Tag Archives: #moisture

Self-healing Concrete For Regions With High Moisture and Seismic Activity (Civil Engineering)

Preparing regular concrete scientists replaced ordinary water with water concentrate of bacteria Bacillus cohnii, which survived in the pores of cement stone. The cured concrete was tested for compression until it cracked, then researchers observed how the bacteria fixed the gaps restoring the strength of the concrete. The engineers of the Polytechnic Institute of Far Eastern Federal University (FEFU), together with colleagues from Russia, India, and Saudi Arabia, reported the results in Sustainability journal.

During the experiment, bacteria activated when gained access to oxygen and moisture, which occurred after the concrete cracked under the pressure of the setup. The “awakened” bacteria completely repaired fissures with a width of 0.2 to 0.6 mm within 28 days. That is due to microorganisms released a calcium carbonate (CaCO3), a product of their life that crystallized under the influence of moisture. After 28 days of self-healing experimental concrete slabs retrieved their original compressive strength. In the renewed concrete, the bacteria “fell asleep” again.

“Concrete remains the world’s number one construction material because it is cheap, durable, and versatile. However, any concrete gets cracked over time because of various external factors, including moisture and repetitive freezing/thawing cycles, the quantity of which in the Far East of Russia, for example, is more than a hundred per year. Concrete fissuring is almost irreversible process that can jeopardize the entire structure.” Says engineer Roman Fediuk, FEFU professor. “What we have accomplished in our experiment aligns with international trends in construction. There is pressing demand for such “living” materials with the ability to self-diagnose and self-repair. It’s very important that bacteria healed small fissures-forerunners of serious deep cracks that would be impossible to recover. Thanks to bacteria working in the concrete, one can reduce or avoid at all technically complex and expensive repair procedures.”

Spores of Bacillus cohnii capable of staying alive in concrete for up to two hundred years and, theoretically, can extend the lifespan of the structure for the same period. This is almost 4 times more than the 50-70 years of conventional concrete service life.

Self-healing concrete is most relevant for construction in seismically risky areas, where small fissures appear in buildings after earthquakes of a modest magnitude, and in areas with high humidity and high rainfall where a lot of oblique rain falls on the vertical surfaces of buildings. Bacteria in concrete also fill the pores of the cement stone making them smaller and less water gets inside the concrete structure.

Scientists have cultivated the bacteria Bacillus cohnii in the laboratory using a simple agar pad and culture medium, forcing them to survive in the conditions of the pores of the cement stone and to release the desired “repair” composition. Fissures healing was assessed using a microscope. The chemical composition of the bacteria repairing life product was studied via electron microscopy and X-ray images.

Next, the scientists plan to develop reinforced concrete, further enhancing its properties with the help of different types of bacteria. That should speed up the processes of material self-recovery.

A scientific school of the scientific school of geomimetics run at FEFU. Engineers follow the principle of nature mimicking in the development of composites for special structures and civil engineering. Concrete, as conceived by the developers, should have the strength and properties of natural stone. The foundations of geomimetics were laid by Professor Valery Lesovik from V.G. Shukhov BSTU, Corresponding Member of the Russian Academy of Architecture and Construction Sciences.

Featured image: The slab of self-healing concrete is measured for its compressive strength. © FEFU press office


Reference: Sumathi, Arunachalam; Murali, Gunasekaran; Gowdhaman, Dharmalingam; Amran, Mugahed; Fediuk, Roman; Vatin, Nikolai I.; Deeba Laxme, Ramamurthy; Gowsika, Thillai S. 2020. “Development of Bacterium for Crack Healing and Improving Properties of Concrete under Wet–Dry and Full-Wet Curing” Sustainability 12, no. 24: 10346. https://doi.org/10.3390/su122410346


Provided by Far Eastern Federal University

Novel Film That Evaporates Sweat Six Times Faster and Holds 15 Times More Moisture (Material Science)

Promising applications include underarm pads, insoles and shoe linings; Moisture harvested could power small wearable electronics.

A team of researchers from the National University of Singapore (NUS) has created a novel film that is very effective in evaporating sweat from our skin to keep us cool and comfortable when we exercise, and the moisture harvested from human sweat can be used to power wearable electronic devices such as watches, fitness trackers, and more.

