Mil-Aero Industries Eye Carbon Nanotubes as They Target Cost Savings

Ultra-lightweight carbon nanotubes may replace copper wires.

Today’s aerospace and aircraft industries focus on size, weight, power, and cost (SWaP-C), and cost is now often figured for program or operational life, which may total thousands of dollars per pound. This gives tremendous impetus and justification to accept high-cost new technology to obtain weight savings.

Reducing F-35 by 20 Pounds Could Provide $230M Savings

Satellites have always paid extra to reduce weight since each payload pound may cost more than $5,000 to launch. Studies by the Center for Strategic and Budgetary Assessments (CSBA) show that the new F-35 has a $4,500 cost per pound over the aircraft’s operational program life

until 2070. (For comparison, the cost per pound for the F-22 is estimated at $3,500.) The F-35 has projected production of2,557 aircraft for the U.S. and nine for export customers scheduled through 2037. Therefore, a weight reduction of just 20lbs per plane could result in savings of $230,000,000! Even if this is off by 50%, the expected benefits already are driving new industry developments.

In addition to fighter aircraft, each ounce is also critical in future soldier wearables, UAVs, portable radars, vehicle communications, and other equipment to increase survivability, mission endurance, and success.

Interconnect weight savings are being obtained by incorporating higher contact density, composite materials, combinational multi-port connectors, and other approaches. However, a new technology involving carbon nanotubes (CNTs) is emerging and offers a lightweight alternative to copper wire and other conductive shielding materials. A carbon nanotube is produced as a layer of carbon atoms in a tubular configuration, in single- or multiple-walled versions.

CNTs are being mixed with polymers to create high-strength, lightweight composite materials. CNT fibers can be made into conductive sheets and tapes, which offer a myriad of potentials. Optimal performance may result from spinning CNT fibers into conductive threads (referred to as yarn) to potentially replace copper wires in harnesses, motor windings, and shields.

Another important gain is reliability. CNT fibers and yarn can withstand millions of bending cycles, while standard fiber/wire would have yielded many times. The minimum bending radius requirements of today’s cable is not applicable for CNT fibers and cables.

Market potentials for CNT technology are bringing new companies into the forefront. Nanocomp Technologies offers commercial CNT fibers created using a carbon vapor deposition (CVD) reactor and then formed into sheets or fibers that can be twisted into shields or primary conductors. Another supplier is Syscom Advanced Materials Inc., which provides a variety of metal-clad fibers.

DexMat Inc. in Houston produces CNT fiber using a wet acid process that draws multiple fibers that can be shaped into a shield or primary conductor, and future developments for  include flat tape. The company boasts a strong Ph.D. cadre from nearby Rice University where they have successfully fabricated coaxial cable inner and outer conductors by coating a solution of CNTs in chlorosulfonic acid to achieve a two-times better conductivity than seen previously. This may prove an attractive alternative to commercial coax cable using tin-coated-copper with comparable attenuation and greater mechanical durability with 97% reduced mass, according to the company.

Usually, the outer conductor is the heaviest portion of today’s cables. In coax, the outer conductor provides both signal transmission and electromagnetic shielding. While shielding does not require high conductivity in the outer conductor, signal loss (i.e., signal attenuation) through the transmission line is significantly affected by the conductivity and architecture of the outer conductor. The new solution-coated CNT outer conductors offer near-term application potentials. Several connector companies are reportedly studying termination techniques.

Carbon Nanotube Materials Provide Shielding

TE Connectivity has been working to use CNT materials for shielding and data transmission cables. In a paper presented at the 2012 IWCS Conference, Dr. Stefanie Harvey, senior manager for corporate strategy, reported that they had achieved greater than 50dB shielding effectiveness in the GHz range, and their “data transmission cables using a yarn format perform comparably to MIL-STD-1553.” In the January 5, 2016 issue of ASSEMBLY, Dr. Harvey reviewed how replacing the braid in RG-58 cable would reduce weight from 38.8 grams per meter (g/m) to 11.5g/m, while replacing the center conductor with CNT yarn would further reduce weight to 7.3g/m for a combined weight reduction of 80%.

Composites are used to replace heavy copper wire with metal plated aramid fibers for use in wire and cable EMI shielding. EMI shielding made with plated aramid fibers can reduce weight by as much as 80%, leading to major weight reduction depending on the size of the aircraft or satellite. Aramid fibers are a class of strong, heat-resistant synthetic fibers, the best known of which is DuPont™ Kevlar®, used in ballistic-rated body armor.

