Technical / Research - Page 2

Researchers from the Taiyuan Institute of Technology have introduced a novel graphene RF NEMS capacitive switch and conducted an extensive analysis of its RF performance within the UWB frequency range of DC ~ 140 GHz. 

Schematic representation of the proposed graphene RF NEMS capacitive switch: (a) a 3D isometric view; (b) a top view. Image credit: Scientific Reports

The monolayer graphene RF NEMS switch is characterized by its low pull-in voltage, rapid switching time, and superior RF performance, contrasting with the comparatively inferior performance of multilayer graphene RF NEMS switches. 

University of Illinois Chicago scientists have created a new platform to study materials at the level of individual molecules. The approach is a significant breakthrough for creating nanotechnologies that could revolutionize computing, energy and other fields.

Two-dimensional materials, such as graphene, are made from a single layer of atoms. Studying and designing these ultrathin materials requires highly specialized methods. The laboratory of Nan Jiang, associate professor of chemistry and physics at UIC, pioneered a new method to simultaneously examine the structural, electronic and chemical properties of these nanomaterials. The platform combines two scientific approaches — scanning probe microscopy and optical spectroscopy — to view materials and assess how they interact with chemicals.

While silk protein has been used in designer electronics, its use is currently limited in part because silk fibers are a messy tangle of spaghetti-like strands. To address this, researchers from Pacific Northwest National Laboratory, University of Washington, Lawrence Berkeley National Laboratory, North Carolina State University and Xiamen University have developed a uniform two-dimensional (2D) layer of silk protein fragments, or "fibroins," on graphene. 

Scheme of silk fibroin assembly on highly oriented pyrolytic graphite (HOPG) characterized by in situ AFM. Image from Science Advances

The scientists explained that their work provides a reproducible method for silk protein self-assembly that is essential for designing and fabricating silk-based electronics. They said that the system is nontoxic and water-based, which is vital for biocompatibility.

Researchers from Kumamoto University and Hiroshima University have announced a significant development in hydrogen ion barrier films using graphene oxide (GO) without internal pores. This approach could be beneficial for protective coatings for various applications.

In their study, the research team successfully synthesized and developed a pore-free GO (Pf-GO) membrane with controlled oxygen functional groups. Traditionally, GO has been known for its high ionic conductivity, which made it challenging to use as an ion barrier. However, by eliminating the internal pores, the team created a material with dramatically improved hydrogen ion barrier properties.

Researchers from the University of Cambridge, University College London, Imperial College London, Kumoh National Institute of Technology (KIT) and Beihang University have developed a wearable ‘smart’ choker for speech recognition, that has the potential to redefine the field of silent speech interface (SSI) thanks to embedded ultrasensitive textile strain sensor technology.

Where verbal communication is hindered, such as in locations with lots of background noise or where an individual has an existing speech impairment, SSI systems are a cutting-edge solution, enabling verbal communication without vocalization. As such, it is a type of electronic lip-reading using human-computer interaction. In their recent research, the scientists applied an overlying structured graphene layer to an integrated textile strain sensor for robust speech recognition performance, even in noisy environments.

A team of scientists from the University of Manchester has gained new understanding of lithium-ion storage within the thinnest possible battery anode - composed of just two layers of carbon atoms. Their work shows an unexpected ‘in-plane staging’ process during lithium intercalation in bilayer graphene, which could pave the way for advancements in energy storage technologies.

Lithium-ion batteries, which power everything from smartphones and laptops to electric vehicles, store energy through a process known as ion intercalation. This involves lithium ions slipping between layers of graphite - a material traditionally used in battery anodes, when a battery is charged. The more lithium ions that can be inserted and later extracted, the more energy the battery can store and release. While this process is well-known, the microscopic details have remained unclear. The Manchester team’s discovery sheds new light on these processes by focusing on bilayer graphene, the smallest possible battery anode material.

Researchers at Swansea University, in collaboration with China's Wuhan University of Technology and Shenzhen University, have developed a technique for producing large-scale graphene current collectors that could significantly enhance the safety and performance of lithium-ion batteries (LIBs).

Their recent study details the first successful protocol for fabricating defect-free graphene foils on a commercial scale. These foils offer excellent thermal conductivity - nearly ten times higher than traditional copper and aluminium current collectors used in LIBs.

Hot-carrier transistors are a class of devices that leverage the excess kinetic energy of carriers. Unlike regular transistors, which rely on steady-state carrier transport, hot-carrier transistors modulate carriers to high-energy states, resulting in enhanced device speed and functionality. These characteristics are essential for applications that demand rapid switching and high-frequency operations, such as advanced telecommunications and cutting-edge computing technologies. However, their performance has been limited by how hot carriers have traditionally been generated.

A team of researchers, led by Prof. Liu Chi, Prof. Sun Dongming, and Prof. CHeng Huiming from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences, has proposed a novel hot carrier generation mechanism called stimulated emission of heated carriers (SEHC). The team has also developed an innovative hot-emitter transistor (HOET), achieving an ultralow sub-threshold swing of less than 1 mV/dec and a peak-to-valley current ratio exceeding 100. The study provides a prototype of a low power, multifunctional device for the post-Moore era.

Researchers from Nagoya University, Osaka University and National Taiwan University recently developed a method for the high-speed, large-area deposition of two-dimensional (2D) materials, including oxides, graphene oxide, and boron nitride. This innovative technique, known as the "spontaneous integrated transfer method," was discovered by chance; however, it could significantly improve the production of nanosheets.

Traditionally, methods like chemical vapor deposition (CVD) and the Langmuir-Blodgett (LB) technique have been employed for nanosheet fabrication. However, these methods have significant disadvantages, including difficulties in achieving uniform, large-area deposition and complications in the substrate transfer process. Aiming to develop a more effective deposition technology, the research team discovered a fascinating phenomenon completely by chance: when nanosheets get wet, they spontaneously align themselves on the surface of water, forming dense films within a mere 15 seconds. This process, termed the "spontaneous spreading phenomenon," suggested a more effective deposition technology.

Pulsed laser micropropulsion (PLMP) offers a promising avenue for miniature spacecraft, yet conventional propellants face challenges in balancing efficiency and stability. Researchers from Wuhan University, Henan Academy of Sciences and Purdue University have proposed an optical-propulsion metastructure strategy using metal-organic frameworks (MOFs) to generate graphene-metal metastructures (GMM), which significantly enhances PLMP performance.

A) Illustration of PLMP mechanism and the possible applications of MOFs-derived GMM-based PLMP. B) Preparation schematic of GMM. Image from: Advanced Materials

MOFs, which consist of metal cations or clusters coordinated with organic ligands, can serve as ideal precursors for creating hybrid structures that combine the benefits of both carbon and metal components. By employing ultrafast laser interactions with MOFs, researchers have been able to synthesize GMMs with precisely controlled metal nanoparticle sizes, graphene layers, and inter-particle gaps, all in an ambient air environment. These GMMs exhibit remarkable properties, including high light absorption efficiency, enhanced energy transfer, and improved material stability.