Category Archives: Features

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Inspired by nature—Getting underwater robots to work together, continuously

Nina Mahmoudian, Mechanical Engineering-Engineering Mechanics
Nina Mahmoudian, Mechanical Engineering-Engineering Mechanics

Imagine deploying multiple undersea robots, all in touch and working together for months, even years, no matter how rigorous the mission, brutal the environment, or extreme the conditions.

It is possible, though not quite yet. “Limited energy resources and underwater communication are the biggest issues,” says Michigan Tech Researcher Nina Mahmoudian. Grants from a National Science Foundation CAREER Award and the Young Investigator Program from the Office of Naval Research are helping Mahmoudian solve those issues and pursue her ultimate goal: the persistent operation of undersea robots.

“Autonomous underwater vehicles (AUVs) are becoming more affordable and accessible to the research community,” she says. “But we still need multipurpose long-lasting AUVs that can adapt to new missions quickly and easily.”

Mahmoudian has already developed a fleet of low-cost, underwater gliders, ROUGHIEs, to do just that. Powered by batteries, they move together through the water simply by adjusting their buoyancy and weight. Each one weighs about 25 pounds. “ROUGHIE, by the way, stands for Research-Oriented Underwater Glider for Hands-on Investigative Engineering,” adds Mahmoudian.

“My most exciting observation was a Beluga mother and calf swimming together. It’s very similar to our recharge on-the-fly concept.”

Nina Mahmoudian

“The ROUGHIE’s open control architecture can be rapidly modified to incorporate new control algorithms and integrate novel sensors,” she explains. “Components can be serviced, replaced, or rearranged in the field, so scientists can validate their research in situ.” Research in underwater control systems, communication and networking, and cooperative planning and navigation all stand to gain.

Mahmoudian observes Mother Nature to design robotic systems. “There is so much to learn,” she says. “My most exciting observation was a Beluga mother and calf swimming together. It’s very similar to our recharge on-the-fly concept. The technology is an early stage of development.”

Mahmoudian’s students apply and implement their algorithms on real robots and test them in real environments. They also give back to the community, by teaching middle school students how to design, build, and program their own low-cost underwater robots using a simple water bottle, called a GUPPIE.

“As a girl growing up, I first thought of becoming an architect,” says Mahmoudian. “Then, one day I visited an exhibition celebrating the 30th anniversary of space flight. That’s when I found my passion.” Mahmoudian went on to pursue aerospace engineering in Iran, and then graduate studies at Virginia Tech in the Department of Aerospace and Ocean Engineering. “Underwater gliders share the same physical concepts as airplanes and gliders, but deal with different fluid density and interactions,” she says.

Now at Michigan Tech, Mahmoudian’s work advances the abilities of unmanned robotic systems in the air, on land, and under sea. “Michigan Tech has easy access to the North Woods and Lake Superior—an ideal surrogate environment for testing the kind of autonomous systems needed for long term, challenging expeditions, like Arctic system exploration, or searching for signs of life on Europa, Jupiter’s moon.” She developed the Nonlinear and Autonomous Systems Laboratory (NAS Lab) in 2011 to address challenges that currently limit the use of autonomous vehicles in unknown, complex situations.

More than scientists and engineers, Mahmoudian wants simple, low-cost AUV’s to be available to anyone who may need one. “I envision communities in the Third World deploying low-cost AUVs to test and monitor the safety and quality of the water they use.”

Demand dispatch—Balancing power in the grid in a nontraditional way

According to the National Renewable Energy Lab (NREL), distributed energy resources like these photovoltaic (PV) systems in a Boulder neighborhood—especially when they are paired with on-site storage—may eventually make large centralized power plants obsolete. Photo Credit: Topher Donahue
According to the National Renewable Energy Lab (NREL), distributed energy resources like these photovoltaic (PV) systems in a Boulder neighborhood—especially when they are paired with on-site storage—may eventually make large centralized power plants obsolete. Photo Credit: Topher Donahue

Traditionally, in the electric power grid, generation follows electric power consumption, or demand. Instantaneous fluctuation in demand is primarily matched by controlling the power output of large generators.

Sumit Paudyal, Electrical & Computer Engineering
Sumit Paudyal, Electrical & Computer Engineering

As renewable energy sources including solar and wind power become more predominant, generation patterns have become more random. Finding the instantaneous power balance in the grid is imperative. Demand dispatch—the precise, direct control of customer loads—makes it possible.

Michigan Tech researcher Sumit Paudyal and his team are developing efficient real-time control algorithms to aggregate distributed energy resources, and coordinate them with the control of the underlying power grid infrastructure.

