The ME Course Column is a recurring publication about the unique classes and labs that mechanical engineers can take while at the University of Colorado Boulder. Follow the series to understand the core curriculum, discover elective course options and learn the broad applications of mechanical engineering skills.

Most mechanical engineers will work with materials such as metals, polymers, ceramics and composites during their careers. However, a course taught by Department of Mechanical Engineering Professors Francois Barthelat and Franck Vernerey asks students to draw inspiration from another material – snow.

“I am a backcountry skier and as such, you have to learn a lot about avalanches and take courses for safety,” Vernerey said. “You realize there is so much mechanics involved with snow.”

MCEN 4228/5228: Mechanics of Snow motivates students to look at their environment and the materials around them in an analytical way. The idea behind the course is to teach students the science behind certain phenomena by looking at the fundamentals of snow and ice from the atomic level to the mechanics of the snowpack.

“Snow in itself is an interesting material to study, you do not necessarily think of looking at snow in the context of mechanics of materials, but there is a lot to learn from this approach,” Barthelat said. “This is a great a way to expose students to state-of-the-art experimental and modeling techniques that people use in engineering.”

While studying the properties of natural versus artificial snow, the mechanics of sliding on skis and snowboards, or the conditions that trigger avalanches, students also master theoretical tools such as fracture mechanics and heat transfer. They also learn about the relationship between molecular structures, thermodynamics, and micromechanics, including viscoelasticity.

The professors explained that applying these critical engineering concepts to snow helps students better understand the information. It allows them to see that these concepts are real and happening in our environment.

“We often teach mechanics of materials and students are not always connected to the course because they have not worked with the materials before,” Vernerey said. “They learn the equations but may have difficulties connecting them to the real world. This course allows them to better connect because they already have an idea about the material. They are much more motivated to learn.”

�鶹��Ժ in Mechanics of Snow conducted their own research out in the elements on March 10, after Boulder received about four inches of snow. They measured the densities of the fresh and old snow, assessed their compressive strength and calculated the snow’s coefficients of friction on skis and snowboards.

The class will take one more field trip outside to conduct strength and fracture tests on the snow before completing final projects to wrap up the semester. Some students are looking at avalanche conditions, while others are studying the impact mechanics of snowballs or snow construction such as igloos and walls.

“A big takeaway from this course is that students will be exposed to a vast number of topics in engineering and physics,” Barthelat said. “If they need these in their professional life later on, they know that the concepts exist and where to find more information.”

Mechanics of Snow is a technical elective open to upper-level undergraduate and graduate mechanical engineering students.

View all the Mechanical Engineering Technical Elective Courses

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 has received a patent for new technology that will help physicians diagnose and treat gastrointestinal illness more effectively. The medical device startup, cofounded by Paul M. Rady Department of Mechanical Engineering Professor Mark Rentschler, created a micro-textured medical balloon for endoscopies.

The new patent covers the startup company's Pillar^TM Technology, the small nubs on the balloon made of silicone. The pillars are shaped and spaced out in a way that creates more friction, which allows doctors to secure the balloon in the small intestine. Medical balloons made by other companies are smooth and tend to slip in the mucus lining the intestine. Those balloons make endoscopies technically challenging and time-consuming.

"We feel like we're able to give better traction and better anchoring with less force," Rentschler explained. "Speed for the physician, deeper access for the patient, less trauma and full diagnosis and treatment that first time."

Balloon endoscopy is the standard to diagnose and treat small bowel disease. The balloon is inflated when inserted into the intestine, making room for a scope to move through. The procedure allows physicians to see the entire small intestine.

One of Rentschler’s goals is to “figure out a way to try to make a bigger impact with our discoveries at the bedside with the patient and the physician.” His new Pillar ^TM Technology helps push that mission forward.

Engineering the micro-textured balloon 

Companies have tried designing balloons with texture before, but not like this. Rentschler said the idea in the early 2000s was to use mesh around a balloon. When the balloon was inflated, it would squish through the holes of the mesh to create nubs intended to secure the balloon.

