Area-Controlled Soft Contact Probe: Non-Destructive Robust Electrical Contact with 2D and Fragile Materials.

We developed a soft contact probe capable of making electrical contact with a specimen without causing damage. This probe is now commercially available. However, the contact area with the probe changes according to the pressure applied during electric contact, potentially affecting electric measurements when current density or electric field strength is critical. To address this, we developed methods to control the area of electric contact. This article reports on these methods, as well as variations in probe size, pressure for electric contact, probe materials, and attachment to commercial probers.

AC Electromagnetic Field Controls the Biofilms on the Glass Surface by Escherichia coli & Staphylococcus epidermidis Inhibition Effect.

Biofilms, mainly comprised of bacteria, form on materials' surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials' specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz-12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface.

Quantitative Analyses of Biofilm by Using Crystal Violet Staining and Optical Reflection.

Biofilms have caused many problems, not only in the industrial fields, but also in our daily lives. Therefore, it is important for us to control them by evaluating them properly. There are many instrumental analytical methods available for evaluating formed biofilm qualitatively. These methods include the use of Raman spectroscopy and various microscopes (optical microscopes, confocal laser microscopes, scanning electron microscopes, transmission electron microscopes, atomic force microscopes, etc.). On the other hand, there are some biological methods, such as staining, gene analyses, etc. From the practical viewpoint, staining methods seem to be the best due to various reasons. Therefore, we focused on the staining method that used a crystal violet solution. In the previous study, we devised an evaluation process for biofilms using a color meter to analyze the various staining situations. However, this method was complicated and expensive for practical engineers. For this experiment, we investigated the process of using regular photos that were quantified without any instruments except for digitized cameras. Digitized cameras were used to compare the results. As a result, we confirmed that the absolute values were different for both cases, respectively. However, the tendency of changes was the same. Therefore, we plan to utilize the changes before and after biofilm formation as indicators for the future.

Proposal for Some Affordable Laboratory Biofilm Reactors and Their Critical Evaluations from Practical Viewpoints.

Biofilms are a result of bacterial activities and are found everywhere. They often form on metal surfaces and on the surfaces of polymeric compounds. Biofilms are sticky and mostly consist of water. They have a strong resistance to antimicrobial agents and can cause serious problems for modern medicine and industry. Biofilms are composed of extracellular polymeric substances (EPS) such as polysaccharides produced from bacterial cells and are dominated by water at the initial stage. In a series of experiments, using Escherichia coli, we developed three types of laboratory biofilm reactors (LBR) to simulate biofilm formation. For the first trial, we used a rotary type of biofilm reactor for stirring. For the next trial, we tried another rotary type of reactor where the circular plate holding specimens was rotated. Finally, a circular laboratory biofilm reactor was used. Biofilms were evaluated by using a crystal violet staining method and by using Raman spectroscopy. Additionally, they were compared to each other from the practical (industrial) viewpoints. The third type was the best to form biofilms in a short period. However, the first and second were better from the viewpoint of "ease of use". All of these have their own advantages and disadvantages, respectively. Therefore, they should be properly selected and used for specific and appropriate purposes in the future.

Impedance Characteristics of Monolayer and Bilayer Graphene Films with Biofilm Formation and Growth.

Biofilms are the result of bacterial activity. When the number of bacteria (attached to materials' surfaces) reaches a certain threshold value, then the bacteria simultaneously excrete organic polymers (EPS: extracellular polymeric substances). These sticky polymers encase and protect the bacteria. They are called biofilms and contain about 80% water. Other components of biofilm include polymeric carbon compounds such as polysaccharides and bacteria. It is well-known that biofilms cause various medical and hygiene problems. Therefore, it is important to have a sensor that can detect biofilms to solve such problems. Graphene is a single-atom-thick sheet in which carbon atoms are connected in a hexagonal shape like a honeycomb. Carbon compounds generally bond easily to graphene. Therefore, it is highly possible that graphene could serve as a sensor to monitor biofilm formation and growth. In our previous study, monolayer graphene was prepared on a glass substrate by the chemical vapor deposition (CVD) method. Its biofilm forming ability was compared with that of graphite. As a result, the CVD graphene film had the higher sensitivity for biofilm formation. However, the monolayer graphene has a mechanical disadvantage when used as a biofilm sensor. Therefore, for this new research project, we prepared bilayer graphene with high mechanical strength by using the CVD process on copper substrates. For these specimens, we measured the capacitance component of the specimens' impedance. In addition, we have included a discussion about the possibility of applying them as future sensors for monitoring biofilm formation and growth.

Tool for Designing Breakthrough Discovery in Materials Science.

A database of material property relationships, which serves as a scientific principles database, and a database search system are proposed and developed. The use of this database can support a broader research perspective, which is increasingly important in the era of automated computer-aided experimentation and machine learning of experimental and calculated data. Examples of the wider use of scientific principles in materials research are presented. The database and its advantages are described. An implementation of the proposed database and search system as a prototype software is reported. The usefulness of the database and search system is demonstrated by an example of a surprising but reasonable discovery.

Research Activities in Materials Science and Engineering with Academic-Industrial Alliances during the COVID-19 Pandemic.

During the COVID 19 pandemic, the importance of global academia-industrial alliances has increased. It is hoped that the alliances will help us to solve the current problems caused by the pandemic. In this paper, we introduce the application of IT tools and communication skills utilized in a special educational project for an academia-industrial collaboration. Some concrete examples from 2020 are provided from the viewpoint of the national alliance project in Japan. A discussion is included that describes the plans available to increase and strengthen the national project in the future.

Bi3Cr2.91O11: a ferromagnetic insulator from Cr(4+)/Cr(5+) mixing.

The search for materials with ferromagnetic and semiconducting/insulating properties has intensified recently because of their potential use in spintronics. However, the number of materials is rather limited because of conflicting requirements needed for the appearance of ferromagnetic and insulating properties. Here we show that Bi3Cr2.91O11 belongs to the scarce family of ferromagnetic insulators. Bi3Cr2.91O11 was synthesized at high pressure of 6 GPa and high temperature of 1570 K. Its crystal structure and properties were studied using single crystals. It crystallizes in the KSbO3-type structure with space group Pn3 and the lattice parameter a = 9.2181(2) Å. Bi3Cr2.91O11 has almost a 1:1 mixture of Cr(4+) and Cr(5+) ions distributed in one octahedral crystallographic site. Bi3Cr2.91O11 is a rare example of oxides having chromium ions in unusual oxidation states. The presence of Cr(4+) and Cr(5+) results in ferromagnetic properties with ferromagnetic Curie temperature TC = 220 K.

Evaluation of various metallic coatings on steel to mitigate biofilm formation.

In marine environments and water systems, it is easy for many structures to form biofilms on their surfaces and to be deteriorated due to the corrosion caused by biofilm formation by bacteria. The authors have investigated the antibacterial effects of metallic elements in practical steels so far to solve food-related problems, using Escherichia coli and Staphylococcus aureus. However, from the viewpoint of material deterioration caused by bacteria and their antifouling measures, we should consider the biofilm behavior as aggregate rather than individual bacterium. Therefore, we picked up Pseudomonas aeruginosa and Pseudoalteromonas carageenovara in this study, since they easily form biofilms in estuarine and marine environments. We investigated what kind of metallic elements could inhibit the biofilm formation at first and then discussed how the thin films of those inhibitory elements on steels could affect biofilm formation. The information would lead to the establishment of effective antifouling measures against corrosion in estuarine and marine environments.