Tag Archives: immersion Rotary Jet-Spinning (iRJS)

Suit up with nanofiber for protection against explosions and high temperatures

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Where explosions are concerned you might expect to see some army research and you would be right. A June 29, 2020 news item on ScienceDaily breaks the news,

Since World War I, the vast majority of American combat casualties has come not from gunshot wounds but from explosions. Today, most soldiers wear a heavy, bullet-proof vest to protect their torso but much of their body remains exposed to the indiscriminate aim of explosive fragments and shrapnel.

Designing equipment to protect extremities against the extreme temperatures and deadly projectiles that accompany an explosion has been difficult because of a fundamental property of materials. Materials that are strong enough to protect against ballistic threats can’t protect against extreme temperatures and vice versa. As a result, much of today’s protective equipment is composed of multiple layers of different materials, leading to bulky, heavy gear that, if worn on the arms and legs, would severely limit a soldier’s mobility.

Now, Harvard University researchers, in collaboration with the U.S. Army Combat Capabilities Development Command Soldier Center (CCDC SC) and West Point, have developed a lightweight, multifunctional nanofiber material that can protect wearers from both extreme temperatures and ballistic threats.

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A June 29, 2020 Harvard University news release (also on EurekAlert) by Leah Burrows, which originated the news item, expands on the theme,

“When I was in combat in Afghanistan, I saw firsthand how body armor could save lives,” said senior author Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and a lieutenant colonel in the United States Army Reserve. “I also saw how heavy body armor could limit mobility. As soldiers on the battlefield, the three primary tasks are to move, shoot, and communicate. If you limit one of those, you decrease survivability and you endanger mission success.”

“Our goal was to design a multifunctional material that could protect someone working in an extreme environment, such as an astronaut, firefighter or soldier, from the many different threats they face,” said Grant M. Gonzalez, a postdoctoral fellow at SEAS and first author of the paper.

In order to achieve this practical goal, the researchers needed to explore the tradeoff between mechanical protection and thermal insulation, properties rooted in a material’s molecular structure and orientation.

Materials with strong mechanical protection, such as metals and ceramics, have a highly ordered and aligned molecular structure. This structure allows them to withstand and distribute the energy of a direct blow. Insulating materials, on the other hand, have a much less ordered structure, which prevents the transmission of heat through the material.

Kevlar and Twaron are commercial products used extensively in protective equipment and can provide either ballistic or thermal protection, depending on how they are manufactured. Woven Kevlar, for example, has a highly aligned crystalline structure and is used in protective bulletproof vests. Porous Kevlar aerogels, on the other hand, have been shown to have high thermal insulation.

“Our idea was to use this Kevlar polymer to combine the woven, ordered structure of fibers with the porosity of aerogels to make long, continuous fibers with porous spacing in between,” said Gonzalez. “In this system, the long fibers could resist a mechanical impact while the pores would limit heat diffusion.”

The research team used immersion Rotary Jet-Spinning (iRJS), a technique developed by Parker’s Disease Biophysics Group, to manufacture the fibers. In this technique, a liquid polymer solution is loaded into a reservoir and pushed out through a tiny opening by centrifugal force as the device spins. When the polymer solution shoots out of the reservoir, it first passes through an area of open air, where the polymers elongate and the chains align. Then the solution hits a liquid bath that removes the solvent and precipitates the polymers to form solid fibers. Since the bath is also spinning — like water in a salad spinner — the nanofibers follow the stream of the vortex and wrap around a rotating collector at the base of the device.

By tuning the viscosity of the liquid polymer solution, the researchers were able to spin long, aligned nanofibers into porous sheets — providing enough order to protect against projectiles but enough disorder to protect against heat. In about 10 minutes, the team could spin sheets about 10 by 30 centimeters in size.

To test the sheets, the Harvard team turned to their collaborators to perform ballistic tests. Researchers at CCDC SC in Natick, Massachusetts simulated shrapnel impact by shooting large, BB-like projectiles at the sample. The team performed tests by sandwiching the nanofiber sheets between sheets of woven Twaron. They observed little difference in protection between a stack of all woven Twaron sheets and a combined stack of woven Twaron and spun nanofibers.

