Faculty

Why are hourglasses filled with sand and not water?

Alexander James Servantez — Wed, 13 Aug 2025 20:29:47 +0000

Why are hourglasses filled with sand and not water? Alexander Jame… Wed, 08/13/2025 - 14:29

Alexander Servantez

The hourglass, one of mankind’s earliest forms of timekeeping, is at the forefront of a new, interactive display in the basement of the Engineering Center.

A group of former seniors in the Paul M. Rady Department of Mechanical Engineering designed a series of hourglass displays for their Senior Design capstone class this past semester. The project aimed to answer a simple question: why are hourglasses filled with sand and not water?

But be warned—the team’s Logistics Manager Max Van Cleave says the question isn’t as straightforward as you might think.

Associate Professor Nathalie Vriend standing in front of the hourglass display in front of her lab window.

“Water is governed by Bernoulli’s Law, which physically states that the flow rate changes as the fluid level changes. The more water you have, the faster it will flow out and vice versa,” said Van Cleave. “Sand is different—it creates force chains that transmit the load to the edges of an hourglass. The friction created keeps the sand particles together and allows the sand to descend at a constant rate.”

There are other factors that play a role, as well. Things like the angle and shape of the hourglass, or even the size of the sand particles can affect the speed in which the sand and water flow down the funnel.

Van Cleave mentioned it was difficult for his team to account for all of these different variables. But he said it was also extremely interesting to see how much complexity and nuance can be packed into something as small and ancient as an hourglass.

“This question we answered—it’s not really a question you even think about until you absolutely have to. Everyone has used an hourglass, but they don’t realize how advanced they are,” Van Cleave said. “There was a lot of physics involved in this project and it was fun to play around with all of those factors.”

A closer look at the detachable, lightweight aluminum frame the senior design team used to mount their hourglass display.

The project features three motorized hourglass units mounted on a lightweight aluminum frame. Two of them are filled with sand and one is filled with water.

Equipped with wheels, the detachable aluminum frame functions like a cart, allowing the group to transport the display with ease. It’s also fitted with modular components, making it easy to extend or adapt if needed.

With one click of a button on the control panel, users can flip the hourglass displays individually or all at once and observe various flow behaviors firsthand. Project sponsor and Associate Professor Nathalie Vriend says the display is a great way to demonstrate complex fluid dynamics principles in an understandable way.

“I chose the prompt because I was looking for something nice and educational to put in front of my lab windows,” said Vriend. “There’s some interesting science hidden in these hourglasses. It’s fun, interactive and we can use it to teach high school and middle school students at outreach events.”

Van Cleave is returning to CU Boulder as a part of Rady Mechanical Engineering’s Bachelor’s-Accelerated Master’s program. Every time he passes Vriend’s lab windows he will see his hard work front and center, like many others already have.

But he says the real fulfillment will come from how others interact with the project.

“It feels great to know that people enjoy it,” Van Cleave said. “It’s hard to boil down granular flow principles into something anybody can engage with, so it’s awesome that people are already learning a thing or two from the display.”

You can try out the hourglass display yourself in the Granular Flow Laboratory located at ECNW 1B90 in the basement of the Engineering Center.

A group of former senior designed a series of hourglass displays for their Senior Design capstone class this past semester that currently sit in the window of Associate Professor Nathalie Vriend's Granular Flow Laboratory. The project, located at ECNW 1B90 in the basement of the Engineering Center, aims to answer a simple question: why are hourglasses filled with sand and not water?

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Milford discusses the potential devastating impacts of EPA cuts

Alexander James Servantez — Thu, 24 Jul 2025 20:34:19 +0000

Milford discusses the potential devastating impacts of EPA cuts Alexander Jame… Thu, 07/24/2025 - 14:34

Due to Trump administration research cuts, the Environmental Protection Agency (EPA) announced last week it will begin to dissolve its Office of Research and Development. Professor Emeritus Jana Milford says the decision could have wide-ranging impacts on human health and conservation efforts.

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ME startup Point Designs announces major prosthetics partnership

Alexander James Servantez — Fri, 18 Jul 2025 17:53:30 +0000

ME startup Point Designs announces major prosthetics partnership Alexander Jame… Fri, 07/18/2025 - 11:53

Nine years ago, a group of researchers from the Paul M. Rady Department of Mechanical Engineering at CU Boulder launched a pioneering medical device startup called Point Designs in an effort to commercialize prosthetic technology.