“Sensors, smart meters, smart appliances, home energy management systems, and other smart grid technologies facilitate the realization of the demand dispatch concept,” Paudyal explains.

“The use of demand dispatch has promising potential in the US, where it is estimated that one-fourth of the total demand for electricity could be dispatchable using smart grid technologies.”

Sumit Paudyal

Coordination and control in real time is crucial for the successful implementation of demand dispatch on a large scale. “Our goal is to enable control dispatch distributed resources for the very same grid-level applications—frequency control, regulation, and load following—traditionally provided by expensive generators,” adds Paudyal.
“We have solved the demand dispatch problem of thermostatically-controlled loads in buildings and electric vehicle loads connected to moderate-size power distribution grids. The inherent challenge of the demand dispatch process is the computational complexity arising from the real-time control and coordination of hundreds to millions of customer loads in the system,” he adds. “We are now taking a distributed control approach to achieve computational efficiency in practical-sized, large-scale power grids.”

Vital signs—Powering heart monitors with motion artifacts

Electrocardiogram research Ye Sarah Sun

More than 90 percent of US medical expenditures are spent on caring for patients who cope with chronic diseases. Some patients with congestive heart failure, for example, wear heart monitors 24/7 amid their daily activities.

Ye Sarah Sun
Ye Sarah Sun, Mechanical Engineering-Engineering Mechanics

Michigan Tech researcher Ye Sarah Sun develops new human interfaces for heart monitoring. “There’s been a real trade-off between comfort and signal accuracy, which can interfere with patient care and outcomes,” she says. Sun’s goal is to provide a reliable, personalized heart monitoring system that won’t disturb a patient’s life. “Patients need seamless monitoring while at home, and also while driving or at work,” she says.

Sun has designed a wearable, self-powered electrocardiogram (ECG) heart monitor. “ECG, a physiological signal, is the gold standard for diagnosis and treatment of heart disease, but it is a weak signal,” Sun explains. “When monitoring a weak signal, motion artifacts arise. Mitigating those artifacts is the greatest challenge.”

Sun and her research team have discovered and tapped into the mechanism underlying the phenomenon of motion artifacts. “We not only reduce the in uence of motion artifacts but also use it as a power resource,” she says.

Their new energy harvesting mechanism provides relatively high power density compared with traditional thermal and piezoelectric mechanisms. Sun and her team have greatly reduced the size and weight of an ECG monitoring device compared to a traditional battery-based solution. “The entire system is very small,” she says, about the size of a pack of gum.

“We not only reduce the influence of motion artifacts but also use it as a power resource.”

Ye Sarah Sun

Unlike conventional clinical heart monitoring systems, Sun’s monitoring platform is able to acquire electrophysiological signals despite a gap of hair, cloth, or air between the skin and the electrodes. With no direct contact to the skin, users can avoid potential skin irritation and allergic contact dermatitis, too—something that could make long-term monitoring a lot more comfortable.

Ye Sarah Sun self-powered ECG heart monitor
Sun’s self-powered ECG heart monitor works despite a gap of hair, cloth or air between the user’s skin and the electrodes.

Where rubber becomes the road—Testing sustainable asphalt technologies

Zhanping You research team
A Michigan Tech research team led by Zhanping You tests a new, cooler way to make rubberized asphalt.

Over 94% of the roads in the United States are paved with asphalt mix. Each year, renovating old highways with new pavement consumes about 360 million tons of raw materials. It also generates about 60 million tons of old pavement waste and rubble.

Zhanping You, Civil & Environmental Engineering
Zhanping You, Civil & Environmental Engineering

Recycling these waste materials greatly reduces the consumption of neat, unmodified asphalt mix and lowers related environmental pollution. But blending recycled asphalt pavement (RAP) with fresh asphalt mix presents several challenges, potentially limiting its usefulness.

Not to Michigan Tech researcher Zhanping You. “One noticeable issue of using RAP in asphalt pavement is the relatively weaker bond between the RAP and neat asphalt, which may cause moisture susceptibility,” he explains. “Modifying the asphalt mix procedure and selecting the proper neat asphalt can effectively address this concern.”

You tests a variety of recycled materials to improve asphalt pavement performance. Crumb rubber, made from scrap tires, is one such material. “Crumb rubber used in asphalt reduces rutting and cracks, extends life, and lowers noise levels. Another plus—building one mile of road with crumb rubber uses up to 2,000 scrap tires. Hundreds of millions of waste tires are generated in the US every year,” he adds.

