DexMat recently attended the Advanced Functional Fabrics of America (AFFOA) Membership Summit in Boston to demonstrate prototype garments capable of measuring ECG signals using dry-contact skin electrodes made of Galvorn yarn.
AFFOA is an organization dedicated to supporting and fostering collaborations between industry, government, and university research groups developing advanced functional fiber and textile technology; their mission is to revitalize the United States domestic textile industry by fostering the development of entirely new types of fabric and wearable devices. DexMat has been a member of AFFOA since 2020, with the goal of developing Galvorn carbon nanotube fibers and fabrics into an important part of this emerging advanced textile industry.
With funding from AFFOA, DexMat partnered with Hexoskin Health sensors & AI, a manufacturer of wearable health monitoring garments based in Montreal, to make & test prototype versions of the Hexoskin vest that use Galvorn carbon nanotube (CNT) yarn electrodes. Our electrodes consisted of Galvorn yarn embroidered into pieces of elastic fabric, which were then sewn into the interior lining of the vests and connected to a set of lead wires that carry signal to a recording device. The prototypes that we produced for the AFFOA event showed that Galvorn CNT yarn electrodes could collect high-quality ECG data from a user going about daily activities over long periods of time.
Stretchable grid pattern of Galvorn CNT yarn embroidered on the inside surface of a prototype wearable vest, as an electrode surface for ECG signals. In an ECG-monitoring garment, three such electrodes are positioned at different locations on the torso.
We were able to confirm that these prototypes could be subjected to at least 6 washing cycles in a laundry machine without any degradation in their electrical properties. Our expectation is that further testing will show that this remains the case over many more wash cycles, since CNT do not oxidize or tarnish easily in water. Wash cycle durability is a weak point for metallized textile fibers and fabrics, one of the categories of material that are commonly used for dry-contact skin electrodes in wearable garments; the thin layers of metal coated onto textile materials can increase dramatically in electrical resistance as they oxidize, rendering electrodes ineffective after 50 to 100 washing cycles. If Galvorn CNT fibers can exceed this limit, they may be useful in the creation of a new generation of health-monitoring garments with longer usable lifetimes.
If you would like to learn more about our Galvorn CNT yarns and fabrics please visit the link below to see a full list of specifications of our standard products and please support our work towards commercialization by purchasing some yarn and fabric for your wearable electronics projects.
GREEN-SCALING NANOTECHNOLOGY IN HOUSTON'S ADVANCED MATERIALS SECTOR
Greater Houston Partnership recently highlighted the unique position Houston has created for companies like DexMat to foster growth in what is considered the "Energy Capital of the World". Development of advanced materials like the carbon nanotube products made by DexMat can be scaled for commercialization with net-zero greenhouse gas emissions while at the same time producing hydrogen.
See the full article by the Greater Houston Partnership here:
For further information on DexMat's efforts to develop a clean source of CNT materials please see our post here. To learn more about Rice University's Carbon Hub, you can Take a look at the Carbon Hub Youtube channel or the Carbon Hub website to learn a bit more about the state of carbon technology. And, if you would like to learn more about our carbon nanotube products that could eventually be made with decarbonized forms of carbon, follow the link to our online store below!
GALVORN CARBON NANOTUBE FABRICS: FIRST LOOK
We are proud to announce that our first fabric products made using Galvorn carbon nanotube yarn are now available for sale in our online store. Please visit https://store.dexmat.com/galvorn-cnt-fabric/ to request a custom quote for Galvorn CNT fabric!
DEPARTMENT OF ENERGY AWARDS $200,000 TO DEXMAT, INC FOR PHASE I STTR
Department of Energy Awards $200,000 for Small Business Research and Development to DexMat, Inc.
One of 259 Grants Totaling $53Million Nationwide to Support Scientific Innovation in Clean Energy Development and Climate Solutions
May 20, 2022 -- U.S. Energy Secretary Jennifer Granholm today announced that DexMat, Inc. will receive $200,000 as part of 259 Department of Energy grants totaling $53 million to 210 small businesses in 38 states. The awards include projects relating to particle accelerators and fusion technology, applied nanoscience, quantum information applications, and dark matter research along with a wide range of other efforts.