“We wanted something super thin,” Rentschler said. “While we want the textures, we don’t want them to break. We want them to be as small as reasonably possible.”

While Rentschler pointed out that molding technology has improved in the last five years, the process to create such small pillars is not easy.

“In fall 2019, we started proving out our technology by transitioning to manufacturing and building our first micro-textured balloons at scale,” Rentschler explained. “That itself was a huge challenge. Most contract manufacturers wouldn’t even try to create these balloons with us because they didn’t think it was possible.”

Once Aspero Medical found a vendor ready for the challenge, the startup began building the balloons in spring 2020.

Rentschler created the Pillar ^TM Technology with Dr. Steven Edmundowicz, Aspero Medical’s chief medical officer and the medical director of the  at the . The foundational intellectual property was developed at the University of Colorado. The CU Board of Regents owns the patent.

Utilizing the technology on medical products

Aspero Medical uses the micro-textured balloon in a product the company has lined up to submit for FDA approval.

The Ancora^TM Balloon Overtube attaches the pillared balloon to a silicone tube for endoscopies. Physicians move a scope through the silicone tube to visualize the digestive tract. Rentschler and Edmundowicz will apply for FDA approval this year. Rentschler said if all goes well, they expect approval three months after submitting. From there it’s commercialization.

Aspero Medical also plans to use the Pillar ^TM Technology on a product for colonoscopy procedure. The company intends to submit that product for FDA approval in 2022. The Pillar ^TM Technology is designed so that it could work with other balloons as well. That could include balloons used in cardiovascular or urology procedures.

“This product (Ancora Balloon Overtube) is for GI. Our second product is for colonoscopy, again GI,” Rentschler said. “We’re starting to put our heads together on what we think could be third.”

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The Rocky Mountain Seminar Series provides CU Boulder faculty, staff and students with the opportunity to hear from researchers across disciplines from various institutions.

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Researchers at CU Boulder are collaborating to develop a new kind of biocompatible actuator that contracts and relaxes in only one dimension, like muscles. Their research may one day enable soft machines to fully integrate with our bodies to deliver drugs, target tumors, or repair aging or dysfunctional tissue.

Professor Franck Vernerey of the Paul M. Rady Department of Mechanical Engineering and Assistant Professor Carson Bruns of the Paul M. Rady Department of Mechanical Engineering and ATLAS Institute received $477,000 from the National Science Foundation to begin this three-year project in January 2021.

“We are investigating an emerging class of materials known as slide ring polymers that resemble beads on a string,” said Vernerey. “When the network is subjected to a controlled stimulus, the bead-like molecules can slide around, which allows for a new way to actuate the material.”

Naturally occurring molecular machines in the body perform vital cell functions, such as gene replication, protein synthesis or transportation of intracellular cargo. Artificial molecular machines—inspired by those in nature—were recognized by the 2016 Nobel Prize, awarded to early pioneers in this area. Now, Bruns and Vernerey aim to scale up these tiny machines from nanoscale to macroscale using networks.

Instead of one molecule, a network incorporates numerous molecules, linked and working together, as occurs naturally in muscle. The process of starting small and scaling up allows the manmade material to copy how nature organizes molecular machines. To ensure the best results, Vernerey will also create a multiscale model to generate predictions that will help determine exactly how to tweak the molecular structure for the most effective scaling.

“The part that Franck’s group is doing is the first of its kind for these materials,” said Bruns. “It keeps my group from having to go into the lab and make hundreds of networked molecular machines until we find the property that we’re most interested in.”

Likewise, Vernerey said there would be no models without Bruns. “We make for a very cool integration,” said Vernerey.

Hydrogels currently are the main available actuator based on molecular interactions, which change shape based on temperature, pH or pulses of electricity. However, these actuators are limited in that they cannot change shape in only one dimension. When a soft material experiences a change in volume instead of just length, its movements are slower, harder to control and a less efficient use of energy.

“Imagine the actuator is a sponge soaked in water, and it takes a long time for the water to leave,” said Vernerey. “The larger the actuator, the longer you have to push out. This means when you want to scale it up, this approach becomes unrealistically slow. The only way to make things fast is to contract without volume change.”

