Tag Archives: soap bubbles

Branched flows of light look like trees say “explorers of experimental science” at Technion

Enhancing soap bubbles for your science explorations? It sounds like an entertaining activity you might give children for ‘painless’ science education. In this case, researchers at Technion – Israel Institute of Technology have made an exciting discovery, The following video is where I got the phrase “explorers of experimental science,”

A July 1, 2020 news item on Nanowerk announces the work (Note: A link has been removed),

A team of researchers from the Technion – Israel Institute of Technology has observed branched flow of light for the very first time. The findings are published in Nature and are featured on the cover of the July 2, 2020 issue (“Observation of branched flow of light”).

The study was carried out by Ph.D. student Anatoly (Tolik) Patsyk, in collaboration with Miguel A. Bandres, who was a postdoctoral fellow at Technion when the project started and is now an Assistant Professor at CREOL, College of Optics and Photonics, University of Central Florida. The research was led by Technion President Professor Uri Sivan and Distinguished Professor Mordechai (Moti) Segev of the Technion’s Physics and Electrical Engineering Faculties, the Solid State Institute, and the Russell Berrie Nanotechnology Institute.

A July 2, 2020 Technion press release, which originated the news item, delves further into the research,

When waves travel through landscapes that contain disturbances, they naturally scatter, often in all directions. Scattering of light is a natural phenomenon, found in many places in nature. For example, the scattering of light is the reason for the blue color of the sky. As it turns out, when the length over which disturbances vary is much larger than the wavelength, the wave scatters in an unusual fashion: it forms channels (branches) of enhanced intensity that continue to divide or branch out, as the wave propagates.  This phenomenon is known as branched flow. It was first observed in 2001 in electrons and had been suggested to be ubiquitous and occur also for all waves in nature, for example – sound waves and even ocean waves. Now, Technion researchers are bringing branched flow to the domain of light: they have made an experimental observation of the branched flow of light.

“We always had the intention of finding something new, and we were eager to find it. It was not what we started looking for, but we kept looking and we found something far better,” says Asst. Prof. Miguel Bandres. “We are familiar with the fact that waves spread when they propagate in a homogeneous medium. But for other kinds of mediums, waves can behave in very different ways. When we have a disordered medium where the variations are not random but smooth, like a landscape of mountains and valleys, the waves will propagate in a peculiar way. They will form channels that keep dividing as the wave propagates, forming a beautiful pattern resembling the branches of a tree.” 

In their research, the team coupled a laser beam to a soap membrane, which contains random variations in membrane thickness. They discovered that when light propagates within the soap film, rather than being scattered, the light forms elongated branches, creating the branched flow phenomenon for light.

“In optics we usually work hard to make light stay focused and propagate as a collimated beam, but here the surprise is that the random structure of the soap film naturally caused the light to stay focused. It is another one of nature’s surprises,” says Tolik Patsyk. 

The ability to create branched flow in the field of optics offers new and exciting opportunities for investigating and understanding this universal wave phenomenon.

“There is nothing more exciting than discovering something new and this is the first demonstration of this phenomenon with light waves,” says Technion President Prof. Uri Sivan. “This goes to show that intriguing phenomena can also be observed in simple systems and one just has to be perceptive enough to uncover them. As such, bringing together and combining the views of researchers from different backgrounds and disciplines has led to some truly interesting insights.”

“The fact that we observe it with light waves opens remarkable new possibilities for research, starting with the fact that we can characterize the medium in which light propagates to very high precision and the fact that we can also follow those branches accurately and study their properties,” he adds.