“Supporting small businesses will ensure we are tapping into all of America’s talent to develop clean energy technologies that will help us tackle the climate crisis,” said Steve Binkley, Acting Director of the DOE’s Office of Science. “DOE’s investments will enable these economic engines to optimize and commercialize their breakthroughs, while developing the next generation of science leaders and ensuring U.S. scientific and economic competitiveness that will benefit all Americans.”
Through the SBIR/STTR program across the federal government, small business powers the U.S. economy and generates thousands of jobs, both directly and indirectly, the DOE notes. DOE Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) awards aim at transforming DOE-supported science and technology breakthroughs into viable products and services. The awards also support the development of specialized technologies and instruments that aid in scientific discovery.
DexMat, Inc. will receive $200,000 to develop enhanced thermal conductivity carbon nanotube (CNT) fibers for use as lightweight motor windings and for thermal management in battery and electronics applications.
Dexmat is excited to partner with Geoff Wehmeyer’s group at Rice University to develop enhanced thermal conductivity CNT fibers for this DOE STTR award and we anticipate getting excellent results that will enable broader application of Galvorn CNT fibers for motors and electronic devices.
On Friday, October 8th 2021, The department of Energy's advanced materials manufacturing division announced the winners of the CABLE Conductors Manufacturing Prize. In order to compete for this prize, teams of researchers submitted their plans for developing improved electrical conductors for energy applications in the near future. Researchers from the Pasquali-Irvin lab at Rice Univeristy joined forces with DexMat and entered this competition under the team name "Clean Carbon Conductors", proposing a focused effort to develop enhanced conductivity carbon nanotube conductors. We are happy to announce that we have been chosen as one of the ten winning teams!
Recent Rice University research suggests that a focused effort on CNT fiber conductivity enhancements could lead to CNT conductors with electrical conductivity greater than 112% IACS (i.e., 112% the conductivity of copper at room temperature) in the next 5-10 years. Furthermore, these CNTs can be synthesized with net-zero greenhouse gas emissions via methane pyrolysis while producing hydrogen fuel as a co-product. DexMat has a low-cost, scalable, fluid phase production method for manufacturing CNT conductors, and by partnering with Rice University to deliberately focus on enhancing electrical conductivity, we believe that the Clean Carbon Conductors team can one day produce CNT yarns with >65 MS/m electrical conductivity.
Below, you can check out the video we submitted along with our team's application to the contest; it highlights our proposed plan to increase the conductivity of CNT materials while working towards a net-zero carbon emission energy future!
Please stay tuned to see our progress in the American-Made Challenge as we proceed to Stage 2 of the competition!
RICE UNIVERSITY MONITORS HEARTS WITH CARBON NANOTUBE WEARABLE SENSORS
This month in The Lab we'd like to highlight more of the great work being done by Rice University on carbon nanotube yarn applications. Most recently, researchers at Rice have demonstrated 'smart clothing' in which carbon nanotube yarns act as skin-contact EKG electrodes and as conductive wires that carry the EKG signals to Bluetooth data transmitters on the side of the garment. This health-monitoring shirt is comfortable, flexible, and washable. Check out the full press release about this work on Rice's media page here.
Wearable electronics is one of the application areas that we are particularly excited to pursue with Galvorn materials in the near future. You can check out our previous work on lab-scale wearable or skin-contact electrode prototype devices at thesepastblog posts. It's great to see this integrated demonstration of the technology from the team at Rice!
As always, if you are curious to try out DexMat's Galvorn carbon nanotube yarns, fibers, or films for your particular engineering appllications, follow the link below.
BUILDING CLEAN CARBON AND FUELING A NEW TOMORROW
DexMat co-founder and Rice University Professor Matteo Pasquali and Dr. Carl Mesters of the Shell Technology Center in Houston have written an opinion article in the the upcoming issue of the Proceedings of the National Academy of Sciences, expanding further on the idea that hydrocarbons can and should be used in new ways that will produce clean hydrogen and useful carbon materials without releasing greenhouse gasses into the atmosphere.
