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Researchers devise efficient power converter for internet of things

Researchers devise efficient power converter for internet of things

By Larry Hardesty


CAMBRIDGE, Mass. – The “internet of things” is the idea that vehicles, appliances, civil structures, manufacturing equipment, and even livestock will soon have sensors that report information directly to networked servers, aiding with maintenance and the coordination of tasks.

Those sensors will have to operate at very low powers, in order to extend battery life for months or make do with energy harvested from the environment. But that means that they’ll need to draw a wide range of electrical currents. A sensor might, for instance, wake up every so often, take a measurement, and perform a small calculation to see whether that measurement crosses some threshold. Those operations require relatively little current, but occasionally, the sensor might need to transmit an alert to a distant radio receiver. That requires much larger currents.

Generally, power converters, which take an input voltage and convert it to a steady output voltage, are efficient only within a narrow range of currents. But at the International Solid-State Circuits Conference last week, researchers from MIT’s Microsystems Technologies Laboratories (MTL) presented a new power converter that maintains its efficiency at currents ranging from 500 picoamps to 1 milliamp, a span that encompasses a 200,000-fold increase in current levels.

“Typically, converters have a quiescent power, which is the power that they consume even when they’re not providing any current to the load,” says Arun Paidimarri, who was a postdoc at MTL when the work was done and is now at IBM Research. “So, for example, if the quiescent power is a microamp, then even if the load pulls only a nanoamp, it’s still going to consume a microamp of current. My converter is something that can maintain efficiency over a wide range of currents.”

Paidimarri, who also earned doctoral and master’s degrees from MIT, is first author on the conference paper. He’s joined by his thesis advisor, Anantha Chandrakasan, the Vannevar Bush Professor of Electrical Engineering and Computer Science at MIT.

Packet perspective

The researchers’ converter is a step-down converter, meaning that its output voltage is lower than its input voltage. In particular, it takes input voltages ranging from 1.2 to 3.3 volts and reduces them to between 0.7 and 0.9 volts.

“In the low-power regime, the way these power converters work, it’s not based on a continuous flow of energy,” Paidimarri says. “It’s based on these packets of energy. You have these switches, and an inductor, and a capacitor in the power converter, and you basically turn on and off these switches.”

The control circuitry for the switches includes a circuit that measures the output voltage of the converter. If the output voltage is below some threshold — in this case, 0.9 volts — the controllers throw a switch and release a packet of energy. Then they perform another measurement and, if necessary, release another packet.

If no device is drawing current from the converter, or if the current is going only to a simple, local circuit, the controllers might release between 1 and a couple hundred packets per second. But if the converter is feeding power to a radio, it might need to release a million packets a second.

To accommodate that range of outputs, a typical converter — even a low-power one — will simply perform 1 million voltage measurements a second; on that basis, it will release anywhere from 1 to 1 million packets. Each measurement consumes energy, but for most existing applications, the power drain is negligible. For the internet of things, however, it’s intolerable.

Clocking down

Paidimarri and Chandrakasan’s converter thus features a variable clock, which can run the switch controllers at a wide range of rates. That, however, requires more complex control circuits. The circuit that monitors the converter’s output voltage, for instance, contains an element called a voltage divider, which siphons off a little current from the output for measurement. In a typical converter, the voltage divider is just another element in the circuit path; it is, in effect, always on.

But siphoning current lowers the converter’s efficiency, so in the MIT researchers’ chip, the divider is surrounded by a block of additional circuit elements, which grant access to the divider only for the fraction of a second that a measurement requires. The result is a 50 percent reduction in quiescent power over even the best previously reported experimental low-power, step-down converter and a tenfold expansion of the current-handling range.

“This opens up exciting new opportunities to operate these circuits from new types of energy-harvesting sources, such as body-powered electronics,” Chandrakasan says.

The work was funded by Shell and Texas Instruments, and the prototype chips were built by the Taiwan Semiconductor Manufacturing Corporation, through its University Shuttle Program.