Distinguished Prof. Moti Segev looks to the future. “I always educate my team to think beyond the horizon,” he says, “to think about something new, and at the same time – look at the experimental facts as they are, rather than try to adapt the experiments to meet some expected behavior. Here, Tolik was trying to measure something completely different and was surprised to see these light branches which he could not initially explain. He asked Miguel to join in the experiments, and together they upgraded the experiments considerably – to the level they could isolate the physics involved. That is when we started to understand what we see. It took more than a year until we understood that what we have is the strange phenomenon of “branched flow”, which at the time was never considered in the context of light waves. Now, with this observation – we can think of a plethora of new ideas. For example, using these light branches to control the fluidic flow in liquid, or to combine the soap with fluorescent material and cause the branches to become little lasers. Or to use the soap membranes as a platform for exploring fundamentals of waves, such as the transitions from ordinary scattering which is always diffusive, to branched flow, and subsequently to Anderson localization. There are many ways to continue this pioneering study. As we did many times in the past, we would like to boldly go where no one has gone before.” 

The project is now continuing in the laboratories of Profs. Segev and Sivan at Technion, and in parallel in the newly established lab of Prof. Miguel Bandres at UCF. 

Here’s a link to and a citation for the paper,

Observation of branched flow of light by Anatoly Patsyk, Uri Sivan, Mordechai Segev & Miguel A. Bandres Nature volume 583, pages60–65 (2020) DOI: https://doi.org/10.1038/s41586-020-2376-8 Published: 01 July 2020 Issue Date: 02 July 2020

This paper is behind a paywall.

Solar cells and soap bubbles

The MIT team has achieved the thinnest and lightest complete solar cells ever made, they say. To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble. Photo: Joel Jean and Anna Osherov

The MIT team has achieved the thinnest and lightest complete solar cells ever made, they say. To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble. Photo: Joel Jean and Anna Osherov

That’s quite a compelling image and it comes to us courtesy of researchers at MIT (Massachusetts Institute of Technology). From a Feb. 25, 2016 MIT news release (also on EurekAlert),

Imagine solar cells so thin, flexible, and lightweight that they could be placed on almost any material or surface, including your hat, shirt, or smartphone, or even on a sheet of paper or a helium balloon.

Researchers at MIT have now demonstrated just such a technology: the thinnest, lightest solar cells ever produced. Though it may take years to develop into a commercial product, the laboratory proof-of-concept shows a new approach to making solar cells that could help power the next generation of portable electronic devices.

Bulović [Vladimir Bulović ], MIT’s associate dean for innovation and the Fariborz Maseeh (1990) Professor of Emerging Technology, says the key to the new approach is to make the solar cell, the substrate that supports it, and a protective overcoating to shield it from the environment, all in one process. The substrate is made in place and never needs to be handled, cleaned, or removed from the vacuum during fabrication, thus minimizing exposure to dust or other contaminants that could degrade the cell’s performance.

“The innovative step is the realization that you can grow the substrate at the same time as you grow the device,” Bulović says.

In this initial proof-of-concept experiment, the team used a common flexible polymer called parylene as both the substrate and the overcoating, and an organic material called DBP as the primary light-absorbing layer. Parylene is a commercially available plastic coating used widely to protect implanted biomedical devices and printed circuit boards from environmental damage. The entire process takes place in a vacuum chamber at room temperature and without the use of any solvents, unlike conventional solar-cell manufacturing, which requires high temperatures and harsh chemicals. In this case, both the substrate and the solar cell are “grown” using established vapor deposition techniques.

One process, many materials

The team emphasizes that these particular choices of materials were just examples, and that it is the in-line substrate manufacturing process that is the key innovation. Different materials could be used for the substrate and encapsulation layers, and different types of thin-film solar cell materials, including quantum dots or perovskites, could be substituted for the organic layers used in initial tests.

But already, the team has achieved the thinnest and lightest complete solar cells ever made, they say. To demonstrate just how thin and lightweight the cells are, the researchers draped a working cell on top of a soap bubble, without popping the bubble. The researchers acknowledge that this cell may be too thin to be practical — “If you breathe too hard, you might blow it away,” says Jean [Joel Jean, doctoral student] — but parylene films of thicknesses of up to 80 microns can be deposited easily using commercial equipment, without losing the other benefits of in-line substrate formation.

A flexible parylene film, similar to kitchen cling-wrap but only one-tenth as thick, is first deposited on a sturdier carrier material – in this case, glass. Figuring out how to cleanly separate the thin material from the glass was a key challenge, explains Wang [Annie Wang, research scientist], who has spent many years working with parylene.

