A demonstration of a test of ultimate tensile break force performed on a carbon nanotube yarn manufactured by DexMat.
Researchers in South Korea made a tiny loudspeaker, and then used it to play a violin concerto
A variety of nanomaterials have been used over the years in loudspeakers and microphones. Nanoparticles have replaced permanent magnets in loudspeakers and a thin film of carbon nanotubes has done pretty much the same. And, of course, someone tried to use graphene to reproduce sound for microphones.
Now researchers at Ulsan National Institute of Science and Technology (UNIST) in South Korea have made a nanomembrane out of silver nanowires to serve as flexible loudspeakers or microphones. The researchers even went so far as to demonstrate their nanomembrane by making it into a loudspeaker that could be attached to skin and used it to play the final movement of a violin concerto—namely, La Campanella by Niccolo Paganini.
In research described in the journal Science Advances, the Korean researchers embedded a silver nanowire network within a polymer-based nanomembrane. The decision to use silver nanowires rather than the other types of nanomaterials that have been used in the past was based on the comparative ease of hybridizing the nanowires into the polymer.
In addition, the researchers opted for nanowires because the other materials like graphene and carbon nanotubes are not as mechanically strong at nanometer-scale thickness when in freestanding form, according to Hyunhyub Ko, an associate professor at UNIST and coauthor of the research. It is this thickness that is the critical element of the material.
“The biggest breakthrough of our research is the development of ultrathin, transparent, and conductive hybrid nanomembranes with nanoscale thickness, less than 100 nanometers,” said Ko. “These outstanding optical, electrical, and mechanical properties of nanomembranes enable the demonstration of skin-attachable and imperceptible loudspeaker and microphone.”
The nanomembrane loudspeaker operates by emitting thermoacoustic sound through the oscillation of the surrounding air brought on by temperature differences. The periodic Joule heating that occurs when an electric current passes through a conductor and produces heat leads to these temperature oscillations.
For the operation of the microphone, the hybrid nanomembrane is sandwiched between elastic films with tiny patterns. In this way, the nanomembrane can precisely detect the sound and the vibration of the vocal cords based on a triboelectric voltage that results from the contact with the elastic films. In these loudspeakers and microphones, the silver nanowires enable both the electrical conductivity and give the nanomembranes their freestanding strength.
While the researchers demonstrated the technology by applying a thin film of the nanomembrane on skin, this may not turn out to be a practical application of the technology, according to the researchers. This is because the performance of the thermoacoustic loudspeaker is proportional to the speaker size and temperature change of the speaker.
If it were directly attached to the skin, the input power level per unit area would increase too much for the generation of a large sound.
Ko added: “For the commercial applications, the mechanical durability of nanomebranes and the performance of loudspeaker and microphone should be improved further.”
Here we show the difference between raw carbon nanotubes and the carbon nanotube yarns and films that we make at DexMat.
|(Nanowerk News) Ingested or injected pharmaceuticals can target specific molecules involved in disease processes, but get distributed throughout the body where they can cause unwanted side effects. An approach known as electroceuticals aims to avoid systemic exposure by using small wires to electrically monitor and manipulate individual nerves that control organ function and carry information about disease. Despite the promise of electroceuticals, it has been challenging to develop long-term therapies due to the lack of biocompatible wires.|
|Now, NIBIB-funded researches have spun carbon nanotubes into flexible, nerve-sized wires or yarns capable of high-fidelity long-term connections in live animals. The development of these biocompatible yarns opens the possibility of new bioelectric diagnostics and therapies through regulation of internal organ function at the single nerve level.|
|Individual carbon nanotubes are pulled from a substrate and spun into the flexible carbon nanotube yarn. (© NPG)|
|All the organs of the body such as the heart, lungs, liver, and kidneys are automatically controlled by nerves that stretch from the brainstem to each organ. These nerves control organ functions such as heartbeat, breathing rates, and blood pressure, making constant adjustments in response to environmental and physiological changes. Variations in the electrical activity in this area of the brain, known as the autonomic nervous system, can also be predictors, indicators or causes of disease development.|
|“Monitoring and manipulating the autonomic nervous system to both understand and potentially treat disease has been an intriguing yet understudied approach to medicine,” explains Michael Wolfson, Ph.D., director of the NIBIB program in Rehabilitation Engineering and Implantable Medical Devices. “This is largely due to technical limitations in being able to insert wires into nerves that can reliably and safely record electrical activity over long periods of time and under different physiological conditions.”|
