Could washing our clothes with detergent become a thing of the past? Even though the research is in its early stages, an investigation as to whether washing or cleaning can be done with purified water instead of detergent solution looks promising.
“Our goal is to develop a scientific model that explains what happens both chemically and physically when dirt is removed in purified water. When it comes to washing with detergents we already know what happens, but this is an unexplored area,” says Andriani Tsompou, Ph.D. candidate at Malmö University.
Professor Vitaly Kocherbitov adds, “In the long run, our research can solve environmental problems with water pollution caused by detergents. To succeed in this, we need to better understand the intermolecular forces that act in purified water.”
The hypothesis is that in purified water—water that has been filtered and deionised so that impurities and especially ions are removed—repulsive forces between charged objects become stronger. As a result, dirt particles easier detach from surfaces and form a finely dispersed colloidal system in water.
Tsompou explains, “When you have salt in the system, the dirt you want to remove will clump together more and make it harder for the water to remove the particles from the material.”
According to earlier results of a study published in the Journal of Colloid and Interface Science, Tsompou and her colleagues used water with different properties: tap water, water with added salt, and two grades of purified water. In a QCM-D measurement—a surface-sensitive real-time technique for analyzing surface interaction and layer properties in thin films—a 90% purification of Vaseline on a glass slide was achieved for both grades of purified water at 25-degres.
In later trials, they have been experimenting with several washing cycles and with different temperatures and achieved a degree of purification of 100% in purified water at 40 degrees in two washing cycles.
In these trials, however, the most favorable conditions have been assumed by choosing surfaces and dirts that form weak bonds. “We have used water-friendly surfaces such as glass and silicate which have a negative charges and then olive oil or Vaseline, which also can get negative charges, so that they release each other easily, explains Tsompou.
The idea is to gradually increase the bond strength and change the materials so that they finally approach real conditions.
“Because these are such complicated processes, we have to build up knowledge from less complicated areas. The next step will be oil on plastic which stronger attach to each other. The end goal is of course to test on real fabric,” says Tsompou.
These bio-based foams avoid the need for petroleum products. Credit: Srikanth Pilla, CC BY-ND
A new plant-based substitute for polyurethane foam eliminates the health risk of the material, commonly found in insulation, car seats and other types of cushioning, and it’s more environmentally sustainable, our new research shows.
Polyurethane foams are all around you, anywhere a lightweight material is needed for cushioning or structural support. But they’re typically made using chemicals that are suspected carcinogens.
Polyurethanes are typically produced in a very fast reaction between two chemicals made by the petrochemical industry: polyols and isocyanates. While much work has gone into finding replacements for the polyol component of polyurethane foams, the isocyanate component has largely remained, despite its consequences for human health. Bio-based foams can avoid that component.
We created a durable bio-based foam using lignin, a byproduct of the paper pulping industry, and a vegetable oil-based curing agent that introduces flexibility and toughness to the final material.
At the heart of the innovation is the ability to create a system that “gels,” both in the sense that the materials are compatible with one another and that they physically create a gel quickly so that the addition of a foaming agent can create the lightweight structure associated with polyurethane foams.
Lignin is a difficult material to convert into a usable chemical, given its complicated and heterogeneous structure. We used this structure to create a network of bonds that enabled what we believe is the world’s first lignin-based nonisocyanate foam.
The foam can also be recycled because it has bonds that can unzip the chemical network after it has formed. The main components used to produce the foam can then be extracted and used again.
How the chemicals in bio-based foams can be recycled and reused. Credit: Srikanth Pilla, CC BY-ND
Why it matters
Polyurethane foams are the world’s sixth-most-produced plastic yet among the least recycled materials. They are also designed for durability, meaning they will remain in the environment for several generations.
The fully bio-based origin of our foams addresses the issue of carbon neutrality, and the chemical recycling capability ensures that waste plastic has a value attached to it so it is less likely to be thrown away. Ensuring waste has value is a hallmark of the circular approach to manufacturing—attaching a monetary value to things tends to decrease the amount that is discarded.
We hope the nature of these foams inspires others to design plastics with the full life cycle in mind. Just as plastics need to be designed according to properties of their initial application, they also need to be designed to avoid the final destination of 90% of plastic waste: landfills and the environment.
What’s next
Our initial versions of bio-based foams produce a rigid material suitable for use in foam-core boards used in construction or for insulation in refrigerators. We have also created a lightweight and flexible version that can be used for cushioning and packaging applications. Initial testing of these materials showed good durability in wet conditions, increasing their chance of gaining commercial adoption.
Polyurethane foams are used so extensively because of their versatility. The formulation that we initially discovered is being translated to create a library of precursors that can be mixed to produce the desired properties, like strength and washability, in each application.
More information: James Sternberg et al, Chemical recycling of a lignin-based non-isocyanate polyurethane foam, Nature Sustainability (2023). DOI: 10.1038/s41893-022-01022-3
New research from Rohit Pappu’s lab shows that within condensates, the molecules are organized into a small-world structure that we readily recognize from the hub-and-spoke network structure of airports for commercial airlines. Credit: Pappu lab
Before mixing an oil-and-vinegar-based salad dressing, the individual drops of vinegar are easily seen suspended in the oil, each with a perfectly circular boundary that delineates the two liquids. In the same way, our cells contain condensed bundles of proteins and nucleic acids called condensates delineated by clear boundaries. The boundaries are known as interfaces and given that condensates talk to one another through their interfaces, the structural features of the interface are of significant interest.
