Ultrafine Bubbles Research Articles

Ultrafine bubbles as an augmenting agent for ozone-based advanced oxidation.

In this study, the influence of nanobubbles (NBs) application in ozone (O3) based advanced oxidation processes (AOP) is investigated. The results demonstrate the potential of NBs application to O3 - based AOP. It was observed that NBs suppress the negative influence of pH and operating temperatures on the efficiency of ozonation. In addition, the application of NBs tends to improve the solubility of O3 and the rate of mass transfer under the influence of a broad range of temperature and pH conditions. The results of this research indicate that application of NBs minimized the reduction in concentration of dissolved O3 with an increase in temperature. Furthermore, application of NBs highly improved the OH radical formation in acidic conditions. The results of this research depicted for first time that the application of NBs strongly encourages the initiation of reactions involving OH radicals. It was found by this research that NBs can boost the concentration of OH radicals up to 3.5 fold compared to equivalent MB-supported ozonation systems. This is assumed to improve the efficiency of currently existing conventional bubble supported O3 - based AOP systems.

Ultrafine bubble water mitigates plant growth in damaged soil.

Water containing ultrafine/nano bubbles (UFBs) promoted the growth of tomato (Solanum lycopersicum) in soil damaged by cultivation of tomato in the previous year or bacterial wilt-like disease and also promoted the growth of lettuce (Lactuca sativa) when lettuce was grown in the soil damaged by repeated cultivation of lettuce. On the other hand, UFB supply did not affect plant growth in rock wool or healthy soil. Furthermore, the growth of lettuce was not affected by UFB water treatment in the soil damaged by the cultivation of tomato. UFB water partly suppressed the growth of the pathogen of bacteria wilt disease, Ralstonia solanacearum in vitro. These data suggest that UFB water is effective to recover the plant growth from soil damage.

Theranostic nanobubbles towards smart nanomedicines

Targeted therapy and early accurate detection of malignant lesions are essential for the effectiveness of treatment and prognosis in cancer patients. The development of gaseous system as a versatile platform for the fabricated nanobubbles, has attracted much interest in improving the efficacy of ultrasound therapeutic, diagnostic, and theranostic platforms. Nano-sized bubble, as an ultrasound contrast agent, with spherical gas-filled structures exhibited contrast enhancement capability due to their inherent EPR effect. Additionally, nanobubbles exhibited good stability with extended retention time in the blood stream. The current review summarized various nanobubbles and discussed about the crucial parameters affecting the stability of ultrafine bubbles. Furthermore, therapeutic and theranostic gaseous systems for fighting against cancer were described.

Nutrition and Cancer Risk from the Viewpoint of the Intestinal Microbiome

There are various important factors in reducing the risk of cancer development and progression; these factors may correct an unbalanced intake of nutrients to maintain the living body’s homeostasis, detoxify toxic materials, acting as an external factor, and maintain and strengthen the body’s immune function. In a normal cell environment, nutrients, such as carbohydrates, lipids, proteins, vitamins, and minerals, are properly digested and absorbed into the body, and, as a result, an environment in which cancer can develop and progress is prevented. It is necessary to prevent toxic materials from entering the body and to detoxify poisons in the body. If these processes occur correctly, cells work normally, and genes cannot be damaged. The most important factor in the fight against cancer and prevention of the development and progression of cancer is the immune system. This requires a nutritional state in which the immune system works well, allowing the intestinal microbiome to carry out all of its roles. In order to grow intestinal microbiota, the consumption of prebiotics, such as organic vegetables, fruits, and dietary fiber, and probiotics of effective intestinal microbiota, such as fermented foods and supplements, is required. Symbiosis, in which these organisms work together, is an effective means of reducing the risk of cancer. In addition, fecal microbiota transplantation (FMT) using ultrafine bubble water, produced specially by the Association for Clinical Research of Fecal Microbiota Transplantation Japan, is also useful for improving the nutritional condition and reducing the risk of cancer.

