BLOGS

applied_physics (14)

Transformers...

 

Topics: 3D Printing, Applied Physics, Research, Robotics, Soft Matter Physics


The researchers likely watched a lot of Saturday morning cartoons in the 1980s: original intro.

(CAMBRIDGE, Mass.) — The majority of soft robots today rely on external power and control, keeping them tethered to off-board systems or rigged with hard components. Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Caltech have developed soft robotic systems, inspired by origami, that can move and change shape in response to external stimuli, paving the way for fully untethered soft robots.

The research is published in Science Robotics.
 

3D-printed active hinges change shape in response to heat
Leah Burrows, SEAS Communications, Wyss Institute, Harvard

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Hologram Printer...

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The new printer uses low-power continuous wave lasers to create holograms on a highly sensitive photomaterial developed by the researchers. Credit: C Yves GENTET

 

Topics: 3D Objects, 3D Printing, Applied Physics, Holograms, Optics, Research


Researchers have developed a new printer that produces digital 3-D holograms with an unprecedented level of detail and realistic color. The new printer could be used to make high-resolution color recreations of objects or scenes for museum displays, architectural models, fine art or advertisements that do not require glasses or special viewing aids.

"Our 15-year research project aimed to build a hologram printer with all the advantages of previous technologies while eliminating known drawbacks such as expensive lasers, slow printing speed, limited field of view and unsaturated colors," said research team leader Yves Gentet from Ultimate Holography in France. "We accomplished this by creating the CHIMERA printer, which uses low-cost commercial lasers and high-speed printing to produce holograms with high-quality color that spans a large dynamic range."

 

New printer creates extremely realistic colorful holograms, The Optical Society, Phys.org

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Twisted Fridge...

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Fridge-freezer: twistocaloric cooling could be coming to a kitchen near you. (Courtesy: iStock/Allevinatis)

 

Topics: Applied Physics, Green Tech, Research, Thermodynamics


A new refrigeration technology based on the twisting and untwisting of fibers has been demonstrated by a team led by Zunfeng Liu at Nankai University in China and Ray Baughman at the University of Texas at Dallas in the US. As the demand for refrigeration expands worldwide, their work could lead to the development of new cooling systems that do not employ gases that are harmful to the environment.

The cooling system relies on the fact that some materials undergo significant changes in entropy when deformed. As far back as 1805 – when the concepts of thermodynamics were first being developed – it was known that ordinary rubber heats up when stretched and cools down when relaxed. In principle, such mechanocaloric materials could be used in place of the gases that change entropy when compressed and expanded in commercial refrigeration systems. Replacing gas-based systems is an important environmental goal because gaseous refrigerants tend to degrade the ozone layer and are powerful greenhouse gases.

In their experiments, Liu and Baughman’s team studied the cooling effects of twist and stretch changes in twisted, coiled and supercoiled fibers of natural rubber, nickel-titanium and polyethylene fishing line. In each material, they observed a surface cooling as high as 16.4 °C, 20.8 °C, and 5.1 °C respectively, which they achieved through techniques including simultaneous releases of twisting and stretching, and unraveling bundles of multiple wires.

 

Refrigerator works by twisting and untwisting fibers, Materials, Physics World

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The Next FET...

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Source: Modeling Carbon Nanotube FET Physics in COMSOL Multiphysics®
 

Topics: Applied Physics, Carbon Nanotubes, Field Effect Transistors, Nanotechnology


Silicon field-effect transistors (FETs) were developed in the late 1950s as a scaled-down, energy-efficient substitute for bipolar junction transistors. They paved the way for the high-density integrated circuits that today underlie most electronics (see the article by Alan Fowler, Physics Today, October 1993, page 59). With their lower gate voltages, carbon nanotube FETs could surpass silicon FET energy efficiency by nearly a factor of 10. In 2013 Subhasish Mitra, Max Shulaker (then at Stanford University), and coworkers made the first CNFET microprocessor; it comprised 178 transistors and could run a single operation.