The researchers lift the entire parylene/solar cell/parylene stack off the carrier after the fabrication process is complete, using a frame made of flexible film. The final ultra-thin, flexible solar cells, including substrate and overcoating, are just one-fiftieth of the thickness of a human hair and one-thousandth of the thickness of equivalent cells on glass substrates — about two micrometers thick — yet they convert sunlight into electricity just as efficiently as their glass-based counterparts.

No miracles needed

“We put our carrier in a vacuum system, then we deposit everything else on top of it, and then peel the whole thing off,” explains Wang. Bulović says that like most new inventions, it all sounds very simple — once it’s been done. But actually developing the techniques to make the process work required years of effort.

While they used a glass carrier for their solar cells, Jean says “it could be something else. You could use almost any material,” since the processing takes place under such benign conditions. The substrate and solar cell could be deposited directly on fabric or paper, for example.

While the solar cell in this demonstration device is not especially efficient, because of its low weight, its power-to-weight ratio is among the highest ever achieved. That’s important for applications where weight is important, such as on spacecraft or on high-altitude helium balloons used for research. Whereas a typical silicon-based solar module, whose weight is dominated by a glass cover, may produce about 15 watts of power per kilogram of weight, the new cells have already demonstrated an output of 6 watts per gram — about 400 times higher.

“It could be so light that you don’t even know it’s there, on your shirt or on your notebook,” Bulović says. “These cells could simply be an add-on to existing structures.”

Still, this is early, laboratory-scale work, and developing it into a manufacturable product will take time, the team says. Yet while commercial success in the short term may be uncertain, this work could open up new applications for solar power in the long term. “We have a proof-of-concept that works,” Bulović says. The next question is, “How many miracles does it take to make it scalable? We think it’s a lot of hard work ahead, but likely no miracles needed.”

Here’s a link to and a citation for the paper,

In situ vapor-deposited parylene substrates for ultra-thin, lightweight organic solar cells by Joel Jean, Annie Wang, Vladimir Bulović. Organic Electronics Volume 31, April 2016, Pages 120–126 doi:10.1016/j.orgel.2016.01.022

This paper is behind a paywall.

DNA (deoxyribonucleic acid), music, and data storage

David Bruggeman (Pasco Phronesis blog) has written up, as he so often does, a fascinating art/science piece in his May 28, 2015 post (Note: A link has been removed),

Opening next month [June 2015] at the Dilston Grove Gallery at GDP London is Music of the Spheres, an exhibition that uses bioinformatics to record music.  Dr. Nick Goldman of the European Bioinformatics Institute has been working on new technologies for encoding large amounts of information into DNA.  Collaborating with Charlotte Jarvis, the two have worked on installations of bubbles that would contain DNA encoded with music (the DNA is suspended in soap solution).

There’s more information about the exhibit on the Music of the Spheres webpage on the CGP London website,

Music of the Spheres utilises new bioinformatics technology developed by Dr. Nick Goldman to encode a new musical recording by the Kreutzer Quartet into DNA.

The DNA has been suspended in soap solution and will be used by visual artist Charlotte Jarvis to create performances and installations filled with bubbles. The recording will fill the air, pop on visitors skin and literally bathe the audience in music.

Dr. Nick Goldman and Charlotte Jarvis have been working together for the past year to create a series of moving visual and musical experiences that explore the scope and future ubiquity of DNA technologies.

The Kreutzer Quartet’s new composition for string quartet loosely follows the traditional form of a concerto, in comprising of three musical movements. The second movement only exists in the form of a recording encoded into DNA.

For the exhibition the DNA will be suspended in soap solution and used to create silent installations filled with bubbles. The bubbles will be accompanied by a video projection showing the musicians playing in the server room of the European Bioinformatics Institute, Cambridge.