An NUS research team led by Assistant Professor Tan Swee Ching (seated, left) and Professor Ding Jun (seated right) has developed a novel film that is extremely effective in evaporating sweat from our skin. Promising applications include shoe insoles and linings, as well as underarm pads for sweat absorption. © National University of Singapore

Sweating is a natural process for our body to reduce thermal stress. “Sweat is mostly composed of water. When water is evaporated from the skin surface, it lowers the skin temperature and we feel cooler. In our new invention, we created a novel film that is extremely effective in evaporating sweat from our skin and then absorbing the moisture from sweat. We also take this one step further – by converting the moisture from sweat into energy that could be used to power small wearable devices,” explained research team leader Assistant Professor Tan Swee Ching, who is from the NUS Department of Material Science and Engineering.

The main components of the novel thin film are two hygroscopic chemicals – cobalt chloride and ethanolamine. Besides being extremely moisture-absorbent, this film can rapidly release water when exposed to sunlight, and it can be ‘regenerated’ and reused for more than 100 times.

To make full use of the absorbed sweat, the NUS team has also designed a wearable energy harvesting device comprising eight electrochemical cells (ECs), using the novel film as the electrolyte. Each EC can generate about 0.57 volts of electricity upon absorbing moisture. The overall energy harvested by the device is sufficient to power a light-emitting diode. This proof-of-concept demonstration illustrates the potential of battery-less wearables powered using human sweat.

This technological breakthrough was reported in the September print issue of the scientific journal Nano Energy.

Absorbing moisture for personal comfort

Conventional hygroscopic materials such as zeolites and silica gels have low water uptake and bulk solid structures, making them unsuitable for absorbing moisture from sweat evaporation. In comparison, the new moisture-absorbing film developed by NUS researchers takes in 15 times more moisture and do this 6 times faster than conventional materials.

A team of researchers from the National University of Singapore invented a novel thin film that evaporates sweat six times faster and holds 15 times more moisture than conventional materials. In this prototype, the insole coated with the novel thin film turns from blue to pink as it absorbs moisture. The insole can be easily ‘regenerated’ by putting it under the sun, and be reused for more than 100 times. © National University of Singapore

In addition, this innovative film shows a colour change upon absorbing moisture, from blue to purple, and finally pink. This feature can be used an indicator of the degree of moisture absorption.

The NUS team packaged the film into breathable and waterproof polytetrafluoroethylene (PTFE) membranes, which are flexible and commonly used in clothing, and successfully demonstrated the application of the moisture-absorption film for underarm pad, shoe lining and shoe insole.

Asst Prof Tan said, “Underarm sweating is embarrassing and frustrating, and this condition contributes to the growth of bacteria and leads to unpleasant body odour. Accumulation of perspiration in the shoes could give rise to health problems such as blisters, calluses, and fungal infections. Using the underarm pad, shoe lining and shoe insole embedded with the moisture-absorbing film, the moisture from sweat evaporation is rapidly taken in, preventing an accumulation of sweat and provides a dry and cool microclimate for personal comfort.”

“The prototype for the shoe insole was created using 3D printing. The material used is a mixture of soft polymer and hard polymer, thus providing sufficient support and shock absorption,” explained research team co-leader Professor Ding Jun, who is also from the NUS Department of Material Science and Engineering.

The NUS team now hopes to work with companies to incorporate the novel moisture-absorption film into consumer products.

Reference: Xueping Zhang, Jiachen Yang, Ramadan Borayek, Hao Qu, Dilip Krishna Nandakumar, Qian Zhang, Jun Ding, Swee Ching Tan, “Super-hygroscopic film for wearables with dual functions of expediting sweat evaporation and energy harvesting”, Nano Energy, Volume 75, 2020, 104873, ISSN 2211-2855,
https://doi.org/10.1016/j.nanoen.2020.104873.
(http://www.sciencedirect.com/science/article/pii/S2211285520304304)

Provided by National University of Singapore

Fingerprints Moisture-regulating Mechanism Strengthens Human Touch (Biology)

Human fingerprints have a self-regulating moisture mechanism that not only helps us to avoid dropping our smartphone, but could help scientists to develop better prosthetic limbs, robotic equipment and virtual reality environments, a new study reveals.

Fingerprints’ moisture mechanism could be boon to robotics experts © University of Birmingham

Primates – including humans, monkeys and apes – have evolved epidermal ridges on their hands and feet with a higher density of sweat glands than elsewhere on their bodies. This allows precise regulation of skin moisture to give greater levels of grip when manipulating objects.

