Tag Archives: Hui Sun

Nanofabrication, silk microneedles, and agriculture

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In demonstrations, the team showed their new technique could be used to give plants iron to treat a disease known as chlorosis, and to add B12 to tomato plants to make them more nutritious for humans. Credit: Courtesy of Benedetto Marelli

What a gorgeous tomato plant! Here’s more about the work that went into this plant and others in an April 29, 2025 news item on ScienceDaily,

When farmers apply pesticides to their crops, 30 to 50 percent of the chemicals end up in the air or soil instead of on the plants. Now, a team of researchers from MIT [Massachusetts Institute of Technology] and Singapore has developed a much more precise way to deliver substances to plants: tiny needles made of silk.

In a study published today in Nature Nanotechnology, the researchers developed a way to produce large amounts of these hollow silk microneedles. They used them to inject agrochemicals and nutrients into plants, and to monitor their health.

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An April 29, 2025 Massachusetts Institute of Technology (MIT) news release (also on EurekAlert) by Zach Winn, which originated the news item, delves further into the research, Note: Links have been removed,

“There’s a big need to make agriculture more efficient,” says Benedetto Marelli, the study’s senior author and an associate professor of civil and environmental engineering at MIT. “Agrochemicals are important for supporting our food system, but they’re also expensive and bring environmental side effects, so there’s a big need to deliver them precisely.”

Yunteng Cao PhD ’22, currently a postdoc [at?] Yale University, and Doyoon Kim, a former postdoc in the Marelli lab, led the study, which included a collaboration with the Disruptive and Sustainable Technologies for Agricultural Precision (DiSTAP) interdisciplinary research group at the Singapore-MIT Alliance for Research and Technology (SMART). 

In demonstrations, the team used the technique to give plants iron to treat a disease known as chlorosis, and to add vitamin B12 to tomato plants to make them more nutritious. The researchers also showed the microneedles could be used to monitor the quality of fluids flowing into plants and to detect when the surrounding soil contained heavy metals.

Overall, the researchers believe the microneedles could serve as a new kind of plant interface for real-time health monitoring and biofortification.

“These microneedles could be a tool for plant scientists so they can understand more about plant health and how they grow,” Marelli says. “But they can also be used to add value to crops, making them more resilient and possibly even increasing yields.”

The inner workings of plants

Accessing the inner tissues of living plants requires scientists to get through the plants’ waxy skin without causing too much stress. In previous work, the researchers used silk-based microneedles to deliver agrochemicals to plants in lab environments and to detect pH changes in living plants. But these initial efforts involved small payloads, limiting their applications in commercial agriculture.

“Microneedles were originally developed for the delivery of vaccines or other drugs in humans,” Marelli explains. “Now we’ve adapted it so that the technology can work with plants, but initially we could not deliver sufficient doses of agrochemicals and nutrients to mitigate stressors or enhance crop nutritional values.”

Hollow structures could increase the amount of chemicals microneedles can deliver, but Marelli says creating those structures at scale has historically required clean rooms and expensive facilities like the ones found inside the MIT.nano building.

For this study, Cao and Kim created a new way to manufacture hollow silk microneedles by combining silk fibroin protein with a salty solution inside tiny, cone-shaped molds. As water evaporated from the solution, the silk solidified into the mold while the salt forms crystalline structures inside the molds. When the salt was removed, it left behind in each needle a hollow structure or tiny pores, depending on the salt concentration and the separation of the organic and inorganic phases.

“It’s a pretty simple fabrication process. It can be done outside of a clean room — you could do it in your kitchen if you wanted,” Kim says. “It doesn’t require any expensive machinery.”

The researchers then tested their microneedles’ ability to deliver iron to iron-deficient tomato plants, which can cause a disease known as chlorosis. Chlorosis can decrease yields, but treating it by spraying crops is inefficient and can have environmental side effects. The researchers showed that their hollow microneedles could be used for the sustained delivery of iron without harming the plants.

The researchers also showed their microneedles could be used to fortify crops while they grow. Historically, crop fortification efforts have focused on minerals like zinc or iron, with vitamins only added after the food is harvested.

In each case, the researchers applied the microneedles to the stalks of plants by hand, but Marelli envisions equipping autonomous vehicles and other equipment already used in farms to automate and scale the process.

As part of the study, the researchers used microneedles to deliver vitamin B12, which is primarily found naturally in animal products, into the stalks of growing tomatoes, showing that vitamin B12 moved into the tomato fruits before harvest. The researchers propose their method could be used to fortify more plants with the vitamin.