“The capabilities of the CCDC SC allow us to quantify the successes of our fibers from the perspective of protective equipment for warfighters, specifically,” said Gonzalez.

“Academic collaborations, especially those with distinguished local universities such as Harvard, provide CCDC SC the opportunity to leverage cutting-edge expertise and facilities to augment our own R&D capabilities,” said Kathleen Swana, a researcher at CCDC SC and one of the paper’s authors. “CCDC SC, in return, provides valuable scientific and soldier-centric expertise and testing capabilities to help drive the research forward.”

In testing for thermal protection, the researchers found that the nanofibers provided 20 times the heat insulation capability of commercial Twaron and Kevlar.

“While there are improvements that could be made, we have pushed the boundaries of what’s possible and started moving the field towards this kind of multifunctional material,” said Gonzalez.

“We’ve shown that you can develop highly protective textiles for people that work in harm’s way,” said Parker. “Our challenge now is to evolve the scientific advances to innovative products for my brothers and sisters in arms.”

Harvard’s Office of Technology Development has filed a patent application for the technology and is actively seeking commercialization opportunities.

Here’s a link to and a citation for the paper,

para-Aramid Fiber Sheets for Simultaneous Mechanical and Thermal Protection in Extreme Environments by Grant M. Gonzalez, Janet Ward, John Song, Kathleen Swana, Stephen A. Fossey, Jesse L. Palmer, Felita W. Zhang, Veronica M. Lucian, Luca Cera, John F. Zimmerman, F. John Burpo, Kevin Kit Parker. Matter DOI: https://doi.org/10.1016/j.matt.2020.06.001 Published:June 29, 2020

This paper is behind a paywall.

While this is the first time I’ve featured clothing/armour that’s protective against explosions I have on at least two occasions featured bulletproof clothing in a Canadian context. A November 4, 2013 posting had a story about a Toronto-based tailoring establishment, Garrison Bespoke, that was going to publicly test a bulletproof business suit. Should you be interested, it is possible to order the suit here. There’s also a February 11, 2020 posting announcing research into “Comfortable, bulletproof clothing for Canada’s Department of National Defence.”

Portable nanofibre fabrication device (point-of-use manufacturing)

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A portable nanofiber fabrication device is quite an achievement although it seems it’s not quite ready for prime time yet. From a March 1, 2017 news item on Nanowerk (Note: A link has been removed),

Harvard researchers have developed a lightweight, portable nanofiber fabrication device that could one day be used to dress wounds on a battlefield or dress shoppers in customizable fabrics. The research was published recently in Macromolecular Materials and Engineering (“Design and Fabrication of Fibrous Nanomaterials Using Pull Spinning”)

A schematic of the pull spinning apparatus with a side view illustration of a fiber being pulled from the polymer reservoir. The pull spinning system consists of a rotating bristle that dips and pulls a polymer jet in a spiral trajectory (Leila Deravi/Harvard University)

A March 1, 2017 Harvard University news release (also on EurekAlert) by Leah Burrow,, which originated the news item, describes the current process for nanofiber fabrication and explains how this technique is an improvement,

There are many ways to make nanofibers. These versatile materials — whose target applications include everything from tissue engineering to bullet proof vests — have been made using centrifugal force, capillary force, electric field, stretching, blowing, melting, and evaporation.

Each of these fabrication methods has pros and cons. For example, Rotary Jet-Spinning (RJS) and Immersion Rotary Jet-Spinning (iRJS) are novel manufacturing techniques developed in the Disease Biophysics Group at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering. Both RJS and iRJS dissolve polymers and proteins in a liquid solution and use centrifugal force or precipitation to elongate and solidify polymer jets into nanoscale fibers. These methods are great for producing large amounts of a range of materials – including DNA, nylon, and even Kevlar – but until now they haven’t been particularly portable.

The Disease Biophysics Group recently announced the development of a hand-held device that can quickly produce nanofibers with precise control over fiber orientation. Regulating fiber alignment and deposition is crucial when building nanofiber scaffolds that mimic highly aligned tissue in the body or designing point-of-use garments that fit a specific shape.