Variability caused by the production process has made moving beyond that proof-of-concept computer challenging. Gage Hills, Christian Lau, and coworkers in Shulaker’s group at MIT have now overcome that hurdle with a protocol for wafer-scale CNFET microprocessor production. Their technique is also compatible with existing CMOS infrastructure, which lowers the bar for future commercial implementation.

To remove carbon nanotube aggregates—a common contaminant from CNT deposition on silicon wafers—the researchers spin-coated a layer of adhesive polymer over the device and then removed the aggregates using ultrasonic vibrations. In previous attempts, sonication damaged the nonaggregated CNTs. Using the photoresist binds them to the wafer, which preserves their function while removing more than 99% of the aggregates.

 

Production of carbon nanotube microprocessors gets scaled up
Christine Middleton, Physics Today

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Second Harmonic Microscopy...

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Fig. 1 Typical geometry for the SH microscopy investigation of poled x-cut LNOI.

 

Topics: Applied Physics, Optical Physics, Thin Films


Abstract

Thin film lithium niobate has been of great interest recently, and an understanding of periodically poled thin films is crucial for both fundamental physics and device developments. Second-harmonic (SH) microscopy allows for the noninvasive visualization and analysis of ferroelectric domain structures and walls. While the technique is well understood in bulk lithium niobate, SH microscopy in thin films is largely influenced by interfacial reflections and resonant enhancements, which depend on film thicknesses and substrate materials. We present a comprehensive analysis of SH microscopy in x-cut lithium niobate thin films, based on a full three-dimensional focus calculation and accounting for interface reflections. We show that the dominant signal in backreflection originates from a copropagating phase-matched process observed through reflections, rather than direct detection of the counterpropagating signal as in bulk samples. We simulate the SH signatures of domain structures by a simple model of the domain wall as an extensionless transition from a −χ(2) to a +χ(2) region. This allows us to explain the main observation of domain structures in the thin-film geometry, and, in particular, we show that the SH signal from thin poled films allows to unambiguously distinguish areas, which are completely or only partly inverted in depth.

 

Second harmonic microscopy of poled x-cut thin film lithium niobate: Understanding the contrast mechanism
Journal of Applied Physics 126, 114105 (2019); https://doi.org/10.1063/1.5113727

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Nanocones...

Nanocones.jpg
A carbon nanocone includes nitrogen atoms around the periphery to improve the material’s solubility. Carbon atoms are shown in gray; hydrogen in white; nitrogen in blue; and oxygen in red.

 

Topics: Applied Physics, Chemistry, Graphene, Nanotechnology


Graphene, buckyballs, and carbon nanotubes now have a new family member, the nanocone, adding to the types of all-carbon nanostructures with remarkable electronic and optical characteristics and bringing its own promising properties. (J. Am. Chem. Soc., 2019, DOI: 10.1021/jacs.9b06617) Such molecules could be useful for developing efficient organic solar cells or as sensor molecules.

Organic chemist Frank Würthner and postdoctoral researcher Kazutaka Shoyama of the University of Würzburg came up with the method for synthesizing the nanocones, which are 1.68 nm in diameter and 0.432 nm tall. A five-atom ring of carbons forms the cone’s tip. The team used a cross-coupling annulation cascade to add hexagons around the edges of the ring until the molecule grew to 80 carbons. The team added five nitrogen atoms around the periphery of the cone, increasing the crystal’s solubility.

 

Nanocones extend the graphene toolbox, Neil Savage, Chemical & Engineering News

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Lamina Tenuissima...

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Illustration of a tungsten disulfide monolayer suspended in air and patterned with a square array of nanoholes. Upon laser excitation, the monolayer emits photoluminescence. A portion of this light couples into the monolayer and is guided along the material. At the nanohole array, periodic modulation in the refractive index causes a small portion of the light to decay out of the plane of the material, allowing the light to be observed as guided mode resonance. Courtesy: E Cubukcu, UCSD

 

Note: lamina tenuissima = thinnest (Latin)

Topics: Applied Physics, Nanotechnology, Optical Physics, Photonics


Researchers have succeeded in making the thinnest ever optical device in the form of a waveguide just three atomic layers thick. The device could lead to the development of higher density optoelectronic chips.