Source: MIT News Office

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Academic and research collaboration to improve people to people contacts for peace and progress

Syed Faisal ur Rahman

Muslim world especially Middle East and surrounding regions, where we live, are facing some of the worst political turmoil of our history. We are seeing wars, terrorism, refugee crisis and resulting economic. The toughest calamities are faced by common people who have very little or no control over the policies which are resulting in the current mess. Worst thing which is happening is the exploitation of sectarianism as a tool to forward foreign policy and strategic agenda. Muslims in many parts of the world are criticizing western powers for this situation but we also need to seriously do some soul searching.

We need to see why are we in this mess?

For me one major reason is that OIC members have failed to find enough common constructive goals to bring their people together.

After the Second World War, Europe realized the importance of academic and economic cooperation for promoting peace and stability. CERN is a prime example of how formal foes can join hands for the purpose of discovery and innovation.

France and Germany have established common institutes and their universities regularly conduct joint research projects. UK and USA, despite enormous bloodshed the historical American war of independence, enjoy exemplary people to people relationships and academic collaboration is a major part of it. It is this attitude of thinking big, finding common constructive goals and strong academic collaboration, which has put them in the forefront of science and technology.

Over the last few decades, humanity has sent probes like Voyager which are challenging the limits of our solar system, countries are thinking about colonizing Mars, satellites like PLANCK and WMAP are tracking radiation from the early stages of our universe, quantum computing is now looking like a possibility and projects are being made for hyper-sonic flights. But in most of the so called Muslim world, we are stuck with centuries old and good for nothing sectarian issues.

Despite some efforts in the defense sector, OIC member countries largely lack the technology base to independently produce jets, automobiles, advanced electronics, precision instruments and many other things which are being produced by public or independent private sector companies in USA, China, Russia, Japan and Europe. Most of the things which are being indigenously produced by OIC countries rely heavily on foreign core components like engine or high precision electronics items. This is due to our lack of investment on fundamental research especially Physics.

OIC countries like Turkey, Pakistan, Malaysia, Iran, Saudi Arabia and some others have some basic infrastructure on which they can build upon to conduct research projects and joint ventures in areas like sending space probes, ground based optical and radio astronomy, particle physics, climate change and development of strong industrial technology base.  All we need is the will to start joint projects and promote knowledge sharing via exchange of researchers or joint academic and industrial research projects.

These joint projects will not only be helpful in enhancing people to people contacts and improving academic research standards but they will also contribute positively in the overall progress of humanity. It is a great loss for humanity as a whole that a civilization, which once led the efforts to develop astronomy, medicine and other key areas of science, is not making any or making very little contribution in advancing our understanding of the universe.

The situation is bad and if we look at Syria, Afghanistan, Iraq, Yemen or Libya then it seems we have hit the rock bottom. It is “Us” who need to find the way out of this mess as no one is going to solve our problems especially the current sectarian mess which is a result of narrow mindsets taking weak decisions. To come out of this dire state, we need broad minds with big vision and a desire of moving forward through mutual respect and understanding.


Science, politics, news agenda and our priorities

By Syed Faisal ur Rahman


Recent postponement of the first Organization of Islamic Countries (OIC) summit on Science and Technology and COMSTECH 15th general assembly meeting, by the government of Pakistan due to security reasons tells a lot about our national priorities.

The summit was first of its kind meeting of the heads of state and dignitaries from the Muslim world on the issue of science and technology.

Today most Muslim countries are known in other parts of the world as backward, narrow minded and violent regions. Recent wars in the Middle East, sectarian rifts and totalitarian regimes are also not presenting a great picture either. While rest of the world is sending probes towards the edge of our solar system, sending missions to Mars and exploring moons of Saturn, we are busy and failing in finding moon on the right dates of the Islamic calendar.

