Dedicated to the thousands of lives lost in landslides, the new atlas assesses landslide risk in 13 districts in the Indian state of Kerala.

The Western Ghats trailing the western edge of India are a global hotspot for biodiversity. The southern reach of the range extends into Kerala, where the steep slopes, soft soils and heavy monsoon rains greatly increase the risk of landslides.

Thomas Oommen, a professor of geological engineering at Michigan Technological University, is from Kerala, and he produced the Landslide Atlas of Kerala with colleague K.S. Sajinkumar, an assistant professor of geology at the University of Kerala. Their work started in 2016 while Sajinkumar was a postdoctoral fellow at Michigan Tech under Oommen’s guidance. The atlas, which provides detailed, up-to-date data about landslide risks in the state, was written for practical use by those who need it most — folks on the ground in the region. Each section focuses on a specific district and is accompanied by geographic information system (GIS) maps.

Landslide Atlas

Debris flows — muddy mixes of water, soil and organic material — are the most common type of landslide in Kerala, typically occurring between June and November, when monsoon rains soak the landscape. Landslides can be easily triggered by human activity like farming or construction, and coastal cliffs are also vulnerable.

“Kerala is an area with extensive chemical weathering and deep soils leading to a parent material that is easily moved by landslides,” says Scott Burns. The Portland State University professor, who wrote the atlas foreward, is also president of the International Association for Engineering Geology and the Environment.

“Loss of property and loss of life are two main problems that people of the region are faced with,” Burns writes, adding that “local inhabitants and decision makers can see where the largest chances of landslides can occur in each region with these outstanding maps.”

GIS-TISSA

The atlas includes a districtwide landslide susceptibility map, which notes key influencing risk factors, major landslides and descriptions of where they occurred, along with large engineering projects taking place.

Oommen and Sajinkumar compiled all of the maps using a new tool called GIS-TISSA. TISSA stands for Tool for Infinite Slope Stability Analysis and was developed within a GIS environment. The program’s algorithms calculate how different factors interact with one another and assess the landslide vulnerability of an area.

GIS-TISSA uses Python to interface with one of the most widely used geospatial tools in the world: ArcGIS. It will help the geospatial community evaluate landslide hazards caused by rainfall and earthquakes through a GIS tool they are already comfortable using. Oommen’s graduate student Jonathan Sanders and postdoctoral fellow Rudiger Escobar-Wolf also contributed to GIS-TISSA development.

The Landslide Atlas of Kerala sets a new standard for determining risk in a landslide-prone region and will help the residents and policymakers of the state make decisions to better mitigate life-threatening disasters.

Michigan Tech students took home top honors — the Artemis Award — in NASA’s Breakthrough, Innovative and Game-changing (BIG) Idea Challenge.

Students from Michigan Technological University want to shine a light on the darkest places of the moon. Their design, a rover called Tethered permanently shadowed Region EXplorer (T-REX), deploys a lightweight, superconducting cable to keep other lunar rovers powered and provide wireless communication as they operate in the extreme environments of the moon’s frigid, lightless craters.

Eight university teams competed in the BIG Idea Challenge for 2020, called the Lunar PSR Challenge. The goal? Demonstrating different technologies and designs to study and explore the moon’s permanently shadowed regions (PSRs), which NASA officials note are a formidable challenge for space exploration.

“Think about T-REX as a recharging station and comms tower in a small, portable package,” said Marcello Guadagno, Michigan Tech’s student lead on the project. “The whole time we were holding our breath and cheered when our team was announced as the winner of the competition. This was a major victory for our lab, which was only just founded in 2019.”

NASA awarded nearly $1 million through the BIG Idea grant in February 2020, including $162,637 to the Michigan Tech team. Then the pandemic hit.

“When we think about tenacity, one of our University’s core values, it was important to keep everyone healthy and still move forward with the project,” said Paul Van Susante, assistant professor of mechanical engineering at Michigan Tech and the T-REX team’s faculty adviser. “The pandemic required us to adapt and overcome, and the team rose magnificently to that challenge.”

As the NASA press release notes, “Studying permanently shadowed regions in or near the Moon’s poles could help improve understanding of the Moon’s history and composition. When NASA lands the first woman and next man at the Moon’s South Pole with the Artemis program, new technologies will be needed to allow astronauts to live and work on the Moon for extended missions.”