Optical waveguides are crucial components in data communication technologies but scaling them down to the nanoscale has proved to be no easy task, despite important advances in nano-optics and nanomaterials. Indeed, the thinnest waveguide used in commercial applications today is hundreds of nanometres thick and researchers are studying nanowire waveguides down to 50 nm in the laboratory.

“We have now pushed this limit down to just three atoms thick,” says Ertugrul Cubukcu of the University of California at San Diego, who led this new research effort. “Such a thin waveguide, which is at the ultimate limit for how thin an optical waveguide can be built, might potentially lead to a higher density of waveguides or optical elements on an optoelectronic chip – in the same way that ever smaller transistors have led to a higher density of these devices on an electronic chip.”

Cubukcu and colleagues’ waveguide is just six angstroms thick. This makes it 104 times thinner than a typical optical fiber and about 500 times thinner than on-chip optical waveguides in integrated photonic circuits.

 

Three-atom-thick optical waveguide is the thinnest ever, Belle Dumé, Physics World

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Cyclocarbon...

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From left to right, precursor molecule C24O6, intermediates C22O4 and C20O2 and the final product cyclo [18]carbon C18 created on surface by dissociating CO masking groups using atom manipulation. The bottom row shows atomic force microscopy (AFM) data using a CO functionalized tip. Credit: IBM Research

 

Topics: Applied Physics, Atomic Force Microscopy, Chemistry, Nanotechnology, Research


A team of researchers from Oxford University and IBM Research has for the first time successfully synthesized the ring-shaped multi-carbon compound cyclocarbon. In their paper published in the journal Science, the group describes the process they used and what they learned about the bonds that hold a cyclocarbon together.

Carbon is one of the most abundant elements, and has been found to exist in many forms, including diamonds and graphene. The researchers with this new effort note that much research has been conducted into the more familiar forms (allotropes) how they are bonded. They further note that less well-known types of carbon have not received nearly as much attention. One of these, called cyclocarbon, has even been the topic of debate. Are the two-neighbor forms bonded by the same length bonds, or are there alternating bonds of shorter and longer lengths? The answer to this question has been difficult to find due to the high reactivity of such forms. The researchers with this new effort set themselves the task of finding the answer once and for all.

The team's approach involved creating a precursor molecule and then whittling it down to the desired form. To that end, they used atomic force microscopy to create linear lines of carbon atoms atop a copper substrate that was covered with salt to prevent the carbon atoms from bonding with the subsurface. They then joined the lines of atoms to form the carbon oxide precursor C24O6, a triangle-shaped form. Next, the team applied high voltage through the AFM to shear off one of the corners of the triangle, resulting in a C22O4 form. They then did the same with the other two corners. The result was a C18 ring—an 18-atom cyclocarbon. After creating the ring, the researchers found that the bonds holding it together were the alternating long- and short-type bonds that had been previously suggested.

 

Ring-shaped multi-carbon compound cyclocarbon synthesized, Bob Yirka , Phys.org

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Smart Packaging...

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Cheaper flexible integrated circuits open up new markets. (Courtesy: PragmatIC)

 

Topics: Applied Physics, Moore's Law, Semiconductor Technology, Nanotechnology


For more than 50 years, progress in the electronics industry has been guided by Moore’s law: the idea that the number of transistors in a silicon-based integrated circuit (IC) will double approximately every 18 months. The consequences of this doubling include a continual reduction in the size of silicon ICs, as it becomes possible to provide increasingly complex and high-performance functionality in smaller and smaller areas of silicon, and at progressively lower cost relative to the circuits’ processing power.

Moore’s law is an empirical rule of thumb rather than a robust physical principle, and much has been written about how, why and when it will eventually fail. But even before we reach that point, manufacturers are already finding that, in practice, the cost savings associated with reducing the size, or “footprint”, of ICs will only carry them so far. The reason is that below a certain minimum size, ICs become difficult to handle easily or effectively. For highly complex circuitry, such as that found in computers with many millions of transistors in a single IC, this limit on handling size may not be a consideration. However, for applications that require less complex circuits, the size constraint imposed by the physical aspect of handling ICs becomes a limiting factor in their cost.

