The building blocks of these microrobots are iron oxide nanoparticles that have both catalytic and magnetic activity. Using a magnetic field, researchers could direct their motion and configuration to form either bristle-like structures that sweep away dental plaque from the broad surfaces of teeth, or elongated strings that can slip between teeth like a length of floss. In both instances, a catalytic reaction drives the nanoparticles to produce antimicrobials that kill harmful oral bacteria on site.

Experiments using this system on mock and real human teeth showed that the robotic assemblies can conform to a variety of shapes to nearly eliminate the sticky biofilms that lead to cavities and gum disease. The Penn team shared their findings establishing a proof-of-concept for the robotic system in the journal ACS Nano.

“Routine oral care is cumbersome and can pose challenges for many people, especially those who have hard time cleaning their teeth” says Hyun (Michel) Koo, a professor in the Department of Orthodontics and divisions of Community Oral Health and Pediatric Dentistry in Penn’s School of Dental Medicine and co-corresponding author on the study. “You have to brush your teeth, then floss your teeth, then rinse your mouth; it’s a manual, multi-step process. The big innovation here is that the robotics system can do all three in a single, hands-free, automated way.”

“Nanoparticles can be shaped and controlled with magnetic fields in surprising ways,” says Edward Steager, a senior research investigator in Penn’s School of Engineering and Applied Science and co-corresponding author. “We form bristles that can extend, sweep, and even transfer back and forth across a space, much like flossing. The way it works is similar to how a robotic arm might reach out and clean a surface. The system can be programmed to do the nanoparticle assembly and motion control automatically.”

Disrupting oral care technology

“The design of the toothbrush has remained relatively unchanged for millennia,” says Koo.

While adding electric motors elevated the basic ‘bristle-on-a-stick format’, the fundamental concept has remained the same. “It’s a technology that has not been disrupted in decades.”

Several years ago, Penn researchers within the Center for Innovation & Precision Dentistry (CiPD), of which Koo is a co-director, took steps toward a major disruption, using this microrobotics system.

Their innovation arose from a bit of serendipity. Research groups in both Penn Dental Medicine and Penn Engineering were interested in iron oxide nanoparticles but for very different reasons. Koo’s group was intrigued by the catalytic activity of the nanoparticles. They can activate hydrogen peroxide to release free radicals that can kill tooth-decay-causing bacteria and degrade dental plaque biofilms. Meanwhile Steager and engineering colleagues, including Dean Vijay Kumar and Professor Kathleen Stebe, co-director of CiPD, were exploring these nanoparticles as building blocks of magnetically controlled microrobots.

With support from Penn Health Tech and the National Institutes of Health’s National Institute of Dental and Craniofacial Research, the Penn collaborators married the two applications in the current work, constructing a platform to electromagnetically control the microrobots, enabling them to adopt different configurations and release antimicrobials on site to effectively treat and clean teeth.

“It doesn’t matter if you have straight teeth or misaligned teeth, it will adapt to different surfaces,” says Koo. “The system can adjust to all the nooks and crannies in the oral cavity.”

The researchers optimized the motions of the microrobots on a small slab of tooth-like material. Next, they tested the microrobots’ performance adjusting to the complex topography of the tooth surface, interdental surfaces, and the gumline, using 3D-printed tooth models based on scans of human teeth from the dental clinic. Finally, they trialed the microrobots on real human teeth that were mounted in such a way as to mimic the position of teeth in the oral cavity.

On these various surfaces, the researchers found that the microrobotics system could effectively eliminate biofilms, clearing them of all detectable pathogens. The iron oxide nanoparticles have been FDA approved for other uses, and tests of the bristle formations on an animal model showed that they did not harm the gum tissue.

Indeed, the system is fully programmable; the team’s roboticists and engineers used variations in the magnetic field to precisely tune the motions of the microrobots as well as control bristle stiffness and length. The researchers found that the tips of the bristles could be made firm enough to remove biofilms but soft enough to avoid damage to the gums.

The customizable nature of the system, the researchers say, could make it gentle enough for clinical use, but also personalized, able to adapt to the unique topographies of a patient’s oral cavity.