Any average person can figure out that we need something drastic to change this situation. This summit was exactly the kind of step we needed for a jump start. Some serious efforts were made by the COMSTECH staff under the leadership of Dr. Shaukat Hameed Khan and even the secretary general of OIC was pushing hard for the summit. According to reports, OIC secretary general personally visited more than a dozen OIC member countries to successfully convince their head of states to attend the summit.

This summit would have also provided an opportunity to bring harmony and peace in the Muslim world as many Muslim countries are at odds with each other on regional issues like in Syria, Iraq, Yemen and Afghanistan.

Last century saw enormous developments in the fields of fundamental science, which also helped countries to rapidly develop their potential in industry, medical sciences, defense, space and many other sectors. Countries which made science and technology research and education as priority areas emerged as stronger nations as compared to those who merely relied on agriculture and the abundance of natural resources. We are now living in an era where humanity is reaching to the end points of our solar system through probes like Voyager 1, sent decades ago by NASA with messages from our civilization; Quantum computing is well on its way to become a reality; Humanity is also endeavoring to colonize other planets through multi-national projects; We are also looking deepest into the space for new stars, galaxies and even to some of the earliest times after the creation of our universe through cosmic microwave background probes like Planck.

Unfortunately, in Pakistan, anti-science and anti-research attitudes are getting stronger. The lack of anti-science and anti-research attitude is not just limited to the religious zealots but the so called liberals of Pakistan do not simply put much heed to what is going around in the world of science.

If you are one of the regular followers of political arena, daily news coverage on the media and keep your ears open to hear what is going around in the country then you can easily get the idea what are our priorities as a nation. How many talk shows we saw on the main stream media over the cancellation of the summit? How many questions were raised in the parliament?

The absence or very unnoticeable presence of such issues is conspicuous and apart from one senator, Senator Sehar Kamran, who wrote a piece in a news paper, no politician even bothered to raise the relevant questions.

Forget about main stream media or politicians. If we go to social media or drawing room discussions, did you hear anyone discussing the issue in a debate when we make  fuss about issues like what kind of dress some xyz model was wearing on her court hearing in a money laundering case or which politician’s marriage is supposedly in trouble or whose hand Junaid Jamshed was holding in group photo?

We boast about our success in reducing terrorism through successful military operations and use that success to attract investors, sports teams and tourists but on the other hand we are using security concerns as an excuse to cancel an important summit on the development of science and technology. This shows that either we are confused or hypocrites or we are simply not ready for any kind of intellectual growth.

There is a need to seriously do some brain storming and soul searching about our priorities.  One thing which I have learned as a student of Astronomy is that we are insignificant as compared to the vastness of our universe, the only thing which can make us somewhat special as compared to other species on earth or a lifeless rock on Pluto is that we can challenge our thinking ability to learn, to explore and to discover. Unfortunately, in our country we are losing this special capacity day by day.

Researchers use engineered viruses to provide quantum-based enhancement of energy transport:MIT Research

Quantum physics meets genetic engineering

Researchers use engineered viruses to provide quantum-based enhancement of energy transport.

By David Chandler


CAMBRIDGE, Mass.–Nature has had billions of years to perfect photosynthesis, which directly or indirectly supports virtually all life on Earth. In that time, the process has achieved almost 100 percent efficiency in transporting the energy of sunlight from receptors to reaction centers where it can be harnessed — a performance vastly better than even the best solar cells.

One way plants achieve this efficiency is by making use of the exotic effects of quantum mechanics — effects sometimes known as “quantum weirdness.” These effects, which include the ability of a particle to exist in more than one place at a time, have now been used by engineers at MIT to achieve a significant efficiency boost in a light-harvesting system.

Surprisingly, the MIT researchers achieved this new approach to solar energy not with high-tech materials or microchips — but by using genetically engineered viruses.

This achievement in coupling quantum research and genetic manipulation, described this week in the journal Nature Materials, was the work of MIT professors Angela Belcher, an expert on engineering viruses to carry out energy-related tasks, and Seth Lloyd, an expert on quantum theory and its potential applications; research associate Heechul Park; and 14 collaborators at MIT and in Italy.