New research has uncovered unique features of interfaces of model condensates. The findings are relevant because the features interfaces are relevant to the seeding of fibrillar conformations that are associated with neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS).
A team of researchers led by Rohit Pappu, the Gene K. Beare Distinguished Professor and Director of the Center for Biomolecular Condensates in the McKelvey School of Engineering at Washington University in St. Louis, recently focused on defining the molecular scale features of interfaces of condensates. The research, driven by Mina Farag, an MD/Ph.D. student in the Pappu lab and first author of the paper, were generated in collaboration with Tanja Mittag and her lab at St. Jude Children’s Research Hospital. The results were published in Nature Communications Dec. 13, 2022.
A surprising finding was that interfaces, which might seem to be uniform and infinitesimally thin from the vinegar in oil picture, are thick and defined by specific shape and size preferences at the molecular level, Pappu said. Within condensates, the molecules are organized into a small-world structure that we readily recognize from the hub-and-spoke network structure of airports for commercial airlines.
“There is a particular type of connectivity that defines the way these molecules are organized, and that is because they have viscoelastic properties that makes them either elastic on short timescales and viscous on long timescales, much like putty,” Pappu said.
As the protein molecules go through the interface, the shapes and sizes of the molecules change in a way that these are unique to the interface, the team’s research found.
“We made a very striking observation that the conformations, or the shapes, of these molecules were very distinctive as they go through the interface, and those types of conformations poise them to be reactive,” Pappu said. “That can be good for facilitating biochemical reactions inside a cell, or be deleterious in the context of ALS, whereby the interface catalyzes the fibrillar growth in motor neurons.”
In Pappu’s lab, Farag used data from Mittag’s lab to train a machine learning model that describes the interactions among the molecules. This allowed them to simulate condensate formation in a computer. The simulations reproduce condensation for 30 different variants of a specific protein domain that is associated with ALS. Importantly, the simulation paradigm affords a way to design proteins with bespoke condensate structures and interfacial properties.
“We think that the distinct conformational preferences in interfaces contribute to low interfacial tensions of condensates. However, the specific chemistries of different interfaces are likely to enable functional selectivity. This seems like a very happy medium between physics and chemistry, as gleaned using engineering-based methods.”
More information: Mina Farag et al, Condensates formed by prion-like low-complexity domains have small-world network structures and interfaces defined by expanded conformations, Nature Communications (2022). DOI: 10.1038/s41467-022-35370-7
Gut-on-a-chip integrated with sensors. a) Device fabrication process. b) Annotated device decomposition diagram. The top and bottom microchannels were separated by the porous membrane. Simultaneous integration of three-electrode sensors and an Ag/AgCl electrode for in situ detection of Hg(II) and TEER. c) Photograph of the gut-on-a-chip integrated with sensors. Credit: Microsystems & Nanoengineering (2023). DOI: 10.1038/s41378-022-00447-2
The transport of mercury ions across intestinal epithelial cells can be studied for toxicology assessments by using animal models and static cell cultures. However, the concepts do not reliably replicate conditions of the human gut microenvironment to monitor in situ cell physiology. As a result, the mechanism of mercury transport in the human intestine is still unknown.
They proposed to explore the dynamic concept to simulate the physical intestinal barrier and mirror biological transport and adsorption mechanisms of mercury ions. The scientists recreated the cellular microenvironment by applying fluid shear stress and cyclic mechanical strain.
Wang and the team studied mercury adsorption and the physical damage caused by the toxic element on epithelial cells via the performance of electrochemical sensors after exposing them to intestinal cells growing under diverse concentrations of mercury mixed in the cell culture medium. The team noted the corresponding expression and upregulation of Piezo1 and DMT1 (divalent metal transporter), both mechanosensory ion channels and iron transporters respectively on the cell surface.
While mercury adsorption occurs predominantly in the small intestine, high levels of mercury ingestion can cause internal bleeding and perforation in a short timeframe. The long-term intake of low concentrations of mercury ions can also lead to chronic intestinal diseases. Since the intestinal epithelium provides an initial barrier to limit the penetration of ingested mercury in the blood stream and reduce its harmful effects; a reasonable intestinal model is of great significance to explore transport mechanisms of mercury in the lab. Although animal models and static cell cultures are traditionally used to study intestinal adsorption and mercury transport, these models do not efficiently recapitulate the intestinal microenvironment to emulate the living intestine.
Quantification of physical properties in gut-on-a-chip. a) FEA results of fluid shear stress in a microchannel. b) Calibration relationship between the actual flow rate of the culture medium into the gut-on-a-chip and the input flow by the syringe pump. Inset (I): Calibration experimental platform. Inset (II): Microscopic image of fluid flow in the gut-on-a-chip (scale bar, 200 μm). c) The FEA results of shear stress in the gut-on-a-chip were compared with the actual results (n = 3). d Quantitation of the mechanical strain produced in the adherent gut epithelial cells as a function of pressure applied by the vacuum controller. Black lines represent linear fitting lines (y = 0.099 + 0.270x; R2 = 0.988). Inset (I): Comparison of cell masses on porous membranes before and after stretching by 3% (scale bar, 20 μm). e Variation in the pore diameter of the porous film within 10 days under 1% tensile strain. RSD = 1.81% (n = 3). f) The change in Young’s modulus of the porous membrane under 1% tensile strain within 10 days. RSD = 0.07% (n = 3). Credit: Microsystems & Nanoengineering (2023). DOI: 10.1038/s41378-022-00447-2
In this work, the researchers developed a gut-on-a-chip model integrated with label-free sensors, to non-invasively monitor changes in transepithelial electrical resistance (TEER) during cellular behavior of mercury absorption, in real time. The team identified key features of the gut via electrical measurements and immunohistochemistry studies, to assess the effect on mechanosensory ion channels.