Natural muscle, the inspiration for this project, does this quickly in the body. Each molecular machine pulls on polymer ropes in a microscopic tug-of-war, and the movements collectively result in the muscle shortening to contract and fully extending to relax.

“Another consideration is that our materials can be made to be self-healing, and they are biodegradable, both properties of muscle,” said Bruns.  

Bruns said their materials are made of non-toxic, food-grade products. This is significant, because most other actuators—especially those that rely on electricity—are not safe to use inside the body.

“While we hope there will be applications, we are equally interested in better understanding these systems,” said Bruns. To this end, Bruns and Vernerey are also developing interactive lessons in this area for high-school and undergraduate students.

“If you tell a student in high school, I’m just building a polymer, they might not be that excited,” said Vernerey. “But this project has great applications which will help them to be excited about the physics.”

Whether their findings help in tissue engineering or in developing soft micro-robots to mimic and guide cells, among other applications, Bruns and Vernerey said they are excited to be on the frontier of nanotechnology, gaining a better understanding of molecular machines and networks.  

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, a spinout company of CU Boulder’s Paul M. Rady Department of Mechanical Engineering and CU Anschutz Medical Campus was . This award will allow the company to further technologies in the field of gastroenterology, specifically their C-Tube product line that incorporates proprietary Pillar™ micro-texture technology.

Their design improves the grip of medical balloons used in endoscopies and other gastrointestinal procedures. Unlike the balloons currently used which are smooth and round, Aspero Medical has discovered that when textures smaller than the eye can see are applied to a surface, they have a significant impact on the stability and grip of the device on the gastrointestinal wall. 

Aspero Medical began in response to a desire on the part of Professor Mark Rentschler of the Paul M. Rady Department of Mechanical Engineering to translate his laboratory's fundamental research to influence patient outcomes in a positive manner. He co-founded the company with Steven Edmundowicz, MD, professor and medical director of the Digestive Health Center at the University of Colorado Anschutz Medical Campus. Today, Allison Lyle (MSMechEngr’12) also serves as their director of engineering. Through several proof-of-concept grants from Venture Partners and the Colorado Office of Economic Development and International Trade, the base technology was proved. They also pursued market discovery and business plan development, seeking guidance from advisors. Since 2018, they have devoted time and effort to establishing and executing their intellectual property strategy. 

In light of new developments, Rentschler answered questions about the SBIR Phase I program, upcoming research and what it means to be an entrepreneur.

Question: What will this award enable?

Answer: Annually, there are nearly 20 million colonoscopies performed in the United States. The majority of these procedures are screenings related to colon cancer. An incomplete colonoscopy can result in missed colorectal cancer and ultimately increased healthcare expenditures related to follow-up procedures. The goal of this project is to demonstrate feasibility of an integrated balloon overtube that can be used intraoperatively, a mid-procedure, time-efficient addition on the endoscope to aid in completing challenging colonoscopies and minimize the occurrence of incomplete colonoscopies. Aspero Medical will use the awarded funds to create an effective intraoperative balloon overtube solution and demonstrate use effectiveness.

Question: What will the next stage of development look like for this technology?

Answer: Research outcomes of this NSF SBIR Phase I grant will demonstrate proof of concept. Follow-on research and development efforts will target transitioning this concept to cost-effective manufacturing, more extensive clinical evaluation and user studies and ultimately translation from bench-to-bedside.

Question: What does being an entrepreneur mean to you?

Answer: For me, my passion is to positively impact society, primarily through my faculty roles in teaching, research, and service. Our laboratory’s fundamental research in the areas of medical devices and surgical robotics has positioned us to routinely interact with physician collaborators and patients and to keep these end users of our technology in mind. As a faculty member, I have been fortunate to have a unique set of entrepreneurial resources and opportunities available to me. So much so, that when our research approaches a translational threshold, not trying to move the technology forward to the marketplace would seem like a lost opportunity. In addition to teaching, research and service, I look at entrepreneurship as one more tool that we can use to make a positive impact.

