Category Archives: nanotechnology

Increased food security with hexanal for younger looking, fresher tasting fruits and vegetables

Also known as an anti-aging agent for your fruit and vegetables, hexanal is an environmentally friendly chemical, which is found naturally. Research has led to a synthesized nanotechnology-enabled product now being commercialized. I’ve been following the story off and on since 2012 (see my ‘India, Sri Lanka, and Canada team up for nanotechnology-enabled food packaging‘ posting). I last wrote about the project in a December 29, 2015 posting.

For some reason, hexanal hit the news hard in 2019 having been preceded by some interest in 2018. What follows is an update and a timeline of sorts.

January 2019: More funding

A January 24,2019 essay (also published on the University of Guelph website on January 29, 2019) by Jayasankar Subramanian and Elizabeth Finnis, both are lead researchers on the the project and professors at the University of Guelph (Canada), provides an overview and an update of the hexanal project (Note: Links have been removed) ,

Fruits like mangoes, bananas, papayas and limes are shipped long distances before they get to your table. Many fruits are delicate, and there may be a long period of time that elapses between when the fruit is picked and its arrival in grocery stores and other markets. They’re often picked before they’re truly ripe in order to increase their shelf life.

Even so, globally, up to 40 per cent of all picked fruit can be lost and this represents billions of dollars. But what if we had the technology to delay fruit’s natural degradation process? This is where hexanal can make a difference.

Fruits like mangoes, bananas, papayas and limes are shipped long distances before they get to your table. Many fruits are delicate, and there may be a long period of time that elapses between when the fruit is picked and its arrival in grocery stores and other markets. They’re often picked before they’re truly ripe in order to increase their shelf life.

Even so, globally, up to 40 per cent of all picked fruit can be lost and this represents billions of dollars. But what if we had the technology to delay fruit’s natural degradation process? This is where hexanal can make a difference.

Hexanal is naturally produced by plants to ward off pests; our research at the University of Guelph has found that when it’s applied externally, hexanal can also slow down the aging process.

Like everything else, fruit ages with time. The shrivelling and rot is triggered by the enzyme phospholipase D (PLD), which causes the eventual collapse of the fruit’s membrane. Essentially, fruit membranes are snug, and function like a brick wall of phospholipid bilayers. Phospholipase D breaks the alignment of the bricks, causing the membrane to crumble. Hexanal acts by reducing and slowing the formation of PLD, which in turn slows the collapse of the fruit’s membrane.

In partnership with agricultural and social science researchers in Canada and five other countries, we have tested nine hexanal technologies. These include a spray formulation that gets applied to fruit when they’re still on trees, post-harvest dips, fruit wraps, stickers and sachets embedded with hexanal.

Our findings have implications for consumers, retailers and, more importantly, farmers. For example, when applied as a pre-harvest spray, hexanal can keep fruit on trees longer and keep it fresher after harvest — up to three weeks longer for mangoes.

Hexanal is naturally produced by all plants and is already found as an additive in some food products. Hexanal is also approved by Health Canada as a flavour formula. Our tests of synthesized hexanal sprays, dips and other technologies showed that there were no negative effects on plants, insects or other animals. In addition, hexanal evaporates within 24 hours, which means there’s no residue left on fruit.

Farmers who participated in hexanal testing in Canada and elsewhere were happy with the product both in terms of its effectiveness and bio-safety.

Currently, hexanal for agricultural use is in the two-year regulatory clearance process in Canada and the U.S. Once the process is complete, hexanal formulations are expected to be available for farmer use and can be accessed through companies with a license for production.

Hexanal slows down the ripening and aging process in fresh produce. Author provided

That’s a stunning difference, eh?


At about the same time as the Conversation essay by Subramanian and Finnis, the University of Guelph published (on the Council of Ontario Universities website) a January 27, 2019 news release announcing new funds for the project,

A University of Guelph research project that has already improved the livelihoods of small-scale Asian farmers will further expand worldwide, thanks to more than $4.2 million in federal support announced Friday afternoon.

The project involves innovative packaging developed in part by Guelph researchers using nanotechnology to improve the shelf life of mangoes, a major fruit crop in much of the world.

Already, the technology has helped to significantly reduce post-harvest losses in Sri Lanka and India. Poor storage meant that farmers routinely lost up to 40 per cent of their crops, worth upwards of $800 million a year. The new technology has also boosted per-acre revenue.

New funding support from the International Development Research Centre (IDRC) and Foreign Affairs, Trade and Development Canada will allow researchers to broaden this successful initiative to Kenya, Tanzania, and Trinidad and Tobago.

Researchers will also look at other fruit — bananas, grapes, papaya, nectarines and berries — and investigate ways to commercialize the technologies.

… it will also be a main pillar of the Guelph-East Africa Initiative, which U of G established to bring together stakeholders to support research and teaching in food, health, water, education, environment and community.

“This confirms our commitment to improve agriculture in East Africa and around the world.” [said John Livernois, interim vice-president {research} ]

The project involves the use of hexanal, a natural plant product that delays fruit ripening and aging. Guelph plant agriculture professor Gopi Paliyath holds an American patent on the discovery of hexanal as a post-harvest agent. It’s also an FDA-approved food additive.

The project also involves Guelph plant agriculture professors Paliyath and Al Sullivan; Loong-tak Lim from Food Science; and Elizabeth Finnis, Sociology and Anthropology. Foreign research partners are based at Tamil Nadu Agricultural University, India; Industrial Technical Institute, Sri Lanka; University of Nairobi, Kenya; Sokoine University of Agriculture, Tanzania; and the University of [the] West Indies, Trinidad and Tobago.

