" electrode structure.  The first advance by Hayner and Kung used graphene in the battery anode, encapsulating particles of silicon. The second advance by Hersam incorporated graphene in the cathode, to encapsulate manganese-based oxides.

The resulting electrodes consist of graphene-coated active materials that have substantially improved properties, such as increased battery power, lifetime, and safety, as well as diminished likelihood of safety problems such as a violent reaction.

Another important feature of these technologies is that they enable lithium-ion batteries to function at temperatures well below the freezing point -- a capability critical for electric car owners in cold regions.

"CEES is especially proud that the award-winning research has given birth to two startups," noted Fenter. A startup company co-founded by Kung and Hayner in 2012 (NanoGraf) is commercializing the graphene-based silicon anode, while a startup company co-founded by Hersam in 2018 (Volexion) is bringing the graphene-based cathode to market.

"We owe our entire existence as a company to the research and people who are part of CEES," said NanoGraf co-founder Hayner. "The transformative discoveries made by CEES scientists has enabled us to further develop these technologies and bring them to the market to drive a cleaner, more sustainable future."

The award presentation took place on July 29 in Washington, DC. The Center for Electrochemical Energy Science is an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

Tags:  Cary Hayner  CEES  Graphene  Harold Kung  Mark Hersam  NanoGraf  Paul Fenter 

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