Today, those same researchers are announcing a new collaboration that can lift the company’s prosthetic innovation and patient care to another level.

Point Designs, a pioneering medical device startup launched by researchers and alumni from the Paul M. Rady Department of Mechanical Engineering.

Boulder-based startup Point Designs has announced that it has entered an agreement of impending acquisition with Hanger, Inc., a leading provider of orthotic and prosthetic (O&P) patient care services and solutions. The company, co-founded by Research Professor Jacob Segil, Associate Research Professor Richard Weir at CU Anschutz, and Rady Mechanical Engineering alums Levin Sliker (MechEngr’10; MS’12; PhD’15) and Stephen Huddle (MechEngr’99; MS’13), says the agreement can have a profound impact on the future of prosthetic design.

“We are very excited about the opportunity to join the Hanger family and to expand our ability to positively impact the lives of those with upper limb loss or limb difference,” said CEO Levin Sliker. “Hanger’s commitment to scientific research and innovation for the betterment of the global O&P community aligns perfectly with our values as a company.”

Founded in 2016, Point Designs integrates advanced engineering with clinical insight to create rugged, ratcheting prostheses that restore function and independence. The company specializes in high strength, 3D-printed titanium prosthetic fingers for people with partial hand amputations.

With expertise in additive manufacturing and mechanical engineering and decades of research experience spanning neural interfaces, myoelectric control algorithms and upper limb prosthetic design, the Point Designs team believes the acquisition will help the two companies develop and expand a comprehensive ecosystem of products, services and care for patients across the globe.

Click here to read the full press release for more details

Point Designs, co-founded by Research Professor Jacob Segil, Associate Research Professor Richard Weir at CU Anschutz, and Rady Mechanical Engineering alums Levin Sliker (MechEngr’10; MS’12; PhD’15) and Stephen Huddle (MechEngr’99; MS’13), is announcing a new collaboration that they believe can have a profound impact on the future of prosthetic design.

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A closer look at Point Design's prosthetic technology in action. (Credit: Point Designs)

Researchers testing next-generation ankle braces for stroke survivors

Alexander James Servantez — Tue, 15 Jul 2025 18:30:06 +0000

Researchers testing next-generation ankle braces for stroke survivors Alexander Jame… Tue, 07/15/2025 - 12:30

Alexander Servantez

Nearly 80% of all stroke survivors experience walking issues, according to a study in the American Heart Association journal.

For some of them, the solution is simple: ankle-foot orthoses (AFOs), otherwise known as ankle braces. These wearable, assistive devices are designed to enhance mobility and make walking easier post-stroke.

But the functionality of these braces is still very limited. In fact, a report in the National Library of Medicine said that only a third of stroke patients see walking improvements when paired with an AFO.

That’s why Cara Welker, an assistant professor in the Paul M. Rady Department of Mechanical Engineering, is leading a new, collaborative research project that aims to redefine this relationship. Her team is developing a next-generation AFO that doesn’t just support movement—it enhances it.

A quick look at the next-generation AFO prototype, designed by Associate Professor Elisa Arch at the University of Delaware.

“Stroke survivors or others using these assistive devices walk slower, and it takes more effort for them to move,” said Welker, who is also affiliated with the Biomedical Engineering Program, the Robotics Program and the BioFrontiers Institute. “Movement is important, not just for getting around, but for our quality of life and physical health. If we can help someone walk faster or get closer to how a healthy person walks, then we see that as a success.”

Funded by the National Science Foundation (NSF), the three-year, $600,000 project is a collaboration with Associate Professor Elisa Arch at the University of Delaware. It begins with a unique AFO prototype that the two believe has the potential to transform the way assistive devices are designed.

Current ankle brace technology offers only a single stiffness profile that operates like a simple spring. They can be effective for some, but Welker says the human ankle is much more complex than that.

“The single stiffness profile doesn’t mimic normal ankle function when walking,” Welker said. “It can’t adapt to the stiffness or the biological angle of a human ankle, which means many brace users still have trouble walking.”

To address this, Arch developed a new AFO that can transition between two different stiffness profiles instead of one. Think of it as a more personalized brace that is tailored to the complexity of the ankle—as a person walks and their ankle angle changes, the brace can change how it behaves to provide better support.

