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Nanomaterials September 2017 Viewpoints

Technology Analyst: Marianne Monteforte

Edible Antibacterial Nanospray Coatings

Why is this topic significant?

Korean researchers have developed an edible antibacterial nanospray that prolongs the shelf life of perishable produce by more than a month. The significance of the nanospray is that it is material independent, providing it with the potential for use not only in agriculture but also in other applications, such as in antibacterial coatings on glasses and commodity goods.

Description

Recently, a team of researchers at the Korea Advanced Institute of Science and Technology (KAIST) developed and field-tested a sprayable antibacterial nanocoating. The plant-based nanocoating comprises a nanosolution of polyphenol-iron complex (iron(iii)-tannic acid metal-organic coordination complex) that is recognized as safe under US Food and Drug Administration (FDA) regulation. Polyphenols give the spray antibacterial properties and are also antioxidants and potential anticarcinogens.

The KAIST researchers' field tests of the nanospray on postharvest fruit—mandarin oranges and strawberries—revealed that the spray significantly prolonged the shelf life of the perishable produce (by up to one month) in comparison with the same unsprayed produce varieties. It also provided nutrients to the produce. The researchers claim that the nanospray method is fast (5 seconds of spray coating forms a 5-nanometer-thick coating) and can provide full coverage of the produce.

Unlike numerous other antibacterial coating options, the KAIST nanospray is material independent, making it compatible with multiple target substrates. The researchers demonstrated the practical potential of the spray as an antibacterial coating in other applications, including the surface of glasses (eyewear) and insoles of shoes.

Implications

Nanospray coating technologies are still in their infancy but offer great potential to a range of industries—in particular, the agriculture and consumer-goods industries. Although the FDA generally recognizes the material in KAIST's edible nanospray technology as safe—which helps the spray on its path to commercialization—the spray will also need to undergo detailed toxicity studies before it finds widespread use.

Most conventional solution-based coatings options have intrinsic limitations to their use, such as material dependence, restricting their use to just one product type, or time-consuming application processes, such as dip coating. The KAIST researchers' use of an aerosol enables a fast and scalable application method. The potential occupational health-and-safety consequences of using nanosprays will need consideration. However, this spray is plant based, so it is unlikely to be harmful to humans.

Impacts/Disruptions

High food prices, crop failures, and an ever-expanding global population are changing the way people think about food and agriculture. Some societies, particularly in developed economies, waste food on an enormous scale. For example, although the precise volume of food waste is quite difficult to put a number on, the Food and Agriculture Organization of the United Nations estimates that overall food waste by consumers in Europe and in North America is 95 to 115 kilograms per year. Widespread use of antibacterial nanosprays by the agriculture industry has the potential to cut global food waste dramatically and allow merchants to manage their perishable-food inventory more easily. However, the rate of adoption of nanospray could depend on the success of other competing technologies. For example, radio-frequency-identification tags have proven benefits for the reduction and recycling of food waste. Nevertheless, nanospray technologies may be of immediate commercial interest as antibacterial coatings in industries—such as the consumable goods and sporting industries—that already readily use nanoparticle-based antibacterial options.

Scale of Impact

  • Low
  • Medium
  • High
The scale of impact for this topic is: Medium

Time of Impact

  • Now
  • 5 Years
  • 10 Years
  • 15 Years
The time of impact for this topic is: Now to 5 Years

Opportunities in the following industry areas:

Agriculture, consumable goods, commodity goods, sports equipment

Relevant to the following Explorer Technology Areas:

Developments in Two-Dimensional Heterostructures

Why is this topic significant?

Stacking different two-dimensional materials into heterostructured architectures can enable scientists to combine the best properties of two materials into one superior material for use in next-generation electronic and photoelectronic devices. A recent study by researchers at the University of Manchester (UoM) provides new insights into heterostructures that could lead to developers' changing the design of their heterostructure-manufacturing processes.

Description

Contamination of nanomaterials with impurities, such as hydrocarbons, can alter the intended electronic properties of the material. A common assumption among scientists is that this issue is absent in layers of 2D materials because they exhibit a self-cleaning phenomenon, leaving large areas completely free of impurities. However, a recent study by UoM researchers of transition metal dichalcogenides (TMDC) heterostructures revealed a larger gap between the layers than the theoretical value and showed that this gap is the direct result of the presence of impurities in the structures.

The researchers used scanning-transmission-electron microscopy to analyze the TMDCs from a cross-sectional (side) view. The results of their study revealed the presence of hydrocarbon impurities and gas between the 2D sheet assemblies. The researchers claim that the intrinsic flexibility of the 2D sheets enables the material layers to deform, trapping the impurities between the layers. Also, their findings show that the self-cleaning mechanism pushes contamination away from the sheets, causing the impurities to form a bubble.

Implications

The properties of heterostructure devices can rely heavily on the environment in which developers make them. The UoM research reveals the presence of impurities at the atomic interfaces of heterostructures that can occur during the manufacturing stage. Such impurities can alter the intended properties of the material and, in turn, the function of the heterostructure device. Thus, the UoM researchers' findings are important for developers of heterostructures, indicating the need for them to reconsider their manufacturing methods in order to minimize the presence of impurities in the heterostructure. For example, to reduce the presence of impurities in the TMDC heterostructures, developers may need an inert, contamination-free environment, which will incur huge manufacturing costs. In addition, studies of the heterostructures from a cross-sectional view could lead to a better understanding of their stacking behavior and highlight properties that developers may have previously missed.

Impacts/Disruptions

Two-dimensional materials are at the center of numerous fundamental R&D studies. The intense research interest in graphene is drawing attention to the potential of a wider range of 2D materials for use in electronic devices. With sufficient R&D focus and industrial commitment, heterostructures could one day play an important role in electronic devices, such as in the production of tunneling transistors, resonant-tunneling diodes, and light-emitting diodes. Future developments in heterostructures could lead to their use in photoelectronics applications that could help to expand current energy-storage technologies greatly.

Although methods to manufacture heterostructures by large-area transfer are advancing, scientists still need to overcome many issues associated with large-area-materials production to progress toward the commercialization of 2D materials.

Scale of Impact

  • Low
  • Medium
  • High
The scale of impact for this topic is: Medium

Time of Impact

  • Now
  • 5 Years
  • 10 Years
  • 15 Years
The time of impact for this topic is: 5 Years to 10 Years

Opportunities in the following industry areas:

Consumer electronics, flexible electronics, LEDs, photoelectronics, energy storage

Relevant to the following Explorer Technology Areas: