New York, NY—August 23, 2021—A new way to control the motion of bubbles from researchers at Columbia Engineering might one day help separate useful metals from useless dirt using much less energy and water than is currently needed.

When mining for metals such as the copper used in most electronics and the lithium used in many batteries, only a small fraction of the material that is mined is useful metal, with the vast majority just useless dirt-like particles.

"We have to separate the useful metals from the useless particles, and we do this by blowing air bubbles up through them," said Chris Boyce, assistant professor of chemical engineering at Columbia Engineering. However, "this process utilizes a large amount of energy and water, causing climate change and water shortages, thus creating problems we are trying to prevent. We have this issue in part because we currently cannot control the motion of these bubbles."

Now Boyce and his colleagues reveal that if they vibrate these particles while blowing air up through them, the normally chaotic motion of these bubbles becomes orderly and controllable. The vibrations cause the particles to quickly shift between solid-like to fluid-like behavior, which in turn helps structure the bubbles into regularly spaced triangular arrays.

"I think the simple addition of vibration to go from chaos to order is beautiful," Boyce said. Their study appears August 23 in the journal Proceedings of the National Academy of Sciences.

Having a way to control the behavior of these bubbles can help scale up and optimize separation techniques. "We expect that the ability to create structure in flows can reduce energy and water use in mining as well as improve the efficiency of many clean energy processes," Boyce said.

The researchers now aim to apply this structured bubbling to sustainable mining separation techniques.

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Columbia Engineering

Columbia Engineering, based in New York City, is one of the top engineering schools in the U.S. and one of the oldest in the nation. Also known as The Fu Foundation School of Engineering and Applied Science, the School expands knowledge and advances technology through the pioneering research of its more than 220 faculty, while educating undergraduate and graduate students in a collaborative environment to become leaders informed by a firm foundation in engineering. The School’s faculty are at the center of the University’s cross-disciplinary research, contributing to the Data Science Institute, Earth Institute, Zuckerman Mind Brain Behavior Institute, Precision Medicine Initiative, and the Columbia Nano Initiative. Guided by its strategic vision, “Columbia Engineering for Humanity,” the School aims to translate ideas into innovations that foster a sustainable, healthy, secure, connected, and creative humanity.

About the Study

The study is titled "Dynamically structured bubbling in vibrated gas-fluidized granular materials."

The study appeared in the journal Proceedings of the National Academy of Sciences on August 23, 2021.

Authors are: Qiang Guo, Yuxuan Zhang, Azin Padash, Kenan Xi, Thomas M. Kovar, and Christopher M. Boyce.

Department of Chemical Engineering, Columbia Engineering.

The researchers received support from the China Scholarships Council and the Bakhmeteff Fellowship for Fluid Mechanics.

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Can you tell us a bit more about compound rain clusters and why is this happening?

An open question has been whether the climate will become “stickier” or more random as it warms - stickier meaning that the wind patterns just persist for longer periods of time, random meaning things get disorganized. It seems that there are modest but detectable changes -- at least over the United States -- where the incidence of persistent patterns in which waves of moisture are repeatedly directed to the same places is increasing. Each wave brings rain that starts to fill up dams and then, if a bigger rain event happens and the reservoir is vulnerable, there is the potential for failure.

Our study is the first analysis of rainfall sequences and events associated with recent

hydrologic failures of 552 dams in the U.S. We found that persistent atmospheric circulation patterns that lead to recurrent rainfall events, rather than just more moisture in the atmosphere, are a possible reason. The probability of these compound precipitation risks has increased across part of the country. With over 90,000 aging dams still in service, the increasing likelihood of intense rainfall sequences raises urgent concerns about future dam failures.

What are the near-term solutions?

We need to visit the portfolio of more than 90,000 dams in the U.S. and check not just their state of maintenance but also how they are being operated to decide which ones should be demolished, which ones repaired, and which ones given better strategies to hold on to water they already contain while we improve our predictions of floods or droughts. We need to improve the near-term prediction of persistent rainfall patterns. It’s urgent that we do a portfolio risk analysis that considers the climate, fragility, and operational risk factors with a mapping to potential impacts from dam failure so that we can better understand the collective risk of cascading failure of critical infrastructure that would be triggered by dam failure and its socio-economic impacts.