To advance this technology to the clinic, the Penn team is continuing to optimize the robots’ motions and considering different means of delivering the microrobots through mouth-fitting devices.

They’re eager to see their device help patients.

“We have this technology that’s as or more effective as brushing and flossing your teeth but doesn’t require manual dexterity,” says Koo. “We’d love to see this helping the geriatric population and people with disabilities. We believe it will disrupt current modalities and majorly advance oral health care.”

Hyun (Michel) Koo is a professor in the Department of Orthodontics and divisions of Community Oral Health and Pediatric Dentistry in the School of Dental Medicine and co-director of the Center for Innovation & Precision Dentistry at the University of Pennsylvania.

Edward Steager is a senior research investigator in Penn’s School of Engineering and Applied Science.

Koo and Steager’s coauthors on the paper are Penn Dental Medicine’s Min Jun Oh, Alaa Babeer, Yuan Liu, and Zhi Ren and Penn Engineering’s Jingyu Wu, David A. Issadore, Kathleen J. Stebe, and Daeyeon Lee.

This work was supported in part by the National Institute for Dental and Craniofacial Research (grants DE025848 and DE029985), Procter & Gamble, and the Postdoctoral Research Program of Sungkyunkwan University.

In a paper published in Physical Review Letters, the researchers created a model that describes the spread and speed of tornado-like vortex tubes in superfluids. Vortex tubes are a key ingredient of turbulence, which is widely studied in classical physics. The motion of vortex tubes is relevant in a wide range of scenarios, such as the formation of hurricanes, the airborne transmission of viruses and the chemical mixing in star formation. But it is poorly understood in quantum fluids.

This work expands on a previous study that reported experimental results obtained in superfluid helium-4 within a narrow temperature range. Superfluids are liquids that can flow without resistance, and therefore without a loss of kinetic energy. When they are stirred, they form vortices that rotate indefinitely.

“By validating this model and showing that it describes the movement of vortices at a wide range of temperatures, we are confirming a universal rule for this phenomenon,” said Wei Guo, an associate professor of mechanical engineering at the FAMU-FSU College of Engineering. “This discovery may aid the development of advanced theoretical models of quantum fluid turbulence.”

In the previous study, Guo and his team traced the vortex tubes that appeared in superfluid helium-4, a quantum fluid that exists at extremely low temperatures. In that research, the team used tiny particles that were caught in the vortices to trace their movement. They found that the vortices spread out much faster than one would expect based on the tubes’ apparently random motion. This rapid spread is known as superdiffusion.

In the latest work, the researchers built a numerical model and used findings from their previous study to validate the model’s accuracy by reproducing experimental results. That allowed them to predict how vortex tubes might form and spread within superfluids at a wider temperature range. The simulation also produced unequivocal evidence supporting the physical mechanism that the authors proposed for explaining the observed vortex superdiffusion.

Researchers aim to understand turbulence in quantum fluids for the basic research benefits as well as for possible use in practical applications, such as the fabrication of nanowires. Vortex tubes attract particles that group together in incredibly thin lines. Controlling that process allows for manufacture of so-called nanowires, which have a thickness measured in nanometers.

“Particle dispersion in turbulent flow is a very active topic in the classical turbulence field, but it has received less attention in the quantum-fluid community,” said Yuan Tang, a co-lead author and a postdoctoral researcher at the FSU-headquartered National High Magnetic Field Laboratory. “Our work may stimulate more future research on particle dispersion in quantum fluids.”

Paper co-authors include Satoshi Yui and Makoto Tsubota from Osaka Metropolitan University, Japan, and Hiromichi Kobayashi from Keio University, Japan. This paper was selected by Physical Review Letters as an Editors’ Suggestion, a designation for papers that are particularly important, interesting and well written.

This research was supported by the National Science Foundation and the U.S. Department of Energy. Additional resources were provided by the National High Magnetic Field Laboratory at Florida State University, which is supported by the National Science Foundation and the State of Florida. This work was also supported by the Japan Society for the Promotion of Science.

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Materials provided by Florida State University. Original written by Bill Wellock. Note: Content may be edited for style and length.