The current methods of hydrocarbon use, in which oil and natural gas are burned directly to release energy along with carbon dioxide and other greenhouse gasses, may soon give way to a cleaner technology, allowing us to use those same hydrocarbon resources to build a better tomorrow. Instead of burning them, we can split the hydrocarbons into carbon, which can be used to make useful solid materials, and hydrogen, which can be used as a clean-burning fuel. As described in this opinion to PNAS and in previous articles in local Houston press, this change would have multiple other benefits, since it would allow the existing oil and gas industry to shift into a new mode of production without much economic disruption, decarbonize industrial emissions, and it may allow us to replace materials that are particularly energy-intensive and environmentally unfriendly to create with replacements made from carbon.
The strength of the incentive for the oil and gas industry to make this change will depend in large part on the usefulness of the various carbon materials that can be made out of the carbon derived from this process. This is where materials such as high-performance carbon nanotube yarns and films can come into the picture; however, in order to realistically use the giga-tons of carbon that could be generated from hydrocarbons, these materials themselves need to become less expensive to produce. Research efforts such as those carried out at Rice University's Carbon Hub may help bridge that gap by finding more affordable ways to produce high-performance solid carbon materials.
Pasquali and Mesters end their opinion piece with a call to action, pointing out that effort is required not only from industry, but also from researchers, philanthropists, and government agencies in order to meet the challenge of making this energy & material transition. They point out that each of these different groups may benefit from this work in different ways, and that all of them can do work now to accelerate this change towards a brighter future.
If you would like to learn more about Rice University's Carbon Hub, you can Take a look at the Carbon Hub youtube channel or the Carbon Hub website to learn a bit more about the state of carbon technology. And, if you would like to learn more about our carbon nanotube products that could eventually be made with decarbonized forms of carbon, follow the link to our online store below!
CARBON NANOTUBE YARNS PART 1: TWISTED YARNS
This article is the first of a two-part series about how carbon nanotube (CNT) fibers can be twisted or braided into finished yarns. In this article we will introduce the reasons for making CNT yarn products and discuss the construction, as well as the pros and cons, of twisted yarns. In the second article we will discuss the basic structure of our braided CNT yarns.
Fibers vs. Yarns
DexMat’s Galvorn CNT fiber products are available in three basic formats. The first format is that of an individual, solid fiber filament formed by our proprietary process, which transforms disordered CNTs into an aligned structure. These filaments range in size from 10 microns to around 100 microns in diameter, and the CNTs that compose them are densely packed and highly aligned along the fiber axis. The (relatively) high density and high degree of alignment achievable in this format allows it to achieve high values in many of the material properties we look for in CNT fibers, including tensile modulus, electrical conductivity, and thermal conductivity. However, there is a natural limit to the size that we can achieve in an individual fiber filament, particularly if we want to make compact fibers with a reasonably round cross-section. For this reason, it is difficult to fabricate individual fibers with diameters larger than 100 microns.
For applications that require larger diameters, either to bear more mechanical load or to achieve a lower total electrical or thermal resistance, it is necessary for us to combine individual fiber filaments into larger yarns. When making a yarn, we start not with individual CNT fibers but with a number of parallel fibers collected together in a bundle; several such bundles are then combined together to make the yarn. The total linear mass of the yarn will depend on the size of the individual fibers, the number of fibers in the bundle, and the number of bundles that are combined together into the final yarn; the yarn diameter will depend on the packing density of the chosen yarn structure in addition to the above factors. We offer Galvorn CNT yarns in two formats: plied and twisted yarns with diameters ranging from 130 microns to 500 microns, and braided yarns with diameters ranging from 600 microns to 1000 microns.
Combining individual fibers into larger yarns does introduce some drawbacks in terms of achievable material properties. Even if a yarn composed of many individual filaments is tightly wound, it will always have a density somewhat lower than the density of those filaments; for this reason, properties that are normalized by cross section, such as tensile strength and conductivity, will be lower in a yarn. On the other hand, the yarn structure imparts properties that the individual CNT fiber filaments do not possess on their own: an increase in abrasion resistance, an increase in stretchability, and a stable shape that is more resistant to deformation when bent or compacted. These properties, along with the flexibility and overall density of the yarn, depend to a great extent on the style of construction that is chosen.