Is this happening across the globe, not just in the U.S.?

Yes, we see similar behavior in the data in many places around the world, especially in the higher latitudes (>30), where the storm tracks organize and then persist. But a more comprehensive study is needed.

What have been some of the successes out of this collaboration to date? 

Our work has generated the first air pollution data from highly populated cities such as Kinshasa, Democratic Republic of the Congo. We are leading the state of the science in low-cost sensor applications, building relationships with local decision makers and informing policy in India, and increasing capacity among thousands of local practitioners on air quality management and air pollution science. 

Dams in which areas of the U.S. are more prone to collapsing and why?

We have concerns with older dams that are not being maintained; these are primarily concentrated in the Northeast, Upper Midwest, and Southeast. And while Western dams tend to be newer and larger, in 2017 the tallest U.S. dam operated by the State of California -- Oroville -- nearly failed, and 200,000 people had to be evacuated. Persistently high, but not extraordinarily high, rainfall was implicated. The reservoir was full because the operators wanted to hang on to the water in case they lapsed back into drought, and a modest amount of rain forced them to use the overflow spillway (which was in poor repair), and it failed - the concrete just ripped off as the water went over it. They switched to the emergency spillway, which also failed.

Are hurricanes playing a major role in these scenarios? 

Hurricanes are really concerning since the amount of water that they can drop could easily overwhelm the capacity of local reservoir managers to cope with. In 2015, 52 dams failed in South Carolina in just one hurricane event–Hurricane Joaquin. With Hurricane Harvey, the Addicks and Barker Reservoirs in Houston were very vulnerable to failure, and a last-ditch effort to release water from them and flood downstream areas– in the middle of the night–prevented a more catastrophic failure. 

There has been a concern that hurricanes will be more frequent and stronger with global warming, and evidence has been presented in favor of and against this argument. Harvey persisted in place and kept on raining longer than any prior hurricane in the region, so the emerging question is whether we will see more of that. If we do, the vulnerability of dams may go way up since they may not be able to handle the resulting deluge.

What do you think about all this?

This seems to be a silent crisis so far. Since 2000, we’ve had a dam failure due to overtopping, on average every two weeks in the U.S. Luckily, most of these have been small dams, and the loss of life and immediate impact have not been catastrophic. But if a large dam were to fail above a major population center or a power plant or a super fund site or a bridge, the impacts could be devastating and long-lasting. The silence would be broken with a bang.

Lead Photo Credit: Kirk Fisher/Shutterstock

This year, the Blavatnik Acceleration Fund at Columbia Engineering will support four teams researching bladder cancer, embryonic brain development, spontaneous preterm birth, and the basis of common language disorders. These awards are supported by the School’s Blavatnik Fund for Engineering Innovations in Health, made possible with the generous support from the Blavatnik Family Foundation, headed by Columbia Engineering alumnus Len Blavatnik MS’91. 

Established in 2018, the Blavatnik Fund for Engineering Innovations in Health focuses on research at the intersection of engineering and health, with the aim to expedite the development, application, and commercialization of breakthrough discoveries. 

The fund has supported 24 projects across seven cohorts, teams rooted in cross collaboration. Those investigations have led to breakthroughs in understanding the foundations of memory, enabled the development of an important new technique for stem cell therapy, and supported the construction of a prototype robotic walker that helps children with cerebral palsy learn to walk. 

In addition to sponsoring research projects, the Blavatnik Fund for Engineering Innovations in Health also supports talented doctoral students at a critical stage in their research. Since its inception in 2018, the Blavatnik Doctoral Fellowships have been awarded to 39 students across a range of areas of study–from biomedical optics to single-cell genomics and protein engineering to cutting-edge drug delivery.

The interdisciplinary nature of the research projects supported by the Blavatnik Fund for Engineering Innovations and Health underscores the Engineering School’s strong ties with collaborators at Columbia University Irving Medical Center, including the Vagelos College of Physicians and Surgeons, all working towards a common goal of bringing innovative solutions to engineering and medicine.

