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, SLIPS

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

The Perfect Fluid...

If collisions between small projectiles -- protons (p), deuterons (d), and helium-3 nuclei (3He) -- and gold nuclei (Au) create tiny hot spots of quark-gluon plasma, the pattern of particles picked up by the detector should retain some 'memory' of each projectile's initial shape. Measurements from the PHENIX experiment match these predictions with very strong correlations between the initial geometry and the final flow patterns. Credit: Javier Orjuela Koop, University of Colorado, Boulder

Topics: Astrophysics, Fluid Mechanics, Nuclear Physics, Relativity, Theoretical Physics

Nuclear physicists analyzing data from the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC)—a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at Brookhaven National Laboratory—have published in the journal Nature Physics additional evidence that collisions of miniscule projectiles with gold nuclei create tiny specks of the perfect fluid that filled the early universe.

Scientists are studying this hot soup made up of quarks and gluons—the building blocks of protons and neutrons—to learn about the fundamental force that holds these particles together in the visible matter that makes up our world today. The ability to create such tiny specks of the primordial soup (known as quark-gluon plasma) was initially unexpected and could offer insight into the essential properties of this remarkable form of matter.

"This work is the culmination of a series of experiments designed to engineer the shape of the quark-gluon plasma droplets," said PHENIX collaborator Jamie Nagle of the University of Colorado, Boulder, who helped devise the experimental plan as well as the theoretical simulations the team would use to test their results.

Compelling evidence for small drops of perfect fluid, Brookhaven National Laboratory, Phys.org

In Time for the Holidays...

A glass of beer, deconstructed. (a) At the beer’s surface sits a head of foam. (b) A trail of bubbles rises from a nucleation site along the glass wall. The rising of bubbles from different nucleation sites induces a global circulation (sketched here with white arrows). (c) Cellulose fibers serve as nucleation sites; gas cavities inside the fiber are clearly visible. (d) A 3-mm-wide mushroom-shaped bubble plume arises from the implosion of a millimeter-sized bubble when a beer bottle is gently tapped. (e) Surface bubbles seen from below are nearly on edge. (Panels a and b courtesy of Rodrigo Viñas, TresArt Collective.)

Topics: Chemistry, Fluid Mechanics, Physics Humor

Carbonation can also occur by fermentation. When yeast eats simple sugars, it primarily excretes ethanol and CO₂. If the process occurs in a closed container, the pressure rises as the amount of CO₂ increases. In turn, as the pressure rises, the gas dissolves. Although beer making dates back thousands of years,³ it is unclear how bubbly beer could have been originally—old ceramic containers were most likely unsealed. Sparkling wine was discovered later—in the 17th century—and its carbonation comes from a secondary fermentation inside the bottle.

The presence of alcohol and other molecules during fermentation, such as proteins and enzymes, makes the physical description even more interesting. They affect the liquid’s surface tension, viscosity, density, and other properties, which in turn affect the formation, motion, and surface stability, or lifetime, of the bubbles. No less important is the bubbles’ ability to accelerate the absorption of alcohol in the body and thus the rapidity of intoxication.⁴

Alcoholic or not, bubbly drinks are full of physics. Figure 1 illustrates the processes that occur when a carbonated drink is poured into a tall glass. If the liquid is poured shortly after the bottle is opened, the birth of bubbles is visible inside the liquid and on the surface of the glass. Streams of bubbles continuously form and induce convection that affects their production rate and motion. As they grow, the bubbles rise and eventually reach the surface. Once there, depending on the properties of the liquid, the bubbles either burst or float.

The fluid mechanics of bubbly drinks, Physics Today
Roberto Zenit (zenit@unam.mx) is a professor and researcher at the National Autonomous University of Mexico in Mexico City.
Javier Rodríguez-Rodríguez is a fluid mechanics professor at the Carlos III University of Madrid in Spain.

Two-Phased H2O...

Illustration showing fluctuations between regions of two different local structures of water. High density is shown as red and low density as blue. (Courtesy: Stockholm University)

Topics: Fluid Mechanics, Materials Science, Thermodynamics

Water could exist in two different liquid phases with different densities. That is the conclusion of researchers in Sweden, Japan and Korea, who have used ultrafast X-ray scattering to measure the properties of supercooled water droplets.

Despite being the most ubiquitous and important liquid on Earth, water is a deeply puzzling substance with physical properties that deviate significantly from those of an idealized liquid. Several theories have been advanced to account for some of water’s idiosyncrasies, but experimental data have been lacking.

Solid ice is the most stable phase of water below 0° C, but the liquid phase remains metastable at sub-zero temperatures. Under normal circumstances, impurities such as dust particles provide nuclei around which ice crystals can form, so freezing occurs quickly. In the laboratory, however, it is relatively easy to supercool liquid water to well below 0° C by removing impurities. As the temperature goes down further, however, molecular motion slows and, below around -40° C, water molecules begin to form crystals around one another, allowing even pure water to crystallize very rapidly.

Supercooled water could exist in two liquid phases, Tim Wogan, Physics World

Crystal Cavitation...

Time sequence showing the growth of a cavitation bubble. The large circle is an obstruction to the flow of a liquid crystal, which is moving from left to right. The cavitation bubble is forming at the right side of the obstruction. (Courtesy: Max Planck Institute for Dynamics and Self-Organization)

Topics: Condensed Matter Physics, Fluid Mechanics, Materials Science

The formation and subsequent collapse of bubbles has been seen for the first time in a flowing liquid crystal. This process is called cavitation and occurs when the pressure drop in a flowing fluid is large enough to allow some of the fluid to vaporize and create a bubble. Cavitation is of great interest in hydrodynamics because the collapsing bubbles can dissipate large amounts of energy in small regions and cause significant damage to machinery such as propellers.

