Tag Archives: silver nanowires (Ag NWs)

E-tattoos for plants

Silver nanowires, which appear as a faint circle on a leaf’s surface, provide insight into a plant’s health before symptoms appear by measuring natural electrochemical impedance..IEEE Spectrum; Original imagery: Tianyiyi He, Jinge Wang, et al [downloaded from https://spectrum.ieee.org/plant-health-monitoring-electronic-tattoo]

Meghie Rodrigues’ June 2, 2025 article for the IEEE [Institute of Electrical and Electronics Engineers] Spectrum magazine discusses electronic tattoos (e-tattoos) for plants, Note: Links have been removed,

Imagine a future in which farmers can tell when plants are sick even before they start showing symptoms. That ability could save a lot of crops from disease and pests—and potentially save a lot of money as well.

A team of researchers in Singapore and China have taken a step toward that possibility with their development of ultrathin electronic tattoos—dubbed e-tattoos—to study plant immune responses without the need for piercing, cutting, or bruising leaves.

The e-tattoo is a silver nanowire film that attaches to the surface of plant leaves. It conducts a harmless alternating current—in the microampere range—to measure a plant’s electrochemical impedance to that current. That impedance isa telltale sign of the plant’s health.

Lead author Tianyiyi He, an associate professor of the Shenzhen MSU-BIT University’s [MSU is Moscow State University and BIT is Beijing Institute of Technology] Artificial Intelligence Research Institute, says that a healthy plant has a characteristic impedance spectrum—it’s as unique to the plant as a person’s fingerprints. “If the plant is stressed or its cells are damaged, this spectrum changes in shape and magnitude. Different stressors—dehydration, immune response—cause different changes.”

This is because plant cells, He explains, are like tiny chambers with fluids passing through them. The membranes of plant cells act like capacitors, resisting the flow of electrical current. “When cells break down—like in an immune response—the current flows more easily, and impedance drops,” He adds.

Detecting Plant Stress Early with E-Tattoos

Different problems yield different electrical responses: Dehydration, for example, looks different than an infection. Changes in a plant’s impedance spectrum means that something is not right—and by looking at where and how that spectrum changed, He’s team could spot what the problem was, up to three hours before physical symptoms started appearing.

The team tested the film on lab-grown thale cress (Arabidopsis thaliana) for 14 days. They mixed the nanowires in water so that they could transfer smoothly to the plant, by simply dripping the mix onto the leaves. Then they applied the e-tattoo in two different positions—side by side on a single leaf and on opposite faces of a leaf—to see how the current would flow. Then, with a droplet of galistan (a liquid metal alloy composed of gallium, indium, and tin), they attached a copper wire with the diameter of a human hair to the e-tattoo’s surface to apply an AC current from a small generator. He’s team collected data every day to see how plants would react.

He says liquid-carried silver nanowires worked better than other highly conductive metals such as copper or nickel because they were not soft enough to entirely “glue” to plants’ leaves and stay perfectly plastered even as the leaf bends or wrinkles. And in the case of thale cresses, they also have tricomas, tiny hairlike structures that usually protect and keep leaves from losing too much water. Tricomas, He explains, hinder perfect attachment since they make a leaf’s surface uneven—but silver nanowires managed to get around the problem in a better way than other materials.

Advancements in Plant Impedance Spectroscopy

This isn’t the first time tattoos or electrical impedance spectroscopy have been used for plants, says Stavrinidou.[Eleni Stavrinidou, principal investigator in the electronic plants research group from Linköping University’s Laboratory of Organic Electronics in Sweden, who was not involved in the work. He’s {Tianyiy He} team published its work on 4 April {2025} in Nature Communications.]

What’s new in the study, Stavrinidou says, “is the validation—they show this approach works on delicate plants like Arabidopsis and links clearly to immune responses.”

Here’s a link to and a citation to He and team’s study,

Epidermal electronic-tattoo for plant immune response monitoring by Tianyiyi He, Jinge Wang, Donghui Hu, Yanqin Yang, Eunyoung Chae & Chengkuo Lee. Nature Communications volume 16, Article number: 3244 (2025) DOI: https://doi.org/10.1038/s41467-025-58584-x Published: 04 April 2025

This paper is open access.

