All posts by Kim Geiger

EP&SE Journal Article on Bio-Jet Fuel Tops Altmetrics Charts

Camelina sativa
Camelina sativa

According to AIChE’s online news site, ChEnected.com, “Camelina-Derived Jet Fuel and Diesel: Sustainable Advanced Biofuels,” by Chemical Engineering Professor David R. Shonnard, director of the Michigan Tech Sustainable Futures Institute, Larry Williams of Targeted Growth, Inc., and Tom N. Kalnes of UOP LLC, a Honeywell Company, has an outstanding Altmetric Attention Score of 128. That places it in the top 5% of all research outputs scored by Altmetric.

Professor David Shonnard, Chemical Engineering, Michigan Technological University
Professor David Shonnard, Chemical Engineering, Michigan Technological University

Even though published in the AIChE journal Environmental Progress & Sustainable Energy (EP&SE) in 2010, the article is currently trending online. It has been mentioned this year by 14 news outlets, including Scientific AmericanSmithsonian, and Popular Mechanics. Altmetrics track the use and discussion of research from online discussions and forums, including social media, research blogs, public policy documents, news articles, and more.

In the article, Shonnard, Williams, and Kalnes discuss how bio-jet fuels derived from oil-rich feedstocks, such as camelina and algae, have been successfully tested in proof-of-concept flights. The American Society for Testing and Materials (ASTM) has approved a 50:50 blend of petroleum-based jet fuel and hydroprocessed renewable jet fuel for commercial and military flights.

Honeywell UPO LLC and Targeted Growth, Inc. funded the research on bio-jet fuel derived from camelina seeds developed by a Bozeman, Montana company, Sustainable Oil.

“Camelina, an oil seed crop, can be grown in more arid climates compared to many other plants that oil is derived from,” notes Shonnard. “Targeted Growth Inc. has identified 5 million acres across the country where camelina would be suitable as a rotation energy crop that would not interrupt food production. This could produce approximately 800 million gallons of camelina oil for conversion to renewable diesel or jet.”

In 2010, Shonnard completed a life cycle analysis (LCA) comparing camelina jet fuel with petroleum jet fuel, factoring in the greenhouse gas emissions from fertilizing production and use, growing, harvesting, oil recovery and conversion to jet fuel, and use of the renewable jet in applications. “Conventional camelina, that is camelina grown with current seed stock, can cut greenhouse gas emissions by 60 to 70 percent, with no loss of performance for the fuel.  A newer strain of camelina, one that needs less fertilizer and yield more pounds per acre,could cut greenhouse gas emissions by up to 84 percent compared with jet fuel from petroleum, says Shonnard. “Next generation biofuels are true hydrocarbons and on a molecular level indistinguishable from fossil fuels,” he notes.

“With expected future gains in yields/acre, camelina oil production and hydroprocessing has the potential to provide the United States an estimated 800 million gallons per year of high-quality, climate-friendly, renewable jet fuel,” the study concludes. Read the Environmental Progress & Sustainable Energy (EP&SE) article for a limited time for free.


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.”


The Secrets of Talking Nerdy, Part 1

Libby Titus Giving the First-Year Lecture
Libby Titus Giving the First-Year Lecture, Fall 2017

Are you an engineer or a scientist? Then you’re a writer and communicator, too. Libby Titus tells how to be an amazing geek who can also write.

More than 1,200 first-year engineering and computer science students learned the “Secrets of Talking Nerdy” from Michigan Tech Alumna Elizabeth (Libby) Titus ’96 at Michigan Tech’s annual First-Year Engineering Lecture on September 6. Here are some highlights from her talk.

It was 1990. Libby Titus was deciding where to go to college. She knew she wanted to get as far away from home as possible without incurring out-of–state tuition. That put Michigan Tech, a 12-hour drive, into the running. “Also, at the time, the only person in my family who had gone to college was my uncle Bob, and he had gone to Michigan Tech. After graduation, he was happily designing kegerators and brewing craft beer. I like beer, so I chose Michigan Tech,” Titus admits.