But the challenge of the research project isn’t necessarily in the design. Welker says brace customization is currently largely based on trial and error. The lack of precise modeling makes it difficult to pair different stiffness profiles and properties with the needs of the user.

“The device we have is very promising, but we don’t know how to prescribe these different stiffnesses based on someone’s specific set of weaknesses,” said Welker. “It might likely be different from one person to another since stroke manifests itself in many ways.”

A series of tests, using the powered exoskeleton, motion capture cameras and integrated treadmills, being performed inside of the Welker Lab space.

Using her cutting-edge Welker Lab space—equipped with a powered exoskeleton, motion capture cameras, ground-integrated treadmills and force plates—Welker’s role is to test the device. The goal is to see the AFO in action, model how changing these device parameters affect walking, and optimize along the way wherever possible.

“There’s this technique called human-in-the-loop optimization. It involves changing behavior of an assistive device and measuring how these changes affect certain user metrics that are deemed important,” Welker said. “We want to use this technique to measure things like walking speed or energy expenditure. By doing this, we can select the parameters that best optimize for outcome metrics we care about for a specific person.”

Welker has aspirations beyond the NSF-funded project, as well. She believes their research can be manufactured at scale and prescribed in clinics, helping stroke survivors and brace users around the world achieve normal ankle function.

She also believes the work done during this project can positively impact her other projects. Whether it’s in the realm of AFOs or other assistive devices like prosthetics, Welker’s research is well-rounded and diverse. But she says her unique lab space with different assistive devices and the ability to quantify how people interact with them ties it all together.

“We work on many different projects, but it’s great because we can integrate them under the same human motion analysis system,” said Welker. “I’m excited to work on these types of studies, not just for people post-stroke, but also amputees. I believe the work we do will help improve the quality of life for many people.”

Nearly 80% of all stroke survivors experience walking issues and turn to ankle braces for increased support, but ankle braces are still very limited and many stroke survivors report no improvements when using them. Assistant Professor Cara Welker is leading a new, collaborative research project that aims to transform the way these assistive devices are designed.

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How slashing university research grants impacts economy, national innovation

Alexander James Servantez — Thu, 10 Jul 2025 20:37:30 +0000

How slashing university research grants impacts economy, national innovation Alexander Jame… Thu, 07/10/2025 - 14:37

Federal funding cuts in the billions have impacted dozens of universities in the U.S. Read from Professor and Senior Vice Chancellor for Research and Innovation Massimo Ruzzene on why this research is important for everybody.

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Bruns researches cybernetic human advancement with New Frontiers Grant

Alexander James Servantez — Fri, 20 Jun 2025 17:51:14 +0000

Bruns researches cybernetic human advancement with New Frontiers Grant Alexander Jame… Fri, 06/20/2025 - 11:51

Associate Professor Carson Bruns has received a $50,000 grant through CU Boulder's New Frontier Grant Program. The funding will allow Bruns and a couple of key collaborators to develop a new suite of body-integrated technology that can help monitor health, help with mobility challenges and enable peak performance in a range of daily activities.

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Bruns explores nanotech that turns plastic into fertilizer with RIO seed grant

Alexander James Servantez — Mon, 16 Jun 2025 15:42:54 +0000

Bruns explores nanotech that turns plastic into fertilizer with RIO seed grant Alexander Jame… Mon, 06/16/2025 - 09:42

Assistant Professor Carson Bruns was recently awarded a seed grant from CU Boulder's Research and Innovation Office to turn agricultural materials into bio-based plastics that can be more easily recycled, composted or even used as fertilizer.

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New discovery could make a risky heart failure treatment safer

Alexander James Servantez — Thu, 12 Jun 2025 18:36:49 +0000

New discovery could make a risky heart failure treatment safer Alexander Jame… Thu, 06/12/2025 - 12:36

Left ventricular assist devices (LVAD) designed to improve blood flow throughout the body can aid nearly 26 million people globally struggling with heart failure. But these implantable devices come with risks. New research by Assistant Professor Debanjan Mukherjee suggests that studying patient blood flow patterns could help determine who’s at risk of dangerous side effects from LVADs and lead to improvements that could make them safer.

