Flexible - Page 2

Partners of the European Project 'Graphene Flagship' at the University of Strasbourg and CNRS (France), along with an international team of collaborators, created new 'switches' that respond to light. The team combined light-sensitive molecules with layers of graphene and other 2D materials to create new devices that could be used in sensors, optoelectronics and flexible devices.

The researchers designed a molecule that can reversibly undergo chemical transformations when illuminated with ultraviolet and visible light. This molecule (a photoswitchable spiropyran) can be then attached to the surface of materials like graphene or molybdenum disulfide, thus generating an atomically precise hybrid macroscopic superlattice. When illuminated, the whole supramolecular structure experiences a collective structural rearrangement, which could be directly visualized with a sub-nanometer resolution by scanning tunneling microscopy.

China-based display maker BOE Group announced that it is looking into adopting graphene for next-generation touch screens.

The company says that graphene has several advantages over current technologies, though production capacity remains insufficient at this stage.

Surwon Technology, a Hong Kong based materials developer, has reported a new graphene-based technique with the potential of doubling the life-time performance of conventional lithium-ion batteries.

The challenge for all energy dependent applications lies in creating a more robust, efficient battery fuel cell. We have found that graphene provides us with substantial flexibility as we continue to manipulate electrical behavior at the atomic level, commented Surwon Technology’s Chief Technology Officer.

Researchers from Zhejiang University in China have developed a safe, flexible, fast-charging aluminum-graphene battery. The team's design relies on using graphene films as the anode and metallic aluminum as the cathode. It was reported that the battery could work well after quarter-million cycles and can be fully charged in seconds.

Experiments showed that the battery retains 91% of its original capacity after 250,000 recharges, surpassing all the previous batteries in terms of cycle life. In quick-charge mode, the battery can be fully charged in 1.1 seconds, according to the team. The assembled battery also works well in temperatures range of minus 40 to 120 degrees Celsius. It can be folded, and does not explode when exposed to fire.

Researchers from The City University of New York (CUNY) describe a process for creating diamene: flexible, layered sheets of graphene that temporarily become harder than diamond and impenetrable upon impact. The material is fascinating as it is as flexible and lightweight as foil but becomes stiff and hard enough to stop a bullet on impact. Such a material may be beneficial for applications like wear-resistant protective coatings and ultra-light bullet-proof films.

Photo by Red Orbit

The team worked to theorize and test how two layers of graphene could be made to turn into a diamond-like material upon impact at room temperature. The team also found the moment of conversion resulted in a sudden reduction of electric current, suggesting diamene could have interesting electronic and spintronic properties.

A team of researchers at the University of Minnesota and Northwestern University, USA, have developed a printing method to produce flexible graphene micro-supercapacitors with a planar architecture suitable for integration in portable electronic devices.

The new process, referred to as ‘self-aligned capillarity-assisted lithography for electronics’ (SCALE), begins with the creation of a polymer template, generated by stamping a UV-curable polymer with a PDMS mold. High-resolution inkjet printing is then used to deposit a graphene ink into the template, which is annealed using a xenon lamp to form the electrodes. In the final step, a polymer gel electrolyte is printed onto the template over the electrodes to complete the configuration.

Researchers at Chalmers University have developed a flexible detector for terahertz frequencies (1000 gigahertz) using graphene transistors on plastic substrates. It is said to be the first of its kind, and can extend the use of terahertz technology to applications that require flexible electronics, like wireless sensor networks and wearable technology.

At room temperature, the translucent and flexible device detects signals in the frequency range 330 to 500 gigahertz. The technique can be used for imaging in the terahertz area (THz camera), but also for identifying different substances (sensor). It may also be of potential benefit in health care, where terahertz waves can be used to detect cancer. Other areas where the detector could be used are imaging sensors for vehicles or for wireless communications.

OLED displays are very sensitive to oxygen and moisture, and the need to protect the displays is one of the major challenges of this next-generation display technology. First generation OLED displays were protected with a glass barrier, but glass is not easily flexible and so cannot be used in flexible OLEDs. Flexible OLEDs are today encapsulation with a thin-film encapsulation layer made from both organic and in-organic materials, and companies are searching for better OLED encapsulation technologies.

Graphene is the world's most impermeable material, and so the idea of using graphene as a barrier layer for OLED has been around for a while. In 2015 the UK launched a collaboration project called Gravia to develop graphene-based encapsulation, and the project's team has now reported their results.

Researchers from Tsinghua University in China have designed a low-cost energy storage device using a TiO2-assisted UV reduction of sandwiched graphene components. The sandwich structure consists of two active layers of reduced graphene oxide hybridized with TiO2, with a graphene oxide separator (rGO-TiO2/rGO/rGO-TiO2). In the device, the separator layer also acts as a reservoir for the electrolyte, which affects ion diffusion—a known problem for layered membrane devices—and affects both the capacity and rate performance.

The team explained that a step-by-step vacuum filtration process is used to form the membrane structure, and the amount of graphene oxide used in the filtration solutions can be adjusted to precisely tune the thickness of each layer. Irradiation of the dried membrane with UV light then reduces the graphene oxide to rGO with assistance from the TiO2.

A team of researchers from Hong Kong Polytechnic University (PolyU) has developed sensors which can be sprayed directly onto flat or curved surfaces. The sensors, made from a hybrid of carbon black (CB), graphene, other conductive nano-scale particles, and polyvinylidene fluoride (PVDF), can be networked to extract rich real-time information on the health status of the structure being monitored.

The technology includes a sensor network with a number of the sprayed nanocomposite sensors and an ultrasound actuator to actively detect the health condition of the structure to which they are fixed. When the ultrasound actuator emits guided ultrasonic waves (GUWs), the sensors will receive and measure the waves. If damage is detected, such as a crack in the structure, propagation of GUWs will be interfered by the damage, leading to the wave scattering phenomena to be captured by the sensor network. The damage can then be characterised quantitatively and accurately.