Science AMA Series: We’re members of a team at Lawrence Livermore National Laboratory that is creating “second skin,” a breathable smart material that can respond to and protect against chemical or biological agents, for futuristic military uniforms. AMA!

Abstract

Hi Reddit,

I’m Francisco Fornasiero, a Staff Scientist within the Physical and Life Sciences Directorate at LLNL and I am part of a team working on the development of highly breathable “smart” materials aimed at protecting soldiers from chemical and biological threats. I obtained a Ph.D. in Chemical Engineering from the University of California at Berkeley in 2005, and had post-doctoral experiences at Stanford Research Institute (Menlo Park, CA) and at LLNL (Livermore, CA). During the graduate and post-graduate programs, I got interested in the use of carbon nanotubes (CNTs), i.e. tubular graphitic nanomaterials, for the fabrication of high performance membranes and composite films. Recently, our team has developed flexible polymeric membranes with carbon nanotube channels acting as moisture conductive pores. We have demonstrated that these nanochannels can sustain very rapid water vapor transport rates, and thus membranes made of these materials allow perspiration to escape efficiently. Because these pores are less than five nanometers in size, about 5,000 times smaller than the width of the human hair, the material prevents bioagents from getting in. While current uniforms are based on heavyweight, full-barrier protection, these moisture permeable uniforms would provide protection from bio-contaminated environments while preventing heat-stress and exhaustion. We believe that a material with this combination of properties holds great promises as the first key component of futuristic smart military uniforms that will respond to environmental hazards. With our collaborators, we are now developing responsive coating to actively block the permeation also of chemical threat without sacrificing breathability.

I am Ngoc Bui. I am currently a postdoc fellow in the Physical and Life Sciences Directorate at Lawrence Livermore National Laboratory (LLNL). My research interests lie at the interface of nanomaterials and membrane science and engineering for sustainable water, energy and life sciences. At LLNL, I join a team striving to develop smart dynamic fabric materials that can sense and protectively respond to chemical and biological warfare agents for in-the-filed military-personnel protection. I earned my PhD in Chemical Engineering under the advisement of Professor Jeffrey McCutcheon at the University of Connecticut. My PhD research focused on pioneering the development of a new and effective generation of nanofiber-supported thin film composite membrane platform for sustainable water and energy production by harnessing salinity-gradient energy via osmotically-driven membrane processes. My thesis also focused on developing as thorough a mathematical transport model as possible to de-convolute all mass transfer resistances in water and salt transport across the membrane, offering opportunities for better predictive models and advanced membrane and system designs with precise control to be proposed.

I’m Eric Meshot and I am a staff scientist at LLNL, bringing nearly a decade of expertise in carbon nanotube synthesis and structural characterization to the “Second Skin” program. My research interests revolve around hierarchical materials, energy storage, and in situ and multiscale characterization. This range of interests is informed by my diverse background in engineering, having studied engineering physics at the University of California at Berkeley (Go Bears!) before studying mechanical engineering and materials science at the University of Michigan (Go Blue!), where I got my PhD. Then, just prior to joining LLNL, I was awarded a research fellowship through the Belgian American Education Foundation to investigate novel optoelectronic devices made from carbon nanostructures at imec and KU Leuven in Belgium. I am fascinated by the seemingly endless potential uses for carbon nanomaterials, and I am thrilled to be pushing this particular second skin application forward from conception to reality.

My name is Kuang Jen Wu and I’m the group leader of Biosecurity and Bio-nanosciences group at LLNL. I received my Ph.D. in physics from University of Oregon. My research interest involves applying nanoscience and nanotechnology to problems relevant to national biosecurity applications. I work with a multidisciplinary team with expertise in physical science, life science and engineering. This unique cross-cutting expertise allows us to establish cutting edge science and engineering capabilities to support LLNL?s mission needs. Our current research focus includes developing novel detection methods for biological agents, advanced bioanalytical and molecular imaging instrumentations for nanoscale characterization, novel carbon nanotube fabrics that repels chemical and biological agents and nanolipidprotein technology as a medical countermeasure to biological threats.

That's all we have time for today. Thanks for all your questions! For more info on our work, check out https://www.llnl.gov/news/%E2%80%98second-skin%E2%80%99-uniform-protects-soldiers-biological-and-chemical-agents-field

Sorry to go off on a tangent right off the bat, but when I started reading this, my immediate thought was applying it to SCUBA advances.

Any thoughts in that direction?

All_Your_Base

Eric here. Thanks for the tangent!