Adding crumb rubber to asphalt mix has its own share of problems. “When crumb rubber is blended into asphalt binder, the stiffness of the asphalt binder is increased. A higher mixing temperature is needed to preserve the flowability. Conventional hot-mix asphalt uses a lot of energy and releases a lot of fumes. We use a foaming process at lower temperatures that requires less energy and reduces greenhouse gas emissions.”

“Building one mile of road with crumb rubber uses up to 2,000 scrap tires. Hundreds of millions of waste tires are generated in the US every year.”

—Zhanping You

You and his team integrate state-of-the-art rheological and accelerated-aging tests, thermodynamics, poromechanics, chemical changes, and multiscale modeling to identify the physical and mechanical properties of foamed asphalt materials. With funding from the Michigan Department of Environmental Quality, they have constructed test sections of road in two Michigan counties to monitor field performance.

Another possible solution is asphalt derived from biomass. You’s team used bio oil in asphalt and found it improved pavement performance. They’re also investigating nanomaterial-modified asphalt. “Soon we’ll have mix recipes to adapt to all environmental and waste supply streams,” he says.

The holy grail of energy storage—Solving the problems of lithium anodes

Samsung exploded phone
A damaged Samsung Galaxy Note 7 after its lithium battery caught fire. Photo Credit: Shawn L. Minter, Associated Press

State-of-the-art mechanical characterization of pure lithium metal, performed at submicron-length scales, provides signifcant physical insight into critical factors that limit the performance of next generation energy storage devices.

Erik Herbert, Michigan Tech
Erik Herbert, Materials Science & Engineering

Compared to competing technology platforms, a pure lithium anode potentially offers the highest possible level of volumetric and gravimetric energy density. Gradual loss of lithium over the cycle life of a battery prevents the full fruition of this energy technology.

Michigan Tech researchers Erik Herbert, Stephen Hackney, and their collaborators at Oak Ridge National Laboratory and the University of Michigan are investigating the behavior of a lithium anode accessed through, and protected by, polycrystalline superionic solid electrolytes. Their goals: Mitigate the loss of lithium; prevent dangerous side reactions; and enable safe, long-term, and high-rate cycling performance.

“We want to maintain efficient cycling of lithium in a battery over many cycles, something that’s never been done before,” says Herbert. “The fundamental challenge is figuring out how to maintain a coherent interface between the lithium anode and the solid electrolyte. Defects formed in the lithium during cycling determine the stability and resistivity of the interface. Once we see how that happens, it will reveal design rules necessary to successfully fabricate the solid electrolyte, and the battery packaging.”

The team is launching parallel efforts to address these issues. Herbert, for his part, wants to learn exactly how lithium is consumed on a nanoscale level, in real time. “We want to know why the interface becomes increasingly resistive with cycling, how the electrolyte eventually fails, how defects in the lithium migrate, agglomerate, or anneal with further cycling or time, and whether softer electrolytes can be used without incursion of metallic lithium into the electrolyte,” he says. “We also want to learn how processing and fabrication affect interface performance.”

“We want to maintain efficient cycling of lithium in a battery over many cycles, something that’s never been done before.”

Erik Herbert

polycrystalline lithium film
Surface of the polycrystalline lithium film, with over 100 residual impressions from targeted test sites

To answer these questions, Herbert conducts nano-indentation studies on vapor-deposited lithium films, various sintered solid electrolytes, and lithium films in fully functional solid-state batteries.

“The data from these experiments directly enable exam-ination of the complex coupling between lithium’s micro-structure, its defects, and its mechanical behavior,” says Herbert. “So far we’ve gained a better understanding of the mechanisms lithium utilizes to manage pressure (stress) as a function of strain, strain rate, temperature, defect structure, microstructural length scale, and in-operando cycling of the battery.”

Phosphorus eaters—Using bacteria to purify iron ore

eiseleresearchMany iron ore deposits around the world are extensive and easy to mine, but can’t be used because of their high phosphorus content. Phosphorus content in steel should generally be less than 0.02 percent. Any more and steel becomes brittle and difficult to work. 

Tim Eisele
Tim Eisele
Chemical Engineering

Beneficiation plant processing, which treats ore to make it more suitable for smelting, only works if the phosphorus mineral grains are bigger than a few micrometers in size. Often, phosphorus is so finely disseminated through iron ore that grinding and physically separating out the phosphorus minerals is impractical.

Michigan Tech researcher Tim Eisele is developing communities of live bacteria to inexpensively dissolve phosphorus from iron ore, allowing a low-phosphorus iron concentrate to be produced. “For finely dispersed phosphorus, until now, there really hasn’t been a technology for removing it,” he says.