Characteristics of the intestinal epithelium in the gut-on-a-chip. a) Tight junctional integrity of the epithelium quantified by measuring TEER (n = 3). b) AKP activity under static (3 days, 7 days and 21 days) and dynamic (3 days and 7 days) cultures (n = 3; *P < 0.05, **P < 0.01). c) (I) Confocal fluorescence view of a tight junction protein (ZO-1; red) and brush border protein (ezrin; green) in static (3 days; 21 days) and dynamic cultures (3 days) (scale bar 20 μm). (II) Confocal fluorescence view of vertical cross section of cell monolayer in static (3 days; 21 days) and dynamic culture (3 days) (scale bar 10 μm). d) Average fluorescence intensity analysis of ZO-1 and ezrin proteins in static and dynamic cultures (3 days) (n = 3; ***P < 0.001). e) Average cell height cultured in static and dynamic cultures (n = 3; *P < 0.05). f) Microscope top-down views of intestinal villi-like structures (scale bar 100 μm). g) An SEM image of intestinal villi-like structures. h) A fluorescence microscopic view highlighting the nuclei (DAPI) of intestinal villi-like structures (scale bar 100 μm). i) A photograph showing the proposed gut-on-a-chip with its monitoring and culturing component. Credit: Microsystems & Nanoengineering (2023). DOI: 10.1038/s41378-022-00447-2
Numerical analysis of the device
The research team developed a chip that showed mechanical behavior similar to the living intestine and introduced representative fluid flow and cyclic mechanical stretching. For instance, a shear stress approximating 0.02 dyne/cm2 produced a fluid flow required for intestinal epithelial morphogenesis. Based on additional calculations on the organ chip, the team obtained a flow rate of 160 μL/hour for the corresponding dimensions of shear stress.
They then simulated the tensile strain/stress dynamics via finite element analysis to understand the effects of the parameters on the physical properties of the instrument including its pore diameter and their impact on the cytodifferentiation by analyzing the catalytic activity of alkaline phosphatase; typically used as a marker of bone and liver damage. The team noted greater catalytic activity among cells under fluid flow and those undergoing mechanical strain on a chip after only seven days of cell culture.
Damage to cells caused by Hg(II). a) Immunofluorescence of cells exposed to different concentrations of Hg(II) for 5, 12, and 24 h in static culture (red: dead cells; green: living cells). b) Changes in cell activity under the treatment of different concentrations of Hg(II). The cell activity remained above 80% within 24 h under low concentrations of Hg(II) (1, 10 μM) (n = 3). c) Epithelial cells were exposed to 100 μM Hg(II), and LDH was detected at 5, 12′ and 24 h. Within 24 h, the results of LDH detection showed that the expression of LDH in static samples was 1.3-fold higher than that in dynamic samples (n = 3; *P < 0.05). d) The change rate of TEER in static and dynamic cultures of cells exposed to 100 μM Hg(II) within 24 h. The TEER under dynamic conditions was 4.4-fold higher than that under static conditions (n = 3; *P < 0.05). e) In the absence or presence of Hg(II) (100 μM), confocal immunofluorescence of ZO-1 (red) and ezrin (green) protein was observed (scale bar 20 μm). (f, g) Analysis of the average fluorescence intensity of ZO-1 and ezrin proteins after epithelial cell injury. Compared with the control group, the fluorescence intensity of ZO-1 and ezrin decreased by 1.8-fold (n = 3; ***P < 0.001). Credit: Microsystems & Nanoengineering (2023). DOI: 10.1038/s41378-022-00447-2
The outcomes highlighted the biomimetic approach and the capacity for growth and differentiation of the cell monolayer under mechanical stimulation. The gut-on-a-chip instrument provided biomimetic intestinal villus-like structures to maintain the integrity of the tissue barrier and represented a key physiologically relevant human intestine.
a) The TEER value of the cell monolayer on the 7th day under different mechanical stretching conditions (1%, 3%, 5%). The TEER values were 26.65 ± 1.17 kΩ cm2, 32.21 ± 1.05 kΩ cm2 and 34.10 ± 0.93 kΩ cm2, and the cell barrier ability was increased by 20.86% and 27.95% (1% mechanical stimulation as the control group) (n = 3). b) Changes in intestinal epithelial cell monolayer absorption of Hg(II) within three hours under different mechanical stretching conditions (1%, 3%, 5%). The concentrations of Hg(II) absorbed by cells under three mechanical stretching stimuli were 1.78 ± 0.11 μM, 1.98 ± 0.03 μM, and 2.20 ± 0.14 μM (n = 3). c) The change in the Papp value under different mechanical stretching (1%, 3%, 5%). Compared with 1% mechanical stimulation, the ability of cells to absorb Hg(II) increased by 11.65% and 17.96% under 3% and 5% mechanical stimulation, respectively (n = 3). d) The expression of Piezo1 protein and DMT1 protein under different mechanical stretching conditions (Piezo1: red; DMT1: green; nucleus: blue) (scale bar 20 μm). Credit: Microsystems & Nanoengineering (2023). DOI: 10.1038/s41378-022-00447-2
Functional assays
The research team next exposed the cells to mercury under static culture conditions to understand the process of cell death. And noted an increase to the process when upon increasing the mercury concentration and culture time. They noted that the activity of lactate dehydrogenase (LDH) increased with time in the assays to show equal effects of the toxin across both cell cultures. However, the degree of injury between the two cultures differed. For instance, the expression of LDH was greater in the static culture compared to the dynamic cell cultures after mercury treatment.