|In a study reported in the journal Scientific Reports (“Chronic interfacing with the autonomic nervous system using carbon nanotube (CNT) yarn electrodes”), bioengineers at Case Western Reserve University in Cleveland, Ohio describe the development of highly flexible carbon nanotube (CNT) yarn electrodes that were capable of months-long electrical recording in major nerves of the autonomic nervous system in rats.|
|The CNT yarns are essentially, just that, yarns made from a “forest” of hundreds of carbon nanotubes that are pulled from the metal surface they are grown on and spun into a highly flexible, highly conductive wire 1/100th the size of a human hair.|
|The carbon nanotube yarn is wound around a tungsten needle for insertion into a nerve. The coiling of the yarn causes it to remain solidly embedded in the nerve after the needle is withdrawn. Actual needle and yarn (top). Diagram showing detail of how yarn is wrapped around the needle for insertion (bottom). (© NPG)|
|Current technologies for recording electrical signals from nerves include relatively large stiff tungsten needles used by neurologists to obtain readings from single nerves of patients for several hours, but must be removed before causing lasting nerve damage. Other wire electrode technologies can record nerve signals for short periods but because of their dimensions and stiff mechanical properties they are not suitable for long-term recording in small nerves.|
|“The currently available electrode technologies simply do not match the mechanical properties of nerves,” explains Dominique Durand, Ph.D., Professor of Biomedical Engineering at Case Western and senior researcher on the CNT yarn work. “With those types of electrodes, it’s often like sticking glass into spaghetti. Our CNT yarns are similar in size and flexibility to actual nerves. These properties allow them to be stealthily inserted into specific nerves and remain there for months without destroying the tissue or inducing an attack by the immune system.”|
|The combination of the biocompatibility of the CNT yarns and their outstanding ability to carry an electrical signal that is 10 times stronger than current technologies makes them ideal for long term recording of specific nerve signals. Finally, the lack of nerve damage keeps the surrounding axons intact, which helps to eliminate background noise. Thus, the CNT yarns have an excellent signal to noise ratio (SNR), which is critical for this type of research.|
|The group tested the CNT yarns in two major nerves in the autonomic system in rats. One study involved the vagus nerve, which stretches throughout the body to connect to numerous organs. The nerve is known to control and monitor a range of functions including heart rate, digestive tract movement, sweating, and immune response.|
|CNT yarn electrodes were also inserted into the glossopharyngeal nerve. The nerve is connected to a number of organs including the carotid artery, and parts of the ear, tongue and salivary glands where it is known to be involved in swallowing.|
|Carbon nanotube yarn embedded into the vagus nerve of a rat. (© NPG)|
|In both nerves, recordings of stable electrical activity were maintained over a 10-week period. Pulses of nerve activity were also monitored while the animal responded to physiological challenges. The challenges included distension of the rat’s stomach with saline solution, and short durations where the rats were in low oxygen environments. In each case, the physiological changes induced by the challenge resulted in easily detectable changes in electrical activity that were recorded using the CNT yarn implants over the entire 10-week period of the experiments.|
|“Although this is early research, we believe the results demonstrate that this technology can be used for reliable long term electrical monitoring of physiological functions,” says Durand. “This is an important step in pursuing monitoring of disease progression through the nerves that control the function of the diseased organ.”|
|Durand explains that the goal is to learn what electrical signatures or profiles are indicative of disease development and to use that for early intervention, potentially by electrical stimulation or even blocking of the nerve. For example, one therapy for severe hypertension is the cutting of the renal nerve. This is obviously irreversible. Durand, explained that CNT yarn electrodes could be used to block the nerve impulse without cutting the nerve, making the treatment reversible.|
|The group is also excited about the potential of this recording method to improve prosthetics. “When an arm has been amputated there are tens of thousands of neurons remaining,” said Durand. “The approach would be to insert the CNT yarns into individual nerves and record the electrical signals that are created as the individual thinks about moving the missing arm—essentially learning the electrical signals that are formed by the intention to move the arm.” The ultimate goal is to develop neural interfaces capable of translating those electrical signals into better control of the prosthetic by the user.|
|Source: National Institute of Biomedical Imaging and Bioengineering|
Physicists from the University of Cincinnati will soon be able to charge smartphones using clothes made from carbon nanotubes. With the assistance of their colleagues from the BBC, Wright-Patterson, the experts intend to create a special material, which because of the peculiarities of carbon nanotubes would be exceptionally heat-resistant conducting electricity, and will also differ for their durability. Professor mark Schultz, is also involved in the study declared that the task of scientists is to use the resistance and conductivity for energy storage, which can charge a variety of gadgets.