Field trials to determine the efficacy of aerators to mitigate hypoxia in inland waterways

Following a series of fish deaths in the lower Darling River in the austral summer of 2018–19, several field trials were undertaken over two summers to determine the efficacy of various aerators to mitigate the effects of hypoxia to prevent fish deaths. The aerators evaluated included: low-powered, solar bubble-plume diffusers; high-flow, single-port Venturi systems; pontoon-mounted multi-port Venturi systems; and an ultra-fine bubble generator. The effectiveness of bubble diffusers appears related to their power, the number of units used and their running time. Pontoon-mounted multi-port Venturi aerators and high-flow, single-port Venturi aerators were much more successful in maintaining oxygen levels and may have prevented fish deaths in the Darling River in early 2019. However, the Venturi aerators were expensive to run, consuming hundreds to thousands of litres of diesel fuel per week. Trial of an ultra-fine oxygen bubble pump showed promise because it supersaturated the water with dissolved oxygen while not elevating total gas pressure to levels that would cause gas-bubble trauma in fish. Although aerators may play a role in emergency responses to hypoxic fish deaths, they have limitations regarding their area of influence (at best thousands of square metres) and their cost to deploy and operate.

A Study on the Development of UFB(Ultra Fine Bubble) device for Heat Source

UFB(Ultra Fine Bubble)라 함은 100 ~ 300 [㎚] 사이즈의 기포인 Nano size의 직경을 가지는 기포(氣泡)를 말하며 이와 관련한 산업분야들을 살펴보면 이·미용, SPA, 테라피, 반도체 세정, 의료 등 다양한 분야를 창출 할 수 있을 것으로 판단되고 매년 UFB에 관련한 산업분야로는 농산물에 대한 세척, 수산물에 대한 생장속도 향상 외에도 녹조를 제거하거나 오염물질을 정화시키는 분야에까지 활용하여 다양하게 확장되고 있다. 본 연구에서는 Heat Source 기능을 담당하는 UFB Generator를 설계하기 위해서 100 ~ 300 ㎚의 직경을 가지는 초미세 기포를 발생시킬 수 있고, 이러한 초미세기포를 ㎖당 5억 개 이상을 생산할 수 있으며, 개발된 장치의 전력 소모를 줄일 수 있도록 400Wh 이하의 저전력 전기장치를 실험을 통해 가능성을 입증하였다. 또한 불완전 연소로 인해 발생되어지는 미세먼지, NOx 등에 대한 유해물질이 발생되지 않아 대기환경 오염 유발없이 Heat source 로서의 역할을 할 수 있을 것으로 판단된다.

Ultrafine Bubbles Technology for Breaking Dormancy of Sandalwood Seeds (Santalum album L.

Sandalwood seed has two types of dormancy, namely physical dormancy and physiological dormancy which is a combination of the Two-part is called morph oph ysiological dormancy. T here is fo r breaks dormancy in sandalwood for earlier embryo maturation and elongation also it has hard and impermeable skin. Its structure consists of layers of thick-walled palisade-like cells especially on the outermost surface and the inside has a waxy coating and curse material. The objective of this study was to break of seed dormancy with technology Ultrafine Bubbles (UFB) on the morphophysiological dormancy on sandalwood seeds. The experiments used a randomized complete block designed (RCBD) with 3 replications. The data were analyzed using ANOVA and will be continued using the DMRT test at the 5% level. The research was conducted from February - March 0f 2020. The results showed that immersion using UFB water with oxygen 20 ppm or either UFB free oxygen for 24 and 48 hours combined with physical scarification and chemical scarification could accelerate germination in 13 days after germination ( appeared radicle ), percentage of growth speed (GS) is 4 . 67% , m aximum growth (MG) in 21 days after sowing is 66 . 67% with normal sprouts 2-4 leaves have grown .