The scientists used an electrochemical sensor array integrated into a gut-on-a-chip device to observe epithelial cell interactions with mercury. They explored the transport mechanism of the element relative to its absorption on epithelial cells and investigated the expression of key proteins such as Piezo1 and DMT1 relative to mechanosensory ion channels and active iron transporters. They studied the effects of different tensile strains on the cell barrier and noted that an increase in mechanical stimulation led to increased adsorption of mercury via intestinal epithelial cells, where the mechanosensory ion channels too showed a positive correlation.
Outlook
In this way, Li Wang and colleagues developed a gut-on-a-chip device integrated with transepithelial electrical resistor sensors and multiple electrochemical sensors to stimulate mercury transport in the human intestine in vitro. The chip dynamics emulated a physical intestinal barrier and microenvironment to observe the transport of mercury in real-time. The team noted the cell monolayer on the gut-on-a-chip to differentiate to form a complete cellular barrier via imaging and immunohistochemistry. The team intends to further understand additional mechanisms underlying human intestinal diseases using organ chips to promote personalized drug development.
More information: Li Wang et al, Gut-on-a-chip for exploring the transport mechanism of Hg(II), Microsystems & Nanoengineering (2023). DOI: 10.1038/s41378-022-00447-2
Sangeeta N Bhatia et al, Microfluidic organs-on-chips, Nature Biotechnology (2014). DOI: 10.1038/nbt.2989
The new sensor consists of a silver nanowire network embedded in an elastic polymer. The polymer features a pattern of parallel cuts of a uniform depth, alternating from either side of the material: one cut from the left, followed by one from the right, followed by one from the left, and so on. This feature – the patterned cuts – is what enables a greater range of deformation without sacrificing sensitivity. Credit: Shuang Wu, NC State University
Researchers at North Carolina State University have developed a stretchable strain sensor that has an unprecedented combination of sensitivity and range, allowing it to detect even minor changes in strain with greater range of motion than previous technologies. The researchers demonstrated the sensor’s utility by creating new health monitoring and human-machine interface devices.
Their research paper, “Highly Sensitive, Stretchable, and Robust Strain Sensor Based on Crack Propagation and Opening,” is published in the journal ACS Applied Materials & Interfaces.
Strain is a measurement of how much a material deforms from its original length. For example, if you stretched a rubber band to twice its original length, its strain would be 100%.
“And measuring strain is useful in many applications, such as devices that measure blood pressure and technologies that track physical movement,” says Yong Zhu, corresponding author of a paper on the work and the Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State.
To demonstrate how far the sensors can be deformed, the researchers created a wearable device for monitoring motion in a person’s back, which has utility for physical therapy. Credit: Shuang Wu, NC State University
“But to date there’s been a trade-off. Strain sensors that are sensitive—capable of detecting small deformations—cannot be stretched very far. On the other hand, sensors that can be stretched to greater lengths are typically not very sensitive. The new sensor we’ve developed is both sensitive and capable of withstanding significant deformation,” says Zhu. “An additional feature is that the sensor is highly robust even when over-strained, meaning it is unlikely to break when the applied strain accidently exceeds the sensing range.”
The new sensor consists of a silver nanowire network embedded in an elastic polymer. The polymer features a pattern of parallel cuts of a uniform depth, alternating from either side of the material: one cut from the left, followed by one from the right, followed by one from the left, and so on.
“This feature—the patterned cuts—is what enables a greater range of deformation without sacrificing sensitivity,” says Shuang Wu, who is first author of the paper and a recent Ph.D. graduate at NC State.
To demonstrate the sensor’s utility in human-machine interface devices, the researchers created a three-dimensional touch controller that can be used to control a video game. Credit: Shuang Wu, NC State University
The sensor measures strain by measuring changes in electrical resistance. As the material stretches, resistance increases. The cuts in the surface of the sensor are perpendicular to the direction that it is stretched. This does two things. First, the cuts allow the sensor to deform significantly. Because the cuts in the surface pull open, creating a zigzag pattern, the material can withstand substantial deformation without reaching the breaking point. Second, when the cuts pull open, this forces the electrical signal to travel further, traveling up and down the zigzag.
“To demonstrate the sensitivity of the new sensors, we used them to create new wearable blood pressure devices,” Zhu says. “And to demonstrate how far the sensors can be deformed, we created a wearable device for monitoring motion in a person’s back, which has utility for physical therapy.”
“We have also demonstrated a human-machine interface,” Wu says. “Specifically, we used the sensor to create a three-dimensional touch controller that can be used to control a video game.”
“The sensor can be easily incorporated into existing wearable materials such as fabrics and athletic tapes, convenient for practical applications,” Zhu says. “And all of this is just scratching the surface. We think there will be a range of additional applications as we continue working with this technology.”