Lloyd, a professor of mechanical engineering, explains that in photosynthesis, a photon hits a receptor called a chromophore, which in turn produces an exciton — a quantum particle of energy. This exciton jumps from one chromophore to another until it reaches a reaction center, where that energy is harnessed to build the molecules that support life.

But the hopping pathway is random and inefficient unless it takes advantage of quantum effects that allow it, in effect, to take multiple pathways at once and select the best ones, behaving more like a wave than a particle.

This efficient movement of excitons has one key requirement: The chromophores have to be arranged just right, with exactly the right amount of space between them. This, Lloyd explains, is known as the “Quantum Goldilocks Effect.”

That’s where the virus comes in. By engineering a virus that Belcher has worked with for years, the team was able to get it to bond with multiple synthetic chromophores — or, in this case, organic dyes. The researchers were then able to produce many varieties of the virus, with slightly different spacings between those synthetic chromophores, and select the ones that performed best.

In the end, they were able to more than double excitons’ speed, increasing the distance they traveled before dissipating — a significant improvement in the efficiency of the process.

The project started from a chance meeting at a conference in Italy. Lloyd and Belcher, a professor of biological engineering, were reporting on different projects they had worked on, and began discussing the possibility of a project encompassing their very different expertise. Lloyd, whose work is mostly theoretical, pointed out that the viruses Belcher works with have the right length scales to potentially support quantum effects.

In 2008, Lloyd had published a paper demonstrating that photosynthetic organisms transmit light energy efficiently because of these quantum effects. When he saw Belcher’s report on her work with engineered viruses, he wondered if that might provide a way to artificially induce a similar effect, in an effort to approach nature’s efficiency.

“I had been talking about potential systems you could use to demonstrate this effect, and Angela said, ‘We’re already making those,’” Lloyd recalls. Eventually, after much analysis, “We came up with design principles to redesign how the virus is capturing light, and get it to this quantum regime.”

Within two weeks, Belcher’s team had created their first test version of the engineered virus. Many months of work then went into perfecting the receptors and the spacings.

Once the team engineered the viruses, they were able to use laser spectroscopy and dynamical modeling to watch the light-harvesting process in action, and to demonstrate that the new viruses were indeed making use of quantum coherence to enhance the transport of excitons.

“It was really fun,” Belcher says. “A group of us who spoke different [scientific] languages worked closely together, to both make this class of organisms, and analyze the data. That’s why I’m so excited by this.”

While this initial result is essentially a proof of concept rather than a practical system, it points the way toward an approach that could lead to inexpensive and efficient solar cells or light-driven catalysis, the team says. So far, the engineered viruses collect and transport energy from incoming light, but do not yet harness it to produce power (as in solar cells) or molecules (as in photosynthesis). But this could be done by adding a reaction center, where such processing takes place, to the end of the virus where the excitons end up.

The research was supported by the Italian energy company Eni through the MIT Energy Initiative. In addition to MIT postdocs Nimrod Heldman and Patrick Rebentrost, the team included researchers at the University of Florence, the University of Perugia, and Eni.

Source:MIT News Office

This artist’s impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 metres deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 kilometres.

ESO/M. Kornmesser

UAE’s Al-Amal Mars Mission: A Great Initiative with Even Greater Intent

The mission will be launched in 2020 and the landing is expected to be in 2021
 By Syed Faisal ur Rahman

Recently UAE has announced details of its mission to Mars named ‘Al-Amal’. Amal is an Arabic word and name meaning ‘hope’ or ‘aspiration’ and the program truly represents the desires of many in Arab or even the whole Muslim world to contribute something big in humanity’s endeavors to explore the universe.

There was a time when Muslim and especially Arab astronomers used to contribute or even lead in many areas of science. From algebra to astronomy and medicine, we can find a lot of literature in history highlighting the contribution of Muslim scientists and engineers.