Prior to more funding: a memorandum of understanding

I’m having to guess as the document about the memorandum of understanding (MOU) to commercialize hexanal is not dated but it seems to have been produced in March 2018. (Canada’s International Development Research Centre ([IDRC] has a webpage about the memorandum but no memorandum that I could find.) I stumbled across this account of the event where the MOU was signed,

Ms. Jennifer Daubeny, Consulate General of Canada, delivered the special address narrating the significance of Canadian fundingin developing nanotechnologies to reduce post-harvest losses that enables food security in Asian Countries. Dr. K. Ramasamy, Vice Chancellor, Tamil Nadu Agricultural University [TNAU], Coimbatore presided over the function and highlighted the role of TNAU in knitting nanotechnology research framework and serving as a torch bearer in the country. He emphasized that the GAC-IDRC Project helped more than 60 students and researchers, developed two technologies, filed patents for two inventions, extensive infrastructure development besides helping more than 12,000 fruit growers in the State of Tamil Nadu. Dr. Jayasankar Subramanian, Professor, University of Guelph, Canada, explained the evolution of the project till reached the stage of technology delivery to benefit farmers. Dr. K.S. Subramanian, NABARD Chair Professor, TNAU, Coimbatore, lead Principal Investigator of the Project for India presented nanotechnologies developed to assist in the entire value chain from the farm to fork. Mr. Arun Nagarajan, President, Tamil Nadu Fruit Growers’ Association, explained that the fruit growers are eager to use the technology to improve their farm income. Mr. Terence Park, Managing Director, Smart Harvest Agri, Canada, [emphasis mine] bestowed interest to take forward the technologies to the farm gate and signed MOU with TNAU for the Commercialization of the Hexanal Formulation. Dr. G.J. Janavi,Professor & Head, Department of Nano Science & Technology, TNAU, Coimbatore welcomed the gathering and Dr. C. Sekar, Dean, Imayam Agricultural College,Turaiyur, and Co-PI of the Project proposed a formal vote of thanks.

The Canadian Consul General Ms. Jennifer Daubeny visited all the exhibits and interacted with students, scholars and researchers besides the NGO partner Myrada. She was very impressed with the technologies developed by TNAU in collaboration with University of Guelph, Canada, and looking forward to support research programs in the near future. More than 200 Scientists and Diplomats from Canada, students, scholars, university officials participated in the event.

Products launch by ITI, Colombo

Two of the project’s technology outputs -hexanal incorporated ITI Bio-wax and the Tree Fresh Formulation spray [emphasis mine] were transferred to Hayleys Agriculture Pvt. Ltd., a reputed Agro Service provider in Sri Lanka. The products were launched on 22ndMarch 2018 at the Taj Samudra Hotel, Colombo. The chief guest at the event was the Hon. Susil Premajayantha, Minister of Science Technology and Research (Min. ST&R). The guest of honour was H.E. David McKinnon, High Commissioner for Canada in Sri Lanka. Others present included the Secretary to the Min. ST&R, The Chairman and Director General, ITI, Mr Rizvi Zaheed, Hayleys Agriculture and his team, the Chairman, National Science Foundation, Sri Lanka, representative of the Chairman Sri Lanka Export Development Board, representatives from the Dialog mobile service provider, the Registrar of Pesticides, representing the Dir. Gen., of Agriculture, President of the Lanka Fruit and Vegetable Producers, Processors and Exporters Association, leading large scale mango, papaya and pineapple growers, several export and fruit processing company representatives, senior officials from the ITI, the multi-disciplinary ITI research team and our partner from CEPA. The press was also well represented and a total of 100 persons were present on this occasion. The Managing Director Hayles, the two PIs’ of the project, the High Commissioner for Canada, The Minister and for ST&R and the Secretary to the Ministry addressed the gathering and the new video clip on the project was viewed. The new products were jointly uncovered for display by the Hon. Minister and H.E., the High Commissioner. Samples of the products were distributed to the President of the Lanka Fruit and Vegetable Producers Processors and Exporters Association and to two leading mango growers. The Project team also took this opportunity to run a presentation on the various stages of the project and related activities, display posters on their research findings and to print and distribute the pamphlets on the same as well as on hexanal, the latter as prepared by our partners from the University of Guelph. The launch ended with a time of fellowship providing a useful opportunity for networking.

A YouTube video about the product launch of hexanal-based Bio-wax and the Tree Fresh Formulation spray (I don’t know if those were the permanent names or if they are specific to Sri Lanka and other countries will adopt other names) helped to establish the date for the MOU. You can find the video here.

Judging from the media stories, the team in India has provided most of the leadership for commercializing hexanal.

Commercialization 2019 and beyond

To sum up, after a memorandum of understanding is signed and some prototype products have been unveiled in India in 2018 then, in early 2019, there’s more funding announced by IDRC to expand the number of countries involved and to continue research into efforts to save other types of produce.

Moving things along is an August 15, 2019 news item on,

Two nano formulations would be commercialized by the Directorate of Agri business development of Tamil Nadu Agricultural University (TNAU) soon.  

Fruity fresh is a liquid nano formulation containing hexanal that keeps fruits and vegetables fresh for more days. The pre-harvest spray of Fruity Fresh extends the shelf life of mango for two weeks on trees and another two weeks under storage conditions by employing post-harvest dip methodology, Dr. A. Lakshmanan, Professor and Head, Department of Nano Science and Technology told a meet on “Linking Nano Stakeholders” held at the University.  

Hexanal has also been successfully encapsulated in polymer matrix either as an electro spun fibre matrix (Nano sticker) or nano-pellets that extends shelf life of fruits by 1-2 weeks during storage and transportation, he said.  

This sticker and pellets technology is highly user friendly and can be placed inside the cartons containing fruits during transport for enhancing the freshness.

According to a November 5, 2019 article by Pearly Neo for, there is pricing for four products. Nano Sticker and Nano Pellet each will cost $US 0.028 and the spray, Fruity Fresh, will cost $US 4.23 to $US 5.65 for a one liter bottle diluted in 50 liters of water (for use on approximately five trees) and the Fruity Fresh dipping solution at $US 0.0071per kg.