The paper was co-authored by Katherine Moody, a Ph.D. student at NC State; and by Abhiroop Kollipara, a former undergraduate at NC State.
More information: Shuang Wu et al, Highly Sensitive, Stretchable, and Robust Strain Sensor Based on Crack Propagation and Opening, ACS Applied Materials & Interfaces (2022). DOI: 10.1021/acsami.2c16741
Using in situ Raman spectroscopy and dynamic kinetic effect, the researchers have experimentally confirmed the positive effect of the Ru/S dual-site mechanism on eNRR over a model Ru-S-C single-atom catalyst. Credit: Chinese Journal of Catalysis
Ammonia (NH3) is an important fertilizer and chemical for human society; however, its production by the traditional Haber-Bosch process consumes substantial fossil fuel energy and produces massive carbon dioxide emissions. Powered by renewable energy, electrocatalytic reduction of nitrogen (N2) to NH3 under eco-friendly and mild conditions provides a highly attractive solution for carbon neutrality.
Despite recent significant progress, electrocatalytic nitrogen reduction reaction (eNRR) still suffers from limited selectivity and activity. This is due to the super-stability of N≡N triple bond. Theoretical and experimental efforts have demonstrated that the electrocatalysts always face a significant challenge to effectively activate N2 and accomplish the first protonation of N2 to form NNH* in the rate-determining step (RDS).
One strategy to break the above limitation of eNRR is to involve multi-reaction sites in catalytic reactions, just like the catalytically active sites in talented metalloenzymes. For instance, in Fe nitrogenase, the S atom adjacent to the Fe center functions as a co-catalytic site to bind protons (H), which electrostatically activates the N2 molecule adsorbed by the Fe center to the optimum state and provides H for the hydrogenation of N2.
Such a close collaboration between the metal center and its coordination atoms enables the nitrogenase to achieve ultrahigh activity and selectivity. Therefore, one can expect that the synergetic work of multiple catalytic sites on the catalyst surface can significantly enhance the activity and selectivity of eNRR.
Recently, a research team led by Prof. Tao Ling from Tianjin University, China, proposed to realize a synergetic work of multi-reaction sites to overcome the limitation of sustainable NH3 production. Herein, using ruthenium-sulfur-carbon (Ru-S-C) catalyst as a prototype, the researchers showed that the Ru/S dual-site cooperated to catalyze eNRR at ambient conditions.
With the combination of theoretical calculations, in situ Raman spectroscopy, and experimental observation, the researchers demonstrated that such Ru/S dual-site cooperation greatly facilitated the activation and first protonation of N2 in the rate-determining step of eNRR. As a result, Ru-S-C catalyst exhibited significantly enhanced eNRR performance compared with the routine Ru-N-C catalyst via a single-site catalytic mechanism.
The specifically designed dual-site collaborative catalytic mechanism could offer new opportunities for advancing sustainable NH3 production.
The results were published in Chinese Journal of Catalysis..
More information: Liujing Yang et al, Dual-site collaboration boosts electrochemical nitrogen reduction on Ru-S-C single-atom catalyst, Chinese Journal of Catalysis (2022). DOI: 10.1016/S1872-2067(22)64136-6
Researchers have developed a transparent temperature sensor capable of precisely and quickly measuring temperature changes caused by light. This technology is expected to contribute to the advancement of various applied bio devices that rely on sensitive temperature changes.
The photothermal effect using plasmonic nanomaterials has recently been widely proposed in various bio-application fields, such as brain nerve stimulation, drug delivery, cancer treatment, and ultra-high-speed PCR due to its unique heating properties using light. However, measuring temperature changes by photothermal phenomena still relies on an indirect and slow measurement method using a thermal imaging camera, leading to the limitation that it is not suitable for local temperature measurement at the level of a single cell, which changes rapidly at the level of several milliseconds to tens of micrometers.
Due to the absence of precise information on temperature changes, photothermal effect technology has raised concerns about the understanding of biological changes and stable clinical application resulting from precise temperature changes, despite the spreading effect of its application.
Accordingly, the joint research team, which included Professor Kang Hong-gi of the Department of Electrical Engineering and Computer Science at DGIST and Dr. Chung Seung-jun of the Soft Hybrid Materials Research Center at KIST, developed a temperature sensor technology that can measure even rapid temperature changes in less than a few milliseconds by using the thermoelectric effect, in which a voltage signal is generated by rapid charge transfer triggered by a difference in temperature.
In particular, the team established a direct photothermal phenomenon measurement technology with reduced interference by light utilizing an organic thermoelectric layer of transparent PEDOT:PSS, a conductive polymer suitable for storing charges.
The 50-nanometer thin PEDOT:PSS thermoelectric sensor secures high transparency at 97% on average in the visible light zone and can be directly applied to the area of photothermal phenomenon, minimizing light interference for various photothermal bioengineering and medical applications. In addition, since a low-temperature solution process could be used for the polymer thermoelectric material used, it was prepared using an inkjet printing process, which is simpler to manufacture than a general semiconductor process, with a high degree of design freedom thus giving it an advantage in the printing process.
The transparent thermoelectric temperature sensor technology developed through this study can be used to understand the mechanism of the optical neural interface for controlling brain activity using light, which has recently been known broadly through optogenetics. It is a key technology in that it can be utilized to analyze the principles in treating cancer cells with local high heat. In addition, it is expected that it can be applied to next-generation semiconductor technologies, such as wearable devices, transparent display devices, and analysis of local deterioration of power semiconductors, based on the principle of powerless operation.