In addition to the Artemis Award, Michigan Tech’s team received multiple peer awards: the Fly Me to the Moon award, after other university teams voted that Michigan Tech’s team was most likely to go to the moon, and the Above and Beyond award. (As Guadagno puts it, “we broke things and then unbroke them.”) The T-REX crew also got the Welcome Llama for being the most inviting team: Specifically, at the start of the final presentation, some of the Northeastern students accidentally stayed on long, so the Michigan Tech team welcomed them as new Huskies.

The team is part of the “Husky Works” Planetary Surface Technology Development Lab and Van Susante jokes that their work was fueled by a lab stockpile of candy and popsicles. Mostly undergraduates and the youngest team in the competition, the experience has encouraged many of the team members to pursue master’s and doctoral degrees.

Guadagno says the team’s hard work, sugar consumption and creativity has paid off. “This technology can play a key role in enabling a sustainable human presence on the Moon,” he said. “We are proud to be part of the Artemis Generation.”

A virus attaches to a cell, picks the lock and enters, then takes control of genetic production and pumps out many versions of itself that explode out through the cell wall.

Get your popcorn. Engineers and virologists have a new way to watch viral infection go down.

The technique uses microfluidics — the submillimeter control of fluids within a precise, geometric structure. On what is basically a tricked-out microscope slide, chemical engineers from Michigan Technological University have been able to manipulate viruses in a microfluidic device using electric fields. The study, published this summer in Langmuir, looks at changes in the cell membrane and gives researchers a clearer idea of how antivirals work in a cell to stop the spread of infection.

Viral Infection Starts with the Capsid

Viruses carry around an outer shell of proteins called a capsid. The proteins act like a lockpick, attaching to and prying open a cell’s membrane. The virus then hijacks the cell’s inner workings, forcing it to mass produce the virus’s genetic material and construct many, many viral replicas. Much like popcorn kernels pushing away the lid of an overfilled pot, the new viruses explode through the cell wall. And the cycle continues with more virus lockpicks on the loose.

“When you look at traditional techniques — fluorescent labeling for different stages, imaging, checking viability — the point is to know when the membrane is compromised,” said Adrienne Minerick, study co-author, dean of the College of Computing and a professor of chemical engineering. “The problem is that these techniques are an indirect measure. Our tools look at charge distribution, so it’s heavily focused on what’s happening between the cell membrane and virus surface. We discovered with greater resolution when the virus actually goes into the cell.”

Dielectrophoresis: Charged Conversation

Watching the viral infection cycle and monitoring its stages is crucial for developing new antiviral drugs and gaining better understanding of how a virus spreads. Dielectrophoresis happens when polarizable cells get pushed around in a nonuniform electric field. The movement of these cells is handy for diagnosing diseases, blood typing, studying cancer and many other biomedical applications. When applied to studying viral infection, it’s important to note that viruses have a surface charge, so within the confined space in a microfluidic device, dielectrophoresis reveals the electric conversation between the virus capsid and the proteins of a cell membrane.

“We studied the interaction between the virus and cell in relation to time using microfluidic devices,” said Sanaz Habibi, who led the study as a doctoral student in chemical engineering at Michigan Tech. “We showed we could see time-dependent virus-cell interactions in the electric field.”

Watching a viral infection happen in real time is like a cross between a zombie horror film, paint drying and a Bollywood epic on repeat. The cells in the microfluidic device dance around, shifting into distinct patterns with a dielectric music cue. There needs to be the right ratio of virus to cells to watch infection happen — and it doesn’t happen quickly. Habibi’s experiment runs in 10-hour shifts, following the opening scenes of viral attachment, a long interlude of intrusion, and eventually the tragic finale when the new viruses burst out, destroying the cell in the process.

Before they burst, cell membranes form structures called blebs, which change the electric signal measured in the microfluidic device. That means the dielectrophoresis measurements grant high-resolution understanding of the electric shifts happening at the surface of the cell through the whole cycle.

Enter the Osmolyte

Viral infections are top of mind right now, but not all viruses are the same. While microfluidic devices that use dielectrophoresis could one day be used for on-site, quick testing for viral diseases like COVID-19, the Michigan Tech team focused on a well-known and closely studied virus, the porcine parvovirus (PPV), which infects kidney cells in pigs.

But then the team wanted to push the envelope: They added the osmolyte glycine, an important intervention their collaborators study in viral surface chemistry and vaccine development.