Co-author Daisuke Urano, a plant scientist with DiSTAP, explains that “through a comprehensive assessment, we showed minimal adverse effects from microneedle injections in plants, with no observed short- or long-term negative impacts.”

“This new delivery mechanism opens up a lot of potential applications, so we wanted to do something nobody had done before,” Marelli explains.

Finally, the researchers explored the use of their microneedles to monitor the health of plants by studying tomatoes growing in hydroponic solutions contaminated with cadmium, a toxic metal commonly found in farms close to industrial and mining sites. They showed their microneedles absorbed the toxin within 15 minutes of being injected into the tomato stalks, offering a path to rapid detection.

Current advanced techniques for monitoring plant health, such as colorimetric and hyperspectral lead analyses, can only detect problems after plants growth is already being stunted. Other methods, such as sap sampling, can be too time-consuming.

Microneedles, in contrast, could be used to more easily collect sap for ongoing chemical analysis. For instance, the researchers showed they could monitor cadmium levels in tomatoes over the course of 18 hours.

A new platform for farming

The researchers believe the microneedles could be used to complement existing agricultural practices like spraying. The researchers also note the technology has applications beyond agriculture, such as in biomedical engineering.

“This new polymeric microneedle fabrication technique may also benefit research in microneedle-mediated transdermal and intradermal drug delivery and health monitoring,” Cao says.

For now, though, Marelli believes the microneedles offer a path to more precise, sustainable agriculture practices.

“We want to maximize the growth of plants without negatively affecting the health of the farm or the biodiversity of surrounding ecosystems,” Marelli says. “There shouldn’t be a trade-off between the agriculture industry and the environment. They should work together.”

This work was supported, in part, by the U.S. Office of Naval Research, the U.S. National Science Foundation, SMART, the National Research Foundation of Singapore, and the Singapore Prime Minister’s Office.

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

Nanofabrication of silk microneedles for high-throughput micronutrient delivery and continuous sap monitoring in plants by Yunteng Cao, Doyoon Kim, Sally Shuxian Koh, Zheng Li, Federica Rigoldi, Julia Eva Fortmueller, Kasey Goh, Yilin Zhang, Eugene J. Lim, Hui Sun, Elise Uyehara, Raju Cheerlavancha, Yangyang Han, Rajeev J. Ram, Daisuke Urano & Benedetto Marelli. Nature Nanotechnology (2025) DOI: https://doi.org/10.1038/s41565-025-01923-2 Published: 29 April 2025

This paper is behind a paywall.

Silk micro or nanoparticles for tracking seeds

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I hadn’t heard of counterfeit seeds before but this March 22, 2023 news item on phys.org describes the problem and announces an approach to prevention,

Average crop yields in Africa are consistently far below expected, and one significant reason is the prevalence of counterfeit seeds whose germination rates are far lower than those of the genuine ones. The World Bank estimates that as much as half of all seeds sold in some African countries are fake, which could help to account for crop production that is far below potential.

There have been many attempts to prevent this counterfeiting through tracking labels, but none have proved effective; among other issues, such labels have been vulnerable to hacking because of the deterministic nature of their encoding systems. But now, a team of MIT [Massachusetts Institute of Technology] researchers has come up with a kind of tiny, biodegradable tag that can be applied directly to the seeds themselves, and that provides a unique randomly created code that cannot be duplicated.

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I found this picture helped me to understand how ‘tracking’ these seeds could be useful,

As a way to reduce seed counterfeiting, MIT researchers developed a silk-based tag that, when applied to seeds, provides a unique code that cannot be duplicated. Credits: Credit: Photograph courtesy of the researchers. Edited by Jose-Luis Olivares, MIT

A March 22, 2023 Massachusetts Institute of Technology (MIT) news release by David Chandler (also on EurekAlert), which originated the news item, describes the work in more detail (Note: I’m glad to see David Chandler is getting bylines again even if it’s on the EurekAlert version only),

The new system, which uses minuscule dots of silk-based material, each containing a unique combination of different chemical signatures, is described today in the journal Science Advances in a paper by MIT’s dean of engineering Anantha Chandrakasan, professor of civil and environmental engineering Benedetto Marelli, postdoc Hui Sun, and graduate student Saurav Maji.

