Scientists have developed a new way to make “polymer nanobrush” — bristly materials which prevent dust from accumulating on various surfaces.
Polymer brushes have been used to coat everything from eyeglass lenses, boats and medical devices — where they keep away smudges, damaging chemicals and germs — to artificial joints and mechanical components in vehicles where they act as a lubricant.
Developed by a team of engineers led by Christopher Li, professor at Drexel University’s college of engineering in Philadelphia, it gives scientists a higher degree of control over the shape of the brush and bristles and is much more efficient.
“The past few decades witnessed exciting progresses in studies on polymer brushes, and they show great promises in various fields, including coating, biomedical, sensing, catalysis to name just a few,” Li said.
His approach involves growing a functional two-dimensional sheet of polymer crystals — similar to a nanoscale piece of double-sided tape. When the sheet is stuck to an existing substrate, and the crystals are dissolved, the remaining polymer chains spring up, forming the bristles of the brush.
“We believe that our discovery of a new way to make polymer brushes is a significant advance in the field and will enable use of the brushes in exciting new ways,” added Li in the study published in the journal Nature Communications.
The new brush is the most densely packed polymer brushes to date, with bristles less than a nanometre apart.
Polymer brush materials are especially useful in situations where pieces need to fit tightly together but need to be able to move without friction throwing a wrench in the works.
These are also effective for keeping important surfaces free of particles, chemicals, proteins and other fouling agents.
Ever Wonder How Two Pendulum Clocks Always Oscillate In Sync?
Two pendulum clocks, hung from the same wooden structure, will always oscillate in synchronicity. Called “Huygens synchronisation” after the renowned Dutch physicist Christiaan Huygens, the secret behind this 350-year-old phenomenon has now been solved.
Researchers from Eindhoven University of Technology along with Mexican colleagues have presented the most accurate and detailed description of “Huygens synchronisation’ to date.
The insights help us understand synchronisation in all kinds of oscillating systems such as the biological rhythms of the human body, they noted.
Lacking the requisite mathematics at the time, Huygens contended that the effect was being caused by tiny vibrations in the wooden structure on which the clocks were hanging.
Henk Nijmeijer, professor of dynamics and control at Eindhoven University, found that Huygens explanation was right.
In the journal Scientific Reports, the team described the most comprehensive study undertaken to date on the effect.
“An odd sympathy” was the way Huygens termed the unexpected discovery he made at home in The Hague in 1665.
The team performed a modern variant of Huygens’ experiment whereby two pendulum clocks specially made for the purpose by the Mexican clock manufacturer Relojes Centenario were placed on a wooden undersurface.
In addition to taking extensive measurements, they analysed and simulated the effect using the most detailed mathematical model developed for this experiment.
This enabled them to dissect the mechanism behind the synchronisation correctly and in detail and consign to the bin the theory proposed two years ago that the synchronisation was attributable to acoustic pulses.
The team also discovered what variables determine whether the clocks swing in parallel with or counter to each other, something that Huygens did not observe.
“Another new discovery is that pendulum clocks are not only synchronous but also move more slowly over time and thus are not very reliable timekeepers,” they noted.
The scientists believe many similar occurrences of synchronisation are present in engineering and in nature like imbalanced rotor motion or the human heartbeat.
There are also indications that certain epileptic attacks are caused by the synchronisation of neurons that takes place in the brain.
Now Don’t Wash Clothes, Just Expose Them To Light
The day when you can look tidy even without washing your clothes does not seem too distant as researchers, including one of Indian origin, have developed a technology to make textiles clean themselves within less than six minutes when put them under a light bulb or out in the sun.
The researchers at RMIT University in Melbourne, Australia, have developed a cheap and efficient new way to grow special nanostructures — which can degrade organic matter when exposed to light — directly onto textiles.
“There’s more work to do to before we can start throwing out our washing machines, but this advance lays a strong foundation for the future development of fully self-cleaning textiles,” said researcher Rajesh Ramanathan.
The research paper was published in the journal Advanced Materials Interfaces.
The work paves the way towards nano-enhanced textiles that can spontaneously clean themselves of stains and grime simply by being put under light.
The process developed by the team had a variety of applications for catalysis-based industries such as agrochemicals, pharmaceuticals and natural products, and could be easily scaled up to industrial levels, Ramanathan said.
“The advantage of textiles is they already have a 3D structure so they are great at absorbing light, which in turn speeds up the process of degrading organic matter,” he explained.
The researchers worked with copper and silver-based nanostructures, which are known for their ability to absorb visible light.
When the nanostructures are exposed to light, they receive an energy boost that creates “hot electrons”.
These “hot electrons” release a burst of energy that enables the nanostructures to degrade organic matter.
The challenge for researchers has been to bring the concept out of the lab by working out how to build these nanostructures on an industrial scale and permanently attach them to textiles.
The RMIT team’s novel approach was to grow the nanostructures directly onto the textiles by dipping them into a few solutions, resulting in the development of stable nanostructures within 30 minutes.
When exposed to light, it took less than six minutes for some of the nano-enhanced textiles to spontaneously clean themselves.
“Our next step will be to test our nano-enhanced textiles with organic compounds that could be more relevant to consumers, to see how quickly they can handle common stains like tomato sauce or wine,” Ramanathan said.
Unprecedented Energy Source Found In Milky Way
A source of cosmic rays radiating energies 100 times greater than those achieved at the largest terrestrial particle accelerator — the Large Hadron Collider at the European Organisation for Nuclear Research (CERN) — has been found in the innermost region of our Milky Way galaxy.
The source was revealed after a detailed analysis of the data collected by the H.E.S.S. observatory in Namibia, which was published in the latest issue of the journal Nature.
H.E.S.S. observatory is being run by an international collaboration of 42 institutions in 12 countries and has been mapping the centre of our galaxy in very high energy gamma rays for over the past 10 years.
“Somewhere within the central 33 light years of the Milky Way there is an astrophysical source capable of accelerating protons to energies of about one petaelectronvolt, continuously for at least 1,000 years,” said Emmanuel Moulin from the Saclay Nuclear Research Centre in France.
Cosmic rays with energies up to approximately 100 teraelectronvolts (TeV)1 are produced in our galaxy by objects such as supernova remnants and pulsar wind nebulae.
Theoretical arguments and direct measurements of cosmic rays reaching the Earth indicate, however, that the cosmic-ray factories in our galaxy should be able to provide particles up to one petaelectronvolt (PeV)2 at least.
While many multi-TeV accelerators have been discovered in recent years, the search for the sources of the highest energy Galactic cosmic rays has been unsuccessful.
The electrically-charged cosmic rays are strongly deflected by the interstellar magnetic fields that pervade our galaxy. Their path through the cosmos is randomised by these deflections, making it impossible to directly identify the astrophysical sources responsible for their production.
Thus, for more than a century, the origin of the cosmic rays has remained one of the most enduring mysteries of science.
In analogy to the “Tevatron” — the first human-built accelerator that reached energies of 1 TeV — this new class of cosmic accelerator has been dubbed a “Pevatron.”
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