Phosphorus is critical to all living organisms. Eisele’s experiments are designed so that organisms can survive only if they are carrying out phosphorus extraction. He uses phosphorus-free growth media.

“We’ve confirmed that when there is no iron ore added to the media, there is no available phosphorus and no bacterial growth.”

Tim Eisele

Eisele is investigating two approaches, one using communities of aerobic organisms to specifically attack the phosphorus, and another using anaerobic organisms to chemically reduce and dissolve the iron while leaving the phosphorus behind. He obtained organisms from local sources—his own backyard, in fact, where natural conditions select for the types of organisms desired. Eisele originally got the idea for this approach as a result of the high iron content of his home well water, caused by naturally-occuring anaerobic iron-dissolving organisms.

On the right, anaerobic bacteria dissolve iron in the ferrous state. On the left, recovered electrolytic iron.
In the beaker on the right, anaerobic bacteria dissolve iron in the ferrous state. On the left, recovered electrolytic iron.

Eisele cultivates anaerobic and aerobic organisms in the laboratory to fully adapt them to the ore. “We use mixed cultures of organisms that we have found to be more effective than pure cultures of a single species of organism. Using microorganism communities will also be more practical to implement on an industrial scale, where protecting the process from contamination by outside organisms may be impossible.”

Verification and validation—Predicting uncertainties early on

Shabakhti Research

Mahdi Shabakhti
Mahdi Shahbakhti
Mechanical Engineering–Engineering Mechanics

The verification and validation (V&V) process for a typical automotive vehicle and powertrain electronic control unit takes approximately two years, and costs several million dollars. V&V are essential stages in the design cycle of an industrial controller, there to remove any gap between the designed and implemented controller. Computer modeling has brought about improvements over the years, but the gap remains.

Michigan Tech researcher Mahdi Shahbakhti has made significant progress to remove that gap, using system models to easily verify controller design. His solution features an adaptive sliding mode controller (SMC) that helps the controller deal with imprecisions in the implementation of the system.

The research is funded by the National Science Foundation GOALI program, or Grant Opportunities for Academic Liaison with Industry. Shahbakhti’s team and fellow researchers from the University of California, Berkeley, and Toyota USA in Ann Arbor, Michigan are nearing the end of their three-year collaborative GOALI project.

“Analog-to-digital conversion (ADC) is one of the main sources of controller implementation imprecisions, mostly due to sampling and quantization,” says Shahbakhti. “Our approach mitigates ADC imprecisions by first identifying them in the early stages of the controller design cycle. We first developed a mechanism for real-time prediction of uncertainties due to ADC and then determined how those uncertainties propagated through the controller. Finally we incorporated those predicted uncertainties into the discrete sliding mode controller (DSMC) design.”

“Analog-to-digital conversion (ADC) is one of the main sources of controller implementation imprecisions, mostly due to sampling and quantization.”

Mahdi Shahbakhti

Shahbakhti and his team tested an actual electronic control unit at Michigan Tech in a real time processor-in-the-loop setup. Their approach significantly improved controller robustness to ADC imprecisions when compared to a baseline sliding controller. In a case study controlling the engine speed and air-fuel ratio of a spark ignition engine, the DSMC design with predicted uncertainty provided a 93 percent improvement compared to a baseline sliding controller.

Toyota works closely with the research team to integrate GOALI project results into the design cycle for its automotive controllers. The company provided team members with an initial week of training on its V&V method of industrial controllers, and also participates with Shabakhti’s team in online biweekly meetings. “The concept of this project is fundamental and generic—it can be applied to any control system, but complex systems, such as those in automotive applications, will benefit most,” notes Shahbakhti.

What’s in the air? Understanding long-range transport of atmospheric arsenic

Coal-fired power plant on the Navajo Nation near Page, Arizona
Coal-fired power plant on the Navajo Nation near Page, Arizona

Once emitted into the atmosphere, many air pollutants are transported long distances, going through a series of chemical reactions before falling back to the Earth’s surface. This makes air pollution not just a local problem, but a regional and a global one.

Shiliang Wu
Shilliang Wu, Geological & Mining Engineering & Sciences, Civil & Environmental Engineering

“If you’d been living in London in December 1952, you’d probably remember what air pollution can do—in just a couple of weeks, a smog event killed thousands of people,” says Michigan Tech researcher Shilliang Wu.

“Today, photos of air pollution in China and India flood the Internet,” he adds. “Air pollution remains a significant challenge for the sustainability of our society, with detrimental effects on humans, animals, crops, and the ecosystem as a whole.”