In response to the growing challenge of storing vast quantities of biological data generated by biomedical research Dr. Nick Goldman and the European Bioinformatics Institute have developed a method to encode huge amounts of information in DNA itself. Every day the huge quantities and speed of data pouring into servers gets larger. When research groups sequence DNA the file sizes are too large to be kept on local computers. It is this problem that was the motivation for Nick Goldman to develop his new technology. Their goal is a system that will safely store the equivalent of one million CDs in a gram of DNA for 10,000 years. Nick’s work was has been featured in The New York Times, The Guardian and on BBC News amongst other media outlets.

The Kreutzer Quartet will play the full-length composition live during the preview on 12 June [2015] timed with the setting of the sun through the large westerly windows. [emphasis mine] During the passage of the second movement the stage will fall silent, the music will be released into the auditorium in the form of bubbles. The performance will be accompanied by film projection and a discussion about the project.

The exhibit runs from June 12 – July 5, 2015. Hours and location can be found on the CGP website.

The Music of the Spheres DNA/music project was first mentioned here in a May 5, 2014 post about the launch of the book ‘Synthetic Aesthetics: Investigating Synthetic Biology’s Designs on Nature’. The launch featured a number of performances and events, scroll down abut 80% of the way for the then description of Music of the Spheres.

‘Soft’ nanoparticles, 2D liquid, and fluid interfaces

There’s a story about University of Pennsylvania research on 2D liquids and ‘soft’ particles in an April 6, 2015 news item on Azonano,

Researchers at the University of Pennsylvania have used ‘soft’ nanoparticles to create a system that behaves as a 2D liquid. A 2D world exists at the place where oil and water meet. This interface has properties that could be useful for engineers and chemists.

Researchers have been able to make a soap molecule stay at the interface and make it behave in a predictable manner. However, they have not been able to make more complex molecules behave in the same manner.

An April 3, 2015 University of Pennsylvania news release (also on EurekAlert), which appears to have originated the news item, describes the research in detail,

Where water and oil meet, a two-dimensional world exists. This interface presents a potentially useful set of properties for chemists and engineers, but getting anything more complex than a soap molecule to stay there and behave predictably remains a challenge.

A University of Pennsylvania team has now shown how to make nanoparticles that are attracted to this interface but not to each other, creating a system that acts as a two-dimensional liquid. By measuring this liquid’s pressure and density, they have shown a way forward in using it for a variety of applications, such as in nanomanufacturing, catalysis and photonic devices.

By creating a system where these particles do not clump into clusters or skins, they have enabled a way of investigating the physical fundamentals of how nanoscale objects interact with one another in two dimensions.

“Things get stuck at the interface between oil and water,” Stebe said. “That’s of tremendous fundamental and technological interest, because we can think of that interface as a two-dimensional world. If we can start to understand the interactions of the things that accumulate there and learn how they are arranged, we can exploit them in a number of different applications.”

Getting nanoparticles to go to and stay at this interface is tricky, however. Their surface chemistry can easily be adapted to either water or oil, but balancing the two to get the particles to stay in this 2-D regime is more difficult.

“We understand how particles work in 3-D,” Crocker said. “If you put polymer chains on the surface that are attracted to the solvent, the particles will bounce off each other and make a nice suspension, meaning you can do work with them. However, people haven’t really done that in 2-D before.”

Even when particles are able to stay at the interface, they tend to clump together and form a skin that can’t be pulled apart into its constituent particles.

“All particles love themselves,” Stebe said. “Just due to Van der Waals interactions, if they can get close enough, they aggregate. But because our nanoparticles have protective ligand arms, they don’t clump together and form a liquid state. They’re in two-dimensional equilibrium.”

The team’s technique for surmounting this problem hinged on decorating their gold nanoparticles with surfactant, or soap-like, ligands. These ligands have a water-loving head and an oil-loving tail, and the way they are attached to the central particle allows them to contort themselves so both sides are happy when the particle is at an interface. This arrangement produces a “flying saucer” shape, with the ligands stretching out more at the interface than above or below. These ligand bumpers keeps the particles from clumping together.