Influence of bulk nanobubble concentration on the intensity of sonoluminescence

The present study mainly examined the effects of the volumetric concentration of nanobubbles (ultrafine bubbles) on the intensity of sonoluminescence (SL). The addition of nanobubbles at high acoustic amplitude enhanced the SL intensity for various bubble concentrations in comparison with that in pure water. This probably means that the resulting high amplitude is over the Blake threshold, and accordingly nanobubbles expand to some extent, leading to higher SL intensity. Therefore, nanobubbles have the potential to provide nucleation sites for sonochemistry. The influence of bubble size on the intensity of SL was also evaluated.

Promoting Effect of Ultra-Fine Bubbles on CO2 Hydrate Formation

When gas hydrates dissociate into gas and liquid water, many gas bubbles form in the water. The large bubbles disappear after several minutes due to their buoyancy, while a large number of small bubbles (particularly sub-micron-order bubbles known as ultra-fine bubbles (UFBs)) remain in the water for a long time. In our previous studies, we demonstrated that the existence of UFBs is a major factor promoting gas hydrate formation. We then extended our research on this issue to carbon dioxide (CO2) as it forms structure-I hydrates, similar to methane and ethane hydrates explored in previous studies; however, CO2 saturated solutions present severe conditions for the survival of UFBs. The distribution measurements of CO2 UFBs revealed that their average size was larger and number density was smaller than those of other hydrocarbon UFBs. Despite these conditions, the CO2 hydrate formation tests confirmed that CO2 UFBs played important roles in the expression of the promoting effect. The analysis showed that different UFB preparation processes resulted in different promoting effects. These findings can aid in better understanding the mechanism of the promoting (or memory) effect of gas hydrate formation.

High-Performance Ultrafine Bubble Aeration on Janus Aluminum Foil Prepared by Laser Microfabrication.

Aeration is a mass transfer process, in which gas is dispersed into a liquid by utilizing air inflation or agitation. Typically, a microporous device is often used for aeration. Increasing the gas flow rate and decreasing the pore size reduce the bubble size, but the surface wettability of the gas/solid interface also has a significant impact on the bubble size, which is rarely studied. In this study, a superhydrophilic/superhydrophobic Janus aluminum foil (JAF) is fabricated by laser microstructuring and low surface energy modification. The gas-repelling superhydrophilic surface not only facilitates ultrafine bubble generation but also allows the bubbles to detach from the aerator surface quickly, while the superhydrophobic surface prevents water from infiltrating into the aeration chamber and reduces the mass transfer resistance. The micropores with different diameters are obtained by adjusting the laser processing parameters. The pore prepared by the laser is uniform, consequently leading to the uniform bubble size. When the pore diameter is set to 30 μm, the diameter of bubbles released from the superhydrophilic surface of the JAF is only 0.326 mm, and the gas dissolution rate is about six times that of the double-sided superhydrophobic aluminum foil. This simple, low-cost, and controllable method of the laser processing JAF has broad applications in wastewater treatment, energy production, and aquaculture.

International Transportation of Ultrafine Bubble Dispersions

Interlaboratory comparison can be effective to obtain consistent findings on ultrafine bubbles (UFBs). In this study, the stability of UFBs during international transportation was reported for the first time. We conducted stability tests in cooperation with German and Canadian institutions. UFBs were measured using two laser-based characterization techniques: particle tracking analysis (PTA) and dynamic light scattering (DLS). Acceleration and temperature during transportation were also measured. The results showed that regardless of transportation, the number concentration of UFBs decreased, while the size of UFBs increased with time. By filling the glass vial with UFB dispersion and minimizing the liquid flow in the vial, the effects of transportation were virtually eliminated. It was also suggested that the liquid flow caused by vibration during transportation may have enhanced the aggregation of UFBs. We report the results of an inter-instrumental comparison among PTA and DLS instruments using the transported UFB dispersions.