Fingerprints help to increase friction when in contact with smooth surfaces, boost grip on rough surfaces and enhance tactile sensitivity. Their moisture-regulating mechanism ensures the best possible hydration of the skin’s keratin layer to maximise friction.

Researchers at the University of Birmingham worked with partners at research institutions in South Korea, including Seoul National University and Yonsei University – publishing their findings today in Proceedings of the National Academy of Sciences (PNAS).

Co-author Mike Adams, Professor in Product Engineering and Manufacturing, at the University of Birmingham commented: “Primates have evolved epidermal ridges on their hands and feet. During contact with solid objects, fingerprint ridges are important for grip and precision manipulation. They regulate moisture levels from external sources or the sweat pores so that friction is maximised and we avoid ‘catastrophic’ slip and keep hold of that smartphone.”

“Understanding the influence of finger pad friction will help us to develop more realistic tactile sensors – for example, applications in robotics and prosthetics and haptic feedback systems for touch screens and virtual reality environments.”

Ultrasonic lubrication is commonly used in touch screen displays that provide sensory ‘haptic’ feedback, but its effectiveness is reduced when a user has dry compared with moist finger pads. Moreover, being able to distinguish between fine-textured surfaces, such as textiles, by touch relies on the induced lateral vibrations but the absence of sliding friction inhibits our ability to identify what we are actually touching.

Fingerprints are unique to primates and koalas – appearing to have the dual function of enhancing evaporation of excess moisture whist providing a reservoir of moisture at their bases that enables grip to be maximised.

The researchers have discovered that, when finger pads are in contact with impermeable surfaces, the sweat from pores in the ridges makes the skin softer and thus dramatically increases friction. However, the resulting increase in the compliance of the ridges causes the sweat pores eventually to become blocked and hence prevents excessive moisture that would reduce our ability to grip objects.

Using hi-tech laser-based imaging technology, the scientists found that moisture regulation could be explained by the combination of this sweat pore blocking and the accelerated evaporation of excessive moisture from external wetting as a result of the specific cross-sectional shape of the epidermal furrows when in contact with an object.

These two functions result in maintaining the optimum amount of moisture in the fingerprint ridges that maximises friction whether the finger pad is initially wet or dry.

“This dual-mechanism for managing moisture has provided primates with an evolutionary advantage in dry and wet conditions – giving them manipulative and locomotive abilities not available to other animals, such as bears and big cats,” added Professor Adams.

Reference: Seoung-Mok Yum, In-Keun Baek, Dongpyo Hong, Juhan Kim, Kyunghoon Jung, Seontae Kim, Kihoon Eom, Jeongmin Jang, Seonmyeong Kim, Matlabjon Sattorov, Min-Geol Lee, Sungwan Kim, Michael J. Adams, Gun-Sik Park, “Fingerprint ridges allow primates to regulate grip”, Proceedings of the National Academy of Sciences Nov 2020, 202001055; DOI: 10.1073/pnas.2001055117 https://www.pnas.org/content/early/2020/11/24/2001055117

Provided by University of Birmingham

Notes to editors:

* The University of Birmingham is ranked amongst the world’s top 100 institutions. Its work brings people from across the world to Birmingham, including researchers, teachers and more than 6,500 international students from over 150 countries.
* ‘Fingerprint ridges allow primates to regulate grip’ – Seoung-Mok Yum, In-Keun Baek, Dongpyo Hong, Juhan Kim, Kyunghoon Jung, Seontae Kim, Kihoon Eom, Jeongmin Jang, Seonmyeong Kim, Matlabjon Sattorov, Min-Geol Leed, Sungwan Kime, Michael J. Adams and Gun-Sik Parka is published in Proceedings of the National Academy of Sciences (PNAS)

The Ultimate Conditions To Get The Most Out Of High-nickel Batteries (Chemistry)

  • The automotive industry has become increasingly interested in the use of high-Ni (nickel) batteries for electric vehicles. However high-Ni cathodes, which make the batteries, are prone to reactivity and instability when exposed to humidity
  • Researchers from WMG, University of Warwick have researched the best way to store Ni cathodes to mitigate degradation and improve performance
  • Humid or ambient conditions for batteries result in premature capacity fade of the battery, whereas the best condition are dry storage at dew points of around -45°C.