The approach we have taken at PragmatIC is to use thin, flexible substrates, rather than rigid silicon, as the base for building our circuits. The low cost of the materials involved and the relatively low complexity of our target applications alters the economics around circuit footprint and overall IC cost. Accepting a larger footprint can lower capital expenditure because it means that ultrahigh-end precision tooling is not required to fabricate our circuits during the manufacturing process. In turn, for low-complexity applications, this can lead to a lower final IC cost.

The resulting flexible integrated circuits, or FlexICs, are thinner than a human hair, so they can easily be embedded in everyday objects. They also cost around 10 times less than silicon ICs, making it economically viable for them to appear in trillions of smart objects that engage with consumers and their environments. Since the technology was developed, PragmatIC FlexICs have been trialed in a wide variety of markets, including consumer goods, games, retail, and the pharmaceutical and security sectors.

 

A smart approach to smart packaging
Catherine Ramsdale is vice-president of device development at PragmatIC

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LMADIS...

Topics: Applied Physics, Electromagnetic Radiation, Politics, Robotics


I normally cheer the usage and applications of recent technology. In light of recent events, this may not be a swift idea. The second through fourth letters of the acronym are quite (and maybe intentionally) ominous.

"War is the continuation of politics by other means." Carl von Clausewitz

 

*****


In June, Iran’s military shot down one of the U.S. Navy’s $130 million Global Hawk drones, claiming it had veered out of international airspace and into the nation’s territory.

Now, the U.S. Navy has returned the favor, using a new directed-energy weapon to disable an Iranian drone in the same region — marking the next-generation device’s first known “kill.”

According to a Department of Defense statement, a fixed wing drone approached the USS Boxer while the ship traveled through the Strait of Hormuz on July 18. The drone then came within a threatening range, prompting the crew to take “defensive action.”

A defense official later told Military.com on the condition of anonymity that the Navy took out the drone using its Light Marine Air Defense Integrated System (LMADIS), a new device that uses radio frequencies to jam drones.

Iran’s Minister of Foreign Affairs Mohammad Javad Zarif, meanwhile, has denied the incident altogether, telling reporters the nation has “no information about losing a drone.”

 

US Navy's Weapon Gets First "Kill," Shoots Down Iranian Drone
Kristin Houser, Futurism

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Your iPhone as Tricorder...

Silicon chips similar to those that would be used in the detection process. Credit: Vanderbilt University/Heidi Hall

 

Topics: Applied Physics, Medical Physics, Nanotechnology, Star Trek


The simplest home medical tests might look like a deck of various silicon chips coated in special film, one that could detect drugs in the blood, another for proteins in the urine indicating infection, another for bacteria in water and the like. Add the bodily fluid you want to test, take a picture with your smart phone, and a special app lets you know if there's a problem or not.

That's what electrical engineer Sharon Weiss, Cornelius Vanderbilt Professor of Engineering at Vanderbilt University, and her students developed in her lab, combining their research on low-cost, nanostructured thin films with a device most American adults already own. "The novelty lies in the simplicity of the basic idea, and the only costly component is the smart phone," Weiss said.

"Most people are familiar with silicon as being the material inside your computer, but it has endless uses," she said. "With our nanoscale porous silicon, we've created these nanoscale holes that are a thousand times smaller than your hair. Those selectively capture molecules when pre-treated with the appropriate surface coating, darkening the silicon, which the app detects."
 

 

iPhone plus nanoscale porous silicon equals cheap, simple home diagnostics
Heidi Hall, Vanderbilt University, Phys.org

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SLIPS...