The discovery was made by Tillmann Stieger and colleagues at the Max Planck Institute for Dynamics and Self-Organization in Göttingen, the Technical University of Berlin and the ETH Zürich. Liquid crystals are fluids that are made of rod-like molecules that tend to align under certain conditions. In its experiments, the team pumped liquid-crystal fluids through tiny channels just 0.1 mm wide. The channels contained obstructions, which increase the speed of the flow and encourage cavitation (see image).

Bubble cavitation spotted in liquid crystals, Hamish Johnston, Physics World

Quantum Spin Liquid...

Data taken with synchrotron diffraction indicates a short range, honeycomb-based nanostructure, which is the basis for the anomalous magnetism of Ba3CuSb2O9. NCNR neutron scattering data confirmed this structure and provided evidence for the resulting quantum spin liquid.
Credit: H. Sawa/Nagoya University
View hi-resolution image

Topics: Ferromagnetic, Fluid Mechanics, NIST, Quantum Mechanics, Spin, Superconductivity, Superfluidity

Back from a "blog break." I saw this article last month, but delayed it until the first due to a series of work-related classes (tiring, but very good I might add). I anticipate a few more, as I have that and two family reunions this summer. Not complaining about my people, but as far as my families, they could stagger these...just saying.

Trivia: Today is my wife's birthday; yesterday we went to Shadows Restaurant - her favorite. It's also (to be seen) the expiration of the Patriot Act. CNN and 24-hour cable news was born on this day in 1980. Since I can recall the era of three major network channels, a few UHF stations and television going off at midnight, I don't know if that's a good thing or not. Due to the massive amounts of competition with channels that produce movies on demand, music and reality shows, cable news has trended towards yellow journalism. Happy 35th birthday CNN, for better or worse...

Gaithersburg, Md.—An international team of researchers including scientists from the National Institute of Standards and Technology (NIST) has found what may be the first known example of a "spin-orbital liquid," a substance in a never-before-seen quantum mechanical state.

The discovery, reported May 4, 2012, in the journal Science, has been sought for years by the physics community. Though the team does not posit immediate applications for the material, its properties relate to the same quantum effects that give rise to superconductivity, in which electricity flows through a material with no resistance, and superfluidity, in which a liquid flows across a surface with no friction.

The term "spin liquid" can be deceptive, as it describes a substance that in many ways fits our conventional understanding of a solid. Indeed, the material the team studied looks like a chunk of earth, but at the molecular level, it is made of copper, oxygen, barium and antimony atoms arranged in a crystalline lattice structure. In this particular structure the copper atoms exhibit unusual properties generally associated with liquids. Specifically, their magnetic orientation remains in a constant state of flux.

When materials with magnetic atoms—like iron—solidify, they generally do so in crystal structures whose atoms have an orderly arrangement of magnetic orientations. (When magnetic atoms interact "ferromagnetically" you get a refrigerator magnet.) Because magnetism stems from a quantum property in the atom's electrons called spin, another way of saying this is that the spins in these atoms' electrons all line up in a single direction. Ferromagnets feature an orderly, static arrangement of electron spins.

NIST Contributes to Discovery of Novel Quantum Spin-Liquid, Chad Boutin

Photonic Bernoulli Forces...

ABSTRACT:
By Bernoulli's law, an increase in the relative speed of a fluid around a body is accompanies by a decrease in the pressure. Therefore, a rotating body in a fluid stream experiences a force perpendicular to the motion of the fluid because of the unequal relative speed of the fluid across its surface. It is well known that light has a constant speed irrespective of the relative motion. Does a rotating body immersed in a stream of photons experience a Bernoulli-like force? We show that, indeed, a rotating dielectric cylinder experiences such a lateral force from an electromagnetic wave. In fact, the sign of the lateral force is the same as that of the fluid-mechanical analogue as long as the electric susceptibility is positive (ε>ε₀), but for negative-susceptibility materials (e.g. metals) we show that the lateral force is in the opposite direction. Because these results are derived from a classical electromagnetic scattering problem, Mie-resonance enhancements that occur in other scattering phenomena also enhance the lateral force.

Physics arXiv: Optical "Bernoulli" Forces

The Physics of Maple Syrup...

..."just when you thought it was safe to go into the IHOP"...

2D cross section through a fiber-vessel pair showing the water, ice and gas regions, the moving interfaces as well as the 1D region corresponding to simplified model geometry. Figure credit: Maurizio Ceseri and John Stockie

Philadelphia, PA—For many of us, maple syrup is an essential part of breakfast—a staple accompaniment to pancakes and waffles—but rarely do we think about the complicated and little-understood physiological aspects of syrup production. Each spring, maple growers in temperate regions around the world collect sap from sugar maple trees, which is one of the first steps in producing this delicious condiment.

However, the mechanisms behind sap exudation—processes that trigger pressure differences causing sap to flow— in maple trees are a topic of much debate. In a paper published today in the SIAM Journal on Applied Mathematics, authors Maurizio Ceseri and John Stockie shed light on this subject by proposing a mathematical model for the essential physiological processes that drive sap flow.

Sugars are produced in the leaves of the maple tree by photosynthesis with the help of absorbed water, carbon dioxide, and sunlight, and are consumed for current growth, or stored as starch. In the cold, dormant season, some of the starch enters the sap, where it remains mostly frozen until the spring. In the period between this dormant state and the active growing season (during cold nights with below-freezing temperatures followed by mild, warm days with above-freezing conditions), the stored starch is converted into sugar and the sap pressure grows, allowing it to exude naturally from the tap hole when tapped.

Society for Industrial and Applied Mathematics: Pancakes with a side of math