“Our main goal for this research was to make a portable machine that you could use to achieve controllable deposition of nanofibers,” said Nina Sinatra, a graduate student in the Disease Biophysics Group and co-first author of the paper. “In order to develop this kind of point-and-shoot device, we needed a technique that could produce highly aligned fibers with a reasonably high throughput.”

The new fabrication method, called pull spinning, uses a high-speed rotating bristle that dips into a polymer or protein reservoir and pulls a droplet from solution into a jet. The fiber travels in a spiral trajectory and solidifies before detaching from the bristle and moving toward a collector. Unlike other processes, which involve multiple manufacturing variables, pull spinning requires only one processing parameter — solution viscosity — to regulate nanofiber diameter. Minimal process parameters translate to ease of use and flexibility at the bench and, one day, in the field.

Pull spinning works with a range of different polymers and proteins. The researchers demonstrated proof-of-concept applications using polycaprolactone and gelatin fibers to direct muscle tissue growth and function on bioscaffolds, and nylon and polyurethane fibers for point-of-wear apparel.

“This simple, proof-of-concept study demonstrates the utility of this system for point-of-use manufacturing,” said Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics and director of the Disease Biophysics Group. “Future applications for directed production of customizable nanotextiles could extend to spray-on sportswear that gradually heats or cools an athlete’s body, sterile bandages deposited directly onto a wound, and fabrics with locally varying mechanical properties.”

Here’s a link to and a citation for the paper,

Design and Fabrication of Fibrous Nanomaterials Using Pull Spinning by Leila F. Deravi, Nina R. Sinatra, Christophe O. Chantre, Alexander P. Nesmith, Hongyan Yuan, Sahm K. Deravi, Josue A. Goss, Luke A. MacQueen, Mohammad R. Badrossamy, Grant M. Gonzalez, Michael D. Phillips, and Kevin Kit Parker. Macromolecular Materials and Engineering DOI: 10.1002/mame.201600404 Version of Record online: 17 JAN 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Stronger more robust nanofibers for everything from bulletproof vests to cellular scaffolds (tissue engineering)

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This work on a new technique for producing nanofibers comes from Harvard University’s School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering (also at Harvard University). From an Oct. 10, 2016 news item on phys.org,

Fibrous materials—known for their toughness, durability and pliability—are used in everything from bulletproof vests to tires, filtration systems and cellular scaffolds for tissue engineering and regenerative medicine.

The properties of these materials are such that the smaller the fibers are, the stronger and tougher they become. But making certain fibers very small has been an engineering challenge.

Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering at Harvard have developed a new method to make and collect nanofibers and control their size and morphology. This could lead to stronger, more durable bulletproof vests and armor and more robust cellular scaffolding for tissue repair.

An Oct. 7, 2016 Harvard University press release by Leah Burrows, which originated the news item, describes the research in more detail (Note: A link has been removed),

Nanofibers are smaller than one micrometer in diameter.  Most nanofiber production platforms rely on dissolving polymers in a solution, which then evaporates as the fiber forms.

Rotary Jet-Spinning (RJS), the technique developed by Kit Parker’s Disease Biophysics Group, works likes a cotton candy machine. Parker is Tarr Family Professor of Bioengineering and Applied Physics at SEAS and a Core Member of the Wyss Institute. A liquid polymer solution is loaded into a reservoir and pushed out through a tiny opening by centrifugal force as the device spins. As the solution leaves the reservoir, the solvent evaporates and the polymers solidify and elongate into small, thin fibers.

“This advance is important because it allows us to manufacture ballistic protection that is much lighter, more flexible and more functional than what is available today,” said Parker, who in addition to his Harvard role is a lieutenant colonel in the United States Army Reserve and was motivated by his own combat experiences in Afghanistan. “Not only could it save lives but for the warfighter, it also could help reduce the repetitive injury motions that soldiers, sailors, marines and airmen have suffered over the last 15 years of the war on terror.”

“Rotary Jet-Spinning is great for most polymer fibers you want to make,” said Grant Gonzalez, a graduate student at SEAS and first author of the paper.  “However, some fibers require a solvent that doesn’t evaporate easily. Para-aramid, the polymer used in Kevlar® for example, is dissolved in sulfuric acid, which doesn’t evaporate off. The solution just splashes against the walls of the device without forming fibers.”