DGIST Department of Electrical Engineering and Computer Science Professor Kang Hong-gi said, “It is significant in that we proposed a technology that directly and precisely measures the photothermal effect, the biggest advantage of which is rapid generation of local heat,” and added, “We look forward to the possibility of in-depth bioengineering analysis and biomedical application by combining it with various bio-electronic chips through micro-semiconductor processes in the future.”
The study was published online in Materials Horizons,
More information: Junhee Lee et al, High temporal resolution transparent thermoelectric temperature sensors for photothermal effect sensing, Materials Horizons (2022). DOI: 10.1039/D2MH00813K
Chemists are often the unsung heroes of scientific breakthroughs that change our lives. Credit: Matej Kastelic/Shutterstock
Real-world technology is often foretold by science fiction. In 1927, characters in the film Metropolis made video calls to each other. Star Trek creator Gene Roddenberry hung flat-screen color monitors on the walls of the Enterprise decades before we did the same in our living rooms.
The most obvious examples of technology in science fiction tend to focus on artificial intelligence, communication and transport. But futuristic chemistry is embraced by sci-fi writers too. For example, a central feature of Aldous Huxley’s 1932 novel Brave New World is a chemical antidepressant.
In recent years we’ve seen incredible leaps in chemical technologies—to the point where, as a chemist, I’m frequently reminded of some of my favorite fiction while reading about the latest big developments.
A plastic world
While environmental issues are a common thread in science fiction, not many deal with the blight of plastics. An exception is the 1972 novel Mutant 59: The Plastic Eaters. This story, featuring a bacteria that digests plastic, would have seemed far fetched a few years ago. After all, plastics have only been around for 80 years or so, which hardly seems long enough for nature to evolve a mechanism to eat them.
Yet plastics are carbon-based compounds, in many ways similar to natural polymers such as collagen (in animals), cellulose (in plants) and bee waxes. Over eons, bacteria and fungi have evolved many biochemical tools to scavenge the carbon from every dead organism.
So maybe it shouldn’t have been a surprise when, in 2016, scientists sifting through a recycling plant in Kyoto, Japan discovered a bacteria literally feeding on plastic bottles. Since then, several other research groups have isolated the digestive enzymes involved and engineered them to be more efficient. The hope is we can use these modified natural systems to clean up our plastic mess.
The most recent attempts to do so have a distinctly futuristic feel. A group in Austin, Texas fed the digestive enzymes’ structure into a neural network. This artificial intelligence predicted the best parts of the enzyme to tweak to increase its efficiency. With the AI’s advice, the group produced an enzyme that completely degraded a plastic punnet in just a couple of days.
Chemical engineers are already developing large-scale recycling plants using bacteria. The bacteria in Mutant 59 was also engineered in a lab—but let’s hope the parallel stops there. In the novel, the bacteria escapes and causes devastation as it rips through our world, rotting the plastic infrastructure that holds society together.
Many fake meats already line our supermarket shelves, but most are formed from plant-based ingredients blended to mimic the taste and texture of flesh. As a vegetarian, I actually quite enjoy them. But they are easily distinguishable from the real meat of my memories.
Growing meat in a vat is a different affair. It is more like brewing, but using animal cells instead of yeast. The process needs people with a good understanding of cell biology, nutritional chemistry and chemical engineering to work.
The process begins by growing a dense broth of cells. The mix of nutrients within the vat is changed, triggering the cells to differentiate into tissue types—muscle, connective tissue, fat cells. Finally, the cells coalesce into something resembling a pulp of meat, which is harvested and processed into your nuggets, burgers and such like. The advantage, of course, is that you get something with the texture, taste and nutritional content of meat, but without the slaughter.
Back in 2013, the first edible burger made this way cost $300,000. Nine years later, costs have plummeted and investors have in poured billions of dollars. The industry is poised to start selling its products, and is just waiting for the regulatory frameworks to be put in place. Singapore led the way in approving cultured meat in 2021, the US Food and Drug Administration recently gave its seal of approval, and UK and EU regulators are not far behind.
A word of caution
However, sometimes aspirations of real-world science struggle to progress from their fictional inspiration. In 2003 Elizabeth Holmes, aged only 19, founded Theranos. Ten years later, the company was worth $10 billion.
Holmes raised the funds with her promise to deliver a revolutionary technology that could deliver cheap, rapid diagnostics from just a drop of blood. The idea seemed closer to the medical scanners in Star Trek sickbays than anything in reality. And it turned out the promises made by Holmes were criminally over-inflated, earning her an 11-year prison sentence for fraud.
The Theranos story may have set back investors’ confidence in plausible applications for the lab-on-a-chip technologies that Holmes championed. But we are actually quite familiar with them already, in the form of COVID lateral flow tests. An even more extraordinary, real example reminded me of the almost-instant DNA sequencing depicted in the 1997 film Gattaca.
Early in 2022 at Stanford University, a small group of researchers sequenced an entire human genome in just over five minutes. Contrast that to the 13 years it took to sequence the first human genome, published in 2003. This could help speed up rare disease diagnosis from years to hours.
These astounding leaps forward in diagnostics, recycling and food are just a few areas of chemistry that were once considered science fiction. Many others—such as high-density batteries allowing quicker and fewer charges, atmospheric cleaning technology to remove C0₂ from the air, and 3D “printed” personalized medication—are also under development. Let’s just hope the dystopias so often depicted in science fiction don’t emerge alongside the technologies they describe.