A novel, highly sensitive molecular sensor together with a first-of-its-kind histamine detector comprise abbieSense, a device that can diagnose and assess the severity of an allergic reaction within five minutes. Credit: Wyss Institute at Harvard University

 

Topics: Applied Physics, Fluid Mechanics, Microfluidics, Nanofluidics, Nanotechnology

 


The need for an inexpensive, super-repellent surface cuts across a vast swath of societal sectors—from refrigeration and architecture, to medical devices and consumer products. Most state-of-the-art liquid repellent surfaces designed in the last decade are modeled after lotus leaves, which are extremely hydrophobic due to their rough, waxy surface and the physics of their natural design. However, none of the lotus-inspired materials designed so far has met the mark: they may repel water but they fail to repel oils, fail under physical stress, cannot self-heal – and are expensive to boot.

‘SLIPS’ technology, inspired by the slippery pitcher plant that repels almost every type of liquid and solid, is a unique approach to coating industrial and medical surfaces that is based on nano/microstructured porous material infused with a lubricating fluid. By locking in water and other fluids, SLIPS technology creates slick, exceptionally repellent and robust self-cleaning surfaces on metals, plastics, optics, textiles and ceramics. These slippery surfaces repel almost any fouling challenge a surface may face—whether from bacteria, ice, water, oil, dust, barnacles, or other contaminants.

 

Wyss Institute, Harvard: Slippery Liquid Infused Porous Surfaces

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Superconductors' never-ending flow of electrical current could provide new options for energy storage and superefficient electrical transmission and generation. But the signature zero electrical resistance of superconductors is reached only below a certain critical temperature and is very expensive to achieve. Physicists in Serbia believe they've found a way to manipulate superthin, waferlike monolayers of superconductors, thus changing the material's properties to create new artificial materials for future devices. This image shows a liquid phase graphene film deposited on PET substrate. Credit: Graphene Laboratory, University of Belgrade

 

Topics: Applied Physics, Superconductors, Thin Films


Superconductors' never-ending flow of electrical current could provide new options for energy storage and superefficient electrical transmission and generation, to name just a few benefits. But the signature zero electrical resistance of superconductors is reached only below a certain critical temperature, hundreds of degrees Celsius below freezing, and is very expensive to achieve.

Physicists from the University of Belgrade in Serbia believe they've found a way to manipulate superthin, waferlike monolayers of superconductors, such as graphene, a monolayer of carbon, thus changing the material's properties to create new artificial materials for future devices. The findings from the group's theoretical calculations and experimental approaches are published in the Journal of Applied Physics.

"The application of tensile biaxial strain leads to an increase of the critical temperature, implying that achieving high temperature superconductivity becomes easier under strain," said the study's first author from the University of Belgrade's LEX Laboratory, Vladan Celebonovic.

 

Strain enables new applications of 2-D materials, Phys.org

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Good Vibes...

Sounding off: theoretical force patterns for an underwater Chladni plate at two different frequencies. The force arrows illustrate why glass beads accumulate at the plate antinodes (shown in yellow and red). (Courtesy: K Latifi, H Wijaya and Q Zhou/Physical Review Letters)

 

Topics: Acoustic Physics, Applied Physics, Research


The behaviour of some particles on the vibrating surfaces of Chladni plates is reversed underwater, a new study reveals. The discovery was made by Kourosh Latifi, Harri Wijaya, and Quan Zhou at Aalto University in Finland. They observed that glass beads on a submerged vibrating plate move towards antinodes, where the plate’s amplitude of vibration is highest. The underwater effect could be useful in a variety of medical and biological applications, including the manipulation of living cells.

In 1787 the German physicist Ernst Chladni put sand on a vibrating plate and observed that the grains settle on the nodal lines where the plate’s amplitude of vibration is zero. In contrast, he observed that finer particles move towards the plate’s antinodes where the amplitude is a local maximum.

A century later, Michael Faraday explained both behaviours. He concluded that the vibrations cause the larger grains to move laterally across the plate until they reach a node – where they no longer get lateral kicks and therefore remain in place. As for why the smaller particles did the opposite, Faraday argued that air currents just above the plates tend to push the lighter particles towards the antinodes – an effect known as acoustic streaming.

 

Vibrations guide tiny glass beads through an underwater maze
Sam Jarman, Physics World

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