“The lack of a universal pond definition causes a lot of confusion, from people wondering about the difference between a pond and a lake, to aquatic monitoring programs with different definitions across governmental agencies, even up to accurately modeling global carbon budgets,” said Meredith Holgerson, assistant professor of ecology and evolutionary biology and co-first author of “A functional definition to distinguish ponds from lakes and wetlands,” published June 21 in Scientific Reports.

“We wanted to evaluate how scientists and policymakers define ponds and examine whether ponds are functionally distinct from lakes and wetlands,” Holgerson said.

Their conclusion: Ponds are small and shallow waterbodies, with a maximum surface area of five hectares, a maximum depth of 5 meters and less than 30% emergent vegetation.

There are hundreds of millions or even billions of ponds globally — more than 95% of the world’s still waterbodies are small (under 10 hectares) — but the humble pond is understudied and has been largely left out of federal and state monitoring and protection programs. This is partly because their numbers make monitoring difficult but also because agencies fail to define them or distinguish them from lakes or wetlands. The neglect has implications for the accuracy of climate modeling, as ponds are high emitters of greenhouse gases, and their contribution to the global carbon budget is uncertain.

Holgerson and her team examined how scientists defined pond in more than 500 relevant scientific papers, coding it for different descriptors, like surface area or depth, and whether the descriptions were qualitative or quantitative.

“We found that there wasn’t one definition that researchers all cited, and the definitions were often qualitative, describing a pond as ‘small,’ for example,” Holgerson said.

The team also conducted a survey of state agencies in charge of waterbody monitoring and conservation. Half of the states had legislation that referenced ponds, but only one state (Michigan) defined ponds. Other states designated ponds as state waters or lumped them in with either lakes or wetlands.

The researchers found that ponds are not the same as lakes or wetlands, however. Further examination of the literature revealed that ponds have distinct ecological structures and function that make their categorization with either lakes or wetlands problematic.

Holgerson and her team plotted the relationships between surface area and various metrics of ecological structure or function. “We looked at parameters like gross primary production, respiration, chlorophyll levels, greenhouse gas emissions, diel temperature ranges, and the rate of gas exchange with the atmosphere,” Holgerson said. “Nine out of the 10 ecosystem parameters related nonlinearly to surface area, suggesting that ponds really are acting differently.”

They also examined how these ecosystem metrics related to depth and emergent vegetation — plants rooted in the bottom that extend to the surface — and again found nonlinear relationships. They used the thresholds for where waterbody functions began to change with surface area, depth, and emergent vegetation to arrive at their definition.

The distinct profile and characteristics of ponds means they shouldn’t be held to the same monitoring standards as lakes or wetlands, Holgerson said. “For example, ponds may have naturally higher nutrient concentrations and higher methane fluxes. We may need to develop unique water quality standards for pond monitoring.”

More research is needed to hone the definition, particularly to better understand waterbodies at the boundaries between wetlands and ponds, and ponds and lakes, and how size, depth, vegetation — and other variables like how sheltered a waterbody is — impact the pond’s functioning and its categorization.

“At the beginning of the study, we weren’t sure if our research would allow us to propose a new definition that we felt confident about, but we think the numbers we offer are solid and a great jumping off point for further research,” Holgerson said. “We do call for more research, especially to look at boundaries between wetlands, ponds, and lakes.”

Holgerson hopes the new definition will also call attention to ponds as distinct, significant ecosystems that are worthy of study, monitoring, and protection. “Researching and monitoring ponds can help us figure out how these globally abundant waterbodies function. There’s also an essential human element,” Holgerson said. “So many people have connections to ponds — they have childhood stories of catching frogs or learning to fish in a nearby pond.”

This research was supported by numerous agencies including the Global Lake Ecological Observatory Network, the National Science Foundation and the St. Olaf Collaborative Undergraduate Research and Inquiry Program.

Distinguished scholar at the National Center of Atmospheric Research (NCAR) and highly cited lead author Kevin Trenberth together with climate scientist and co-author Lijing Cheng have made a new complete inventory of all the various sources of excess heat on Earth. He studied energy changes from the atmosphere, ocean, land, and ice as climate system components from 2000 to 2019 and compared this to the radiation at the top of the Earth’s atmosphere to find the imbalance.