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Robots and chemistry isn’t just a fun combo. Bruns says it’s the future

Alexander James Servantez — Fri, 06 Jun 2025 22:02:21 +0000

Robots and chemistry isn’t just a fun combo. Bruns says it’s the future Alexander Jame… Fri, 06/06/2025 - 16:02

Alexander Servantez

Carson Bruns is working to lend chemists a hand—literally—by bringing collaborative robots into chemical wet labs.

Bruns, an assistant professor in the Paul M. Rady Department of Mechanical Engineering at CU Boulder, is leading the charge on a project that he and his team like to call “robochemistry.” Their goal is to create robotic sidekicks that can assist chemists with burdensome or unsafe tasks that they may encounter in a wet lab on a daily basis.

According to the U.S. Bureau of Labor Statistics, chemists and materials scientists held nearly 100,000 jobs in 2023 and overall employment is expected to grow eight percent over the next 10 years.

But unlike other large and growing industries, Bruns says chemical research and development has remained devoid of robots, often leading to injuries and considerable risks in the workplace.

“There are a lot of potential benefits for introducing robots into a chemical lab that haven’t been explored yet,” said Bruns, who is also affiliated with the ATLAS Institute, Biomedical Engineering Program and Materials Science and Engineering Program. “Our angle involves trying to reduce work burdens and safety risks, develop robots that collaborate with humans instead of replacing them, and increase accessibility so that even people with disabilities can perform chemistry.”

Middle school students exploring the intersections of robotics and chemistry during one of the "robochemistry" interactive workshops led by Bruns and his team.

The project, funded by the National Science Foundation, is in collaboration with researchers from the University of North Carolina at Chapel Hill and CU Boulder’s Department of Computer Science. It started with an extensive observation-based task analysis that allowed Bruns and his team in the Emergent Nanomaterials Lab to develop a strong understanding of the various tasks that chemists were performing regularly in a wet lab.

After observing, interviewing and surveying their chemist test subjects, Bruns and his group were able to identify an array of different tasks that can potentially benefit from human and robot collaboration.

“We learned right away that chemists don’t really like doing a purification task called dialysis that is very common in a wet lab. It’s repetitive, it takes a lot of time and sometimes chemists have to come back to the lab in the middle of the night to change dialysis bags, which they don’t want to do.” Bruns said. “It seemed like a great case for a robot, so we built a robotic system automating the dialysis process.”

Bruns says his team of researchers has a list of other potential benefit areas, as well, including simple tasks like stabilizing a flask or offering a third hand to hold something for chemists when they need it. They are even trying to find solutions for more complex safety issues so that chemists can stay far away from violent and dangerous reactions.

But that’s not where the project ends. There is also an outreach portion aimed at improving science education and enhancing youth interest in science.

Led by PhD student Diane Jung, Bruns and his team ran a four-day interactive workshop series at a local middle school in Boulder. These workshops invited middle school students to build robots with Legos and use them to perform various chemistry experiments—something that’s already happening in Bruns’ lab.

“We’ve been building ordinary automation tools out of Lego because it’s cheaper and reconfigurable. When you don’t need it anymore, you just disassemble it and build it into something else,” said Bruns. “So we thought we could use this Lego thing we had going on in our lab already to appeal to a younger audience and show kids the fun and evolving intersection between chemistry and robotics in real time.”

During the workshop series, Bruns noticed various groups of students approaching experiments with unique perspectives and ideas. He said it was inspiring to see young kids actively engage with the science in front of them.

But most importantly, he saw the kids have fun.

“Thinking back to young Carson when he was a kid—it always just seemed very fun to me,” Bruns said. “I had positive role models in my life who also believed science was fun, so that was our goal with this part of the project. To help kids have a more positive association with the idea of science and engineering.”

Assistant Professor Carson Bruns is leading the charge on an NSF-funded project that he and his team like to call "robochemistry." Their goal is to create robotic sidekicks that can assist chemists with burdensome or unsafe tasks that they may routinely encounter in a wet lab. But that's not all: this unique blend of bots and beakers can also inspire youth interest in science.

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New study shows road emission policies could save 1.9M lives by 2040

Alexander James Servantez — Thu, 22 May 2025 20:45:25 +0000

New study shows road emission policies could save 1.9M lives by 2040 Alexander Jame… Thu, 05/22/2025 - 14:45

A new global study co-authored by Professor Daven Henze reveals that implementing smart policies that address road transport emissions can improve health outcomes across more than 180 countries and 13,000 urban areas.

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