As far as I’m aware none of these products are available in Canada but there is a website for Smart Harvest Agri, Canada although the name used is a little different. First, there’s the Federal Corporation Information listing for Smart Harvest Agritech Limited. You’ll notice there are two directors,

Amanjit Singh Bains
7685 150B Street
Surrey BC V3S 5P1

Terence Park
Yongsan CJ Nine Park
Korea, Republic of

The company’s Smart Harvest website doesn’t list any products but it does discuss something they call “FRESHXtend technology” for fruits and vegetables.

Final comment

I sometimes hear complaints about government funding and what seems to be a lack of follow through with exciting research work being done in Canada. I hope that in the months to come that this story of an international collaboration, which started with three countries and has now expanded to at least six countries and has led to increased food security with an environmentally friendly material and commercialization of research, gets some attention.

From the few sources I’ve been able to find, it seems India and Sri Lanka are leading the commercialization charge while Canada has contributed to an Asian-led project which has now expanded to include Kenya, Tanzania, and Trinidad and Tobago. Bravo t them all!

Purifying carbon nanotubes with dietary fiber

This work comes out of Japan according to a November 2, 2019 news item on Nanowerk,

A new, cheaper method easily and effectively separates two types of carbon nanotubes. The process, developed by Nagoya University researchers in Japan, could be up-scaled for manufacturing purified batches of single-wall carbon nanotubes that can be used in high-performance electronic devices.

Single-wall carbon nanotubes (SWCNTs) have excellent electronic and mechanical properties, making them ideal candidates for use in a wide range of electronic devices, including the thin-film transistors found in LCD displays. A problem is that only two-thirds of manufactured SWCNTs are suitable for use in electronic devices. The useful semiconducting SWCNTs must be separated from the unwanted metallic ones. But the most powerful purification process, known as aqueous two-phase extraction, currently involves the use of a costly polysaccharide, called dextran.

Caption: The unwanted metallic SWCNTs deposited at the bottom of the solution, while the wanted semiconducting ones floated to the top. Credit: Haruka Omachi

An October 29, 2019 Nagoya University press release (also on EurekAlert but dated Nov. 2, 2019), which originated the news item, describes how dextran could be replaced with something much cheaper in the SWCNT purification process,

Organic chemist Haruka Omachi and colleagues at Nagoya University hypothesized that dextran’s effectiveness in separating semiconducting from metallic SWCNTs lies in the linkages connecting its glucose units. Instead of using dextran to separate the two types of SWCNTs, the team tried the significantly cheaper isomaltodextran, which has many more of these linkages.

A batch of SWCNTs was left for 15 minutes in a solution containing polyethylene glycol and isomaltodextrin and then centrifuged for five minutes. Three different types of isomaltodextrin were tried, each with a different number of linkages and a different molecular weight. The team found that metallic SWCNTs separated to the bottom isomaltodextrin part of the solution, while the semiconducting SWCNTs floated to the top polyethylene glycol part.

The type of isomaltodextrin with high molecular weight and the most linkages was the most (99%) effective in separating the two types of SWCNTs. The team also found that another polysaccharide, called pullulan, whose glucose units are connected with different kinds of linkages, was ineffective in separating the two types of SWCNTs. The researchers suggest that the number and type of linkages present in isomaltodextrin play an important role in their ability to effectively separate the carbon nanotubes.

The team also found that a thin-film transistor made with their purified semiconducting SWCNTs performed very well.

Isomaltodextrin is a cheap and widely available polysaccharide produced from starch that is used as a dietary fibre. This makes it a cost-effective alternative for the SWCNT extraction process. Omachi and his colleagues are currently in discussions with companies to commercialize their approach. They are also working on improving the performance of thin-film transistors using semiconducting SWCNTs in flexible displays and sensor devices.

Here’s a link to and a citation for the paper,

Aqueous two-phase extraction of semiconducting single-wall carbon nanotubes with isomaltodextrin and thin-film transistor applications by Haruka Omachi, Tomohiko Komuro, Kaisei Matsumoto, Minako Nakajima, Hikaru Watanabe, Jun Hirotani, Yutaka Ohno, and Hisanori Shinohara. Applied Physics Express, Volume 12, Number 9 DOI: Published 14 August 2019 • © 2019 The Japan Society of Applied Physics

This paper is open access.

Double-walled carbon nanotubes have superior electrical properties?

A March 27, 2020 news item on Nanowerk suggests that double-walled carbon nanotubes (DWCNTs) may offer some advantages over single-walled carbon nanotubes (SWCNTs), NOTE: A link has been removed,

One nanotube could be great for electronics applications, but there’s new evidence that two could be tops.

Rice University engineers already knew that size matters when using single-walled carbon nanotubes for their electrical properties. But until now, nobody had studied how electrons act when confronted with the Russian doll-like structure of multiwalled tubes.

There’s a diagram representing the work,

Caption: Rice University theorists have calculated flexoelectric effects in double-walled carbon nanotubes. The electrical potential (P) of atoms on either side of a graphene sheet (top) are identical, but not when the sheet is curved into a nanotube. Double-walled nanotubes (bottom) show unique effects as band gaps in inner and outer tubes are staggered. Credit: Yakobson Research Group/Rice University

A March 27, 2020 Rice University news release (also on EurekAlert), which originated the news item, delves further (NOTE: Links have been removed),

The Rice lab of materials theorist Boris Yakobson has now calculated the impact of curvature of semiconducting double-wall carbon nanotubes on their flexoelectric voltage, a measure of electrical imbalance between the nanotube’s inner and outer walls.

This affects how suitable nested nanotube pairs may be for nanoelectronics applications, especially photovoltaics.

The theoretical research by Yakobson’s Brown School of Engineering group appears in the American Chemical Society journal Nano Letters.

In an 2002 study, Yakobson and his Rice colleagues had revealed how charge transfer, the difference between positive and negative poles that allows voltage to exist between one and the other, scales linearly to the curvature of the nanotube wall. The width of the tube dictates curvature, and the lab found that the thinner the nanotube (and thus larger the curvature), the greater the potential voltage.

When carbon atoms form flat graphene, the charge density of the atoms on either side of the plane are identical, Yakobson said. Curving the graphene sheet into a tube breaks that symmetry, changing the balance.