“Using our system, we could show time-dependent behavior of the virus and cell membrane. Then we added the osmolyte, which can act as an antiviral compound,” Habibi explained. “We thought it would stop the interaction. Instead, it looked like the interaction continued to happen at first, but then the new viruses couldn’t get out of the cell.”

That’s because glycine likely interrupts the new capsid formation for the replicated viruses within the cell itself. While that specific portion of the viral dance happens behind the curtain of the cell wall, the dielectric measurements show a shift between an infected cycle where capsid formation happens and an infected cell where capsid formation is interrupted by glycine.  This difference in electrical charge indicates that glycine prevents the new viruses from forming capsids and stops the would-be viral lockpickers from hitting their targets.

“When you are working with such small particles and organisms, when you’re able to see this process happening in real time, it’s rewarding to track those changes,” Habibi said.

This new view of the interactions between virus capsids and cell membranes could speed up testing and characterizing viruses, cutting out expensive and time-consuming imaging technology. Perhaps in a future pandemic, there will be point-of-care, handheld devices to diagnose viral infections and we can hope medical labs will be outfitted with other microfluidic devices that can quickly screen and reveal the most effective antiviral medications.

Original Article: https://www.mtu.edu/news/stories/2020/october/microfluidics-helps-engineers-watch-viral-infection-in-real-time.html

There’s a method to modeling cracking in brittle materials.

The strength of teeth is told on the scale of millimeters. Porcelain smiles are kind of like ceramics — except that while china plates shatter when smashed against each other, our teeth don’t, and it’s because they are full of defects. 

Those defects are what inspired the latest paper led by Susanta Ghosh, assistant professor in the Department of Mechanical Engineering-Engineering Mechanics. The research came out recently in the journal Mechanics of Materials. Along with a team of dedicated graduate students — Upendra Yadav, Mark Coldren and Praveen Bulusu — and fellow mechanical engineer Trisha Sain, Ghosh examined what’s called the microarchitecture of brittle materials like glass and ceramics.

“Since the time of alchemists people have tried to create new materials,” Ghosh said. “What they did was at the chemical level and we work at the microscale. Changing the geometries — the microarchitecture — of a material is a new paradigm and opens up many new possibilities because we’re working with well-known materials.”

Shatterproof Glass

Stronger glass brings us back to teeth — and seashells. On the micro level, the primary hard and brittle components of teeth and shells have weak interfaces or defects. These interfaces are filled with soft polymers. As teeth gnash and shells bump, the soft spots cushion the hard plates, letting them slide past one another. Under further deformation, they get interlocked like hook-and-loop fasteners or Velcro, thus carrying huge loads. But while chewing, no one would be able to see the shape of a tooth change with the naked eye. The shifting microarchitecture happens on the scale of microns, and its interlocking structure rebounds until a sticky caramel or rogue popcorn kernel pushes the sliding plates to the breaking point.

That breaking point is what Ghosh studies. Researchers in the field have found in experiments that adding small defects to glass can increase the strength of the material 200 times over. That means that the soft defects slow down the failure, guiding the propagation of cracks, and increasing the energy absorption in the brittle material.

“The failure process is irreversible and complicated because the architectures that trap the crack through a predetermined path can be curved and complex,” Ghosh said. “The models we work with try to describe fracture propagation and the contact mechanics at the interface between two hard-brittle building blocks.”

Finite Element Method

Microarchitecture patterns in nature cut their teeth on an evolutionary timeline. Materials scientists and engineers work in shorter spans, so they are developing tools to figure out the best defects and their ideal geometries. Finite element method (FEM) is one such technique.

FEM is a numerical model that takes apart a complex whole by evaluating separate pieces — called finite elements — then puts everything back together again using the calculus of variations. Humpty Dumpty and all the king’s men would have liked FEM, but it’s no quick roadside trick. To run such complex calculations requires a supercomputer, like Superior at Michigan Tech, and ensuring that the right inputs get plugged in takes diligence, patience, and a keen eye for coding detail. Using FEM for super strong glass means modeling all the possible interactions between the material’s hard plates and soft spots.

Ghosh and his team use several models to study how cracks form in glass; this animation reveals how a crack can be contained within a softer defect until it reaches the breaking point in the more brittle materials. Credit: Susanta Ghosh

Analytical Modeling

Ghosh and his team recognized that although FEM provides accurate solutions, it is time consuming and not suitable when working with a large number of models. So, they came up with an alternative.