Twisting and plying filaments together into a larger structure is a technique that is used to create many yarns and ropes out of a wide variety of fiber materials with a wide variety of sizes. Regardless of the material, the fundamental construction of twisted yarns is the same: bundles of filaments are twisted around their own axes, and then 3 or more such bundles are twisted together into a larger combined cable. The initial twist imparted to the bundles themselves is crucial: the yarn holds together because the direction of twist within the bundles and the direction in which they are twisted around one another are opposed. The elastic energy that would normally induce the bundles to unravel from each other and the elastic energy that would cause each bundle to untwist create a system of forces that oppose and balance each other out. This type of yarn structure is said to be “locked”, and will not unravel spontaneously.
The direction of twist applied to create the final yarn determines the final chirality of the structure. These different chiralities are referred to as “S” or “Z” twists, based on their visual appearance; The image below shows how an “S” and “Z” twist can be identified. In some applications, depending on the types of torque or abrasion forces the yarn is expected to experience, one or the other of these chiralities might be preferred.
Yarn with a twisted structure has several benefits. When a proper degree of twist is applied it promotes a tight packing density between constituent filaments, particularly once the twist is “locked” into place by a balance of stored elastic energy. This close contact between fibers is beneficial for stress transfer, heat transfer, or (in the case of electrically conductive fibers) transfer of electric current. The twisted structure has additional benefits for the mechanical properties of the yarn: by the nature of the structure, any tensile force applied to the yarn will be partially applied to compress the filaments together even more tightly. Finally, for applications in which some degree of elongation or elastic deformation is important, using a twisted yarn structure is the best way to increase or modify the stretchiness of stiff fibers; untwisted Galvorn CNT fibers fall into this category, having an elongation of only 1% - 2% before they break. The creation of comfortable and flexible e-textiles is an example of an application in which imparting a bit of elasticity into CNT yarns will be crucial.
The twisted yarn structure also comes with a few drawbacks. Primarily, in spite of the balance of torsional forces that create a ‘locked’ yarn structure, it is possible for twisted yarns to come apart as they are worked, particularly if they are subject to a lot of twisting motion or if the ends of the bundles are unsecured and free to unravel; this is less of a concern in braided yarns. Additionally, the increase in elongation that a twisted yarn imparts to a stiff fiber material can be a drawback for applications that require high stiffness, such as the creation of ballistic fabric or various uses for ropes and cables in which stability is paramount; for such applications, untwisted fiber bundles or braided yarns might be more suitable.
Galvorn Twisted CNT Yarns
We make our twisted CNT yarns through a typical plying technique, as described above; for this process, we use a machine very similar to the one shown in the video below. This is a roll-to-roll process, which allows us to create continuous lengths of tens or hundreds of meters of twisted yarn without interruption. Payoff spools containing bundles of CNT fiber are loaded onto a circular rotating wheel; these bundles are brought together through a central aperture and strung across the length of the machine to a single take-up roll. The wheel is turned by a motor, twisting the bundles around one another as the take-up roll draws them forward; simultaneously, each of the payoff spools is counter-rotated within its place on the wheel. Variable braking force can be applied to the payoff spools in order to ensure that there is proper tension in the bundles, creating a dense yarn structure as they are combined.
Several parameters can be varied during the production of our Galvorn yarns, and we pay close attention to these parameters to ensure that we maximize the performance and properties of the resulting yarn. One variable is the direction of twist, determining whether the yarn we create will have a “Z” or “S” construction. A second, much more critical, parameter is the degree of twist imparted to the yarn as it is being plied; this can be measured in the number of twists per inch (TPI) of yarn length. Increasing TPI helps us to achieve a high density yarn in which the individual CNT fibers are well packed with one another with very little void space; this is important for the mechanical performance, durability, and abrasion resistance of the yarn. However, we have observed that a high level of twist has a negative impact on CNT yarn conductivity. In addition, the tensile strength of yarn only increases with increased twisting up to a certain point; if the yarn is over-twisted then the tensile strength plateaus and then begins to decline.