Carlisle Interconnect Technologies (formerly Micro-Coax Inc.) provides a unique weight-reducing EMI/RFI shielding solution using their proprietary high-strength ARACON® brand metal clad fibers. Ron Souders, technical director, Carlisle Interconnect Technologies, advises that, for typical applications, switching to ARACON allows a weight savings of 80% when compared to traditional metal braided or woven EMI shielding products. This offers the conductivity of an outer metal coating with the strength, light weight, and flexibility of aramid fiber.

*Note: DexMat also provides products for shielding applications not mentioned in this article.

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Ron Souders further explained that the specific gravity of aramid fiber is only 1.44g/cc, compared to copper at 8.9g/cc, and that, even with the addition of metal coatings, the specific gravity of ARACON fibers ranges from 3 – 5g/cc. The tensile strength (measured in kilopounds per square inch, or Ksi) of the aramid core (350Ksi) is from three to 10 times higher than that of traditional or high-strength copper cores, which typically span 35 to 95Ksi. Since ARACON fibers behave like a textile, they are far more flexible and compliant than metal.

Industry Standardization is Underway

The benefits offered by CNT fiber, whether as EMI/RFI shielding, signal or coaxial cable, or other new components, have prompted the Naval Air Systems Command (NAVAIR) in Patuxent River, Maryland, to sponsor the establishment of suitable “Military Specification for Conductive Carbon Conductors used in Aircraft Wiring,” eventually with QPL sources. The proposed formal qualification program should stabilize components and materials for future use.

CNT technology also was included in a recent multiple-day RF coordination meeting held in February by the Defense Logistics Agency (DLA) at the Defense Supply Center Columbus (DSCC). Suppliers of basic CNT materials, wire, cables, cable assembles, and signal and RF/microwave connectors are now working on both application-specific and generalized products to achieve the weight reduction and reliability benefits offered by CNT and other metallized fibers.

Original story by David Shaff – April 28, 2017

Gamma-ray shielding performance of carbon nanotube film material

This paper aims to explore the shielding potential of light-weight carbon nanotube (CNT) film materials against gamma-ray generated from americium-241 (241Am) and caesium-137 (137Cs). The influence factors of gamma mass attenuation coefficient of CNT film laminates were investigated to reveal structure-property relationship. The results showed that CNT film materials had bigger mass attenuation coefficients than carbon fiber reinforced composites, suggesting stronger radiation interaction induced by CNT’s cylindrical nanostructure. CNT alignment was proved to be conducive to the improvement of mass attenuation coefficient and gamma attenuation ratio. Aligned CNT film laminate with the thickness of 10 mm had a mass attenuation coefficient of 0.086 cm2 /g and attenuation ratio of 4.9% against gamma-ray exposed to 137Cs, which were higher than those of aluminum, iron or copper sheets. CNT film material demonstrated its potential for the application of light-weight gamma-ray safety equipment and devices.

Download full paper at: https://houstontx.library.ingentaconnect.com/content/asp/me/2016/00000006/00000005/art00010

DexMat Cofounders Featured in Forbes 30 Under 30: Manufacturing

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Source: DexMat Cofounders Featured in Forbes 30 Under 30: Manufacturing

Nanotube Fibers Being Tested as a Way to Restore Electrical Health to Hearts

Rice University, Texas Heart Institute will study soft, conductive fibers’ ability to bridge scar tissue

Rice University and Texas Heart Institute researchers are studying the use of soft, flexible fibers made of carbon nanotubes to restore electrical conductivity to damaged heart tissue.

Rice scientist Matteo Pasquali holds a spool of fiber made of pure carbon nanotubes. The fibers are being studied to bridge gaps in the conductivity in damaged heart tissues.

Rice scientist Matteo Pasquali holds a spool of fiber made of pure carbon nanotubes. The fibers are being studied to bridge gaps in the conductivity in damaged heart tissues. Photo by Jeff Fitlow

With support from the American Heart Association, these institutions will test the fibers’ ability to bridge electrical gaps in tissue caused by cardiac arrhythmias that affect more than 4 million Americans each year.

A beating heart is controlled by electrical signals that prompt its tissues to contract and relax. Scars in heart tissue conduct little or no electricity. Soft, highly conductive fibers offer a way to work around those gaps.