That creates a flexoelectric local dipole in the direction of, and proportional to, the curvature, according to the researchers, who noted that the flexoelectricity of 2D carbon “is a remarkable but also fairly subtle effect.”

But more than one wall greatly complicates the balance, altering the distribution of electrons. In double-walled nanotubes, the curvature of the inner and outer tubes differ, giving each a distinct band gap. Additionally, the models showed the flexoelectric voltage of the outer wall shifts the band gap of the inner wall, creating a staggered band alignment in the nested system.

“The novelty is that the inserted tube, the ‘baby’ (inside) matryoshka has all of its quantum energy levels shifted because of the voltage created by exterior nanotube,” Yakobson said. The interplay of different curvatures, he said, causes a straddling-to-staggered band gap transition that takes place at an estimated critical diameter of about 2.4 nanometers.

“This is a huge advantage for solar cells, essentially a prerequisite for separating positive and negative charges to create a current,” Yakobson said. “When light is absorbed, an electron always jumps from the top of an occupied valence band (leaving a ‘plus’ hole behind) to the lowest state of empty conductance band.

“But in a staggered configuration they happen to be in different tubes, or layers,” he said. “The ‘plus’ and ‘minus’ get separated between the tubes and can flow away by generating current in a circuit.”

The team’s calculations also showed that modifying the nanotubes’ surfaces with either positive or negative atoms could create “substantial voltages of either sign” up to three volts. “Although functionalization could strongly perturb the electronic properties of nanotubes, it may be a very powerful way of inducing voltage for certain applications,” the researchers wrote.

The team suggested its findings may apply to other types of nanotubes, including boron nitride and molybdenum disulfide, on their own or as hybrids with carbon nanotubes.

Here’s a link to and a citation for the paper,

Flexoelectricity and charge separation in carbon nanotubes by Vasilii I. Artyukhov, Sunny Gupta, Alex Kutana, Boris I. Yakobson. Nano Lett. 2020, XXXX, XXX, XXX-XXX DOI: [Online] Publication Date:March 10, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

Slippery toilet coating could save water

On a practical level, it’s becoming clear that we need to become more thoughtful about our use of water. We here in Canada tend to take our water for granted, as if we have an inexhaustible supply. According to this August 21, 2008 CBC (Canadian Broadcasting Corporation) online news item, that’s not the case,

Canada’s stores of fresh water are not as plentiful as once thought, and threaten to pinch the economy and pit provinces against each other, a federal document says.

An internal report drafted last December [2007] by Environment Canada warns that climate change and a growing population will further drain resources.

“We can no longer take our extensive water supplies for granted,” says the report, titled A Federal Perspective on Water Quantity Issues.

The Canadian Press obtained the 21-page draft report under the Access to Information Act.

It suggests the federal government take a more hands-on role in managing the country’s water, which is now largely done by the provinces. Ottawa still manages most of the fresh water in the North through water boards.

The Conservatives promised a national water strategy in last fall’s throne speech but have been criticized since for announcing only piecemeal projects.

The Tories, like the previous Liberal government, are also behind in publishing annual reports required by law that show how water supplies are used and maintained.

The last assessment posted on Environment Canada’s website is from 2005-06.

The internal draft report says the government currently does not know enough about the country’s water to properly manage it.

‘This is not a crisis yet. Why would we expect any government, regardless of political leaning or level, to do anything about it?’

“Canada lacks sound information at a national scale on the major uses and user[s] of water,” it says.

“National forecasting of water availability has never been done because traditionally our use of the resource was thought to be unlimited.”

Canada has a fifth of the world’s supply of fresh water, but only seven per cent of it is renewable. The rest comes from ice-age glaciers and underground aquifers.

One per cent of Canada’s total water supply is renewed each year by precipitation, the report says.

Moreover, government data on the country’s groundwater reserves is deemed “sparse and often inadequate.”

That’s in contrast to the United States, which has spent more than a decade mapping its underground water reserves. Canada shares aquifers with the U.S., and the report says: “Our lack of data places Canada at strategic disadvantage for bilateral negotiations with the U.S.”

The most recent update I can find is Ivan Semeniuk’s June 11, 2017 article for the Globe and Mail tilted: Charting Canada’s troubled waters: Where the danger lies for watersheds across the country,

A comprehensive review [World Wildlife Federation: a national assessment of of Canada’s freshwater Watershed Reports; 2017] freshwater ecosystems reveals rising threats from pollution, overuse, invasive species and climate change among other problems. Yet, the biggest threat of all may be a lack of information that hinders effective regulation, Ivan Semeniuk reports. …

Some of that information may be out of date.

Getting back on topic, here’s one possible solution to better managing our use of water.

Toilet coating

A November 18, 2019 news item on announces research that could save water,

Every day, more than 141 billion liters of water are used solely to flush toilets. With millions of global citizens experiencing water scarcity, what if that amount could be reduced by 50%?

The possibility may exist through research conducted at Penn State, released today (Nov. 18) in Nature Sustainability.

“Our team has developed a robust bio-inspired, liquid, sludge- and bacteria-repellent coating that can essentially make a toilet self-cleaning,” said Tak-Sing Wong, Wormley Early Career Professor of Engineering and associate professor of mechanical engineering and biomedical engineering.

Penn State researchers have developed a method that dramatically reduces the amount of water needed to flush a conventional toilet, which usually requires 6 liters. Image: Wong Laboratory for Nature Inspired Engineering

A November 18, 2019 Pennsylvania State University news release (also on EurekAlert,) which originated the news item, describes the research in more detail,

In the Wong Laboratory for Nature Inspired Engineering, housed within the Department of Mechanical Engineering and the Materials Research Institute, researchers have developed a method that dramatically reduces the amount of water needed to flush a conventional toilet, which usually requires 6 liters.

Co-developed by Jing Wang, a doctoral graduate from Wong’s lab, the liquid-entrenched smooth surface (LESS) coating is a two-step spray that, among other applications, can be applied to a ceramic toilet bowl. The first spray, created from molecularly grafted polymers, is the initial step in building an extremely smooth and liquid-repellent foundation.