If you look at the star charts and astronomy catalogues, you will find many Arabic names of celestial objects and that’s because some of the early discoveries in astronomy were made by Muslim scientists in a time when Europe was going through dark ages.

Unfortunately, Muslims lost their way into darkness 7-8 centuries ago and the intellectual leadership was taken over by people who pushed us away from the path of learning physical sciences, reasoning and exploring the uncharted territories. According to the details provided by Mohammed Bin Rashid Space Center MBRSC, the mission will be launched in 2020 and the landing is expected to be in 2021. The mission will not only cover the entire Martian atmosphere for the first time but will also acquire critical data which will help in understanding climate and atmosphere on our own planet “Earth”.

The data from the probe will also help in learning more about Exo-planets and so will also help in finding prospects of life beyond Earth. Sheikh Mohammad of UAE rightly said “The Emirates Mars Mission will be a great contribution to human knowledge, a milestone for Arab civilization, and a real investment for future generations.” It is a good thing that after USA, Europe and Russia, Asian countries like India, China, Japan and now UAE are also excelling in space sector.

It will be good if Pakistan can also accelerate its space program and have put more focus on the civilian aspects of space technology. A right path for us will be to bring more scientists into our decision making structure and like India, make science and technology collaboration, especially in civilian or academic areas, as an important part of our foreign policy goals. Currently, our foreign policy goals mainly revolve around security, energy and aid related issues. We need to be pro-active if we want to be among the successful nations of the world.

In the end, I would like to wish best of luck to our brothers and sisters in UAE for their great initiative and hope that their mission will contribute greatly towards humanity’s goal of exploring worlds beyond our own.

The article is also published in Daily Times Pakistan.

Illustration by Michael S. Helfenbein

Yale physicists find a new form of quantum friction

Physicists at Yale University have observed a new form of quantum friction that could serve as a basis for robust information storage in quantum computers in the future. The researchers are building upon decades of research, experimentally demonstrating a procedure theorized nearly 30 years ago.

The results appear in the journal Science and are based on work in the lab of Michel Devoret, the F.W. Beinecke Professor of Applied Physics.

Quantum computers, a technology still in development, would rely on the laws of quantum mechanics to solve certain problems exponentially faster than classical computers. They would store information in quantum systems, such as the spin of an electron or the energy levels of an artificial atom. Called “qubits,” these storage units are the quantum equivalent of classical “bits.” But while bits can be in states like 0 or 1, qubits can simultaneously be in the 0 and 1 state. This property is called quantum superposition; it is a powerful resource, but also very fragile. Ensuring the integrity of quantum information is a major challenge of the field.

 Illustration by Michael S. Helfenbein
Illustration by Michael S. Helfenbein

Zaki Leghtas, first author on the paper and a postdoctoral researcher at Yale, offered the following metaphor to explain this new form of quantum friction:

Imagine a hill surrounded by two basins. If you put a ball at the top of the hill, it will roll down the sides and settle in one of the basins. As it rolls, it loses energy due to the friction between the ball and the ground, and it slows down. This is why it stops at the bottom of the basin. But friction also causes the ball to leave a path in its wake. By looking at either side of the hill and seeing where grass is flattened and stones are pushed aside, you can tell whether the ball rolled into the right or left basin.

This figure depicts the position of a quantum particle over a time of 19 micro-seconds. Dark colors indicate high probability of the particle existing at the specified position. It is a plot of the time-evolution of the Winger function W (⍺) of the quantum system, with black corresponding to 1.0, white to 0, and blue to –0.05.
This figure depicts the position of a quantum particle over a time of 19 micro-seconds. Dark colors indicate high probability of the particle existing at the specified position. It is a plot of the time-evolution of the Winger function W (⍺) of the quantum system, with black corresponding to 1.0, white to 0, and blue to –0.05.

If you replace the ball with a quantum particle, however, you run into a problem. Quantum particles can exist in many states at the same time, so in theory, the particle could occupy both basins simultaneously. But as the particle is rolling down, the friction between the particle and the hill leaves an impact on the environment, which can be measured. The same friction that stops the particle at the bottom also carves the path. This destroys the superposition and forces the particle to exist in only one basin.