“They’re like extension cords,” said Mehdi Razavi, the director of electrophysiology clinical research at the Texas Heart Institute and the project’s lead investigator. “They allow us to pick up charge from one side of the scar and deliver it to the other side. Essentially, we’re short-circuiting the short circuit.”

The nanotube fibers developed at Rice by the lab of chemist and chemical engineer Matteo Pasquali are about a quarter of the thickness of a human hair. But even an inch-long piece of the material contains millions of nanotubes, microscopic cylinders of pure carbon discovered in the early 1990s.

Though the fibers were developed to replace the miles of cables in commercial airplanes to save weight, their potential for medical applications became quickly apparent, Pasquali said.

“We didn’t design the fiber to be soft, but it turns out to be mechanically very similar to a suture,” he said. “And it has all the electrical function necessary for an application like this.”

Because the fibers are soft, flexible and extremely tough, they are expected to be far more suitable for biological applications than the metal wires used to deliver power to devices like pacemakers. They have already shown potential for helping people with Parkinson’s disease who require brain implants to treat their neurological condition.

Rice University research scientist Flavia Vitale is developing nanotube fiber applications. She is part of a collaboration with Texas Heart Institute to use the fibers as conductive bridges for damaged heart tissue.

Rice research scientist Flavia Vitale is developing nanotube fiber applications. She is part of a collaboration with Texas Heart Institute to use the fibers as conductive bridges for damaged heart tissue. Photo by Jeff Fitlow

“People who progress to heart failure can have the formation of scar tissue over time,” said Mark McCauley, a cardiac electrophysiologist at the Texas Heart Institute. “There are a lot of different ways scarring can affect conduction in the heart. Recently we’ve been most interested in the development of scarring after heart attacks, but we believe this fiber may help us treat all kinds of cardiac arrhythmias and electrical-conduction issues.”

“Metal wires themselves can cause tissue to scar,” said Flavia Vitale, a research scientist in Pasquali’s lab who is developing nanotube fiber applications. “If you think about inserting a needle into your skin, eventually your skin will react and completely isolate it, because it’s stiff. Scar will form around the needle.

“But these fibers are unique,” she said. “They’re smaller and more flexible than a human hair and so strong that they can resist flexural fatigue due to the constant beating of the heart.”

Vitale noted the fibers’ low impedance (its resistance to current) allows electricity to move from tissue to bridge and back with ease, far better than with metal wires.

The researchers are testing the fibers’ biocompatibility but hope human trials are no more than a few years away.

Razavi said a safe, effective way to conduct electricity through scarred heart tissue will revolutionize treatment. “Should these more extensive studies confirm our initial findings, a paradigm shift in treatment of sudden cardiac death will be within reach, as for the first time the underlying cause for these events may be corrected on a permanent basis,” he said.

Pasquali said he is gratified to see a new way in which nanotechnology, for which Rice is renowned, can help save lives. “We’ve been excited from the beginning to learn about each other’s areas and come up with uses for the material,” he said of his friendship – and now collaboration – with Razavi. “We’re determined to find ways to treat rather than manage disease.”

Pasquali is the A.J. Hartsook Professor of Chemical and Biomolecular Engineering, chair of the Department of Chemistry and a professor of materials science and nanoengineering and of chemistry.

Source: Rice University News & Media

Carbon Nanotube Fibers Make Superior Links to Brain

Rice University invention provides two-way communication with neurons

Carbon nanotube fibers invented at Rice University may provide the best way to communicate directly with the brain.

The fibers have proven superior to metal electrodes for deep brain stimulation and to read signals from a neuronal network. Because they provide a two-way connection, they show promise for treating patients with neurological disorders while monitoring the real-time response of neural circuits in areas that control movement, mood and bodily functions.

Pairs of carbon nanotube fibers have been tested for potential use as implantable electrodes to treat patients with neurological disorders like Parkinson’s disease. The fibers invented at Rice University proved to be far better than metallic wires now used to stimulate neurons in the brain. Courtesy of the Pasquali Lab

New experiments at Rice demonstrated the biocompatible fibers are ideal candidates for small, safe electrodes that interact with the brain’s neuronal system, according to the researchers. They could replace much larger electrodes currently used in devices for deep brain stimulation therapies in Parkinson’s disease patients.

They may also advance technologies to restore sensory or motor functions and brain-machine interfaces as well as deep brain stimulation therapies for other neurological disorders, including dystonia and depression, the researchers wrote.

The paper appeared online this week in the American Chemical Society journal ACS Nano.