Well this is my take: a) The material from which wetsuits are made keep our skin on one side warm by insulating from the cold water on the other side. b) I assume deep-sea suits are totally impermeable to water. On the other hand, our carbon nanotube membranes allow water to pass from one side to the other at a remarkably high rate when under pressure, so it does not seem a particularly good fit for scuba suits in either case a) or b)..

However, thinking outside the box, for other exploratory underwater activities, carbon nanotube membranes could be kept on your person, integrated with your scuba suit, for possible/promising use for point-of-use desalination (to make drinking water), energy storage (like a supercapacitor), controlled drug delivery...


Would it protect against VX nerve gas, or say a really strong strain of botulinum?

The_Jenazad

Hi, this is Ngoc. So far the material has not been tested with VX nerve or related gases. That would be our next step. We are currently working with our collaborators on tuning the properties of the active functional layer to enable the responsive protection from these chemical warfare agents. In essence, upon the exposure to these gases, the functional layer could change its conformation, blocking the pores which then allows a higher degree of protection.


So do you think you have any ethical responsibility regarding future biological warfare?

shinebox_leotardo

Eric here.

LLNL’s mission is national security, and so our team’s goal is to push science capabilities forward so that we can provide solutions that keep people safe, whether is in a warfare setting or other first responders and civilians (think Ebola outbreaks in a hospital). Also, please see our response to invictusmonkey’s post for “practical uses besides war”.


I've got an onslaught of small questions:

So this is like a latex bodysuit with carbon nanotubes in it?

Is there special treatment required to orient the nanotubes perpendicular to the membrane?

Do any nanotubes work or is there extreme dependence on the properties of the CNT used, such as the length or amount of walls?

Is there any kind of available measure of this perspiration rate? Would this breath similarly to a common textile or just much better than any alternative?

RaffleChampion

Eric here. Thanks for the onslaught :) Here are my responses in order:

-Yes, the material we are developing is a polymeric film (not quite as elastic as latex) with embedded carbon nanotubes spanning the thickness of that film, creating a large number of narrow transport channels. We envision the suit could eventually be made entirely of this material or be comprised of patches/panels of this material.

-Nanotube alignment: Our membranes are based on what are commonly called vertically aligned carbon nanotube “forests”, which self-align during synthesis, so we get a highly anisotropic/aligned morphology without any post-processing needed -- is what makes our material so special! There are other approaches the we are working with our collaborators to force unaligned nanotubes into aligned configurations as well.

-The precise correlation between structure and performance of carbon nanotubes in membranes remains an open question. For our particular application, which demands high breathability and high protection, it is vital that we employ small-diameter nanotubes to capitalize on rapid water vapor transport and size exclusion of biological threats. Having a high density of nanotubes is also crucial for maximum breathability. The flow dependence on nanotube length is not well established (we can discuss this more if you like), and the number of walls in principle should not matter since the molecules on the inside of the nanotube primarily only “feel” the effects on the innermost wall.

-We measure the performance of our materials in house ourselves using what is called the dynamic moisture permeation method. We demonstrated our carbon nanotube membranes have breathability equal or better than commercial fabrics like Gore-Tex, eVent, Sympatex...


How does it stand up against physical abrasion and general wear-and-tear? What sort of balance are you going to strike between a physically resilient material and a material capable of relaying fine tactile sensation for physical manipulation? How do you foresee the cost comparison to conventional equipment?

Mordrimbor

Hi, the membrane materials have not been tested yet for abrasion and general wear and tear. The primary objective of our work so far was the demonstration of materials with both high breathability and protection from biological threats. Mechanical properties and cost are important for practical realization of suits based on these materials, and will be addressed at later stages.


Awesome. Are you envisioning a "second skin" that protects the user simply through mechanical means or do you see this as a first step toward something with a more active, detect-and-respond counteraction to threats?

adenovato

Hi, this is Ngoc. Yes, this is the first step toward a more active, responsive smart dynamic materials. At the current stage, the protection capability of the materials are based on the size-exclusion mechanism by leveraging the small diameter of carbon nanotube channels. We are currently working with our collaborators on tuning the properties of the active functional layer to enable the responsive protection from chemical warfare agents. In essence, upon the exposure to these gases, the functional layer could respond either by: 1) changing its conformation, collapsing and blocking the pores and allowing a higher degree of protection or 2) destroying the threats and exfoliating from the region of contamination (like the snake skin).


Dr. Fornasiero,

A major issue with using carbon nanotubes is their dispersion characteristics in various matrices. However for this application, I assume modification is unnecessary due to a "layer by layer" design being used?