31P NMR results for phosphate-containing species. (A) 1D NMR spectra from 10 mM sample in (D) taken at every 10 K showing line broadening in orthophosphate. (B) Linewidths for orthophosphate, pyrophosphate, ADP, and ATP as a function of temperature showing monotonic increase with temperature. Solid lines are quadratic fits to data to guide the eye. (C) R1 and R2 curves as a function of molecular tumbling rate from Bloembergen–Purcell–Pound theory. Cartoons illustrate the approximate locations of ionic phosphate, ADP, and a standard protein based on tumbling rates. (D) R2 as extracted from a CPMG pulse sequence and from FWHM for 10 mM and 100 mM monobasic sodium orthophosphate pH 4.5 as a function of temperature, showing monotonic increase in R2 in each case. Solid lines are quadratic fits to data to guide the eye. R1 for 10 mM, 100 mM, monobasic sodium orthophosphate pH 4.5 as a function of temperature showing different curve shapes as a function of concentration. Solid lines are cubic fits to data to guide the eye. Credit: Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2206765120
While conducting an otherwise straightforward investigation into the assembly mechanism of calcium-phosphate clusters, researchers at UC Santa Barbara and New York University (NYU) made a surprising discovery: Phosphate ions in water have a curious habit of spontaneously alternating between their commonly encountered hydrated state and a mysterious, previously unreported ‘dark’ state.
This recently uncovered behavior, they say, has implications for understanding the role of phosphate species in biocatalysis, cellular energy balance and the formation of biomaterials. Their findings are published in the Proceedings of the National Academy of Sciences
“Phosphate is everywhere,” said UCSB chemistry professor Songi Han, one of the authors of a paper in the Proceedings of the National Academy of Sciences. The ion consists of one phosphorus atom surrounded by four oxygen atoms. “It’s in our blood and in our serum,” Han continued. “It’s in every biologist’s buffer, it’s on our DNA and RNA.” It’s also a structural component of our bones and cell membranes, she added.
When bound with calcium, phosphates form small, molecular clusters on their way toward forming mineral deposits in cells and bone. That’s what Han and collaborators Matthew Helgeson at UCSB and Alexej Jerschow at NYU were preparing to study and characterize, in hopes of uncovering quantum behaviors in symmetric phosphate clusters proposed by UCSB physics professor Matthew Fisher. But first, the researchers had to set up control experiments, which involved scans of phosphate ions in the absence of calcium via nuclear magnetic resonance (NMR) spectroscopy and cryogenic transmission electron microscopy (cryo-TEM).
But as the UCSB and NYU students on the project were collecting reference data, which involved the naturally occurring isotope phosphorus 31 in aqueous solutions at varying concentrations and temperatures, their results didn’t match up with expectations. For instance, Han said, the line that represents the spectrum for 31P during NMR scans is supposed to narrow with increasing temperatures.
“The reason is, as you go to higher temperatures, the molecules tumble faster,” she explained. Typically, this rapid molecular motion would average out the anisotropic interactions, or interactions that are dependent on the relative orientations of these small molecules. The result would be a narrowing of resonances measured by the NMR instrument.
“We were expecting a phosphorus NMR signal, which is a simple one, with a peak that narrows with higher temperatures,” she said. “Surprisingly, though, we measured spectra that were broadening, doing the complete opposite of what we expected.”
This counterintuitive result set the team on a new path, following experiment after experiment to determine its molecular-level cause. The conclusion, after a year of eliminating one hypothesis after another? Phosphate ions were forming clusters under a wide range of biological conditions—clusters that were evading direct spectroscopic detection, which is likely why they had not been observed before. Furthermore, the measurements suggested these ions were alternating between a visible “free” state and a dark “assembled” state, hence the broadening of the signal instead of a sharp peak.
Evidence of phosphate assemblies from TEM and MD simulations. (A and B) TEM images of phosphate assemblies (yellow arrows) after heating phosphate solutions show droplet-like features forming at 25 to 50 nm in size. Samples were from different sources and prepared on different days. (A) 100 mM potassium ADP heated to 343 K before vitrification. (B) 100 mM sodium ADP heated to 343 K before vitrification. (C) Cluster size distributions from MD simulations at 343 K show the fraction, P(N), of phosphate ions in a cluster of size Nclust. The insets show snapshots of phosphate assemblies (red and white) and sodium ions (blue) from the simulations. The cluster size distribution and snapshots show that HPO42− strongly assembles in contrast to H2PO4−. When H2PO4− is mixed with HPO42−, the latter induces clustering of H2PO4−. In this mixed system, the HPO42− ions are grayed out to highlight the clustering of H2PO4−. Simulation snapshots are visualized using Visual Molecular Dynamics. Credit: Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2206765120
Additionally, as the temperature increased, the number of these assembled states was also increasing, another temperature-dependent behavior, according to co-lead author Mesopotamia Nowotarski.
“The conclusion from those experiments was that the phosphates are dehydrating and that allows them to come closer together,” she said. At lower temperatures, the vast majority of these phosphates in solution cling to water molecules that form a protective water coat around them. This hydrated state is typically assumed when considering how phosphate behaves in biological systems.
But at higher temperatures, Nowotarski explained, they shed their water shields, allowing them to stick to each other. This concept was confirmed by NMR experiments that probed the phosphate water shell, and further validated by analysis of cryo-TEM images to identify the existence of clusters, as well as modeling the energetics of phosphate assembly by co-lead author Joshua Straub.
