Nano-based Yarns Generate Electricity

An international research team led by scientists at The University of Texas at Dallas and Hanyang University in South Korea has developed high-tech yarns that generate electricity when they are stretched or twisted.

In a study published in the journal Science, researchers describe “twistronyarns and their possible applications, such as harvesting energy from the motion of ocean waves or from temperature fluctuations. When sewn into a shirt, these yarns served as a self-powered breathing monitor.

The easiest way to think of twistron harvesters is, you have a piece of yarn, you stretch it, and out comes electricity,” said Dr. Carter Haines BS’11, PhD’15, associate research professor in the Alan G. MacDiarmid NanoTech Institute at UT Dallas and co-lead author of the article. The article also includes researchers from South Korea, Virginia Tech, Wright-Patterson Air Force Base and China.

Coiled carbon nanotube yarns, created at The University of Texas at Dallas and imaged here with a scanning electron microscope, generate electrical energy when stretched or twisted.
The yarns are constructed from carbon nanotubes, which are hollow cylinders of carbon 10,000 times smaller in diameter than a human hair. The researchers first twist-spun the nanotubes into high-strength, lightweight yarns. To make the yarns highly elastic, they introduced so much twist that the yarns coiled like an over-twisted rubber band.

In order to generate electricity, the yarns must be either submerged in or coated with an ionically conducting material, or electrolyte, which can be as simple as a mixture of ordinary table salt and water.

Fundamentally, these yarns are supercapacitors,” said Dr. Na Li, a research scientist at the NanoTech Institute and co-lead author of the study. “In a normal capacitor, you use energy — like from a battery — to add charges to the capacitor. But in our case, when you insert the carbon nanotube yarn into an electrolyte bath, the yarns are charged by the electrolyte itself. No external battery, or voltage, is needed.

When a harvester yarn is twisted or stretched, the volume of the carbon nanotube yarn decreases, bringing the electric charges on the yarn closer together and increasing their energy, Haines said. This increases the voltage associated with the charge stored in the yarn, enabling the harvesting of electricity.

Source: http://www.utdallas.edu/

How To Hide An Object

Researchers from Queen Mary University of London (QMUL)’s School of Electronic Engineering and Computer Science, worked with UK industry to demonstrate for the first time a practical cloaking device that allows curved surfaces to appear flat to electromagnetic waves.

While the research might not lead to the invisibility cloak made famous in J.K Rowling’s Harry Potter novels quite yet, this practical demonstration could result in a step-change in how antennas are tethered to their platform. It could allow for antennas in different shapes and sizes to be attached in awkward places and a wide variety of materials.
cloak in actionCo-author, Professor Yang Hao from  QMUL’s School of Electronic Engineering and Computer Science, said: “The design is based upon transformation optics, a concept behind the idea of the invisibility cloak. Previous research has shown this technique working at one frequency. However, we can demonstrate that it works at a greater range of frequencies making it more useful for other engineering applications, such as nano-antennas and the aerospace industry.”

The researchers coated a curved surface, similar to the size of a tennis ball with a nanocomposite medium, which has seven distinct layers (called graded index nanocomposite) where the electric property of each layer varies depending on the position. The effect is to ‘cloak’ the object: such a structure can hide an object that would ordinarily have caused the wave to be scattered.

First author Dr Luigi La Spada also from QMUL’s School of Electronic Engineering and Computer Science, said: “The study and manipulation of surface waves is the key to develop technological and industrial solutions in the design of real-life platforms, for different application fieldsWe demonstrated a practical possibility to use nanocomposites to control surface wave propagation through advanced additive manufacturing. Perhaps most importantly, the approach used can be applied to other physical phenomena that are described by wave equations, such as acoustics. For this reason, we believe that this work has a great industrial impact.”

Source: http://www.qmul.ac.uk/