Previously, researchers had been able to take advantage of this friction to trap quantum particles in particular basins. But now, Devoret’s lab demonstrates a new type of friction — one that slows the particle as it rolls, but does not carve a path that tells which side it is choosing. This allows the particle to simultaneously exist in both the left and right basins at the same time.

Each of these “basin” states is both stable and steady. While the quantum particle might move around in the basins, small perturbations won’t kick it out of the basins. Furthermore, any superpositions of these two basin states are also stable and steady. This means they could be used as a basis for storing quantum information.

Technically, this is called a two-dimensional quantum steady-state manifold. Devoret and Leghtas point out that the next step is expanding this two-dimensional manifold to four dimensions — adding two more basins to the landscape. This will allow scientists to redundantly encode quantum information and to do error correction within the manifold. Error correction is one of the key components that must be developed in order to make a practical quantum computer feasible.

Additional authors are Steven Touzard, Ioan Pop, Angela Kou, Brian Vlastakis, Andrei Petrenko, Katrina Sliwa, Anirudh Narla, Shyam Shankar, Michael Hatridge, Matthew Reagor, Luigi Frunzio, Robert Schoelkopf, and Mazyar Mirrahimi of Yale. Mirrahimi also has an appointment at the Institut National de Recherche en Informatique et en Automatique Paris-Rocquencourt.

(Main illustration by Michael S. Helfenbein)

Source: Yale News

Islamic Republic of Pakistan to become Associate Member State of CERN: CERN Press Release

Geneva 19 December 2014. CERN1 Director General, Rolf Heuer, and the Chairman of the Pakistan Atomic Energy Commission, Ansar Parvez, signed today in Islamabad, in presence of Prime Minister Nawaz Sharif, a document admitting the Islamic Republic of Pakistan to CERN Associate Membership, subject to ratification by the Government of Pakistan.

“Pakistan has been a strong participant in CERN’s endeavours in science and technology since the 1990s,” said Rolf Heuer. “Bringing nations together in a peaceful quest for knowledge and education is one of the most important missions of CERN. Welcoming Pakistan as a new Associate Member State is therefore for our Organization a very significant event and I’m looking forward to enhanced cooperation with Pakistan in the near future.”

“It is indeed a historic day for science in Pakistan. Today’s signing of the agreement is a reward for the collaboration of our scientists, engineers and technicians with CERN over the past two decades,” said Ansar Parvez. “This Membership will bring in its wake multiple opportunities for our young students and for industry to learn and benefit from CERN. To us in Pakistan, science is not just pursuit of knowledge, it is also the basic requirement to help us build our nation.”

The Islamic Republic of Pakistan and CERN signed a Co-operation Agreement in 1994. The signature of several protocols followed this agreement, and Pakistan contributed to building the CMS and ATLAS experiments. Pakistan contributes today to the ALICE, ATLAS, CMS and LHCb experiments and operates a Tier-2 computing centre in the Worldwide LHC Computing Grid that helps to process and analyse the massive amounts of data the experiments generate. Pakistan is also involved in accelerator developments, making it an important partner for CERN.

The Associate Membership of Pakistan will open a new era of cooperation that will strengthen the long-term partnership between CERN and the Pakistani scientific community. Associate Membership will allow Pakistan to participate in the governance of CERN, through attending the meetings of the CERN Council. Moreover, it will allow Pakistani scientists to become members of the CERN staff, and to participate in CERN’s training and career-development programmes. Finally, it will allow Pakistani industry to bid for CERN contracts, thus opening up opportunities for industrial collaboration in areas of advanced technology.


1. CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Union, JINR and UNESCO have Observer Status.

Source : CERN


Big Science, Funding and Commercialization. In the context of Pakistan (Survey)

We are conducting a survey on the topic of “Big Science, Funding and Commercialization”. The subject is aimed at the big science research and commercialization in the Pakistani context.