“When it dries, the first spray grows molecules that look like little hairs, with a diameter of about 1,000,000 times thinner than a human’s,” Wang said.

While this first application creates an extremely smooth surface as is, the second spray infuses a thin layer of lubricant around those nanoscopic “hairs” to create a super-slippery surface.

“When we put that coating on a toilet in the lab and dump synthetic fecal matter on it, it (the synthetic fecal matter) just completely slides down and nothing sticks to it (the toilet),” Wang said.

With this novel slippery surface, the toilets can effectively clean residue from inside the bowl and dispose of the waste with only a fraction of the water previously needed. The researchers also predict the coating could last for about 500 flushes in a conventional toilet before a reapplication of the lubricant layer is needed.

While other liquid-infused slippery surfaces can take hours to cure, the LESS two-step coating takes less than five minutes. The researcher’s experiments also found the surface effectively repelled bacteria, particularly ones that spread infectious diseases and unpleasant odors.

If it were widely adopted in the United States, it could direct critical resources toward other important activities, to drought-stricken areas or to regions experiencing chronic water scarcity, said the researchers.

Driven by these humanitarian solutions, the researchers also hope their work can make an impact in the developing world. The technology could be used within waterless toilets, which are used extensively around the world.

“Poop sticking to the toilet is not only unpleasant to users, but it also presents serious health concerns,” Wong said.

However, if a waterless toilet or urinal used the LESS coating, the team predicts these types of fixtures would be more appealing and safer for widespread use.

To address these issues in both the United States and around the world, Wong and his collaborators, Wang, Birgitt Boschitsch, and Nan Sun, all mechanical engineering alumni, began a start-up venture.

With support from the Ben Franklin Technology Partners’ TechCelerator, the National Science Foundation, the Department of Energy, the Office of Naval Research, the Rice Business Plan Competition and Y-Combinator, their company, spotLESS Materials, is already bringing the LESS coating to market.

“Our goal is to bring impactful technology to the market so everyone can benefit,” Wong said. “To maximize the impact of our coating technology, we need to get it out of the lab.”

Looking forward, the team hopes spotLESS Materials will play a role in sustaining the world’s water resources and continue expanding the reach of their technology.

“As a researcher in an academic setting, my goal is to invent things that everyone can benefit from,” Wong said. “As a Penn Stater, I see this culture being amplified through entrepreneurship, and I’m excited to contribute.”

Here’s a link to and a citation for the paper,

Viscoelastic solid-repellent coatings for extreme water saving and global sanitation by Jing Wang, Lin Wang, Nan Sun, Ross Tierney, Hui Li, Margo Corsetti, Leon Williams, Pak Kin Wong & Tak-Sing Wong. Nature Sustainability (2019) DOI: Published 18 November 2019

This paper is behind a paywall. However, the researchers have made a brief video available,

There you have it. One random thought, that toilet image reminded me of the controversy over Marcel Duchamp, the Fountain, and who actually submitted a urinal for consideration as a piece of art (Jan. 23, 2019 posting). Hint: Some believe it was Baroness Elsa von Freytag-Loringhoven.

Are nano electronics as good as gold?

“As good as gold” was a behavioural goal when I was a child. It turns out, the same can be said of gold in electronic devices according to the headline for a March 26, 2020 news item on Nanowerk (Note: Links have been removed),

As electronics shrink to nanoscale, will they still be good as gold?

Deep inside computer chips, tiny wires made of gold and other conductive metals carry the electricity used to process data.

But as these interconnected circuits shrink to nanoscale, engineers worry that pressure, such as that caused by thermal expansion when current flows through these wires, might cause gold to behave more like a liquid than a solid, making nanoelectronics unreliable. That, in turn, could force chip designers to hunt for new materials to make these critical wires.

But according to a new paper in Physical Review Letters (“Nucleation of Dislocations in 3.9 nm Nanocrystals at High Pressure”), chip designers can rest easy. “Gold still behaves like a solid at these small scales,” says Stanford mechanical engineer Wendy Gu, who led a team that figured out how to pressurize gold particles just 4 nanometers in length — the smallest particles ever measured — to assess whether current flows might cause the metal’s atomic structure to collapse.

I have seen the issue about gold as a metal or liquid before but I can’t find it here (search engines, sigh). However, I found this somewhat related story from almost five years ago. In my April 14, 2015 posting (Gold atoms: sometimes they’re a metal and sometimes they’re a molecule), there was news that the number of gold atoms present means the difference between being a metal and being a molecule .This could have implications as circuit elements (which include some gold in their fabrication) shrink down past a certain point.

A March 24, 2020 Stanford University news release (also on Eurekalert but published on March 25, 2020) by Andrew Myers, which originated the news item, provides details about research designed to investigate a similar question, i.e, can we used gold as we shrink the scale?*,

To conduct the experiment, Gu’s team first had to devise a way put tiny gold particles under extreme pressure, while simultaneously measuring how much that pressure damaged gold’s atomic structure.

To solve the first problem, they turned to the field of high-pressure physics to borrow a device known as a diamond anvil cell. As the name implies, both hammer and anvil are diamonds that are used to compress the gold. As Gu explained, a nanoparticle of gold is built like a skyscraper with atoms forming a crystalline lattice of neat rows and columns. She knew that pressure from the anvil would dislodge some atoms from the crystal and create tiny defects in the gold.

The next challenge was to detect these defects in nanoscale gold. The scientists shined X-rays through the diamond onto the gold. Defects in the crystal caused the X-rays to reflect at different angles than they would on uncompressed gold. By measuring variations in the angles at which the X-rays bounced off the particles before and after pressure was applied, the team was able to tell whether the particles retained the deformations or reverted to their original state when pressure was lifted.

In practical terms, her findings mean that chipmakers can know with certainty that they’ll be able to design stable nanodevices using gold — a material they have known and trusted for decades — for years to come.

“For the foreseeable future, gold’s luster will not fade,” Gu says.