The fibers created by the Rice lab of chemist and chemical engineer Matteo Pasquali consist of bundles of long nanotubes originally intended for aerospace applications where strength, weight and conductivity are paramount.

The individual nanotubes measure only a few nanometers across, but when millions are bundled in a process called wet spinning, they become thread-like fibers about a quarter the width of a human hair.

“We developed these fibers as high-strength, high-conductivity materials,” Pasquali said. “Yet, once we had them in our hand, we realized that they had an unexpected property: They are really soft, much like a thread of silk. Their unique combination of strength, conductivity and softness makes them ideal for interfacing with the electrical function of the human body.”

The simultaneous arrival in 2012 of Caleb Kemere, a Rice assistant professor who brought expertise in animal models of Parkinson’s disease, and lead author Flavia Vitale, a research scientist in Pasquali’s lab with degrees in chemical and biomedical engineering, prompted the investigation.

“The brain is basically the consistency of pudding and doesn’t interact well with stiff metal electrodes,” Kemere said. “The dream is to have electrodes with the same consistency, and that’s why we’re really excited about these flexible carbon nanotube fibers and their long-term biocompatibility.”

Flavia Vitale, a postdoctoral researcher at Rice, prepares carbon nanotube fibers for testing. Vitale is lead author of a new study that determined the thread-like fibers made of millions of carbon nanotubes may be suitable as electrodes to stimulate the brains of patients with neurological diseases. Photo by Jeff Fitlow

Weeks-long tests on cells and then in rats with Parkinson’s symptoms proved the fibers are stable and as efficient as commercial platinum electrodes at only a fraction of the size. The soft fibers caused little inflammation, which helped maintain strong electrical connections to neurons by preventing the body’s defenses from scarring and encapsulating the site of the injury.

The highly conductive carbon nanotube fibers also show much more favorable impedance – the quality of the electrical connection — than state-of-the-art metal electrodes, making for better contact at lower voltages over long periods, Kemere said.

The working end of the fiber is the exposed tip, which is about the width of a neuron. The rest is encased with a three-micron layer of a flexible, biocompatible polymer with excellent insulating properties.

The challenge is in placing the tips. “That’s really just a matter of having a brain atlas, and during the experiment adjusting the electrodes very delicately and putting them into the right place,” said Kemere, whose lab studies ways to connect signal-processing systems and the brain’s memory and cognitive centers.

Doctors who implant deep brain stimulation devices start with a recording probe able to “listen” to neurons that emit characteristic signals depending on their functions, Kemere said. Once a surgeon finds the right spot, the probe is removed and the stimulating electrode gently inserted. Rice carbon nanotube fibers that send and receive signals would simplify implantation, Vitale said.

Caleb Kemere shows a brain atlas as he discusses new research aimed at using carbon nanotube fibers invented at Rice as electrodes for deep brain stimulation of patients with neurological disorders like Parkinson’s disease. The flexible fibers are much smaller than the metallic electrodes they would replace and far more effective in stimulating and recording signals from neurons. Photo by Jeff Fitlow

The fibers could lead to self-regulating therapeutic devices for Parkinson’s and other patients. Current devices include an implant that sends electrical signals to the brain to calm the tremors that afflict Parkinson’s patients.

“But our technology enables the ability to record while stimulating,” Vitale said. “Current electrodes can only stimulate tissue. They’re too big to detect any spiking activity, so basically the clinical devices send continuous pulses regardless of the response of the brain.”

Kemere foresees a closed-loop system that can read neuronal signals and adapt stimulation therapy in real time. He anticipates building a device with many electrodes that can be addressed individually to gain fine control over stimulation and monitoring from a small, implantable device.

“Interestingly, conductivity is not the most important electrical property of the nanotube fibers,” Pasquali said. “These fibers are intrinsically porous and extremely stable, which are both great advantages over metal electrodes for sensing electrochemical signals and maintaining performance over long periods of time.” 

Co-authors are Rice alumna Samantha Summerson, a postdoctoral researcher at the University of California, Berkeley, and Behnaam Aazhang, the J.S. Abercrombie Professor of Electrical and Computer Engineering at Rice. Pasquali is the A.J. Hartsook Professor of Chemical and Biomolecular Engineering, chair of the Department of Chemistry and a professor of materials science and nanoengineering and of chemistry. Kemere is an assistant professor of electrical and computer engineering.

The Welch Foundation, the National Science Foundation and the Air Force Office of Scientific Research supported the research.

Source: Rice University News & Media