An assistant professor with a dual appointment in Geological and Mining Engineering and Sciences, and Civil and Environmental Engineering, Wu examines the impacts of human activities on air quality, along with the complicated interactions between air quality, climate, land use, and land cover. Using well-established global models, he investigates a wide variety of pollutants including ozone, nitrogen oxides, volatile organic compounds, aerosols, mercury, and arsenic.

Wu’s research team recently developed the first global model to simulate the sources, transport, and deposition of atmospheric arsenic including source-receptor relationships between various regions. They were motivated by a 2012 Consumer Reports magazine study, which tested more than 200 samples of rice products in the US and found that many of them, including some organic products and infant rice cereals, contained highly toxic arsenic at worrisome levels.

“Our results indicate that reducing anthropogenic arsenic emissions in Asia and South America can significantly reduce arsenic pollution not only locally, but globally.”

Shilliang Wu

“Our model simulates arsenic concentrations in ambient air over many sites around the world,” says Wu. “We have shown that arsenic emissions from Asia and South America are the dominant sources of atmospheric arsenic in the Northern and Southern Hemispheres, respectively. Asian emissions are found to contribute nearly 40 percent of the total arsenic deposition over the Arctic and North America. Our results indicate that reducing anthropogenic arsenic emissions in Asia and South America can significantly reduce arsenic pollution not only locally, but globally.”

Wu’s model simulation is not confined to any region or time period. “We can go back to the past or forward to the future; we can look at any place on Earth. As a matter of fact, some of my colleagues have applied the same models to Mars,” he says, adding: “In any case, the atmosphere is our lab, and we are interested in everything in the air.”


Accelerated healing—Understanding physical and chemical cues in tissue repair

Rajachar Research

Rupak Rajachar
Rupak Rajachar
Biomedical Engineering

Made of fibrous connective tissue, tendons attach muscles to bones in the body, transferring force when muscles contract. But tendons are especially prone to tearing. Achilles tendinitis, one of the most common and painful sports injuries, can take months to heal, and injury often recurs.

Michigan Tech researcher Rupak Rajachar is developing a minimally-invasive, injectable hydrogel that can greatly reduce the time it takes for tendon fibers to heal, and heal well.

“To cells in the body, a wound must seem as if a bomb has gone off,” says Rajachar. His novel hydrogel formulation allows tendon tissue to recover organization by restoring the initial cues cells need in order to function. “No wound can go from injured to healed overnight,” he adds. “There is a process.”

Rajachar and his research team seek to better understand that process, looking at both normal and injured tissue to study cell behavior, both in vitro and in vivo with mouse models. The hydrogel they have created combines the synthetic—polyethylene glycol (PEG), and the natural—fibrinogen.

“Cells recognize and like to attach to fibrinogen,” Rajachar explains. “It’s part of the natural wound healing process. It breaks down into products known to calm inflammation in a wound, as well as products that are known to promote new vessel formation. When it comes to healing, routine is better; the familiar is better.”

“To cells in the body, a wound must seem as if a bomb has gone off.”

Rupak Rajachar

The team’s base hydrogel has the capacity to be a therapeutic carrier, too. One formulation delivers low levels of nitric oxide (NO) to cells, a substance that improves wound healing, particularly in tendons. Rajachar combines NO and other active molecules and cells with the hydrogel, testing numerous formulations. “We add them, then image the gel to see if cells are thriving. The process takes place at room temperature, mixed on a lab bench.”

SEM image of the fibrinogen-based hydrogel

Two commonly prescribed, simple therapies—range of motion exercises that provide mechanical stimulation, and local application of cold/heat—activate NO in the hydrogel, boosting its effectiveness.

“Even a single injection of the PEG-fibrinogen-NO hydrogel could accelerate healing in tendon fibers,” says Rajachar. “ Tendon tissues have a simple healing process that’s easier to access with biomaterials,” he adds. Healing skin, bone, heart, and neural tissue is far more complex. Next up: Rajachar plans to test variations of his hydrogel on skin wounds.

Virus Hydrophobicity is a Science360 Top Story


The Michigan Tech News story “Virus Hydrophobicity Can Help Purify Vaccines” concerning the research of Caryn Heldt made the top story of the online news magazine Science360. Heldt is an associate professor of chemical engineering at Michigan Tech.

The vaccine story, written by Michigan Tech science and technology writer Allison Mills, appeared in Science360 five days after it was published. This multimedia source is edited by the National Science Foundation in order to gather breaking STEM news from scientists, universities, and science and engineering centers.