The problem of counterfeiting is an enormous one globally, the researchers point out, affecting everything from drugs to luxury goods, and many different systems have been developed to try to combat this. But there has been less attention to the problem in the area of agriculture, even though the consequences can be severe. In sub-Saharan Africa, for example, the World Bank estimates that counterfeit seeds are a significant factor in crop yields that average less than one-fifth of the potential for maize, and less than one-third for rice. 

Marelli explains that a key to the new system is creating a randomly-produced physical object whose exact composition is virtually impossible to duplicate. The labels they create “leverage randomness and uncertainty in the process of application, to generate unique signature features that can be read, and that cannot be replicated,” he says.

What they’re dealing with, Sun adds, “is the very old job of trying, basically, not to get your stuff stolen. And you can try as much as you can, but eventually somebody is always smart enough to figure out how to do it, so nothing is really unbreakable. But the idea is, it’s almost impossible, if not impossible, to replicate it, or it takes so much effort that it’s not worth it anymore.”

The idea of an “unclonable” code was originally developed as a way of protecting the authenticity of computer chips, explains Chandrakasan, who is the Vannevar Bush Professor of Electrical Engineering and Computer Science. “In integrated circuits, individual transistors have slightly different properties coined device variations,” he explains, “and you could then use that variability and combine that variability with higher-level circuits to create a unique ID for the device. And once you have that, then you can use that unique ID as a part of a security protocol. Something like transistor variability is hard to replicate from device to device, so that’s what gives it its uniqueness, versus storing a particular fixed ID.” The concept is based on what are known as physically unclonable functions, or PUFs.

The team decided to try to apply that PUF principle to the problem of fake seeds, and the use of silk proteins was a natural choice because the material is not only harmless to the environment but also classified by the Food and Drug Administration in the “generally recognized as safe” category, so it requires no special approval for use on food products.

“You could coat it on top of seeds,” Maji says, “and if you synthesize silk in a certain way, it will also have natural random variations. So that’s the idea, that every seed or every bag could have a unique signature.”

Developing effective secure system solutions have long been one of Chandrakasan’s specialties, while Marelli has spent many years developing systems for applying silk coatings to a variety of fruits, vegetables, and seeds, so their collaboration was a natural for developing such a silk-based coding system towards enhanced security. 

“The challenge was what type of form factor to give to silk,” Sun says, “so that it can be fabricated very easily.” They developed a simple drop-casting approach that produces tags that are less than one-tenth of an inch in diameter. The second challenge was to develop “a way where we can read the uniqueness, in also a very high throughput and easy way.”

For the unique silk-based codes, Marelli says, “eventually we found a way to add a color to these microparticles [emphasis mine] so that they assemble in random structures.” The resulting unique patterns can be read out not only by a spectrograph or a portable microscope, but even by an ordinary cellphone camera with a macro lens. This image can be processed locally to generate the PUF code and then sent to the cloud and compared with a secure database to ensure the authenticity of the product. “It’s random so that people cannot easily replicate it,” says Sun. “People cannot predict it without measuring it.”

And the number of possible permutations that could result from the way they mix four basic types of colored silk nanoparticles [emphasis mine] is astronomical. “We were able to show that with a minimal amount of silk, we were able to generate 128 random bits of security,” Maji says. “So this gives rise to 2 to the power 128 possible combinations, which is extremely difficult to crack given the computational capabilities of the state-of-the-art computing systems.”

Marelli says that “for us, it’s a good test bed in order to think out-of-the-box, and how we can have a path that somehow is more democratic.” In this case, that means “something that you can literally read with your phone, and you can fabricate by simply drop casting a solution, without using any advanced manufacturing technique, without going in a clean room.”

Some additional work will be needed to make this a practical commercial product, Chandrakasan says. “There will have to be a development for at-scale reading” via smartphones. “So. that’s clearly a future opportunity.” But the principle now shows a clear path to the day when “a farmer could at least, maybe not every seed, but could maybe take some random seeds in a particular batch and verify them,” he says.

I’ve looked at the paper (very quickly) and haven’t spotted any mention of silk nanoparticles. It’s all silk microparticles.

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

Integrating biopolymer design with physical unclonable functions for anticounterfeiting and product traceability in agriculture by Hui Sun, Saurav Maji, Anantha P. Chandrakasan, and Benedetto Marelli. Science Advances 22 Mar 2023 Vol 9, Issue 12 DOI: 10.1126/sciadv.adf1978

This paper is open access.