It turned out to be a much bigger decision than she realized. Titus met her former husband, the father of her two children, while walking across campus the very first day. She earned two bachelor’s degrees from Michigan Tech in 1996—one in environmental engineering and the other in scientific and technical communication.

After graduation, Titus packed up a U-Haul and headed West, taking a job in Salt Lake City for ASARCO, a mining company. “I was the first entry-level engineer and the only woman in the group. I quickly discovered that my ability to communicate equaled survival,” she recalls.

The job felt like torture. A friend, also an engineer, said to her, “Engineering is the easy part. Dealing with people is the hard part.”

She had read that for her resume to be taken seriously, she needed to stay in her first job for three years. “I made it three years and one day.” That’s when Titus moved to Seattle, where she lives now, to begin a new career as a consultant, helping clients with their environmental, health, and safety (EHS) obligations.

“I feel lucky,” she says. “My work is important, I feel appreciated, and I like my colleagues.” Titus currently manages EHS regulatory compliance for Novo Nordisk, a biopharmaceutical research center founded 9 years ago. Her job is to ensure her group of 120 Seattle researchers–Novo Nordisk has over 6,000 worldwide–meet all its compliance obligations for federal, state, and local EHS regulations and permits. She does a lot of training, and a lot of writing.

I decided to become a licensed professional engineer solely so I could command respect as a writer.”
Libby Titus

Professional engineers typically spend at least half of their day communicating, notes Titus. With 20 years of substantive experience now under her belt, she offers important advice for anyone entering the field.

“Engineering and science are group activities. It’s very rare for someone to be by themselves on a project,” she says. “No one wants to work with someone who can’t communicate.”

While at Michigan Tech, Titus took an improv class. “We all formed a circle and had to introduce ourselves and pass around some object made of air. It was pure hell, but it helped me. Take every chance you can get to engage with other people,” urges Titus. “Engineers are known for avoiding opportunities to connect with people. If you are not a confident writer or are afraid of public speaking, more writing and more speaking are the only solutions,” she says. “Confidence comes from practice!”

Adds Titus, “In business, written communication is often more important than what you say verbally. Writing is the greatest engineering challenge of all. It’s amazing how much business effort is wasted to fix poor writing. In one of my previous consulting jobs, we called our product ‘The BHB’, which stands for ‘Big Honking Binder’. The longer it takes to write, the more it costs the client.”

Clients are known to fire engineering consultants who cannot write well. “No matter how smart you are, your great ideas mean nothing until they can be effectively communicated. People will judge you by how well you speak and write.”


Interventional devices—Improving quality of life

A section of BSC’s drug-eluting Eluvia stent system, designed to restore blood flow in the peripheral arteries above the knee.
A section of Boston Scientific’s drug-eluting Eluvia stent system, designed to restore blood flow in the peripheral arteries above the knee.

As an R&D director at Boston Scientific Corporation, Heather Getty works with a cross-functional team of experts to develop products and solutions for treating diseases using minimally invasive surgical techniques.

Heather Getty '84, R&D Director, Boston Scientific, earned a BS in Chemical Engineering at Michigan Tech
Heather Getty, an R&D director at Boston Scientific, earned a BS in Chemical Engineering at Michigan Tech in 1984.

The scope of these medical devices includes catheters, stents, and other devices for patients with peripheral artery disease, or PAD, a common circulatory problem in which narrowed arteries reduce blood flow to the limbs. PAD affects more than a quarter of a billion people worldwide. Patients with PAD can suffer significant health consequences, including gangrene, amputation, and triple the risk of heart attack and stroke. Boston Scientific is a market leader in less-invasive treatments for PAD.

“As a medical products company, we rely heavily on the experience and wisdom of the physicians who utilize our products,” says Getty. “A big part of my job is understanding the treatment of PAD from the physician’s perspective. We gain knowledge about customer needs by meeting with physicians, observing clinical cases, and having physicians use our products during development.”

Product development can be extremely challenging. “Taking an idea, and moving it from concept to commercialization while navigating through technical challenges as well as financial and time constraints can be daunting,” says Getty. “A product properly commercialized can stay in the market for over 30 years. Despite that realization and pressure, at the same time, it is also our job to recommend cancellation of any idea that can’t meet expectations.”