Nanomaterial shapes and forms affect passage through blood brain barrier (BBB)

I meant to get this published a lot sooner.

There seems to be a lot of excitement about this research. I got an embargoed press release further in advance than usual and now the embargo is lifted, it’s everywhere except, at the time of this writing (0920 PDT July 6, 2021), on the publisher’s (Proceedings of the National Academy of Sciences [PNAS]) website.

A July 5, 2021 news item on Medical Express announces the news,

Nanomaterials found in consumer and health-care products can pass from the bloodstream to the brain side of a blood-brain barrier model with varying ease depending on their shape—creating potential neurological impacts that could be both positive and negative, a new study reveals.

A July 5, 2021 University of Birmingham press release (also on EurekAlert), which originated the news item, delves into the details,

Scientists found that metal-based nanomaterials such as silver and zinc oxide can cross an in vitro model of the ‘blood brain barrier’ (BBB) as both particles and dissolved ions – adversely affecting the health of astrocyte cells, which control neurological responses.

But the researchers also believe that their discovery will help to design safer nanomaterials and could open up new ways of targeting hard-to-reach locations when treating brain disease.

Publishing its findings today in PNAS, an international team of researchers discovered that the physiochemical properties of metallic nanomaterials influence how effective they are at penetrating the in vitro model of the blood brain barrier and their potential levels of toxicity in the brain.

Higher concentration of certain shapes of silver nanomaterials and zinc oxide may impair cell growth and cause increased permeability of the BBB, which can lead to the BBB allowing easier brain access to these compounds.

The BBB plays a vital role in brain health by restricting the passage of various chemical substances and foreign molecules into the brain from surrounding blood vessels.

Impaired BBB integrity compromises the health of the central nervous system and increased permeability to foreign substances may eventually cause damage to the brain (neurotoxicity).

Study co-author Iseult Lynch, Professor of Environmental Nanosciences at the University of Birmingham, commented: “We found that silver and zinc oxide nanomaterials, which are widely used in various daily consumer and health-care products, passed through our in vitro BBB model, in the form of both particles and dissolved ions.

“Variation in shape, size and chemical composition can dramatically influence nanomaterials penetration through the (in vitro) blood brain barrier. This is of paramount importance for tailored medical application of nanomaterials – for example targeted delivery systems, bioimaging and assessing possible risks associated with each type of metallic nanomaterial.”

The BBB is a physical barrier composed of a tightly packed layer of endothelial cells surrounding the brain which separates the blood from the cerebrospinal fluid allowing the transfer of oxygen and essential nutrients but preventing the access of most molecules.

Recent studies found nanomaterials such as zinc oxide can accumulate on the brain side of the in vitro BBB in altered states which can affect neurological activity and brain health. Inhaled, ingested, and dermally-applied nanomaterials can reach the blood stream and a small fraction of these may cross the BBB – impacting on the central nervous system.

The researchers synthesised a library of metallic nanomaterials with different particle compositions, sizes, and shapes – evaluating their ability to penetrate the BBB using an in vitro BBB model, followed by assessment of their behaviour and fate in and beyond the model BBB.

Co-author Zhiling Guo, a Research Fellow at the University of Birmingham, commented: “”Understanding these materials’ behaviour once past the blood brain barrier is vital for evaluating the neurological effects arising from their unintentional entry into the brain. Neurotoxicity potential is greater in some materials than others, due to the different ways their shapes allow them to move and be transported.”

The research team tested varied sizes of cerium oxide and iron oxide, along with zinc oxide and four different shapes of silver – spherical (Ag NS), disc-like (Ag ND), rod-shaped (Ag NR) and nanowires (Ag NW).

Zinc oxide slipped through the in vitro BBB with the greatest ease. The researchers found spherical and disc-like silver nanomaterials underwent different dissolution regimes – gradually transforming to silver-sulfur compounds within the BBB, creating ‘easier’ entry pathways.