In this case, isn't orientation critical and therefore are these tubes "frozen" in place using a particular method? What polymer matrices are being used for evaluation? Also is chemical modification of the CNTs being considered?

Cost can be a major issue, are MWCNTs being considered? Would graphite also be an option in that case, given better dispersion characteristics?

BlackManonFIRE

Good question. Yes, our approach does not require carbon nanotube dispersion in solutions. We start from vertically aligned nanotube forests and then infiltrate the gaps inbetween the tubes with a vapor-deposited polymer. The deposition from the vapor phase allows maintaining the vertical orientation when forming the composite material. The polymer used so far is Parylene-N. We are exploring other matrices as well.

Yes, chemical modification of the CNTs is under consideration. Together with our collaborators, we are exploring means to functionalize the entrance of the CNT pores with polymers responsive to chemical threats. The polymers will function as gates for transport of molecules and are designed to block chemical agents while permitting water vapor to pass through.

I agree. For practical applications, cost is an important issue. In a parallel effort, we are considering more cost-efficient solution-based fabrication methods and the use of MWNT. In this case, our collaborators are evaluating CNT functionalization strategies for dispersion.


Are you far enough along in your research to be able to speak to projected fabrication cost once your material is produced at scale, or at least speak to your goals for cost?

JediLibrarian

Thank you for your question. We are not far enough along in our research to provide a good cost estimate for large scale production. The long term goal, however, is to be competitive with current protective suits.


What type of conductivity do your membranes have, and are they able to be layered to support hard points on the membrane with power? Also, do you support membranes that are electrochromatic? (an example is a membrane that would change from green to brown in the presence of an electrical charge.

If not, what would it take to do this?

frostfire1337

Hi, Ngoc’s here. In our materials, the carbon nanotube channels are of about 1 - 5% area of the whole membrane. The gap between the tubes are filled with a non-conductive polymer. That being said, we do not necessarily expect to have highly conductive membrane materials. Specifically, the conductivity is higher along the carbon nanotubes length. Tailoring a conductive membrane material is beyond our scope of work. However, for a certain application which requires high membrane conductivity, would a conductive polymer matrix help? And yes, the material can be layered into different composite membrane structures for use in various fields (if that’s what you meant in the question). In our approaches, we are not making membranes that are electrochromatic, although this sounds like a cool idea. Currently, the membrane supports a functional layer that can change its electronic stages, and thus colors when being exposed to solvents like TFA.


Are you talking to any of the military personnel who worked in the ebola treatment centres about what their needs/requirements from such a material would be?

I know a few other people have asked already about its validity as a non-military biocontainment suit for medical PPE... but I'd be really interested in how long it not only offers protection for, but is practical to work in (due to how hot the wearer gets etc). A key difference in future conflict situations is likely to be outbreaks of infectious disease - see the polio outbreak in Syria as an example, and Ebola itself is another example of where a large military response was required in a non-warfare situation - that requires the military to operate for sustained periods in a potentially contaminated environment, not just 'fight through and withdraw' which has previously been the assumed environment in which such PPE is needed (and yes, I know the situation with polio can be solved just by ensuring anyone going in is vaccinated, but was just using this as an example). You do talk about this - and it seems that the material you're working on is an improvement in this regard on what we already have, but I wondered if you are doing any planning around military doctors, or military-supported healthcare staff working for sustained periods (perhaps up to several weeks) in a contaminated environment, as well as just being protected while they withdraw?

JenniferColeRhuk

Eric here. Comfort is vital! The inspiration for creating this material stems from the fact that current PPE cannot be worn for long periods of time without suffering heat exhaustion. Our material provides breathability is better than that of Gore-Tex but delivers a high level of bio-threat protection via size exclusion of the sub-5-nanometer carbon nanotube pores. With these specs, our material is a great fit for warding off viruses like Ebola. We are working closely with the Defense Threat Reduction Agency (DTRA @ DoD) to understand the specific, quantifiable needs of military personnel. And we would be interested in talking with any other potential stakeholder, including medical personnel!


Livermore represent!! Since I live across the street from the lab and rent to interns, I am always happy to the lab mentioned on Reddit!

So my questions to all of you are:

Do you ever get out into the community and enjoy the wineries, breweries, 100 year old lightbulb, etc.?

And will you ever get a chance to speak at the Bankhead theater to discuss your awesome research with the community?

chocolateismyhobby

Eric here.

We do get out of the lab sometimes...but there is always lots of important work to be done as you know. LLNL does not specifically promote any particular establishment, be our team has frequented Garré and Wente for lunch/dinner :)

I am sure someone from our team will do a Science on Saturday talk one of these days. Keep an eye out for us!


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