*The 2015 research measured the gold nanoclusters by the number of atoms within the cluster with the changes occurring at some where between 102 atoms and 144 atoms. This 2020 work measures the amount of gold by nanometers as in 3.9 nm gold nanocrystals . So, how many gold atoms in a nanometer? Cathy Murphy provides the answer and the way to calculate it for yourself in a July 26, 2016 posting on the Sustainable Nano blog ( a blog by the Center for Sustainable Nanotechnology),

Two years ago, I wrote a blog post called Two Ways to Make Nanoparticles, describing the difference between top-down and bottom-up methods for making nanoparticles. In the post I commented, “we can estimate, knowing how gold atoms pack into crystals, that there are about 2000 gold atoms in one 4 nm diameter gold nanoparticle.” Recently, a Sustainable Nano reader wrote in to ask about how this calculation is done. It’s a great question!

So, a 3.9 nm gold nanocrystal contains approximately 2000 gold atoms. (If you have time, do read Murphy’s description of how to determine the number of gold atoms in a gold nanoparticle.) So, this research does not answer the question posed by the 2015 research.

It may take years before researchers can devise tests for gold nanoclusters consisting of 102 atoms as opposed to nanoparticles consisting of 2000 atoms. In the meantime, here’s a link to and a citation for the latest on how gold reacts as we shrink the size of our electronics,

Nucleation of Dislocations in 3.9 nm Nanocrystals at High Pressure by Abhinav Parakh, Sangryun Lee, K. Anika Harkins, Mehrdad T. Kiani, David Doan, Martin Kunz, Andrew Doran, Lindsey A. Hanson, Seunghwa Ryu, and X. Wendy Gu. Phys. Rev. Lett. 124, 106104 DOI: Published 13 March 2020 © 2020 American Physical Society

This paper is behind a paywall.

In the future your clothing may be a health monitor

It’s not ready for the COVID-19 pandemic but if I understand it properly, wearing this clothing will be a little like wearing a thermometer and that could be very useful. A March 4, 2020 news item on Nanowerk announces the research (Note: A link has been removed),

Researchers have reported a new material, pliable enough to be woven into fabric but imbued with sensing capabilities that can serve as an early warning system for injury or illness.

The material, described in a paper published by ACS Applied Nano Materials (“Poly(octadecyl acrylate)-Grafted Multiwalled Carbon Nanotube Composites for Wearable Temperature Sensors”), involves the use of carbon nanotubes and is capable of sensing slight changes in body temperature while maintaining a pliable disordered structure – as opposed to a rigid crystalline structure – making it a good candidate for reusable or disposable wearable human body temperature sensors. Changes in body heat change the electrical resistance, alerting someone monitoring that change to the potential need for intervention.

I think this is an artistic rendering of the research,

Caption: Researchers have reported a new material, pliable enough to be woven into fabric but imbued with sensing capabilities that could serve as an early warning system for injury or illness. Credit: University of Houston

A March 4, 2020 University of Houston (Texas, US) news release (also on EurekAlert) by Jeannie Kever, which originated the news item, describes the work in more detail,

“Your body can tell you something is wrong before it becomes obvious,” said Seamus Curran, a physics professor at the University of Houston and co-author on the paper. Possible applications range from detecting dehydration in an ultra-marathoner to the beginnings of a pressure sore in a nursing home patient.

The researchers said it is also cost-effective because the raw materials required are used in relatively low concentrations.

The discovery builds on work Curran and fellow researchers Kang-Shyang Liao and Alexander J. Wang began nearly a decade ago, when they developed a hydrophobic nanocoating for cloth, which they envisioned as a protective coating for clothing, carpeting and other fiber-based materials.

Wang is now a Ph.D. student at Technological University Dublin, currently working with Curran at UH, and is corresponding author for the paper. In addition to Curran and Liao, other researchers involved include Surendra Maharjan, Brian P. McElhenny, Ram Neupane, Zhuan Zhu, Shuo Chen, Oomman K. Varghese and Jiming Bao, all of UH; Kourtney D. Wright and Andrew R. Barron of Rice University, and Eoghan P. Dillon of Analysis Instruments in Santa Barbara.

The material, created using poly(octadecyl acrylate)-grafted multiwalled carbon nanotubes, is technically known as a nanocarbon-based disordered, conductive, polymeric nanocomposite, or DCPN, a class of materials increasingly used in materials science. But most DCPN materials are poor electroconductors, making them unsuitable for use in wearable technologies that require the material to detect slight changes in temperature.

The new material was produced using a technique called RAFT-polymerization, Wang said, a critical step that allows the attached polymer to be electronically and phononically coupled with the multiwalled carbon nanotube through covalent bonding. As such, subtle structural arrangements associated with the glass transition temperature of the system are electronically amplified to produce the exceptionally large electronic responses reported in the paper, without the negatives associated with solid-liquid phase transitions. The subtle structural changes associated with glass transition processes are ordinarily too small to produce large enough electronic responses.

Here’s a link to and a citation for the paper,

Poly(octadecyl acrylate)-Grafted Multiwalled Carbon Nanotube Composites for Wearable Temperature Sensors by Alexander J. Wang, Surendra Maharjan, Kang-Shyang Liao, Brian P. McElhenny, Kourtney D. Wright, Eoghan P. Dillon, Ram Neupane, Zhuan Zhu, Shuo Chen, Andrew R. Barron, Oomman K. Varghese, Jiming Bao, Seamus A. Curran. ACS Appl. Nano Mater. 2020, XXXX, XXX, XXX-XXX DOI: (Online) Publication Date:January 28, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

Norwegian Institute for Water Research (NIVA) releases study on silver and titanium nanomaterials in wastewater

It turns out that silver and titanium nanomaterials (e.g. silver nanoparticles washed out of athletic clothing) in wastewater may have ‘negative’ and ‘positive’ effects on freshwater and marine life depending on the species.