“The net energy imbalance is calculated by looking at how much heat is absorbed from the Sun and how much is able to radiate back into space,” explains Trenberth, who’s paper was published today, “it is not yet possible to measure the imbalance directly, the only practical way to estimate it is through an inventory of the changes in energy.”

Understanding the net energy gain of the climate system from all origins, how much extra energy there is and where it is redistributed in the Earth system is vital to inform and thus address the climate crisis. Previously, the focus of climate research has been on the rise of the global mean surface temperature on Earth. However, this is just one outcome of the total energy imbalance faced on Earth.

Excess energy affects weather systems, directly increasing the number or intensity of extreme weather events such as heavy rains and flooding, hurricanes, droughts, heat waves, and wildfires. Weather events move energy around and help the climate system to get rid of energy by radiating it into space, which also affects the rise in temperature globally. The study further revealed that 93% of extra heat from the imbalance ends up in the Earth’s oceans, increasing their overall temperature and sea level which resulted in 2021 being the hottest global ocean recorded year to date.

“Modelling the Earth energy imbalance is challenging, and the relevant observations and their synthesis need improvements. Understanding how all forms of energy are distributed across the globe and are sequestered or radiated back to space will give us a better understanding of our future,” adds Lijing Cheng, co-author of the study.

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The R. typus, like other large sharks, may take years or even decades to reach maturity and reproduce, making them vulnerable to population declines, especially when combined with human threats. For instance, they may be caught in fishing nets as bycatch or face the risk of vessel strikes when shipping lanes overlap with their feeding sites. Being able to understand and predict whale shark behavior is a necessary step for protecting the species.

The satellite monitoring of this species, led by STRI marine ecologist Héctor Guzmán, found that whale sharks feed mainly in coastal waters, seamounts and ridges of the Panamanian Pacific, where they can find an abundance of their favorite foods: small fish and plankton. They were also spotted swimming north and southbound along the coast, towards Mexico and Ecuador, and towards the open ocean to feed.

“This species requires clear regional planning,” said Guzmán. “Once the feeding and breeding aggregation areas are identified, some protection measures should be implemented. The newly announced marine protected area expansions across the region provide an interesting platform for large-scale conservation practices.”

Although they used marine protected areas, the whale sharks also spent time in industrial fishing and vessel traffic zones, which could endanger them according to the new article published in Frontiers in Marine Science.

“The study shows how complex it is to protect whale sharks: tagged individuals visited 17 marine protected areas in 5 countries, but more than 77% of their time they were in areas without any protection,” said Catalina Gómez, co-author of the study and marine ecologist at the University of Panama.

Thus, for highly migratory and endangered species such as the whale shark, conservation measures should go beyond the establishment of local marine protected areas.

Efforts should focus on protecting large oceanic areas and establishing marine corridors that transcend national borders, for example: the newly expanded Cordillera de Coiba Marine Protected Area in Panama or the Marine Conservation Corridor of the Eastern Tropical Pacific which connects Coiba with Costa Rica’s Cocos Islands, the Galapagos in Ecuador and Colombia’s Malpelo Island.

“A periodic tagging program should continue for two main reasons: first, we still don’t know where the species reproduces and tracking may lead us in the right direction,” said Guzmán. “Second, we know that they are moving across extensive areas. We have identified potential corridors or seaways, as well as aggregation areas, that require management attention and clear protection rules. Tracking will allow us to better identify those regional routes.”

The satellite tracking also revealed a whale shark migratory pattern that seems to be associated with circular ocean currents called eddies.

“Eddies are recognized as potential feeding areas for migratory species or food epicenters in the oceans, so they can swim in those areas for a long time while foraging and feeding,” said Guzman. “However, eddies are dynamic systems and change constantly in speed or strength, size and location, even seasonally. These feeding areas are important for conservation, especially considering their dynamics and potential changes associated with climate change.”

This research was partially funded by the Smithsonian Tropical Research Institute, MarViva Foundation, the International Community Foundation-CANDEO, the Secretaria Nacional de Ciencia, Tecnologia e Innovacion de Panama (SENACYT) and its Sistema Nacional de Investigación.

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Materials provided by Smithsonian Tropical Research Institute. Original written by Leila Nilipour. Note: Content may be edited for style and length.