“We wanted a simple, approximate model to describe the material,” he said, explaining the team used more basic math equations than the FEM calculations to outline and describe the shapes within the material and how they might interact. “Of course, an experiment is the ultimate test, but more efficient modeling helps us speed up the development process and save money by focusing on materials that work well in the models.”

Both the FEM and analytical microarchitecture modeling from Ghosh’s lab can help make ceramics, biomedical implants and the glass in buildings as tough as our teeth.

Boron nitride nanotubes (BNNT), studied by physicists at Michigan Technological University, encase tellurium atomic chains like a straw, which could be controllable by light and pressure. In collaboration with researchers from Purdue University, Washington University and University of Texas at Dallas, the team published their findings in Nature Electronics this week.

As demand for smaller and faster devices grows, scientists and engineers turn to materials with properties that can deliver when existing ones lose their punch or can’t shrink enough.

For wearable tech, electronic cloth or extremely thin devices that can be laid over the surface of cups, tables, space suits and other materials, researchers have begun to tune the atomic structures of nanomaterials. The materials they test need to bend as a person moves, but not go all noodly or snap, as well as hold up under different temperatures and still give enough juice to run the software functions users expect out of their desktops and phones. We’re not quite there with existing or preliminary technology — yet.

Yoke Khin Yap has studied nanotubes and nanoparticles — discovering the quirks and promises of their quantum mechanical behaviors. He pioneered using electrically insulating nanotubes for electronics by adding gold and iron nanoparticles on the surface of BNNTs. The metal-nanotube structures enhanced the material’s quantum tunneling, acting like atomic steppingstones that could help electronics escape the confines of silicon transistors that power most of today’s devices. More recently, his group also created atomically thin gold clusters on BNNTs. As implied by the “tube” of their nanostructure, BNNTs are hollow in the middle. They’re highly insulating and as strong and bendy as an Olympic gymnast.

That made them a good candidate to pair with another material with great electrical promise: tellurium. Strung into atom-thick chains, which are very thin nanowires, and threaded through the hollow center of BNNTs, tellurium atomic chains become a tiny wire with immense current-carrying capacity.   

“Without this insulating jacket, we wouldn’t be able to isolate the signals from the atomic chains. Now we have the chance to review their quantum behavior,” Yap said. “The is the first time anyone has created a so-called encapsulated atomic chain where you can actually measure them. Our next challenge is to make the boron nitride nanotubes even smaller.”

A bare nanowire is kind of a loose cannon. Controlling its electric behavior — or even just understanding it — is difficult at best when it’s in rampant contact with flyaway electrons. Nanowires of tellurium, which is a metalloid similar to selenium and sulfur, is expected to reveal different physical and electronic properties than bulk tellurium. Researchers just needed a way to isolate it, which BNNTs now provide.

“This tellurium material is really unique. It builds a functional transistor with the potential to be the smallest in the world,” said Peide Ye, the lead researcher from Purdue University, explaining that the team was surprised to find through transmission electron microscopy at the University of Texas at Dallas that the atoms in these one-dimensional chains wiggle.  “Silicon atoms look straight, but these tellurium atoms are like a snake. This is a very original kind of structure.”

The tellurium-BNNT nanowires created field-effect transistors only 2 nanometers wide; current silicon transistors on the market are between 10 to 20 nanometers wide. The new nanowires current-carrying capacity reached 1.5×108 A cm-2, which also beats out most semiconducting nanowires. Once encapsulated, the team assessed the number of tellurium atomic chains held within the nanotube and looked at single and triple bundles arranged in a hexagonal pattern. Additionally, the tellurium-filled nanowires are sensitive to light and pressure, another promising aspect for future electronics. The team also encased the tellurium nanowires in carbon nanotubes, but their properties are not measurable due to the conducting or semiconducting nature of carbon.

While tellurium nanowires have been captured within BNNTs, like a firefly in a jar, much of the mystery remains. Before people begin sporting tellurium T-shirts and BNNT-laced boots, the nature of these atomic chains needs characterizing before its full potential for wearable tech and electronic cloth can be realized.

Historically, as in decades ago, rechargeable lithium metal batteries were dangerous. These batteries were quickly abandoned in favor of Li-ion batteries which contain no metallic lithium and are now widely used. In efforts to continue to drive energy density up and costs down, we are again exploring how to efficiently and safely use lithium metal in batteries. Solid state batteries, free of flammable liquids, may be the solution.  However, progress has been slowed because lithium metal still finds a way to short circuit the battery and limit cycle life.