It is common knowledge in battery manufacturing that many cathode materials are moisture sensitive. However, as the popularity of high nickel-based battery components increases, researchers from WMG, University of Warwick have found that the drier the conditions that these cathodes are stored and processed in, then significant improvement in performance of the battery is gained.

The effects of ambient air storage on the surface of NMC-811. Credit: WMG, University of Warwick

High-Ni (Nickel) batteries are becoming increasingly popular worldwide, with more automotive companies investigating the use of high-Ni batteries for electric vehicles. However, high-Ni cathode materials are prone to reactivity and instability is exposed to humidity, therefore how they are stored in order to offer the best performance is crucial.

In the paper, ‘The effects of Ambient Storage Conditions on the Structural and Electrochemical Properties of NMC-811 Cathodes for Li-ion batteries,’ published in the journal Electrochimica Acta,, researchers from WMG, University of Warwick propose the best way to store high-nickel cathodes in order to mitigate premature degradation.

a-b) Post-mortem NMC811 particle, with no prior exposure to moist air, analysed by FIB-SIMS, targeting Lithium detection. c-d) Post-mortem NMC811 particle, after 28 days exposure to moist air, analysed by FIB-SIMS, targeting Lithium detection. Credit: WMG, University of Warwick

Researchers exposed NMC-811 (high-Ni cathode material) to different temperatures and humidities, then measured the material’s performance and degradation in a battery over a 28 day period, analysing them using a combination of physical, chemical and electrochemical testing. This included high-resolution microscopy to identify the morphological and chemical changes that occurred at the micron and sub-micron scale during the batteries charging and discharging.

The storage conditions included vacuum oven-dried, as exposed (to humidity) and a control measure. Researchers looked for surface impurities, which include carbonates and H2O, and found there were three processes that can be responsible for impurities, including:

  1. Residual impurities emanating from unreacted precursors during synthesis
  2. Higher equilibrium coverage of surface carbonates/hydroxides (present to stabilise the surface of Ni-rich materials after the synthesis process)
  3. Impurities formed during ambient storage time

They found that in all conditions, (oven dried and as-exposed) showed inferior first discharged specific capacity and cycling performance, compared to the control. However the as-exposed measure showed that after 28 days of ambient moisture exposure the H2O and CO2 react with the Li+ ions in the battery cell, resulting in the formation of lithium carbonate and hydroxide species.

Schematic illustration of particle breakdown during charge-discharge of a battery. Credit: WMG, University of Warwick

The formation of carbonates and oxides on the surface of NMC-811 contribute to the loss of the electrochemical performance during ageing of the materials, due to the inferior ionic and electronic conductivity, as well as the electrical isolation of the active particles. This means that they can no longer reversibly store lithium ions to convey “charge”. SEM analysis confirmed the inter-granular porosity and micro-cracks on these aggregate particles, following the 28 days of ambient exposure.

They can therefore conclude that the driest conditions, at dew points of around -45 oC, are the best for storing AND processing the materials, in order to then produce the best battery performance. Humidity conditions and exposure at junctions along the manufacturing process will cause the materials and components to experience; this results in shorter battery lifespan.

Dr Mel Loveridge from WMG at the University of Warwick comments:

“Whilst moisture is well known to be problematic here, we set about to determine the optimal storage conditions that are required to mitigate unwanted, premature degradation in battery performance. Such measures are critical to improve processing capability, and ultimately maintain performance levels. This is also of relevance to other Ni-rich systems e.g. NCA materials.”

Professor Louis Piper from WMG at the University of Warwick adds:

“Considerable global research effort will continue to focus on these materials, including how to protect their surfaces to eliminate risks of parasitic reactions prior to incorporation into electrodes. In the UK, leading research by the Faraday Institution has a project consortium entirely devoted to unravelling the degradation mechanisms of such industry-relevant materials.”

References: Chiara Bus, Meltiani Belekoukia, Melanie J. Loveridge, “The effects of ambient storage conditions on the structural and electrochemical properties of NMC-811 cathodes for Li-ion batteries” , Electrochimica Acta, 2020, 137358, ISSN 0013-4686, doi:
https://doi.org/10.1016/j.electacta.2020.137358.
(http://www.sciencedirect.com/science/article/pii/S0013468620317515)

Provided by University of Warwick