These dynamic phosphate assemblies and hydration shells have important implications for biology and biochemistry, according to the researchers. Phosphate, said chemical engineer Matthew Helgeson, is a commonly understood “currency” used in biological systems to store and consume energy through conversion into adenosine triphosphate (ATP) and adenosine diphosphate (ADP).
“If hydrated phosphate, ADP and ATP represent small ‘bills’ of currency, this new discovery suggests that these smaller currencies can exchange with much larger denominations—say $100—which may have very different interactions with biochemical processes than currently known mechanisms,” he said.
Also, many biomolecular components include phosphate groups that may, similarly, form clusters. Hence, the finding that these phosphates can spontaneously assemble might shed some light on other fundamental biological processes such as biomineralization—how shells and skeletons form, as well as protein interactions.
“We also tested a range of phosphates, including those incorporated into the ATP molecule, and they all appear to show the same phenomenon, and we achieved quantitative analysis for these assemblies,” said co-lead author Jiaqi Lu.
This once overlooked process could also be significant in the realms of cell signaling, metabolism and disease processes such as Alzheimer’s disease, where the attachment of a phosphate group, or phosphorylation, to the protein tau in our brain is commonly found in neurofibrillary tangles—a hallmark of neurodegeneration. Having seen and studied this assembly behavior, the team is now digging deeper, with studies on the effect of pH on phosphate assembly, genetic translation and modified protein assembly, as well as their original work on calcium phosphate assembly.
“It really changes the way we think about the role of phosphate groups that we typically don’t consider a driver of molecular assembly,” Han said.
More information: Joshua S. Straub et al, Phosphates form spectroscopically dark state assemblies in common aqueous solutions, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2206765120
The significant increase in intensity of reflected light for a particular angle of incidence is represented as a peak, and its pattern can be used as a “fingerprint/feature of a compound.” One peak pattern consisting of many peaks corresponds to one compound. The test data diffraction pattern (red curve) is overlaid with the auto-encoder output (blue curve) representing the relevance of peaks in characterization. The peak labeled (a) has significant intensity but low relevancy, a Deep Learning result. Credit: Ryo Maezono from JAIST
X-ray diffraction (XRD) is an experimental technique to discern the atomic structure of a material by irradiating it with X-rays at different angles. Essentially, the intensity of the reflected X-rays becomes high at specific irradiation angles, producing a pattern of diffraction peaks. An XRD serves as a fingerprint for a material since each substance produces a unique pattern.
In research and development, changes in XRDs are used to identify the positions and amounts of additional elements that need to be added to fine-tune a material to help enhance a desired functional property, say, energy storage efficiency in batteries.
However, the peak changes in XRDs are barely discernible to humans. This makes ascertaining the features and relevance of different peaks for material characterization difficult. To this end, a group of Japanese researchers, led by Professor Ryo Maezono from the Japan Advanced Institute of Science and Technology (JAIST), applied a Deep Learning technique called “auto-encoder” to the problem to find hidden regularities in XRDs that could help accelerate the development of new functional materials.
The research team also included Associate Professor Kenta Hongo and Assistant Professor Kousuke Nakano from JAIST. Their work has been published in Advanced Theory and Simulations.
Explaining the fundamentals of the auto-encoder technique, Prof. Maezono says, “The auto-encoder technique captures data features by expressing them as points on a two-dimensional plane (feature space). Based on their scatter, the points get grouped to coarse-grain information. The auto-encoder compresses the data dimension and can efficiently capture the multifaceted XRD pattern analysis in a two-dimensional plane.”
Using a neural network, the researchers applied the auto-encoder to 150 XRD patterns of magnetic alloys with different concentrations. In the feature space, each XRD is projected to a single point. These points form clusters, in which similar materials with similar constituent concentrations are placed closer together. Thus, the distance between the points in the feature space allows the estimation of the concentration of any given sample alloy. This also permits the fine-tuning of alloys by indirectly identifying the XRD peaks that change when new elements are added to an alloy or its constituent element ratios are altered.
The researchers further proposed a novel application of the feature space. When a peak of interest is masked on the original XRD pattern, the point on the feature space shifts. The extent of the shift helps distinguish how relevant a peak is to capturing the properties of a material. Using this technique, the researchers were able to identify which peak is actually relevant to be watched out for estimating the amount of doping etc.—something that could not have been predicted by a human but was revealed using Deep Learning.
The researchers also proposed the application of the auto-encoder for the generation of artificial XRD patterns by interpolating existing ones to handle tiny changes in alloy compositions. The approach would generate plausible datasets, avoiding computationally expensive ab initio simulations.
“The results of this research are not limited to XRD peak patterns. Rather, they provide a general Deep Learning technique that can be used to extract features from material science data. Its framework can find hidden regularity in nature that is not identifiable by humans and is expected to serve as a powerful tool for theorem discovery through data science,” says Prof. Maezono.
The application of the described auto-encoder could accelerate the development of high efficiency, low cost, and low environmental impact materials, ushering in a new era of Deep Learning-based materials science research.
More information: Keishu Utimula et al, Feature Space of XRD Patterns Constructed by an Autoencoder, Advanced Theory and Simulations (2022). DOI: 10.1002/adts.202200613
Provided by Japan Advanced Institute of Science and Technology
