Shake it off no longer: the future of energy absorbers

With the support of the McGill Innovation Fund, a team of McGill researchers are seeking to develop and commercialize a multistate lightweight shock absorbing technology that could transform safety equipment, reduce concussions, and contribute to sustainability


(Editor's note: this team is part of the 2nd cohort, which was awarded funds in 2023. 3rd cohort teams will be featured in future articles.)

Taylor Swift might tell us to “shake it off” but when it comes to concussions, this is most definitely something we should not do. Concussions – also known as Mild Traumatic Brain Injury – are what can result after a head injury occurs, such as getting hit during a football game or falling off a bike.

Concussions can often leave lingering aftereffects. Undiagnosed, these effects can result in severe disability or even death. Take the case of Zackery Lystedt in 2009 who, after suffering a concussion in a football game, returned to play prematurely. He became permanently disabled following the trauma induced by his injuries. His case eventually lead to what is known as the “shake it off law” which prevents youth athletes with signs of concussion from re-entering a game.

Here in Canada, long-term effects of concussions are only now being understood by health authorities. Recent studies have shown that as many as half of people suffering concussions still have symptoms six months later.

McGill employee Robin Koning suffered aftereffects for several months following a bike accident. Sustained, intense pressure in her head and ears, and an inability to handle any elevation were the most debilitating issues, along with persistent vision problems. “It was hell, honestly,” she said looking back at the ordeal.

So what is a brain to do to avoid this risk? Wear a helmet of course – but there is a fundamental problem with helmets: they only work once. After her accident, Koning threw out her bike helmet. “What a big piece of garbage,” she remarked to herself on seeing the object in her trash.

Most protective equipment uses the properties of expanded polystyrene (EPS) to absorb impacts. But EPS, often known as Styrofoam, is not only troublesome to dispose of, it does not have the ability to absorb impact energy without sacrificing their structural integrity. Since the material has a single stable state and is not able to trap energy elastically, its underlying architecture may catastrophically fail when it undergoes an excessive load, hampering its reusability as an impact protective gear. In other words, it’s a one-shot deal.

Canada Research Chair and Bioresource and Mechanical Engineering Professor Hamid Akbarzadeh and his team in Advanced Multifunctional and Multiphysics Metamaterials Lab (AM3L) are working on a new type of material that can not only absorb shock and trap the energy elastically, but also can be restored to its original configuration to be used for absorbing successive shocks.

The technical term for this bit of magic is ‘perforated shellular metamaterials.’, introduced in their articles published and highlighted in Advanced Materials and Advanced Science in 2021 and 2022, respectively.

Perfecting and Perforating the Materials

“One of the issues that we have seen in the many of the energy absorbers around us is that most of the time their structure completely fails under catastrophic circumstances,” explained Akbarzadeh. “It means that after a severe impact they need to be replaced partially, if not entirely.”

Akbarzadeh has been examining the creation of reusable lightweight energy absorbing materials. Building on an existing work by South Korean scientists who discovered intact monostable shellulars in 2015, Akbarzadeh and his team have managed to take the concept a few steps further by discovering how lightweight shellular metamaterials can offer multiple stable states to deliver multimodal functionalities, a research journey that was initiated in early 2016.

“We started developing the next generation of shellulars by introducing perforations on the shell surface which up until then was completely solid” elucidates Akbarzadeh. “These perforations on the surface enables these advanced materials to deliver a series of unprecedented and programmable multifunctional properties, hence named metamaterials.”

The perforations redistributes stresses from the concentrated areas within the solid shell and allow the materials to become multistable. This means that instead of having just one stable configuration, it can have multiple stable configurations – unlike EPS, for example – and as a result in-situ programmability of their functionalities. Based on the amount and history of force that is applied to this type of shell-based mechanical metamaterials, it snaps into one of its multiple possible configurations, a phenomenon that results in both elastic energy trapping and dissipation. Following the energy absorption and release, the perforated shellular metamaterial can be reconfigured to its original configuration for reuse.

“After dissipating and/or storing a significant amount of energy, the protective structure such as a helmet or a car bumper made out of these lightweight shellular metamaterials would remain structurally resilient,” describes Hamid. “You may only need to pop it back up and the material is ready to be reused.”

Benefits of the new technology compared to traditional solutions

The new material created by the team has many benefits compared to traditional energy absorbers, namely it is more sustainable, less expensive, and multifunctional.

The main way in which the material is able to be more sustainable is thanks to the fact that it can be reused. This is not the case for current energy absorbers that need to be removed, discarded, and replaced, all of which comes with an environmental and economic cost.

“Since the conventional energy absorbers are not able to be used easily again, they commonly need to be replaced completely after being impacted. This is an expensive, time-consuming, and not sustainable process from an environmental perspective.”
In addition to being reusable, Akbarzadeh’s energy absorbers and energy storage materials can be compacted into their smallest possible configuration thanks to their multistability. This means that they occupy less space and are easier to ship, saving costs and reducing energy consumption for their logistics.

“In addition to the sustainability offered by its reusability, there are two ways in which the perforated shellular metamaterial presents a more sustainable solution to what is currently available in the market,” clarified Akbarzadeh. “The first is that since the material is lightweight, it requires less energy and material excavation in order to be fabricated. The second is associated with the compactibility trait of the perforated shellulars , as a result they take up less space and consume less energy for transportation.”

MIF support also has impact

Francois Lamoureux
Image by Owen Egan.
Akbarzadeh and his team earned the Discover level award of the McGill Innovation Fund and received $25,000 to explore the project further. They are guided on this journey by Francois Lamoureux, an MIF volunteer and commercialization expert. Originally, the team envisioned the use of their technology in the context of automobile related energy absorbers, but after conversations with their board members are now pivoting towards sport gear applications.

“I told Hamid that while the technology could certainly be used for automobiles, there are a lot of potential applications for it in sports protection equipment that would be easier to start with,” recounts Lamoureux. “The most important thing is to get the technology ready and figure out where we want to take it, and that’s where the MIF advisors and resources come in to help.”

“Through the MIF we were able to discuss our ideas with industrial partners and commercialization experts to better understand all potential functionalities that these metamaterials can deliver for real life utilizations,” recalls Akbarzadeh. “And to identify the niche of application for these structures that we have developed.”

With the sports equipment application now targeted, the team is working on increasing the technological readiness level of its product before reaching out to possible commercial partners.

“For now, we are focusing on helmet designs that are multifunctional and multimodal and are improving its technological readiness level by performing real life tests,” says Hamid. Perhaps the new helmet designs that emerge from these tests will give a new horizon to the phrase ‘shake it off.’

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