Highly interesting work and research are currently underway in defining and standardizing various nanostructures. To enable effective research, reliable and standardized measuring instruments and methods are required. At the RISE Magnetic Sensor Systems Lab, we have successfully developed and standardized measurement instruments and methodology for dynamic magnetic measurement and analysis, which are part of standardized measurement systems for MNPs.

Christer Johansson, senior expert at the Sensor Systems unit at RISE, explains that in dynamic magnetic measurements, an alternating (AC) magnetic field with a specific frequency and amplitude is used on the sample. The resulting dynamic magnetic response, also called AC-susceptometry (ACS), is measured contactless through coils and sensitive magnetic measurement technology.

“The DynoMag system, developed and manufactured at the RISE Magnetic Sensor Systems Lab in Gothenburg, has been central in over 160 scientific articles, particularly in the magnetic analysis of MNP systems. The goal has always been to create a sensitive and user-friendly measurement system with integrated electronics and software, along with associated magnetic models for accurate analysis of measurement data”, says Christer.

The development of DynoMag and other similar ACS systems has been conducted in both internal projects and several EU projects, as well as nationally funded projects. Through the EU projects NanoMag and MagNaStand, the DynoMag system and the measurement methodology have been further developed, resulting in an approved ISO standard for ACS measurement methodology for MNPs. 

“By sweeping the frequency and measuring the sample response, the DynoMag system, with its magnetic models, can identify magnetic relaxations and determine the particle size distribution for MNP systems in colloidal solution”, Christer continues.

Another application is monitoring the stability of MNP systems over time under external influences, or as a quality assurance method in the manufacturing of MNP systems to maintain optimal properties or develop new applications. The ACS response in the frequency domain varies depending on the MNP configuration and the presence of particle aggregates.

Through ACS measurement technology and optimal MNP systems, rheological properties can be determined for different substances, from simple Newtonian fluids, like water and glycerol solutions, to complex non-Newtonian substances like gelatin and Xanthan solutions used in the food industry. In a successful project funded by Formas, RISE, together with Chalmers University of Technology, utilized ACS measurement methodology and optimal MNP systems to measure viscoelastic properties in food research. 

The DynoMag ACS system also enables sensitive detection of biological markers by measuring and analyzing the response from functionalized MNP systems. A successful project in collaboration with Chalmers University of Technology, Karolinska Institute, Uppsala University, and Stockholm University, funded by SSF, resulted in an integrated measurement system for influenza. 

“In summary, the DynoMag system is a key component for the characterization of magnetic nanostructures, rheological studies, and biomedical research, with its applications spanning across various disciplines and fields”, Christer concludes.

Society's need for knowledge about soft values such as health, well-being, behaviors, and abilities is increasing. It is important to be able to compare changes over time or between different groups or areas, to be able to make decisions about priorities, efforts, and effects. RISE has been working for several years to develop quality-assured measurements of latent traits, also called category based measurements. A latent trait or variable is the underlying experience or ability we want to measure, but which cannot be directly observed. For instance, if we want to measure a person's well-being we cannot measure it directly by measuring blood pressure or heart rate. However, we can measure well-being indirectly by asking questions about how the person is feeling, such as through a survey.

"By asking we get answers. But what does the answer mean? Is the person experiencing a high or low level of well-being, and how does it compare to other individuals or groups? How does the well-being of a group change over time? To get those answers we need to use basic metrology principles", says Magnus Johansson, researcher at RISE.

From survey to measurement

Part of going from survey to measurement is to ensure the quality of the survey or test. Do the questions provide sufficient and meaningful information about the latent trait we want to measure? It is also important to investigate whether the questions work equally well for different demographic groups, so that comparisons between measurement values can be made.

"We also need to test and analyze the questionnaire before it is used. For example, the respondents' level of well-being should be related to the probability that the respondent uses a higher response category. People with the same level of well-being should have similar response patterns to the individual questions. These are simple principles, but surveys are rarely tested to ensure this", says Magnus Johansson.

