Power Up

Anything portable needs a battery. We wouldn’t have the cell phones, laptops or other consumer electronic gadgets we use daily without battery technology—the research is ubiquitous. This is especially true of lithium-ion batteries.

The face of battery research has changed since the 1980s where it was considered a “dirty science” and researchers would mix carbon and other elements in their laboratories. Noted as the first generation of lithium-ion batteries, the 1980s gave birth to lithium-metal battery technology, which is now seeing a resurgence today. And, in 1991, when Japan’s Sony first released the lithium-ion battery to power music players and camcorders, they probably didn’t anticipate the crucial impact the technology would have over all society. And they probably didn’t foresee Asia’s dominance in battery technology R&D.

However, now there’s another shift in battery technology happening within transportation and storage on the grid, which are an order-of-magnitude larger than personal electronics. To run electric vehicles and the grid, it will take a bigger battery. And researchers are working on “beyond lithium-ion” solutions to bring battery power to the highest level.

Realizing carbon nanotube integrated circuits

Individual transistors made from carbon nanotubes are faster and more energy efficient than those made from other materials. Going from a single transistor to an integrated circuit full of transistors, however, is a giant leap.

“A single microprocessor has a billion transistors in it,” said Northwestern Engineering’s Mark Hersam. “All billion of them work. And not only do they work, but they work reliably for years or even decades.”

When trying to make the leap from an individual, nanotube-based transistor to wafer-scale integrated circuits, many research teams, including Hersam’s, have met challenges. For one, the process is incredibly expensive, often requiring billion-dollar cleanrooms to keep the delicate nano-sized components safe from the potentially damaging effects of air, water, and dust. Researchers have also struggled to create a carbon nanotube-based integrated circuit in which the transistors are spatially uniform across the material, which is needed for the overall system to work.

Now Hersam and his team have found a key to solving all these issues. The secret lies in newly developed encapsulation layers that protect carbon nanotubes from environmental degradation.

Supported by the Office of Naval Research and the National Science Foundation, the research appears online in Nature Nanotechology. Tobin J. Marks, the Vladimir N. Ipatieff Research Professor of Chemistry in the Weinberg College of Arts and Sciences and professor of materials science and engineering in the McCormick School of Engineering, coauthored the paper. Michael Geier, a graduate student in Hersam’s lab, was first author.

Half diamond, half cubic boron, all cutting business

Diamonds are forever, except when they oxidize while cutting through iron, cobalt, nickel, chromium or vanadium at high temperatures. Conversely, cubic boron nitride possesses superior chemical inertness but only about half of the hardness of diamonds. In an attempt to create a superhard material better suited for a wide variety of materials on an industrial scale, researchers at Sichuan Univ. in Chengdu, China, have created an alloy composed of diamonds and cubic boron nitride (cBN) that boasts the benefits of both.

"Diamond and cubic boron nitride could readily form alloys that can potentially fill the performance gap because of their affinity in structure lattices and covalent bonding character," said Duanwei He, a professor at Sichauan Univ.'s Institute of Atomic and Molecular Physics. "However, the idea has never been demonstrated because samples obtained in previous studies are too small to test their practical performance."

He and his colleagues at the University of Nevada and the Chinese Academy of Sciences detail their procedure in Applied Physics Letters.

Nanoporous gold sponge makes pathogen detector

Sponge-like nanoporous gold could be key to new devices to detect disease-causing agents in humans and plants, according to Univ. of California, Davis (UC Davis) researchers.

In two recent papers in Analytical Chemistry, a group from the UC Davis Dept. of Electrical and Computer Engineering demonstrated that they could detect nucleic acids using nanoporous gold, a novel sensor coating material, in mixtures of other biomolecules that would gum up most detectors. This method enables sensitive detection of DNA in complex biological samples, such as serum from whole blood.

“Nanoporous gold can be imagined as a porous metal sponge with pore sizes that are a thousand times smaller than the diameter of a human hair,” said Erkin Şeker, assistant professor of electrical and computer engineering at UC Davis and the senior author on the papers. “What happens is the debris in biological samples, such as proteins, is too large to go through those pores, but the fiber-like nucleic acids that we want to detect can actually fit through them. It’s almost like a natural sieve.”

Rapid and sensitive detection of nucleic acids plays a crucial role in early identification of pathogenic microbes and disease biomarkers. Current sensor approaches usually require nucleic acid purification that relies on multiple steps and specialized laboratory equipment, which limit the sensors’ use in the field. The researchers’ method reduces the need for purification.

New nanomaterial maintains conductivity in three dimensions

An international team of scientists has developed what may be the first one-step process for making seamless carbon-based nanomaterials that possess superior thermal, electrical and mechanical properties in three dimensions.

The research holds potential for increased energy storage in high-efficiency batteries and supercapacitors, increasing the efficiency of energy conversion in solar cells, for lightweight thermal coatings and more. The study is published online in Science Advances.

In early testing, a 3-D fiber-like supercapacitor made with the uninterrupted fibers of carbon nanotubes and graphene matched or bettered—by a factor of four—the reported record-high capacities for this type of device.

Used as a counter electrode in a dye-sensitized solar cell, the material enabled the cell to convert power with up to 6.8% efficiency and more than doubled the performance of an identical cell that instead used an expensive platinum wire counter electrode.

Carbon nanotubes could be highly conductive along the 1-D nanotube length and 2-D graphene sheets in the 2-D plane. But the materials fall short in a 3-D world due to the poor interlayer conductivity, as do two-step processes melding nanotubes and graphene into three dimensions.

"Two-step processes our lab and others developed earlier lack a seamless interface and, therefore, lack the conductance sought," said Liming Dai, the Kent Hale Smith Professor of Macromolecular Science and Engineering at Case Western Reserve Univ. and a leader of the research.

Laser levitates glowing nanodiamonds in vacuum

Researchers have, for the first time, levitated individual nanodiamonds in vacuum. The research team is led by Nick Vamivakas at the Univ. of Rochester who thinks their work will make extremely sensitive instruments for sensing tiny forces and torques possible, as well as a way to physically create larger-scale quantum systems known as macroscopic Schrödinger Cat states.

While other researchers have trapped other types of nanoparticles in vacuum, those were not optically active. The nanodiamonds, on the other hand, can contain nitrogen-vacancy (NV) centers that emit light and also have a spin quantum number of one. In the paper, published in Nature Photonics, the researchers from Rochester's Institute of Optics explain this is the first step towards creating a "hybrid quantum system." Their system combines the mechanical motion of the nanodiamond with the internal spin of the vacancy and its optical properties to make it particularly promising for a number of applications.

In a previous paper, the researchers had shown that nanodiamonds could be levitated in air using a trapping laser. The new paper now shows this can be done in vacuum, which they say is "a critical advance over previous nanodiamond optical tweezer experiments performed in liquids or at atmospheric pressure."