A November 18, 2019 news item on Nanowerk provides an introduction to the research (Note: Links have been removed),

You may not always think about it when you do your laundry or flush the toilet; but whatever you eat, wear or apply on your skin ends up in wastewater and eventually reaches the environment. The use of nanoparticles in consumer products like textiles, foods and personal care products is increasing.

What is so special about nanoparticles, is their tiny size: One nanometer is one billionth of a meter. The small size gives nanoparticles unique and novel properties compared to their bigger counterparts and may for example reach locations that bigger particles cannot reach.
Further, pristine nanoparticles behave differently from nanoparticles in the environment. In the environment, nanoparticles are transformed by interacting and forming aggregates with other particles, elements or solids, and thereby obtain other physicochemical properties.

The transformation of these tiny particles in wastewater treatment processes and their effect on freshwater and marine organisms, have largely been unknown.
Increased mortality of marine crustaceans.

In a study (“Ecotoxicological Effects of Transformed Silver and Titanium Dioxide Nanoparticles in the Effluent from a Lab-Scale Wastewater Treatment System”) conducted at the Norwegian Institute for Water Research (NIVA), Anastasia Georgantzopoulou and colleagues from NIVA and SINTEF investigated how silver and titanium dioxide nanoparticles behave in wastewater treatment plants, and how marine and freshwater organisms are affected by them.

Exposure to treated wastewater did not have any adverse effects on the freshwater crustacean Daphnia magna. (Photo: NIVA)

A November 18, 2019 NIVA press release, which originated the news item, fills in the details,

The researchers made a laboratory-scale wastewater treatment plant, using sludge from a wastewater treatment plant in Norway. They added environmentally relevant concentrations of silver (Ag) and titanium dioxide (TiO2) nanoparticles over a 5-week period and used the treated wastewater to assess the effects of transformed nanoparticles on freshwater and marine organisms, as well as on gill cells from rainbow trout.

The experiment demonstrated contrasting effects on the two crustacean species. For the marine copepod (Tisbe battagliai), mortality increased by 20-45%, whereas exposure to ttreated wastewater did not have any adverse effects on the freshwater crustacean (Daphnia magna).

“These differences are probably due, at least partly, to the two species’ different feeding habits, in combination with the fact that the nanoparticles showed a strong association to solids present in the wastewater”, Georgantzopoulou says, and explains:

“Daphnia magna is an organism that filters water for food, whereas the marine copepod feeds on bottom surfaces – like effluent solids that have settled out from the water. The bottom feeding crustacean is therefore more likely to ingest nanoparticles, and thereby be affected by solid-associated nanoparticles”. 

Effects on algal species

Nanoparticle-containing treated wastewater also affected algal growth, but the two algae species did not have a common response: The marine algae (Skeletonema pseudocostatum) responded with a 20-40 % growth inhibition, while the algal growth of the freshwater algae (Raphidocelis subcapitata) was actually stimulated, by a 40 % increase, accompanied by increased cell aggregation. The latter is probably some kind of a defense mechanism, aiming to decrease the surface area exposed to toxic particles.

“The results from our study indicate that algal responses to the treated wastewater exposure are species-dependent. This is possibly due to differences in algal cell size, surface area, and cell wall composition”, the NIVA researcher explains.

Increased permeability of fish gill cells

The researchers also found effects of silver and titanium nanoparticles on fish gill cells using an in vitro gill cell line model. As large amounts of water are passing through the gills, and they constitute a barrier to the external environment, this organ is highly exposed to water-borne contaminants, including nanoparticles.

“Exposure to nanoparticle-containing wastewater lead to an increase in reactive oxygen species, a group of molecules that can easily react with and damage cells. This was followed by increased permeability of the gill cells, leading to a compromised barrier function”, Georgantzopoulou says.

“However, the concentrations of silver and titanium nanoparticles in the treated wastewater were too low to fully account for the effects on cell permeability alone. The wastewater effluent is a complex mixture of materials, and the permeability response is probably caused by a combination of the presence of nanoparticles and other stressors”, Georgantzopoulou adds.

Wastewater treatment-transformation of nanoparticles

“We carried out this study on wastewater treatment plant-transformed nanoparticles, and compared them to pristine nanoparticles, as the former is more relevant to what is actually happening in the environment. The increased toxicity of the transformed nanomaterials observed in the study indicates that the effects cannot be predicted by assessing the effects of nanomaterials in their pristine form and highlights the importance of understanding their behavior, environmental transformation and interaction with organisms. Future studies should take nanoparticle transformation into account and focus on a more relevant experimental exposure conditions incorporating transformed nanoparticles in more long-term impact studies to provide a better understanding of their potential impacts”, Georgantzopoulou concludes.

Here’s a link to and a citation for the paper,

Ecotoxicological Effects of Transformed Silver and Titanium Dioxide Nanoparticles in the Effluent from a Lab-Scale Wastewater Treatment System by Anastasia Georgantzopoulou, Patricia Almeida Carvalho, Christian Vogelsang, Mengstab Tilahun, Kuria Ndungu, Andy M. Booth, Kevin V. Thomas, Ailbhe Macken. Environ. Sci. Technol. 2018, 52, 16, 9431-9441 DOI: Publication Date:July 26, 2018 Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Replacing human tissue with nanostructured rubber-like material?

The scientists started out with an idea for creating a bone-like material)and ended up with something completely different. A March 16, 2020 news item on ScienceDaily announces news about a new material that could be used to replace human tissue,

Researchers from Chalmers University of Technology, Sweden, have created a new, rubber-like material with a unique set of properties, which could act as a replacement for human tissue in medical procedures. The material has the potential to make a big difference to many people’s lives. The research was recently published in the highly regarded scientific journal ACS Nano.

In the development of medical technology products, there is a great demand for new naturalistic materials suitable for integration with the body. Introducing materials into the body comes with many risks, such as serious infections, among other things. Many of the substances used today, such as Botox, are very toxic. There is a need for new, more adaptable materials.

In the new study, the Chalmers researchers developed a material consisting solely of components that have already been shown to work well in the body.