“This is a very beautiful system,” Stebe said. “The ability to tune their packing means that we can now take everything we know about the equilibrium thermodynamics in two dimensions and start to pose questions about particle layers. Do these particles behave like we think they should? How can we manipulate them in the future?”

To get at the fundamentals of this system, the researchers needed to deduce the relationships of certain properties, such as how the pressure of their 2-D liquid changes as a function of the packing of the particles. They used a variation of the pendant drop method, in which an oil droplet formed in a suspension of particles in water.  Over time, particles attached to the oil-water interface, producing the 2-D liquid in a form where they could measure those traits.

“We can infer the pressure of this 2-D fluid by the shape of the drop,” Stebe said. “Once we compress the drop by pulling some of the oil back into the syringe, we can determine how the shape changes and relate it to the pressure in the layer.”

The researchers also needed to determine how densely the particles were packed. To do so, they wanted to take advantage of the fact that the drop became more opaque as the density of the particle increased when the drop was compressed. However, it was not possible to simply measure the amount of light that shone through the drop, as plasmonic behavior meant that the properties of the gold nanoparticles changed as they got closer together.

“Fortunately, we discovered another interesting feature of this nanoparticle system,” Garbin said. “If the drop was compressed too much, some particles would fall out of the interface because they didn’t fit anymore. This enabled us to measure the amount of particles that were in that falling plume, since the particles are farther apart from each other there. From that measurement, we could work backwards to the number of particles on the interface”

The smooth relationship between the particles’ packing and the pressure of the 2-D liquid they form provides the basis of universal rules that govern the physics of such systems.

”From this data,” Crocker said, “we can figure out the force versus distance of two nanoparticles. That means we can now make a model of how these particles behave in the 2-D liquid.”

Having these rules will allow researchers to develop functional nanoparticles with different traits, such as longer and more complex ligands that perform some chemical task.

“One application is interface catalysis,” Stebe said. “For example, if you have a reagent that’s in the oil phase, but its product is in the water phase, having a particle on the interface that can help move it from one to the other would be perfect.”

A better understanding of when and why particles get trapped in liquid-liquid interfaces could also underpin future work.

Here’s a link to and  a citation for the paper,

Interactions and Stress Relaxation in Monolayers of Soft Nanoparticles at Fluid-Fluid Interfaces by Valeria Garbin, Ian Jenkins, Talid Sinno, John C. Crocker, and Kathleen J. Stebe. Phys. Rev. Lett. 114, 108301 (Vol. 114, Iss. 10 — 13 March 2015) Published 9 March 2015 DOI: http://dx.doi.org/10.1103/PhysRevLett.114.108301

This paper is behind a paywall.

The Code; a preview of the BBC documentary being released in Canada and the US

The three episodes (Numbers, Shapes, and Prediction)  of The Code, a BBC (British Broadcasting Corporation) documentary featuring Professor Marcus du Sautoy, focus on a ‘code’ that according to du Sautoy unlocks the secrets to the laws governing the universe.

During the weekend (June 16 & 17, 2012) I had the pleasure of viewing the two-disc DVD set which is to be released tomorrow, June 19, 2012, in the US and Canada.  It’s a beautiful and, in its way, exuberant exploration of patterns that recur throughout nature and throughout human endeavours. In the first episode, Numbers, du Sautoy relates the architecture of the Chartres Cathedral (France) , St. Augustine‘s (a Roman Catholic theologian born in an area we now call Algeria) sacred numbers, the life cycle of the periodic cicada in Alabama, US and more to number patterns. Here’s an excerpt of du Sautoy in Alabama with Dr. John Cooley discussing the cicadas’ qualities as pets and their remarkable 13 year life cycle,

In the second episode, Shapes,  du Sautoy covers beehive construction (engineering marvels), bird migrations and their distinct shapes (anyone who’s ever seen a big flock of birds move as one has likely marveled at the shapes the flock takes as it moves from area to another), computer animation, soap bubbles and more, explaining how these shapes can be derived from the principle of simplicity or as du Sautoy notes, ‘nature is lazy’. The question being, how do you make the most efficient structure to achieve your ends, i.e., structure a bird flock so it moves efficiently when thousands and thousands are migrating huge distances, build the best beehive while conserving your worker bees’ energies and extracting the most honey possible, create stunning animated movies with tiny algorithms, etc.?