Reduction of ozone dosage by using ozone in ultrafine bubbles to reduce sludge volume

Sludge ozonation, which promotes sludge disintegration and solubilization, is a promising technology for reducing waste sludge volume from biological wastewater treatment process. However, if this technology is to be widely adopted, reducing the energy consumption associated with ozone generation will be necessary. We used ultra-fine bubbles (UFBs) as ozone carriers to determine if their use could improve the efficiency of ozone treatment and reduce the ozone dose required. We used a spiral, liquid-type UFB generator, which can introduce UFBs directly into a sludge suspension. The death ratio of bacteria in sludge was used as an indicator of sludge reduction. The ozone requirement was reduced by UFBs. The ozone consumption required to achieve a death ratio of 80% was 15 mg-O3/g-MLSS in the sludge treated with ozone supplied by UFBs versus 25 and 45 mg-O3/g-MLSS in sludges treated with ozone supplied as a spiral, liquid-type microbubbles and by a diffuser, respectively. When mixing water ozonated with UFBs with sludge, the depth of the dead cell layer from the surface to the interior of the sludge floc was larger than that of ozonated water lacking UFBs at the same rate of ozone consumption. Ozone in UFBs kills bacteria inside the flocs. However, the fragmentation of sludge flocs by shear forces in the UFB generator made a larger contribution to the acceleration of bacterial death in sludge treated with ozone supplied by UFBs.

Extraction of Type I Collagen from Tilapia Scales Using Acetic Acid and Ultrafine Bubbles

Type I collagen is commonly used in medical materials and cosmetics. While it can be extracted from the skin and bones of mammals, marine collagen has attracted attention recently, since the use of mammalian collagen could result in zoonosis, and products containing mammalian collagen are avoided due to some religious beliefs. Chemical extractions using strong acids and alkalis, thermal extractions, and other nonconventional methods have been used for collagen extraction. However, there are few reports on environmentally friendly methods. Although heat extractions provide higher yields of collagen, they often cause collagen denaturation. Therefore, dilute acetic acid and ultrafine bubbles of oxygen, carbon dioxide, and ozone were used to extract type I collagen from tilapia scales. The extraction performance of the different conditions employed was qualitatively analyzed by SDS-PAGE electrophoresis, and the collagen concentration was quantified using circular dichroism spectroscopy by monitoring the peak intensity at 221 nm, which is specific to the triple helix of type I collagen. Collagen was extracted from tilapia scales with a yield of 1.58% by the aeration of ultrafine bubbles of carbon dioxide gas in a 0.1 M acetic acid solution for 5 h.

Interaction of Bulk Nanobubbles (Ultrafine Bubbles) with a Solid Surface.

The experimental results [Kanematsu, W. Chem. Eng. Sci. 2020, 219, 115594] on the temporal variations of number concentrations of bulk nanobubbles (ultrafine bubbles) in contact with polymer materials are theoretically analyzed based on the dynamic equilibrium model of bulk nanobubbles partly covered with hydrophobic materials (impurities). It is suggested that bulk nanobubbles are adsorbed on a polymer surface by attractive hydrophobic interaction between a polymer surface and a hydrophobic material partly covering the bubble surface, overcoming the repulsive double-layer interaction. There are two mysteries. One is that the maximum surface number concentration of bulk nanobubbles of about 70 nm in diameter adsorbed on a hydrophobic polymer surface is more than an order of magnitude lower than the typical value for colloid particles of a similar or larger size. The other is that the experimental adsorption rate of bulk nanobubbles on hydrophobic polymer surface is several orders of magnitude lower than the theoretically estimated one. The mysteries are resolved if many of the bulk nanobubbles adsorbed on a hydrophobic polymer surface change to surface nanobubbles with a footprint diameter of about 1 μm.

Effect of Ultrafine Bubbles on Pseudomonas Aeruginosa and Staphylococcus Aureus During Sterilization of Machining Fluid