The reason the findings in a popular thermoelectricity paper can’t be replicated

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It seems to me that over the last few years there’s been a lot more discussion about errors in science. There have always been scandals but this public interest in reproducibility of scientific results seems relatively new. In any event, a Nov. 17, 2016 news item on Nanowerk highlights research that explains why scientists have been unable to reproduce results of an influential 2014 paper (Note: A link has been removed),

A team of physicists in Clemson University’s College of Science and Academia Sinica in Taiwan has determined why other scientists have been unable to replicate a highly influential thermoelectricity study published in a prestigious, peer-reviewed journal.

In the April 2014 issue of the journal Nature (“Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals”), a group of scientists described an emerging crystalline material made of tin selenide that provided the highest efficiency ever recorded for thermoelectricity, the process of capturing wasted energy which is released as heat and making it available again as electricity. The paper has been viewed 45,000 times and its findings have been referenced in 600 subsequent studies, according to Google Scholar.

A thermoelectricity (TE) module captures waste energy, released as heat, converts it to electricity and returns it to a device. Image Credit: Thomas Masservy, Clemson University

There appears to have been a mistake in the original research. A Nov. 17, 2016 Clemson University news release, which originated the news item, expands on the theme (Note: A link has been removed),

“If it were true, basically, they would have found a crown jewel,” said Apparao Rao, the Robert A. Bowen professor of Physics and the director of the Clemson Nanomaterials Institute.

On Nov. 3, 2016, Nature ran a brief communication by the Clemson-Sinica team explaining why the 2014 data could not be replicated.

Thermoelectricity could provide enormous monetary and environmental savings because it is sustainable; instead of requiring fuel it continually captures wasted heat energy and puts it to use. And there’s a lot of wasted energy; about 70 percent in most machines, including cars.

“When your laptop gets hot, energy is released as waste heat because it doesn’t use all the supplied electricity. Machines have limited efficiency,” according to Ramakrishna Podila, assistant professor of physics and astronomy at Clemson who co-authored the paper solving the mystery.

But, so far, the perfect material for capturing and creating thermoelectricity has proven elusive.

Heat and electrical current can flow through any material when heat is applied to one side. But to efficiently harness thermoelectricity, the material has to trap heat on one side while letting the current flow. The difference in temperature, from one side to the other, generates energy.

Imagine cookware. Expensive pots and pans are copper or they have copper cores. Copper is a great heat-conducting material: it quickly and evenly spreads heat so food cooks evenly. Copper makes for good cookware, but poor thermoelectric material.

In an ideal thermoelectric material, current-carrying electrons should flow unimpeded from the hot side to the cold side, but heat-carrying phonons, which are atomic vibrations, must be blocked, either by large atoms or defects where the material is of lower density.

Rao; Podila; Sriparna Bhattacharya, a research assistant professor in astronomy and physics; and Jian He, an associate professor in physics and astronomy at Clemson and a thermoelectrics expert, performed their own study on tin selenide in collaboration with Academia Sinica’s Institute of Physics in Taipei.

Right away, Bhattacharya noticed a problem. “The most puzzling thing was that when we measured our own tin-selenide material, we observed the same electrical flow as reported in the 2014 article, but the heat carried by the phonons was relatively higher,” Bhattacharya said.

The original research group “made tin-selenide crystal that was not fully dense,” Bhattacharya said. Ideally, a crystalline material matches its “theoretical density,” meaning it’s as dense as it can be expected to get.

“Instead of reaching 100 percent theoretical density, it reached 89 percent. A 10 percent difference might not seem like much,” she said, but it can have a huge implication on the electron and phonon flow.

The Clemson-Taiwan collaborators are now focusing on their own assessment of thermoelectricity in tin-selenide. They expect to publish soon.

Here’s a link to and a citation to the 2014 thermoelectricity paper and a link to and a citation for the 2016 paper critiquing it,

Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals by Li-Dong Zhao, Shih-Han Lo, Yongsheng Zhang, Hui Sun, Gangjian Tan, Ctirad Uher, C. Wolverton, Vinayak P. Dravid, & Mercouri G. Kanatzidis. Nature 508, 373–377 (17 April 2014) doi:10.1038/nature13184 Published online 16 April 2014

The intrinsic thermal conductivity of SnSe by Pai-Chun Wei, S. Bhattacharya, J. He, S. Neeleshwar, R. Podila, Y. Y. Chen, & A. M. Rao. Nature 539, E1–E2 (03 November 2016) doi:10.1038/nature19832 Published online 02 November 2016

Both papers are behind a paywall.

One final observation, scientists may mistakes as do we all. The point after all is to contribute and the mistakes can be as useful as the successes.