Lasers - Page 3

A research team at the University of Michigan utilized Japanese paper cutting techniques, called kirigami, to create a new type of flexible conductor. The team believes that this technique may open up big possibilities for implantable medical devices, which have to flex and bend within the human body to work. Another option is gadgets that won't break when bending or flexing.

The first prototype of the kirigami stretchable conductor consisted of tracing paper covered in carbon nanotubes. The layout was quite simple, with cuts like rows of dashes. Later concepts were more intricate. for example, conductor sheets made out of graphene oxide, with etching cuts into the surface just a tenth of a millimeter long using laser beams and a plasma of oxygen ions and electrons.

Researchers at the Nankai University in China noticed that when cutting a graphene sponge (a sponge-like material made by fusing crumpled sheets of graphene oxide) with a laser, the light propelled the material forwards. While lasers have been previously used to move single molecules around, the sponge was a few centimeters across and presumably too large to move.

The scientists then placed pieces of graphene sponge in a vacuum and shot them with lasers of different wavelength and intensity. They managed to push sponge pieces upwards by as much as 40 centimeters. They even got the graphene to move by focusing sunlight on it with a lens.

Scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the Stanford Institute for Materials and Energy Sciences (SIMES) collaborated to study the effects of spiraling pulses of laser light on graphene. They discovered that such spiraling laser pulses can theoretically change the electronic properties of graphene, switching it back and forth from a metallic state (where electrons flow freely), to an insulating state.

Such ability could mean that it is possible to use light to encode information in a computer memory, for instance. The study, while theoretical, attempted to work in as close-to-real experimental conditions as possible, right down to the shape of the laser pulses. The team found that the laser's interaction with graphene yielded surprising results, producing a band gap and also inducing a quantum state in which the graphene has a so-called Chern number of either one or zero, which results from a phenomenon known as Berry curvature and offers another on/off state that scientists might be able to exploit.

Scientists at Rice University designed a boric acid-infused graphene microsupercapacitor with quadrupled ability to store an electrical charge, while greatly boosting its energy density. This design may see potential applications in wearable electronics, as well as many other flexible electronics uses.

The scientists used commercial lasers to create thin, flexible supercapacitors by burning patterns into common polymers. The laser burns away everything except for the carbon, to a depth of 20 microns on the top layer, which becomes a foam-like matrix of interconnected graphene flakes. They found that first infusing the polymer with boric acid, resulted in major performance advantages.

German scientists at the University of Siegen, along with scientists from the KTH-Royal Institute of Technology in Kista, Sweden, claim that laser annealing can improve the quality of printed graphene (and other 2D materials) inks. This can be beneficial for various applications like flexible electronics devices, including batteries and supercapacitors, transistors, solar cells and displays.

The researchers succeeded in producing uniform, transparent and conductive graphene thin films by simply drop-casting dispersions of the carbon sheet onto a glass surface and combining this drop-casting step with laser annealing. The annealing process involves scanning a laser beam across the surface of the films, which distinctly improves their transparency and how well they conduct electricity.

A team of researchers from the École polytechnique fédérale de Lausanne (EPFL) in Switzerland claim to have captured the world's first image of light simultaneously showing both wave pattern and particle energy attributes.

The scientists used extremely short pulses of laser light directed at a miniscule nanowire made of silver and suspended on graphene film that acted as an electrical isolator (or metal-graphene dielectric). The nanowire acted as a small antenna that generated radiation patterns with the received laser excitation. The light traveled along the wire in two opposite directions and when these waves bounced back to the middle, they intersected with each other to form a new wave that appeared to be standing in place. This standing wave, radiating around the nanowire, then became the source of light used in the experiment.

Researchers from the University of Birmingham (which lead the research), University of Cambridge and National Centre for Nanoscience & Technology in Beijing designed the world’s thinnest, tunable, lightweight graphene-based lenses.

The project focused on designing Fresnel lenses, which are flat lenses consisting of concentric rings. The rings diffract light to create constructive interference. The other advantage of these lenses is that their optical performance can be tuned by changing the electrical properties of graphene.

In December 2014, Rice University researchers designed a process (called LIG) in which a computer-controlled laser burns through a polymer to create flexible, patterned sheets of multilayer graphene that may be suitable for electronics or energy storage.

Now, their research has advanced to use the LIG process to produce 3D supercapacitors. The scientists made supercapacitors with laser-induced graphene on both sides of a polymer sheet. The sections were stacked with solid electrolytes in between, to get a multilayer construct with multiple micro-supercapacitors.

The Spanish Graphenea collaborated with researchers from the French CNRS and SENSIA SL to design a graphene-based biosensor and develop a graphene-based method to destroy harmful bacteria.

The researchers studied the possibility to kill E. coli pathogens using reduced graphene oxide (rGO-PEG-NH2) and Au nanorods (Nrs) coated with rGO-PEG-NH2 by laser irradiation. The encapsulation of Au NRs with rGO-PEG not only decreases the toxicity of Au NRs, but also enhances the overall photothermal process and thus the temperatures which can be reached. 99% killing efficiency of bacteria was demonstrated in a water solution, at low concentrations (20-49 mg/ml).

Researchers at the University of California at Riverside found a way to introduce magnetism in graphene while still preserving electronics properties. This may represent a significant step forward in the use of graphene in chips and electronics, since doping in the past induced magnetism but damaged graphene's electronic properties. this method can also be used in spintronics - chips that use electronic spin to store data.

The scientists explain they have overcome the problem by moving a graphene sheet very close to an electrical insulator with magnetic properties, since placing graphene on an insulating magnetic substrate can make the material ferromagnetic without disturbing its conductivity. The magnetic graphene is said to acquire new electronic properties, and so new quantum phenomena can take place.