Schulz said that at the moment the science is on the verge of a “carbon revolution,” as this material may soon completely replace metals because of its strength, low weight and various additional properties. Yarns made from nanotubes can store energy, replacing bulky batteries, which soon altogether sink into oblivion.
Full Article: https://sivtelegram.media/physics-charge-smartphones-clothes-made-from-carbon-nanotubes/30672/
Researchers at Tokyo Institute of Technology have developed flexible terahertz imagers based on chemically “tunable” carbon nanotube materials. The findings expand the scope of terahertz applications to include wrap-around, wearable technologies as well as large-area photonic devices.
Carbon nanotubes (CNTs) are beginning to take the electronics world by storm, and now their use in terahertz (THz) technologies has taken a big step forward.
Due to their excellent conductivity and unique physical properties, CNTs are an attractive option for next-generation electronic devices. One of the most promising developments is their application in THz devices. Increasingly, THz imagers are emerging as a safe and viable alternative to conventional imaging systems across a wide range of applications, from airport security, food inspection and art authentication to medical and environmental sensing technologies.
The demand for THz detectors that can deliver real-time imaging for a broad range of industrial applications has spurred research into low-cost, flexible THz imaging systems. Yukio Kawano is of the Laboratory for Future Interdisciplinary Research of Science and Technology, Tokyo Institute of Technology (Tokyo Tech). In 2016 he announced the development of wearable terahertz technologies based on multiarrayed carbon nanotubes.
Kawano and his team have since been investigating THz detection performance for various types of CNT materials, in recognition of the fact that there is plenty of room for improvement to meet the needs of industrial-scale applications.
Now, they report the development of flexible THz imagers for CNT films that can be fine-tuned to maximize THz detector performance.
Publishing their findings in ACS Applied Nano Materials, the new THz imagers are based on chemically adjustable semiconducting CNT films.
By making use of a technology known as ionic liquid gating, the researchers demonstrated that they could obtain a high degree of control over key factors related to THz detector performance for a CNT film with a thickness of 30 micrometers. This level of thickness was important to ensure that the imagers would maintain their free-standing shape and flexibility.
“Additionally,” the team says, “we developed gate-free Fermi-level tuning based on variable-concentration dopant solutions and fabricated a Fermi-level-tuned p?n junction CNT THz imager.” In experiments using this new type of imager, the researchers achieved successful visualization of a metal paper clip inside a standard envelope.
The bendability of the new THz imager and the possibility of even further fine-tuning will expand the range of CNT-based devices that could be developed in the near future.
Moreover, low-cost fabrication methods such as inkjet coating could make large-area THz imaging devices more readily available.
 Ionic liquid gating: A technique used to modulate a material’s charge carrier properties.
 Fermi level: A measure of the electrochemical potential for electrons, which is important for determining the electrical and thermal properties of solids. The term is named after the Italian-American physicist Enrico Fermi.
 p-n junction: Refers to the interface between positive (p-type) and negative (n-type) semiconducting materials. These junctions form the basis of semiconductor electronic devices.
Tokyo Institute of Technology. “Scientists fine-tune carbon nanotubes for flexible, fingertip-wearable terahertz imagers.” ScienceDaily. ScienceDaily, 28 June 2018. <www.sciencedaily.com/releases/2018/06/180628105041.htm>
Abstract: The effects of electromagnetic interactions in electrical systems are of growing concern due to the increasing susceptibility of system components to electromagnetic interference (EMI), use of automated electronic systems, and pollution of the electromagnetic environment with electromagnetic emissions. The effects of EMI can be detrimental to electronic systems utilized in space missions; even small EMI issues can lead to total mission failure, resulting in significant mission delays and economic loss. Additionally, NASA is challenged to find ways of effectively shielding sensitive electronic equipment from EMI without adding significant weight to space flight vehicles and satellites in order to manage fuel costs. The solution for both issues resides in the use of carbon nanotubes (CNTs), which offer the most promising solution for reducing spacecraft wire weight. CNTs are an alluring alternative to conventional conductors used in coaxial data cables because they combine mechanical strength, electrical conductivity, and low density. DexMat has developed a novel CNT deposition process for directly applying CNTs onto dielectric materials to produce an electrically conductive EMI shield. By placing a premium on the quality of raw CNTs, DexMat has created a product with increased potential to reduce cable weight while minimizing insertion losses when incorporated into wire. In the proposed research, DexMat seeks to develop a small-scale CNT Tape production process and continue the development of the CNT separation processes. The need for CNT Tape was discovered while obtaining feedback from potential customers that noted the desire for a product format that allows for quick and easy integration into existing manufacturing processes without the need for outsourcing processes.