Converts answers into measurement values

Once the survey data has been collected, it is time for analysis. Here, Magnus Johansson and his colleagues often use Rasch analysis, which makes it possible to convert the answers in the survey into measurement values for the latent trait. The survey's measurement properties need to meet certain criteria for the conversion to be done correctly.

"Rasch analysis is the only method that, if used correctly and applying basic metrology principles, allows us to sum up and convert survey responses into metric values through a simple conversion table. Then we can go from saying that we asked people what they think about their well-being to saying that people's well-being is at a certain level."

Develops category based measurements

Magnus Johansson works together with his colleagues to spread knowledge and make the methodology available and accessible. An example is a tool that makes the statistical calculations more convenient. With the tool, it becomes relatively easy to carry out the analysis, document what has been done and enable others to reproduce the analysis. The tool is free of charge and the underlying source code and calculation models can be reviewed for those who are curious.

"A lot of knowledge is still required regarding preliminary work, interpretation of the results from the Rasch analysis, and what actions can be taken based on the results. But many of the calculations are basically done automatically. By calling simple functions, I get figures and tables that provide the central information", says Magnus Johansson.

The tool is under development but already available to use.

"I notice it's starting to pick up. Several people have gotten in touch and said that they learned how to do Rasch analysis with the help of the guide that gives examples of how the package can be used. The demand is increasing as more people realize that what we call measurements today are not actually quality-assured measurements. I hope that the tool can help reduce the threshold for working with quality-assured measurements", says Magnus Johansson.

To experience real darkness in Sweden you need to go far north, for example to the area around Sarek. Other than that, there are few really dark places left. The night sky is more or less illuminated by artificial light. Light pollution, lighting that illuminates more than necessary, poses problems for astronomers who want to study the night sky or for insects that are attracted to light. But it can also lead to negative effects for humans. Research shows there may be links to cancer, sleep problems, depression and obesity. But more knowledge is needed.

"In the studies we looked at, there are generally very little information about how much light or what type of light that can be harmful. There is also a lack of good methods to measure the amount of light pollution. What units of measurement do we use? How do we ensure that the results are comparable with other measurements? Often you use satellite images without proper measurement values", says Stefan Källberg, researcher at RISE and technical manager of the National Laboratory for Photometry and Radiometry.

Lighting with a purpose

In a project ending soon, he and his colleagues have gone through the current research in the field, developed new methods to measure the amount of light pollution using a drone, and tested energy-efficient outdoor lighting that can work for both people and animals and the environment.

"We want to limit light pollution to reasonable levels and avoid spreading light where it does no good. All outdoor lighting should have a purpose. It could be to increase traffic safety, to make a walking and cycling path safer or something else."

Drone measurements

Stefan Källberg and his colleagues acquired an ordinary consumer drone, equipped it with a light meter and developed methods for quality-assured measurements of the scattered light. The drone measurements were then used in the outdoor lighting tests.

"Since we know that blue light affects insects and bats the most, for example, it would be good to reduce the proportion of blue light in outdoor lighting. But if you reduce the blue light, the proportion of red light increases, which means that the surroundings are colored red for us humans and it becomes difficult or impossible to distinguish colors. The goal is therefore to find a middle way, a light that can be accepted by people while containing as little blue light as possible."

What did people think?

Several light sources with different proportions of blue light were selected, from an orange tint to more traditional light. These were set up by a lake outside Borås along a small pedestrian and bicycle path. The regular lighting was turned off and then people walked along the route and answered questions about what they thought of the lighting.

"It is always difficult to have an opinion on light. But we can see that younger people preferred the traditional white light and thought the orange color gave an unsafe impression, while older people liked the in-between variant. Everyone agreed that it would not have worked with even redder light, it is perceived as unsafe, says Stefan Källberg."

Potential for development

Although the drone measurements worked well, there is potential to develop them in future projects.

"We have seen that our method makes it possible to get good measurement values, such as seeing which light sources contribute the most to the light in a certain area. With a more advanced drone, you could automate the process, make it fly in certain patterns and thus develop the method and take further steps towards a defined and quality-assured method", says Stefan Källberg.