Please take part in the survey and encourage your friends to take part as well (especially working in academia, tech industry or government sector)

In today’s economic realities, the question of funding big science projects is often discussed in political circles, academia, industry, media and other parts of society. On one hand we see people take interest in big questions related to our universe like it’s origin, accelerated expansion or what gives mass to the particles? But on the other hand there are many critics who question spending so much money on doing big science especially when there is so much poverty in many parts of the world. The idea is to find some solution and one possible way is to use spin-off technologies and knowledge base for commercial purposes in order to fund the big science projects without relying heavily on tax payers’ money.

Questions are available at:


An article on our website discussed the related issues 


Dr Vladlen Shvedov (L) and Dr Cyril Hnatovsky adjusting the hollow laser beam in their lab at RSPE. Image Stuart Hay, ANU

ANU Physicists build reversible tractor beam

We have seen use of laser tractor beams from space ships catching or repelling space ships, objects and people. Science and technology have not developed that much to achieve such feats but Physicists at the Australian National University have done something amazing to push the boundaries science and technology a bit more and closer to that goal.

ANU Laser physicists have built a tractor beam that can repel and attract objects, using a hollow laser beam that is bright around the edges and dark in its centre.

Dr Vladlen Shvedov (L) and Dr Cyril Hnatovsky adjusting the hollow laser beam in their lab at RSPE. Image Stuart Hay, ANU
Dr Vladlen Shvedov (L) and Dr Cyril Hnatovsky adjusting the hollow laser beam in their lab at RSPE. Image Stuart Hay, ANU

It is the first long-distance optical tractor beam and moved particles one fifth of a millimetre in diameter a distance of up to 20 centimetres, around 100 times further than previous experiments.

“Demonstration of a large scale laser beam like this is a kind of holy grail for laser physicists,” said Professor Wieslaw Krolikowski, from the Research School of Physics and Engineering.

The new technique is versatile because it requires only a single laser beam. It could be used, for example, in controlling atmospheric pollution or for the retrieval of tiny, delicate or dangerous particles for sampling.

The researchers can also imagine the effect being scaled up.

“Because lasers retain their beam quality for such long distances, this could work over metres. Our lab just was not big enough to show it,” said co-author Dr Vladlen Shvedov, a driving force behind the ANU project, along with Dr Cyril Hnatovsky.

Unlike previous techniques, which used photon momentum to impart motion, the ANU tractor beam relies on the energy of the laser heating up the particles and the air around them. The ANU team demonstrated the effect on gold-coated hollow glass particles.

The particles are trapped in the dark centre of the beam. Energy from the laser hits the particle and travels across its surface, where it is absorbed creating hotspots on the surface. Air particles colliding with the hotspots heat up and shoot away from the surface, which causes the particle to recoil, in the opposite direction.

To manipulate the particle, the team move the position of the hotspot by carefully controlling the polarisation of the laser beam.

“We have devised a technique that can create unusual states of polarisation in the doughnut shaped laser beam, such as star-shaped (axial) or ring polarised (azimuthal),” Dr Hnatovsky said.

“We can move smoothly from one polarisation to another and thereby stop the particle or reverse its direction at will.”

The work is published in Nature Photonics.

Source : ANU News

KAUST team synthesizes novel metal-organic framework for efficient CO2 removal

By Caitlin Clark

“In Professor Mohamed Eddaoudi’s research group, we are always on the quest to find novel nanostructured functionalized materialsfor specific applications,” explained KAUST Research Scientist Dr. Youssef Belmabkhout, a member of Prof. Eddaoudi’s Functional Materials Design, Discovery, and Development (FMD3) group, part of KAUST’s Advanced Membranes and Porous Materials (AMPM) research center.