Bacterial growth is one of the common causes of putrefaction and deterioration of water-soluble machining fluid. The 16S ribosomal DNA metagenome analysis of the bacterial species composing the microbial flora present in the machining fluid derived after processing demonstrated a high amount of species belonging to the Pseudomonas genus. Therefore, we prepared two types of ultrafine bubbles water (gas species: air and CO2) containing different types of gas and confirmed the bactericidal effect on Pseudomonas aeruginosa (ATCC 10145), a typical Pseudomonas species. The grinding fluid was prepared using sterile purified water containing ultrafine bubbles (hereafter referred to as UFB) as diluted water, and the Pseudomonas aeruginosa was inoculated to obtain 106 CFU/mL. The sterilization rate of the number of bacteria was determined immediately after immersion in each fluid and subsequently after two hours. The sterilization rate was determined to be 100% in the test group using the ultrafine bubbles water of CO2 (CO2-UFB water). As a comparative control, a similar test was performed on Staphylococcus aureus IFO12732, and the sterilization rate was determined as 0%. Fluorescence microscopic observation of bacteria after immersion in the CO2-UFB water demonstrated damage to the cell wall as the cause of death of the Pseudomonas aeruginosa. Therefore, CO2-UFB demonstrated sterilization of machining fluid by killing Pseudomonas aeruginosa in the machining fluid. The bactericidal mechanism of UFB involved the induction of damage in bacterial cell walls. This can be attributed to crushing due to the increase in the particle size of UFB.

Special Issue on Advances in Abrasive Technology

As abrasive technologies are currently indispensable for production processes in the automotive, aerospace, optics, telecommunications, and healthcare industries, among others, it is essential that the application of abrasive processing to production be optimized and improved. To those ends, it is necessary to understand how to approach the task, as there are many processing factors to consider. However, priority is given to understanding the abrasive processing mechanism that determine finishing results, as well as the relationship between the processing factors and individual conditions. Measurement, analysis, and evaluation technologies are also important. Furthermore, the development of new abrasive tools or machining fluids and the active use of physicochemical phenomena are key to the development of advanced abrasive technologies. Cutting-edge studies focusing on advanced abrasive technologies were collected for this special issue, which includes 12 papers covering the following topics: - Quantitative evaluation of surface profile of grinding wheel - Elucidation of grinding mechanism, based on grinding force - Novel grinding wheel - High-efficiency and high-accuracy grinding of difficult-to-cut materials - Polishing technology using magnetic fluid slurry - Application of ultrasonic waves or ultra-fine bubbles to coolants, and their effects on them - Planarization technology for single-crystal silicon carbide This issue is expected to help its readers to understand recent developments in abrasive technologies and to lead to further research. We deeply appreciate the contributions of all authors and thank the reviewers for their incisive efforts.

The influence of the Ultra Fine Bubble (UFB) inserted Coconut oilbased metalworking fluid (MWF) on tool wear modes and mechanisms in turning of Inconel 718

The influence of the Ultra Fine Bubble (UFB) inserted Coconut oilbased metalworking fluid (MWF) on tool wear modes and mechanisms in turning of Inconel 718

A Study of the Salt Rejection from the Surface of Marine Waste using Ultra Fine Bubble

A Study of the Salt Rejection from the Surface of Marine Waste using Ultra Fine Bubble

Study on the Method of Identifying Ultrafine Bubbles Using Ultrasound under the Presence of Solid Nanoparticles

The method of making OH radicals generated by the collapse of ultrafine bubbles as an indicator when applying ultrasound was examined as the method of identifying ultrafine bubbles less than 1 μm in diameter under the presence of mixed solid nanoparticles. First, potassium iodide (KI) method was used to evaluate OH radicals. Since difference in absorbance due to OH radicals generated by the collapse of ultrafine bubbles is very small when using air as contained gas, evaluation using the KI method was difficult; however, a distinct difference in absorbance was confirmed by increasing the amount of OH radicals generated by using ozone as contained gas. Moreover, the higher the ultrasound frequency, the greater the difference in absorbance. On the other hand, a luminescence phenomenon related to the collapse of ultrafine bubbles by ultrasound was confirmed with sonoluminescence observation, confirming further that the luminescence intensity of water added with solid particles of the same diameter and number density as those of ultrafine bubbles is smaller than that of ultrafine bubble water.

Characteristic of Ultra Fine Bubble for Purification and Sterilization

Characteristic of Ultra Fine Bubble for Purification and Sterilization