Solid-state lithium batteries are the Holy Grail of energy storage. With potential impacts on everything from personal mobile devices to industrial renewable energy, the difficulties are worth overcoming. The goal: Build a safe and long lived lithium battery. The challenge: Use a solid-state electrolyte and stop short circuiting from the formation and growth of lithium dendrites.

In a new invited feature paper published in the Journal of Materials Research, materials engineers from Michigan Technological University weigh in on the problem. Their take is an unusual one. They focus on the unique mechanics of lithium at dimensions that are a fraction of the diameter of the hair on your head — much smaller scales than most others consider.

“People think of lithium as being soft as butter, so how can it possibly have the strength to penetrate through a ceramic solid electrolyte separator?” asked Erik Herbert, assistant professor of materials science and engineering at Michigan Tech and one of the study’s leads. He says the answer is not intuitive — smaller is stronger. Tiny physical defects like micro cracks, pores or surface roughness inevitably exist at the interface between a lithium anode and a solid electrolyte separator. Zooming in on the mechanics of lithium metal at length scales commensurate with those tiny interface defects, it turns out that lithium is much stronger than it is at macroscopic or bulk length scales.

“Lithium doesn’t like stress any more than you or I like stress, so it’s just trying to figure out how to make the pressure go away,” Herbert said. “What we’re saying is that at small length scales, where the lithium is not likely to have access to the normal mechanism it would use alleviate pressure, it has to rely on other, less efficient methods to relieve the stress.”

In every crystalline metal like lithium, atomic level defects called dislocations are needed to relieve significant amounts of stress. At macroscopic or bulk length scales, dislocations get rid of stress efficiently because they allow adjacent planes of atoms to easily slide past one another like a deck of cards. However, at small length scales and high temperatures relative to the metal’s melting point, the chance of finding dislocations within the stressed volume is very low. Under these conditions, the metal has to find another way to relieve the pressure. For lithium, that means switching to diffusion. The stress pushes lithium atoms away from the stressed volume – akin to being carried away on an atomic airport walkway. Compared to dislocation motion, diffusion is very inefficient. That means at small length scales, where diffusion controls stress relief rather than dislocation motion, lithium can support more than 100 times more stress or pressure than it can at macroscopic length scales.

Catastrophic problems may occur in what Herbert and his co-lead, MTU professor Stephen Hackney, call the defect danger zone. The zone is a window of physical defect dimensions defined by the stress relief competition between diffusion and dislocation motion. The worst-case scenario is a physical interface defect (a micro crack, pore or surface roughness) that is too big for efficient stress relief by diffusion but too small to enable stress relief by dislocation motion. In this reverse Goldilocks problem, high stresses within the lithium can cause the solid electrolyte and the whole battery to catastrophically fail. Interestingly, the danger zone size is the same size as the observed lithium dendrites.

“The very thin solid-state electrolytes and high current densities required to provide the battery power and short charging times expected by consumers are conditions that favor lithium dendrite failure, so the dendrite problem must be solved for the technology to progress,” Hackney said. “But to make the solid-state technology viable, the power capability and cycle life limitations must be addressed. Of course, the first step in solving the problem is to understand the root cause, which is what we are trying to do with this current work.”

Hackney points out that the smaller is stronger concept is not new. Materials engineers have studied length scale effect on mechanical behavior since the 1950s, though it has not been widely used in considering the lithium dendrite and solid electrolyte problem.

“We think this ‘smaller is stronger’ paradigm is directly applicable to the observed lithium dendrite size, and is confirmed by our experiments on very clean, thick Li films at strain rates relevant to the initiation of the dendrite instability during charging,” Hackney said.

To rigorously examine their hypothesis, Herbert and Hackney perform nanoindentation experiments in high purity lithium films that are produced by a top battery researcher, Nancy Dudney of the Oak Ridge National Laboratory.

“The bulk properties of lithium metal are well characterized, but this may not be relevant at the scale of defects and inhomogeneous current distributions likely acting in very thin solid state batteries,” Dudney said. “The model presented in this paper is the first to map conditions where the much stronger lithium will impact cyclelife performance.  This will guide future investigation of solid electrolytes and battery designs.”

Among the team’s next steps, they plan to examine the effects of temperature and electrochemical cycling on the mechanical behavior of lithium at small length scales. This will help them better understand real-world conditions and strategies to make next-generation batteries immune to the formation and growth of lithium dendrites.