Tag Archives: carbon nanotubes

Let Your Skin Play Music

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.

Source: https://spectrum.ieee.org/

Colorful 3D Printing

People are exploring the use of 3D printing for wide-ranging applications, including manufacturing, medical devices, fashion and even food. But one of the most efficient forms of 3D printing suffers from a major drawback: It can only print objects that are gray or black in color. Now, researchers have tweaked the method so it can print in all of the colors of the rainbow.

THIS BRIGHTLY COLORED DRAGON WAS PRODUCED BY 3D PRINTING, USING GOLD NANORODS AS PHOTOSENSITIZERS.

Selective laser sintering (SLS) printers use a laser to heat specific regions of a powdered material, typically nylon or polyamide, so that the powder melts or sinters to form a solid mass. The printer adds then selectively sinters new powdered material layer by layer until the desired 3D structure is obtained. To reduce the energy requirements of the process, researchers have added compounds called photosensitizers to the polymer powders. These materials, such as carbon nanotubes, carbon black and graphene, absorb light much more strongly than the polymers and transfer heat to them, enabling the use of cheaper, lower-power lasers. However, the carbon-based photosensitizers can only produce printed objects that are gray or black. Gerasimos Konstantatos, Romain Quidant and their coworkers at The Institute of Photonic Sciences (IFCO) wanted to find a photosensitizer that would enable color printing by the SLS method.

The researchers designed gold nanorods to strongly absorb in the near-infrared region of the spectrum while being almost transparent to visible light. They coated them with silica and then mixed them with polyamide powders to print 3D objects. They found that the gold nanorods were much better at converting light from the laser to heat than carbon black, the industry standard. Also, the new photosensitizers could produce much whiter and — when mixed with dyes — brightly colored 3D objects. Importantly, the materials are cost-effective for large-scale production. The researchers have filed several patent applications related to the new technology.

The findings are reported in the ACS journal Nano Letters.

Source: https://www.acs.org/

E- textiles Control Home Appliances With The Swipe Of A Finger

Electronic textiles could allow a person to control household appliances or computers from a distance simply by touching a wristband or other item of clothing — something that could be particularly helpful for those with limited mobility. Now researchers, reporting in ACS Nano, have developed a new type of e-textile that is self-powered, highly sensitive and washable.

CLICK ON THE IMAGE TO ENJOY THE VIDEO

E-textiles are not new, but most existing versions have poor air permeability, can’t be laundered or are too costly or complex to mass-produce. Chinese researchers Jiaona Wang, Hengyu Guo, Congju Li and coworkers wanted to develop an E-textile that overcomes all of these limitations and is highly sensitive to human touch.

The researchers made a self-powered triboelectric nanogenerator by depositing an electrode array of conductive carbon nanotubes on nylon fabric. To make the E-textile washable, they incorporated polyurethane into the carbon nanotube ink, which made the nanotubes firmly adhere to the fabric. They covered the array with a piece of silk and fashioned the textile into a wristband. When swiped with a finger in different patterns, the E-textile generated electrical signals that were coupled to computers to control programs, or to household objects to turn on lights, a fan or a microwave from across the room. The E-textile is breathable for human skin, washable and inexpensive to produce on a large scale, the researchers say.

Source: https://www.eurekalert.org/

Adaptive Materials

Engineers at the U.S. Army Research Laboratory (ARL) and the University of Maryland have developed a technique that causes a composite material to become stiffer and stronger on-demand when exposed to ultraviolet light. This on-demand control of composite behavior could enable a variety of new capabilities for future Army rotorcraft design, performance and maintenance.

ARL‘s Dr. Frank Gardea, a research engineer, said the focus of the research was on controlling how molecules interact with each other. He said the aim was to “have them interact in such a way that changes at a small size, or nanoscale, could lead to observed changes at a larger size, or macroscale.”

Dr. Bryan Glaz, chief scientist of ARL‘s Vehicle Technology Directorate said “an important motivation for this work is the desire to engineer new structures, starting from the nanoscale, to enable advanced rotorcraft concepts that have been proposed in the past, but were infeasible due to limitations in current composites. One of the most important capabilities envisioned by these concepts is a significantly reduced maintenance burden due to compromises we make to fly at high speeds”, he said. The reduced scheduled maintenance of future Army aviation platforms is an important technological driver for future operating concepts.

Army researchers imagine a rotorcraft concept, which represents reactive reinforcements that when exposed to ultraviolet light will increase the mechanical behavior on-demand. The engineers said control of mechanical behavior could potentially lead to increased aerodynamic stability in rotorcraft structures.

The enhanced mechanical properties with potentially low weight penalties, enabled by the new technique, could lead to nanocomposite based structures that would enable rotorcraft concepts that we cannot build today,” Glaz said.

The joint work, recently published in Advanced Materials Interfaces (DOI: 10.1002/admi.201800038), shows that these composite materials could become 93-percent stiffer and 35-percent stronger after a five minute exposure to ultraviolet light. The technique consists of attaching ultraviolet light reactive molecules to reinforcing agents like carbon nanotubes. These reactive reinforcing agents are then embedded in a polymer. Upon ultraviolet light exposure, a chemical reaction occurs such that the interaction between the reinforcing agents and the polymer increases, thus making the material stiffer and stronger.

ource: https://www.arl.army.mil/