Zinc oxide is used as a bulking agent and a colorant. In over-the-counter drug products, it is used as a skin protectant and a sunscreen – reflecting and scattering UV radiation to help reduce or prevent sunburn and premature aging of the skin. Silver is used in cosmetic and skincare products such as anti-aging creams.

There’s still a long way to go with this research. For anyone who’s unfamiliar with the term ‘in vitro’, the rough translation is ‘in glass’ meaning test tubes, petri dishes, etc. are used. Even though the research paper has been peer-reviewed (not a perfect process), once it becomes available there will be added scrutiny from scientists with regard to how the research was conducted and whether or not the conclusions drawn are reasonable. One more question should also be asked, are the results reproducible by other scientists?

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

Biotransformation modulates the penetration of metallic nanomaterials across an artificial blood–brain barrier model by Zhiling Guo, Peng Zhang, Swaroop Chakraborty, Andrew J Chetwynd, Fazel Abdolahpur Monikh, Christopher Stark, Hanene Ali-Boucetta, Sandra Wilson, Iseult Lynch, and Eugenia Valsami-Jones. PNAS 118 (28) e2105245118 DOI: https://doi.org/10.1073/pnas.2105245118 Published: July 13, 2021

This paper appears to be open access.

Improving silver nanowires for flexible transparent conducting electrodes (FTCEs)

This is a very pretty image from the Korea Advanced Institute of Science and Technology (KAIST),

Picture 1: Artistic Rendtition of Light Interaction with Nanomaterials (This image shows flash-induced plasmonic interactions with nanowires to improve silver nanowires (Ag NWs).) Courtesy: KAIST

An April 4, 2017 news item on plys.org announces the research,

Flexible transparent conducting electrodes (FTCEs) are an essential element of flexible optoelectronics for next-generation wearable displays, augmented reality (AR), and the Internet of Things (IoTs). Silver nanowires (Ag NWs) have received a great deal of attention as future FTCEs due to their great flexibility, material stability, and large-scale productivity. Despite these advantages, Ag NWs have drawbacks such as high wire-to-wire contact resistance and poor adhesion to substrates, resulting in severe power consumption and the delamination of FTCEs.

A Korean research team led by Professor Keon Jae Lee of the Materials Science and Engineering Department at KAIST and Dr. Hong-Jin Park from BSP Inc., has developed high-performance Ag NWs (sheet resistance ~ 5 Ω /sq, transmittance 90 % at λ = 550 nm) with strong adhesion on plastic (interfacial energy of 30.7 J m-2) using flash light-material interactions.

An April 5, 2017 KAIST press release (also on EurekAlert), which originated the news item, explains more about the research,

The broad ultraviolet (UV) spectrum of a flash light enables the localized heating at the junctions of nanowires (NWs), which results in the fast and complete welding of Ag NWs. Consequently, the Ag NWs demonstrate six times higher conductivity than that of the pristine NWs. In addition, the near-infrared (NIR) of the flash lamp melted the interface between the Ag NWs and a polyethylene terephthalate (PET) substrate, dramatically enhancing the adhesion force of the Ag NWs to the PET by 310 %.

Professor Lee said, “Light interaction with nanomaterials is an important field for future flexible electronics since it can overcome thermal limit of plastics, and we are currently expanding our research into light-inorganic interactions.”

Meanwhile, BSP Inc., a laser manufacturing company and a collaborator of this work, has launched new flash lamp equipment for flexible applications based on the Prof. Lee’s research.

The results of this work entitled “Flash-Induced Self-Limited Plasmonic Welding of Ag NW Network for Transparent Flexible Energy Harvester (DOI: 10.1002/adma.201603473)”(http://onlinelibrary.wiley.com/doi/10.1002/adma.201603473/pdf) were published in the February 2, 2017 issue of Advanced Materials as the cover article.

Professor Lee also contributed an invited review in the same journal of the April 3 2017 online issue, “Laser-Material Interaction for Flexible Applications,” overviewing the recent advances in light interactions with flexible nanomaterials.

Lately, It seems I’ve stumbled across quite a few stories about wearable technologies and research to improve them.