About the winning projects: 

Engineering tumor painting nanoparticles to promote immunotherapy responsiveness in bladder cancer

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PIs: Santiago Correa, assistant professor of biomedical engineering and member of the Herbert Irving Comprehensive Cancer Center; Nicholas Arpaia, associate professor of microbiology & immunology 

This project introduces a highly innovative strategy to enhance immunotherapy for muscle-invasive bladder cancer (MIBC) through the use of tumor 'painting' nanoparticles. These nanoparticles are designed to deliver immunomodulatory proteins directly to tumors via intravesical administration, meeting the urgent need for safer and more effective treatments. 

With MIBC's grim prognosis (~50% 5-year survival rate) and the limited success of current immunotherapies, their project aims to make tumors more responsive to such therapies, potentially benefiting a larger group of patients. Their research is structured around two main objectives. Aim 1 is to demonstrate that these nanoparticles can precisely target and deliver their protein payloads to MIBC tumors in advanced orthotopic mouse models, evaluating the treatment's efficacy and safety. Aim 2 explores the therapeutic potential of using these nanoparticles to deliver the CXCL13 chemokine, thereby priming the tumor microenvironment to enhance the response to PD-1 checkpoint blockade immunotherapy. The researchers hypothesize that CXCL13 delivery will induce the formation of tertiary lymphoid structures, known to amplify anti-cancer immune responses, as evidenced by recent MIBC clinical trials.

Their proposal integrates cutting-edge nanomedicine with immunology to offer a novel approach that could reduce treatment toxicity, target tumors more precisely, and amplify the effectiveness of existing cancer treatments. 

The genomic and synaptic basis of learned sound association and language disorder

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PIs: David Knowles, assistant professor of computer science and member of the Data Science Institute; David Sulzer, professor of psychiatry, neurology, pharmacology

Learned sound association is the process by which the auditory nervous system associates a sound with a certain outcome. This ability can be impaired in neurodevelopmental conditions such as language disorder and autism spectrum disorder (ASD). 

In this research project, Knowles and Sulzer aim to identify variants and genes affecting language disorder and study the neuronal pathways and circuits involved in sound association along with the mutations that can disrupt them. This will be achieved by using computational approaches to analyze large-scale human genetic data such as genome-wide association studies (GWAS) and post-GWAS analysis methods, and conducting behavioral experiments with fiber photometry in wildtype and mutant mice models using an interactive virtual reality environment.

A multi-omic investigation of the vaginal ecosystem and cervical biomechanical properties in pregnancy

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PIs: Kristin Myers, associate professor of mechanical engineering; Tal Korem, assistant professor of systems biology and reproductive sciences in Obstetrics and Gynecology; Mirella Mourad, assistant professor of obstetrics and gynecology 

Spontaneous preterm birth (sPTB) is one of the leading causes of complications during pregnancy, but there are few ways for physicians to predict or prevent it. Researchers have found that two factors — the community of bacteria living in the vagina and physical changes to the cervix — play a role in sPTB. 

With support from the Blavatnik Acceleration Fund, this research team will investigate how the vaginal ecosystem affects the stiffness of the cervix and its mechanical changes during pregnancy. This comprehensive approach could lead to new ways to identify women at risk of preterm birth and develop treatments to strengthen the cervix and prevent early labor.

Mechanobiology of early embryonic brain development

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PIs: Nandan Nerurkar, assistant professor of biomedical engineering; Maria Tosches, assistant professor of biological sciences

Errors in the earliest stages of brain development can lead to severe neurological disorders, but researchers still don’t fully understand the factors that determine how the embryonic brain’s shape and structure are formed. 

With support from the Blavatnik Acceleration Fund, this research team will study how physical forces and genetic signals work together to shape the developing brain. By combining engineering techniques to measure mechanical forces with advanced molecular biology methods, they aim to uncover how tension in the developing brain influences cell growth and identity.

This interdisciplinary approach could reveal fundamental insights into brain development, helping researchers understand how early disruptions can lead to neurological disorders and potentially guiding future treatments.