About NSF Small Business Programs

powered by NSF awards $200 million annually to startups and small businesses, transforming scientific discovery into products and services with commercial and societal impact. Startups working across almost all areas of science and technology can receive up to $1.75 million to support research and development (R&D), helping de-risk technology for commercial success. America’s Seed Fund is congressionally mandated through the Small Business Innovation Research (SBIR) program. The NSF is an independent federal agency with a budget of about $8.1 billion that supports fundamental research and education across all fields of science and engineering. 

Aspero Medical Updates

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CU Boulder researchers developing advanced electronic skin are now investigating applications surrounding the material's ability to shapeshift.

This technology is being developed by CU Boulder Associate Professor Jianliang Xiao of the Department of Mechanical Engineering in collaboration with Professor Wei Zhang of the Department of Chemistry. Their completely recyclable, self-healing e-skin may one day lead to improvements in human health, robotics, prosthetics and beyond.

A patch of e-skin developed by Associate Professor Jianliang Xiao's research group. 

Their technology was one of 80 designs from across the world displayed at the Beazley Designs of the Year exhibit in London and was displayed at Parsons School of Design in New York at the In:Bodied – The Augmented Self exhibition in March 2019.

E-skin developed by Xiao and his research group on display at the Beazley Designs of the Year exhibit in London. It was also featured at Parsons School of Design in New York at the In:Bodied – The Augmented Self exhibition.

Xiao’s recent focus has been on improving the e-skin’s mechanical performance.

“Previously, the device was flexible but not as stretchable as a rubber band,” Xiao said. “Now, we’re trying to make it so it can be stretched larger without breaking.”

When the material does break, self-healing technology allows for a quick and easy recovery. Because the material contains bonds that are constantly breaking and reforming, when broken parts of the material come into contact with one another, the bonds naturally rebuild. In the past, the group used heat and pressure to initiate this process, but now, it can heal at room temperature on its own, much like human skin.

The material becomes less sensitive the more it breaks, but when e-skin reaches the end of its life, it can be fully recycled for use in future generations of e-skin. When placed in organic solvents, the material breaks into particles and oligomers that are separated for use in newly fabricated e-skin.

“I think this work has huge potential in terms of protecting the environment,” Xiao said. “It improves lives, improves healthcare and at the same time, we have designed it to have no negative effect on the environment.”

Xiao said he hopes e-skin will one day be used in skin grafts and transplants. He also said a patch of e-skin could monitor a person’s vital signs and can increase the capabilities of someone who uses a prosthetic device. A person using a prosthetic hand, for instance, will have better dexterity and can more successfully carry a range of items when he or she is able to sense them. By stimulating the neural system with electrical signals, e-skin sends messages to the brain that portray what the skin is feeling.  In robots, e-skin is being used to improve the way a robot interacts with human environments.

While studying the malleability and shape memory of the material, Xiao has begun developing an antenna that can transform from one shape to another. When exposed to a stimulus, the device transforms and when the stimulus is removed, the elasticity of the material leads it to morph back into its original shape.

Xiao said he has been able to accomplish more than he could have alone with a team whose backgrounds are varied.

“People with different training have different ways of thinking and different philosophies which make the work unique,” Xiao said. “The technology we’ve developed has wide application and can transform human life.”

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Think of it as mathematics with a bite: Researchers at CU Boulder have uncovered the statistical rules that govern how gigantic colonies of fire ants form bridges, ladders and floating rafts.

The research, , takes a unique look at one of the strangest, and potentially painful, networks in nature. Fire ants (Solenopsis invicta) are resourceful builders, using their own bodies to create gigantic structures made up of hundreds to thousands of insects and more.

In the new study, a team led by CU Boulder’s Franck Vernerey set out to lay out the engineering principles that underlie these all-ant structures—specifically, how they become so flexible, changing their shapes and consistencies within seconds. The group used statistical mechanics to calculate the way that ant colonies respond to stresses from the outside, shifting how they hang onto their neighbors based on key thresholds. 

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