As early as the 1970s, Italian authorities began contemplating how to save the city from the water masses, and since 2020, Venice has a unique solution in place: a 1,560-meter-long chain of flood barriers, known as MO.S.E.

However, seawater is an aggressive environment for many materials. Following the first full-scale trial of the system, it was discovered that key parts of the barriers had started to corrode. 

Nicolas Larché, Site Manager at Institut de la Corrosion, a subsidiary of RISE, was hired to inspect the corroded elements of the MO.S.E. barriers and develop a plan of action. He has witnessed up close the destructive forces of nature and humanity's struggle to master climate change.

“The authorities in Venice called us in to understand how the corrosion had occurred, and our preliminary investigation revealed that it was due to an initial incident. Seawater had accumulated along certain tensioners and stagnated, causing corrosion on several surfaces,” he explains.

Thorough inspection yielded positive results

The MO.S.E. barrier consists of 78 hollow gates, which are filled with water when the barrier is lowered. In the face of a flood threat, compressed air is pumped into the gates from underlying plants, or galleries, to drain them of water. This raises them above the surface, protecting the city from up to three meters of water rise. After the commissioning, the seawater that inadvertently had penetrated the galleries had begun to wear down some of the tensioners (hinges) responsible for keeping the gates in place. This insight, along with data indicating atmospheric corrosion inside the galleries, raised concerns.

In collaboration with Euro Anticorrosion Service, EAS, Nicolas Larché optimised and utilized a precise 3D laser technique for measuring and tracking the progression of corrosion. The data was used to quantify the barrier's lifespan and maintenance requirements. They also installed sensors to continuously monitor the corrosivity of the atmosphere near the tensioners. Air conditioning systems were installed in the galleries to purify and dry the air. The tensioners were also treated with a layer of moisture-repellent grease.

Finally, they took samples from the tensioners, which are subjected to very high loads during tidal movements, and conducted tests to simulate how well they withstand the force and frequency of tides, in presence of existing corrosion.

The result was rather reassuring. Despite existing corrosion, the barrier is expected to last for at least another 100 years, provided that all the data is correct, and the circumstances remain roughly the same.

“To be on the safe side, we also conducted a simulation where we doubled the tidal frequency and increased the load with 30 percent. The simulation showed that even then, the lifespan would be over a hundred years. But, of course, we must regularly check that our hypothesis is correct, so we will conduct routine inspections to track the evolution of the corrosion,” says Nicolas Larché.

An effective solution for Venice

The conclusion is that Venice's solution works well for Venice, as long as the corrosion is closely monitored and actively counteracted. But Venice is just one of many cities heavily affected by rising sea levels. What can we learn from MO.S.E. and its challenges?

“Venice is very unique, it's a city out in the sea, in a small lagoon. Seawater can only enter the city through three main gates, making the barrier system possible. Copying the concept in other locations would probably be difficult, but it is not unthinkable that some form of physical barrier could be constructed in places with a similar configuration,” says Nicolas Larché.

Rising sea levels are just one of several problems the world is now facing due to climate change. The increase in temperature has also led to other types of corrosion problems.

“In terms of corrosion, global warming is of great significance. Temperature is a key parameter. A project the Institut de la Corrosion is currently working on concerns corrosion issues due to growth of Sargassum seaweed. The increase in its growth can be due to rising temperatures and human pollution. Sargassum seaweed floats into the coasts where it dries and dies. In the process, it acidifies the environment and releases toxic gas. The atmosphere becomes extremely corrosive and can affect the durability of surrounding metallic structures.”

Important to act

So, how should coastal communities act in the future to tackle the challenges posed by climate change? Nicolas Larché explains that he is not a climate expert, but he believes that authorities worldwide should review the inspection frequency to align it with climate change. This way, problems can be detected and predicted before it's too late. 

“RISE and Institut de la Corrosion can investigate how temperature changes or rising water levels affect infrastructure and provide advice on appropriate measures. We can also help continuously adapt existing anti-corrosion systems to new climate conditions. In addition, we actively develop methodologies to study the effect of corrosion and anti-corrosion systems on the environment. Thus, we do not only study the impact of the environment on the materials, but also consider the impact of the materials on the environment.”