Dr. Osama Shekhah, Senior Research Scientist in the FMD3 group added that the group searches “for materials that will be highly suitable for trace and low CO2 concentration removal using purely physical adsorption. These will help in energy saving and in the reduction of the cost of the production, purification, and enrichment of highly valuable commodities such as CH4, H2, O2, N2, and others.”

Drs. Shekhah and Belmabkhout and a team of researchers from Prof. Eddaoudi’s group recently discovered and synthesized a new porous, moisture-resistant, inexpensive and reusable copper-based metal-organic framework (MOF) called SIFSIX-3-Cu that can selectively adsorb and remove trace CO2 from mixtures of various gases. Their findings were published in the June 25 edition of Nature Communications (DOI: 10.1038/ncomms5228).

MOFs are a promising new class of hybrid solid-state materials for CO2 removal. “Their uniqueness,” explained Prof. Eddaoudi, “resides in the ability to control their assembly and introduce functionality on demand. This feature is not readily available in other solid-state materials.”

The researchers showed for the first time that MOF crystal chemistry permits the assembly of a new isostructural hexafluorosilicate MOF (SIFSIX-3-Cu) based on copper instead of zinc.

“This technology is anticipated to outperform the existing mature technologies for CO2 physical adsorption in terms of energy efficiency,” says Dr. Shekhah. “The key factors for this finding are the combination of suitable pore size and high, uniform charge density in the pores of the MOF.”

Using their newly synthesized MOF, the researchers examined the conditions relevant to direct air capture (DAC), a mechanism to remove CO2 from air and reduce greenhouse gas emissions uniformly around the world.

DAC is more challenging than post-combustion capture, but it may be practical if alternative “suitable adsorbent combining optimum uptake, kinetics, energetics and CO2 selectivity is available at trace CO2 concentration,” the researchers stated.

The team discovered that contracting SIFSIX-3-Cu’s pore system to 3.5 Å enhanced the material’s efficiency, making it able to adsorb relatively large CO2 amounts 10-15 times higher than zinc-based metal-organic adsorbents, such as SIFSIX-3-Zn. In SIFSIX-3-Zn, the pore size is 3.84 Å.

“We attribute this property to enhanced physical sorption through the favorable electrostatic interactions between CO2 molecules and fluorine atoms present on the surface of the adsorbent,” explained Zhijie Chen, a Ph.D. student in the FMD3 group and a co-author of the paper.

Dr. Vincent Guillerm, a post-doctoral fellow in the FMD3 group and a co-author of the paper also noted that, “the pore contraction gives CO2 uptake and selectivity at very low partial pressures. This is relevant to DAC and trace carbon dioxide removal.”

“SIFSIX-3-Cu gives enhanced CO2 physical adsorption properties, uptake, and selectivity in highly diluted gas streams, and this performance is unachievable with other classes of porous materials,” added Dr. Karim Adil, a co-author of the paper and Research Scientist in the FMD3 group.

The researchers are excited about their finding as it offers the potential to be used not only for DAC but also for other applications related to energy, the environment, and the healthcare field. For example, SIFSIX-3-Cu could be used to remove and recycle CO2 in confined spaces, such as in submarines or space shuttles, and could also be used in anesthesia machines, which require efficient CO2 sorbents.

“Our work paves the way for scientists to develop new separation agents suitable for challenging endeavor pertaining to CO2 ultra-purification processing,” said Dr. Shekhah. “Our study is also part of a greater critical effort to develop economical and practical pathways to reduce cumulative CO2 emissions provoking the undesirable greenhouse gas effect.”

Prof. Eddaoudi reiterated that “MOFs offer remarkable CO2 physical adsorption attributes in highly diluted gas streams thanks to their ability for rational pore size modification and inorganic-organics moieties substitution. Other classes of plain materials are unable to attain this.”

In the future, Prof. Eddaoudi’s FMD3 group will continue to develop topologically and chemically different MOFs. “We aim to target novel MOFs with suitable pore size and high charge density,” explained Prof. Eddaoudi. “We will then use these for the important task of removing trace and low and high concentration CO2.”

Source: KAUST