Finally, we can vary the number of CNT fiber bundles that will be combined together to make the yarn. With our current equipment we are able to twist together up to six bundles, and one additional non-twisted bundle can be included to form a core. We have achieved the best yarn properties using a simple 3-ply construction, with three bundles twisted together. However, plying yarn with four or seven bundles is a useful technique when a larger diameter twisted yarn is required. Of course, the yarn diameter can also be increased by increasing the diameter of the constituent bundles, but in some circumstances process limitations or performance requirements may limit the maximum size of the bundles.
The high magnification image below, acquired from a scanning electron microscope, shows off the detailed structure of a Galvorn CNT yarn. This is a 3-ply yarn with a “Z” twist construction; the fiber bundles themselves have a clearly visible “S” twist arising from the counter-twist that was used to lock the yarn during the plying process.
This electron microscope image also provides a useful illustration of one of the drawbacks of twisted / plied yarns compared to braided yarns or individual fibers: plied yarn has a non-uniform diameter and a cross section that is further from being round, especially when it has been plied from only 3 or 4 bundles. This deviation from the more compact cylindrical construction leads to a decrease in the effective density of the yarn. This drawback is more pronounced when larger bundles are used, such as in the creation of large-diameter 3-ply yarn. By following the link below to our online store, you can see that our Galvorn twisted yarn is currently available in diameters up to 500 µm. This does not represent an absolute limit on our capability, but rather a point beyond which we have so far found it easier to achieve high performance using braided yarns, which maintain a more compact cylindrical shape.
More can be said about the challenges and opportunities for optimizing CNT yarn performance, and on the differences between twisted yarn and the various styles of braided yarn. Check back in a week for our next post in this two-part series, in which we will describe the pros and cons of braided constructions. In the meantime, you can follow the link below to see the various yarn products offered in DexMat's online store.
HYDROCARBON ZERO-EMISSIONS FUTURE
Local Houston area news channel KHOU 11 recently ran a great segment explaining the basics of Rice University's Carbon Hub and their efforts to make carbon materials and hydrogen from hydrocarbons. Instead of burning hydrocarbons for energy, creating pollution and carbon dioxide, we can split the hydrocarbons into carbon that can be used to make high-performance materials and hydrogen that can be used as a clean-burning fuel. As Rice University professor Matteo Pasquali puts it in the interview, this process could potentially be used to both build a car and power it.
These zero-emission uses for hydrocarbons are not limited to transportation. The carbon materials that might be produced this way include carbon nanotubes and graphene, and these can be processed using DexMat's technology and other material science techniques to replace textiles, metal wires, or traditional carbon fibers, becoming useful in industries such as biomedical engineering, resource manufacturing, aerospace, industrial goods, and electrical energy storage and distribution.
If you would like to learn more about Rice University's Carbon Hub, you can Take a look at the Carbon Hub youtube channel or the Carbon Hub website to learn a bit more about the state of carbon technology.
REAL ENGINEERING HIGHLIGHTS CARBON NANOTUBES
Earlier this month the Real Engineering Youtube channel posted a great video explaining the basics of carbon nanotubes and their potential to be used in modern technology. We're happy to have some footage of our lab and out carbon nanotube products featured in this segment!
The video does a particularly good job of showing how the atomic structure of carbon gives rise to the different molecular structures of diamond, graphite, and carbon nanotubes, and how that in turn leads to different properties for each material. If you have ever heard a solid state scientist talk about sp2 orbitals and wondered what those were, then this video is a must-see!
Real Engineering also does a good job of quickly summarizing some of the challenges of unlocking the full potential of carbon nanotubes and, on the other hand, highlights a few of the near-term applications that we are excited about, such as smart clothing, lightning protection for airplanes, and biomedical implants.
All in all, this is a fantastic introductory video for anyone interested in learning about carbon nanotubes and the current prospects for carbon nanotube materials. Check out the video on the Real Engineering Youtube channel.
And, if you would like to learn more about our carbon nanotube products, follow the link to our online store below!