Here’s du Sautoy with ‘soap bubbleologist’ Tom Noddy who’s demonstrating geometry in action,

For the final episode, Prediction, du Sautoy brings the numbers and geometry together demonstrating repeating patterns such as fractals which dominate our landscape, our biology, and our universe. du Sautoy visits a Rock Paper Scissors tournament in New York City trying to discern why some folks can ‘win’ while others cannot (individuals who can read other people’s patterns while breaking their own are more successful), discusses geographic profiling with criminal geographic profiler Prof. Kim Rossmo, Jackson Pollock’s paintings and his fractals, amongst other intriguing patterns.

I paid special to the Rossmo segment as he created and developed his geographic profiling techniques when he worked for the Vancouver (Canada) Police Department (VPD) and studied at a nearby university. As this groundbreaking work was done in my neck of the woods and Rossmo was treated badly by the VPD, I felt a special interest. There’s more about Rossmo’s work and the VPD issues in the Wikipedia essay (Note: I have removed links from the excerpt.),

D. Kim Rossmo is a Canadian criminologist specializing in geographic profiling. He joined the Vancouver Police Department as a civilian employee in 1978 and became a sworn officer in 1980. In 1987 he received a Master’s degree in criminology from Simon Fraser University and in 1995 became the first police officer in Canada to obtain a doctorate in criminology. His dissertation research resulted in a new criminal investigative methodology called geographic profiling, based on Rossmo’s formula.

In 1995, he was promoted to detective inspector and founded a geographic profiling section within the Vancouver Police Department. In 1998, his analysis of cases of missing sex trade workers determined that a serial killer was at work, a conclusion ultimately vindicated by the arrest and conviction of Robert Pickton in 2002. A retired Vancouver police staff sergeant has claimed that animosity toward Rossmo delayed the arrest of Pickton, leaving him free to carry out additional murders. His analytic results were not accepted at the time and after a falling out with senior members of the department he left in 2001. His unsuccessful lawsuit against the Vancouver Police Board for wrongful dismissal exposed considerable apparent dysfunction within that department.

… he moved to Texas State University where he currently holds the Endowed Chair in Criminology and is director of the Center for Geospatial Intelligence and Investigation. …

Within what appeared to be chaos, Rossmo found order. Somehow Jackson Pollock did the same thing to achieve entirely different ends, a new form of art. Here’s a video clip of du Sautoy with artist and physicist, Richard Taylor,

Intuitively, Pollock dripped paint onto his canvases creating fractals decades before mathematician, Benoit Mandelbrot, coined the phrase and established the theory.  (I wrote previously about Jackson Pollock [and fluid dynamics] in my June 30, 2011 posting.)

I gather that du Sautoy’s ‘code’ will offer a unified theory drawing together numbers, patterns, and shapes as they are found throughout the universe in nature  and in our technologies and sciences.

The DVDs offer three extras (4 mins. each): Phi’s the Limit (beauty and the golden ratio or Phi), Go Forth and Multiply (a base 2 system developed by Ethiopian traders predating binary computer codes by millenia) and Imagining the Impossible: The Mathematical Art of M. C. Escher  (Dutch artist’s [Escher] experiments with tessellation/tiling).

I quite enjoyed the episodes although I was glad to have read James Gleick‘s book, Chaos (years ago) before viewing the third episode, Prediction and I was a little puzzled by du Sautoy’s comment in the first episode, Numbers, that atoms are not divisible. As I recall, you create an atomic bomb when you split an atom but it may have been one of those comments that didn’t come out as intended or I misunderstood.

You can find out more about The Code DVDs at Athena Learning. The suggested retail cost is $39.99 US or $52.99 CAD (which seems a little steep for Canadian purchasers since the Canadian dollar is close to par these days and, I believe, has been for some time).

In sum, this is a very engaging look at numbers and mathematics.