A March 17, 2020 Chalmers University of Technology press release (also on EurekAlert but published on March 16, 2020), which originated the news item, describes the scientists’ surprising discovery and how they shifted their focus,

The foundation of the material is the same as plexiglass, a material which is common in medical technology applications. Through redesigning its makeup, and through a process called nanostructuring, they gave the newly patented material a unique combination of properties. The researchers’ initial intention was to produce a hard bone-like material, but they were met with surprising results.

“We were really surprised that the material turned to be very soft, flexible and extremely elastic. It would not work as a bone replacement material, we concluded. But the new and unexpected properties made our discovery just as exciting,” says Anand Kumar Rajasekharan, PhD in Materials Science and one of the researchers behind the study.

The results showed that the new rubber-like material may be appropriate for many applications which require an uncommon combination of properties – high elasticity, easy processability, and suitability for medical uses.

“The first application we are looking at now is urinary catheters. The material can be constructed in such a way that prevents bacteria from growing on the surface, meaning it is very well suited for medical uses,” says Martin Andersson, research leader for the study and Professor of Chemistry at Chalmers.

The structure of the new nano-rubber material allows its surface to be treated so that it becomes antibacterial, in a natural, non-toxic way. This is achieved by sticking antimicrobial peptides – small proteins which are part of our innate immune system – onto its surface. This can help reduce the need for antibiotics, an important contribution to the fight against growing antibiotic resistance.

Because the new material can be injected and inserted via keyhole surgery, it can also help reduce the need for drastic surgery and operations to rebuild parts of the body. The material can be injected via a standard cannula as a viscous fluid, so that it forms its own elastic structures within the body. Or, the material can also be 3D printed into specific structures as required.

“There are many diseases where the cartilage breaks down and friction results between bones, causing great pain for the affected person. This material could potentially act as a replacement in those cases,” Martin Andersson continues.

A further advantage of the material is that it contains three-dimensionally ordered nanopores. This means it can be loaded with medicine, for various therapeutic purposes such as improving healing and reducing inflammation. This allows for localised treatment, avoiding, for example, having to treat the entire body with drugs, something that could help reduce problems associated with side effects. Since it is non-toxic, it also works well as a filler – the researchers see plastic surgery therefore as another very interesting potential area of application for the new material.

“I am now working full time with our newly founded company, Amferia, to get the research out to industry. I have been pleased to see a lot of real interest in our material. It’s promising in terms of achieving our goal, which is to provide real societal benefit,” Anand concludes.

The path of the research to societal benefit and commercialisation, through start-up company Amferia and Chalmers Ventures

In order for the discovery of the new material to be useful and commercialised, the researchers patented their innovation before the study was published. The patent is owned by start-up company Amferia, which was founded by Martin Andersson and Anand Kumar Rajasekharan, two of the researchers behind the study, as well as researcher Saba Atefyekta who recently completed a PhD in Materials Science at Chalmers. Anand is now CEO of Amferia and will drive the application of the new material and development of the company.

Amferia has previously been noted for an antibacterial wound patch developed by the same team. Amferia now has the innovation of both the new nano-rubber and the antibacterial wound patch. The development of the company and the innovations’ path to making profit are now being carried out in collaboration with Chalmers Ventures, a subsidiary of Chalmers University of Technology.

Here’s a link to and a citation for the paper,

Tough Ordered Mesoporous Elastomeric Biomaterials Formed at Ambient Conditions by Anand K. Rajasekharan, Christoffer Gyllensten, Edvin Blomstrand, Marianne Liebi, Martin Andersson. ACS Nano 2020, 14, 1, 241-254 DOI: Publication Date:December 17, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Flexible graphene-rubber sensor for wearables

Courtesy: University of Waterloo

This waffled, greyish thing may not look like much but scientists are hopeful that it can be useful as a health sensor in athletic shoes and elsewhere. A March 6, 2020 news item on Nanowerk describes the work in more detail (Note: Links have been removed),

Researchers have utilized 3D printing and nanotechnology to create a durable, flexible sensor for wearable devices to monitor everything from vital signs to athletic performance (ACS Nano, “3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring”).

The new technology, developed by engineers at the University of Waterloo [Ontario, Canada], combines silicone rubber with ultra-thin layers of graphene in a material ideal for making wristbands or insoles in running shoes.

A March 6, 2020 University of Waterloo news release, which originated the news item, delves further,

When that rubber material bends or moves, electrical signals are created by the highly conductive, nanoscale graphene embedded within its engineered honeycomb structure.

“Silicone gives us the flexibility and durability required for biomonitoring applications, and the added, embedded graphene makes it an effective sensor,” said Ehsan Toyserkani, research director at the Multi-Scale Additive Manufacturing (MSAM) Lab at Waterloo. “It’s all together in a single part.”

Fabricating a silicone rubber structure with such complex internal features is only possible using state-of-the-art 3D printing – also known as additive manufacturing – equipment and processes.

The rubber-graphene material is extremely flexible and durable in addition to highly conductive.

“It can be used in the harshest environments, in extreme temperatures and humidity,” said Elham Davoodi, an engineering PhD student at Waterloo who led the project. “It could even withstand being washed with your laundry.”

The material and the 3D printing process enable custom-made devices to precisely fit the body shapes of users, while also improving comfort compared to existing wearable devices and reducing manufacturing costs due to simplicity.

Toyserkani, a professor of mechanical and mechatronics engineering, said the rubber-graphene sensor can be paired with electronic components to make wearable devices that record heart and breathing rates, register the forces exerted when athletes run, allow doctors to remotely monitor patients and numerous other potential applications.

Researchers from the University of California, Los Angeles and the University of British Columbia collaborated on the project.

Here’s a link to and a citation for the paper,

3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring by Elham Davoodi, Hossein Montazerian, Reihaneh Haghniaz, Armin Rashidi, Samad Ahadian, Amir Sheikhi, Jun Chen, Ali Khademhosseini, Abbas S. Milani, Mina Hoorfar, Ehsan Toyserkani. ACS Nano 2020, 14, 2, 1520-1532 DOI: Publication Date: January 6, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.