A critical part of her job: ensuring compliance with regulations across the globe. “We work very closely with our quality engineering department but it is also critical that everyone contributes to the quality and compliance of our products,” she says.

“ A big part of my job is understanding the treatment of PAD from the physician’s perspective.”

– Heather Getty

Getty graduated from Michigan Tech with a bachelor’s degree in Chemical Engineering, and immediately began working at Honeywell. While on the job she completed an MBA from St. Thomas University. After six years in manufacturing she moved into Honeywell’s Material Test and Analysis (MTAC) group, and later began working on the development of demilitarization concepts, including exploring options to reclaim materials from ammunition dumps around the world. After 11 years, she leapt at the chance to join the R&D group at Schneider, now part of Boston Scientific, to follow her passion of improving lives.

Now, with more than 21 years total at Boston Scientific, Getty leads a team of 60 managers, engineers, and technicians who develop new products for the company. “It’s rewarding to be with a company that offers opportunities to improve patient lives but that also manages to do so with integrity and a respect for work-life balance,” Getty asserts.

“Launching a product and having it do well in the market is another rewarding aspect of my work. I love that our products can help improve a person’s quality of life as well as make a physician’s job easier.”


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.”


The healing power of seaweed—Shedding new light on alginate microgels

Bull Kelp, a brown seaweed used to produce alginates, can grow as much as 2 feet per day. Photo credit: Jackie Hindering, www.themarinedetective.com
Bull Kelp, a brown seaweed used to produce alginates, can grow as much as 2 feet per day. Photo credit: Jackie Hindering, www.themarinedetective.com

Using seaweed to treat wounds dates back to Roman times. Alginate extracted from kelp and other brown seaweeds are still used in wound dressings today for skin grafts, burns and other difficult wounds. Biocompatible and biomimetic, alginate forms a gel when exposed to a wound, keeping tissue moist to speed healing, and reduce pain and trauma during dressing changes.

Microgels, a biodegradable biomaterial formed from microscopic polymer filaments, has broad and powerful applications in cell analysis, cell culture, drug delivery, and materials engineering.

Putting the two together to form alginate microgels could enable scientists to make important new inroads in the field of tissue engineering. But when it comes to forming microgels, the gelation process of alginate literally gets in the way.

Chang Kyoung Choi Mechanical Engineering-Engineering Mechanics
Chang Kyoung Choi
Mechanical Engineering-Engineering Mechanics

Michigan Tech researcher Chang Kyoung Choi has found a way around the problem. He creates alginate microgels by photocrosslinking the two in situ to form a bond. He uses ultraviolet (UV) light to easily cure microdroplets into microgels, a process known as photopolymerization. Curing the alginate microgels using UV light takes just tens of seconds. The result: alginate microgels that shrink or swell depending on their surrounding ion concentration, temperature, pH, and other external stimuli.

Perhaps more importantly, Choi is able to control the rate that alginate microgels break down. “A tissue scaffold should degrade at a rate proportional to the formation of new tissue, but until now, uncontrolled degradation of alginate has really limited its usefulness,” Choi says.

“Working in microfluidic devices, we can start applying UV light after the microfluids become steady, and turn off the light if necessary to stop the reaction,” he explains. “This solves the chief problem associated with previous ionic methods of making alginate microgels. Until now, the alginate phase of flow would cure before steady state was achieved, resulting in alginate microgels that clogged the microchannel.”

“Until now, uncontrolled degradation of alginate has really limited its usefulness.”

CK Choi

Choi’s photocrosslinking technique also simplifies current methods of forming nonspherical alginate microgels that are better for observing objects, like cells, encapsulated inside. “Our preliminary results suggest that such high intensity UV does not reduce cell viability,” notes Choi.

Choi and graduate student Shuo Wang use oxidized methacrylated alginate (OMA) developed by their collaborator, Eben Alsberg at Case Western Reserve University. The team fabricated the microfluidic channels for this research at the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory.