Aerosol-jet printing enables graphene-based sensors

As an additive manufacturing method that only deposits material where it is needed, aerosol-jet-printed sensors are said to be low-cost, straightforward to make, and portable. This could potentially enable their use where continuous on-site monitoring of food samples is needed to determine and maintain the quality of products, as well as other applications. The research team, including experts from Northwestern University and Iowa State University, detail their findings in 2D Materials.

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In a statement, senior author Prof. 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 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 200ppm, respectively, with similar detection limits of 2.52ppm and 3.41ppm, respectively. These sensor results are significant, as histamine levels over 50ppm 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.

“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,” said senior author Dr Jonathan Claussen, from Iowa State University. “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.”