Nanofibers are smaller than one micrometer in diameter.  Most nanofiber production platforms rely on dissolving polymers in a solution, which then evaporates as the fiber forms.

Rotary Jet-Spinning (RJS), the technique developed by Kit Parker’s Disease Biophysics Group, works likes a cotton candy machine. Parker is Tarr Family Professor of Bioengineering and Applied Physics at SEAS and a Core Member of the Wyss Institute. A liquid polymer solution is loaded into a reservoir and pushed out through a tiny opening by centrifugal force as the device spins. As the solution leaves the reservoir, the solvent evaporates and the polymers solidify and elongate into small, thin fibers.

“This advance is important because it allows us to manufacture ballistic protection that is much lighter, more flexible and more functional than what is available today,” said Parker, who in addition to his Harvard role is a lieutenant colonel in the United States Army Reserve and was motivated by his own combat experiences in Afghanistan. “Not only could it save lives but for the warfighter, it also could help reduce the repetitive injury motions that soldiers, sailors, marines and airmen have suffered over the last 15 years of the war on terror.”

“Rotary Jet-Spinning is great for most polymer fibers you want to make,” said Grant Gonzalez, a graduate student at SEAS and first author of the paper.  “However, some fibers require a solvent that doesn’t evaporate easily. Para-aramid, the polymer used in Kevlar® for example, is dissolved in sulfuric acid, which doesn’t evaporate off. The solution just splashes against the walls of the device without forming fibers.”

Other methods, such as electrospinning, which uses an electric field to pull the polymer into a thin fiber, also have poor results with Kevlar and other polymers such as alginate used for tissue scaffolding and DNA.

The Harvard team overcame these challenges by developing a wet-spinning platform, which uses the same principles as the RJS system but relies on precipitation rather than evaporation to separate the solvent from the polymer.

In this system, called immersion Rotary Jet-Spinning (iRJS), when the polymer solution shoots out of the reservoir, it first passes through an area of open air, where the polymers elongate and the chains align. Then the solution hits a liquid bath that removes the solvent and precipitates the polymers to form solid fibers. Since the bath is also spinning — like water in a salad spinner — the nanofibers follow the stream of the vortex and wrap around a rotating collector at the base of the device.

Using this system, the team produced Nylon, DNA, alginate and ballistic resistant para-aramid nanofibers. The team could tune the fiber’s diameter by changing the solution concentration, the rotational speed and the distance the polymer traveled from the reservoir to the bath.

“By being able to modulate fiber strength, we can create a cellular scaffold that can mimic skeleton muscle and native tissues,” said Gonzalez.  “This platform could enable us to create a wound dressing out of alginate material or seed and mature cells on scaffolding for tissue engineering.”

Because the fibers were collected by a spinning vortex, the system also produced well-aligned sheets of nanofibers, which is important for scaffolding and ballistic resistant materials.

This is the ‘candy floss’ technique at work,

Rotary Jet-Spinning (RJS) works likes a cotton candy machine. A liquid polymer solution is loaded into a reservoir and pushed out through a tiny opening by centrifugal force as the device spins. As the solution leaves the reservoir, the solvent evaporates and the polymers solidify and elongate into small, thin fibers. Courtesy: Harvard University

Rotary Jet-Spinning (RJS) works likes a cotton candy machine. A liquid polymer solution is loaded into a reservoir and pushed out through a tiny opening by centrifugal force as the device spins. As the solution leaves the reservoir, the solvent evaporates and the polymers solidify and elongate into small, thin fibers. Courtesy: Harvard University

Here’s a link to and a citation for the paper,

Production of Synthetic, Para-Aramid and Biopolymer Nanofibers by Immersion Rotary Jet-Spinning by Grant M. Gonzalez, Luke A. MacQueen, Johan U. Lind, Stacey A. Fitzgibbons, Christophe O. Chantre, Isabelle Huggler, Holly M. Golecki, Josue A. Goss, Kevin Kit Parker. Macromolecular Materials and Engineering DOI: 10.1002/mame.201600365 Version of Record online: 7 OCT 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.