Project Details: https://www.sbir.gov/sbirsearch/detail/1426213
Abstract: Electric wires and cables constitute by far the largest weight portion of aircraft electrical power systems, as well as a large fraction of the entire aircraft weight. For example, a modern transport aircraft contains over 200 miles of wire, and an F-22 aircraft has about 20 miles of wiring. The increased emphasis and reliance on fly-by-wire technology and avionics for modern aircraft has resulted in wiring becoming a critical safety-of-flight system. Aerospace vehicles continue to increase in wire system complexity and volume as traditional mechanical systems, such as flight controls and flight surface control actuators, are converted to all electric systems. This Phase II Proposal involves a dual pronged strategy for developing high temperature CNT-based power cables: 1) Dexmat will seek to improve the underlying CNT yarn conductivity with and without dopants that do not require encapsulation (i.e., non-transitory dopants); 2) Improve the encapsulation process to enable the use of dopants that do require encapsulation.
Project Details: https://www.sbir.gov/sbirsearch/detail/1488599
Abstract: This SBIR Phase I project strives to reduce aircraft wire weight in order to improve aircraft range and reduce operating costs. Commercial and military aerospace companies are heavily concerned with fuel costs associated with aircraft operation, as this expense contributes significantly to the total costs of the company. Substantial reductions in aircraft weight could save millions of dollars per plane over its operating lifetime. For example, eliminating a single pound from a military fighter aircraft can save up to $3,000 over its lifetime, as well as increase its operating range, capacity to carry a larger payload and extend its time-on-station capabilities. These cost savings will benefit commercial aviation companies from decreased expense, resulting in a higher net income. Enhanced financial performance promotes company growth and the creation of more jobs throughout all levels of the organization. Increased income and job growth in this sector with stimulate continued national economic growth, providing benefit to the government via tax collections and increased commercial sector performance. National defense and aerospace sectors would also benefit from fuel cost reductions reducing costs and greenhouse gas emissions. This project directly aligns with the NSF mission to progress science, advance national prosperity and secure the national defense. This project provides innovative contribution to wire development and manufacturing through the use of a carbon nanotube deposition process in order to produce shielding for wires. This process is versatile and can be used to produce cables with a commercial metal inner conductor or a carbon nanotube fiber bundle as inner conductor and a specific conductivity similar to tin. It combines high strength, electrical conductivity and thermal conductivity with low density, which makes them ideal for applications where weight reduction is a priority, specifically in aerospace applications. Until now, only minor reductions in wire weight have been achieved, through advances in composite connectors, thermoplastic cable clamps, downsizing connectors and using thinner wall insulation. The use of carbon nanotubes would remove the need for component removal due to decreased weight. The goal of this project is to prove out a continuous roll-to-roll wire coating process to produce carbon nanotube electromagnetic interference shields suitable for a large volume manufacturing operation. This will be accomplished through the use of foundationary methods of carbon nanotube deposition developed prior to this Phase I project. This project will produce the methods required for developing roll-to-roll continuous carbon nanotube wire coating.
Project Details: https://www.sbir.gov/sbirsearch/detail/1191963
Abstract: In an era of reduced Defense budgets and increasing threats, military planners are seeking new technologies to reduce operating costs and increase operation capabilities for space and aviation platforms, and weight reduction is an attractive target. For example, transportation costs to geosynchronous orbits using a NASA reusable launch vehicle are close to $10,000 per pound of payload. Copper wiring, which makes up as much as one-third of the weight of a 15-ton satellite and 20 miles of an F-22 aircraft, is a clear target for weight reduction. Half of this wire weight is typically in the EMI shielding. Developing new lightweight, conductive materials that replace copper in the shielding and core conductor could serve as a lead candidate for radically reducing this weight. Carbon nanotubes (CNTs) combine high strength, electrical and thermal conductivity with low density, which makes them ideal for applications where weight reduction is a priority. DexMat is commercializing CNT technology that has shown the highest published values for conductivity and mechanical strength of CNT materials. This Phase II Proposal will continue developing CNT-based cables with solution-processing technology capable of producing high performance CNT fibers and coatings, without the use of binders and wetting agents.
Project Details: https://www.sbir.gov/sbirsearch/detail/1412727