Morphable surfaces cut air resistance: Golf ball-like dimples on cars may improve fuel efficiency

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Researchers made this sphere to test their concept of morphable surfaces. Made of soft polymer with a hollow center, and a thin coating of a stiffer polymer, the sphere becomes dimpled when the air is pumped out of the hollow center, causing it to shrink.

There is a story about how the modern golf ball, with its dimpled surface, came to be: In the mid-1800s, it is said, new golf balls were smooth, but became dimpled over time as impacts left permanent dents. Smooth new balls were typically used for tournament play, but in one match, a player ran short, had to use an old, dented one, and realized that he could drive this dimpled ball much further than a smooth one.

Whether that story is true or not, testing over the years has proved that a golf ball's irregular surface really does dramatically increase the distance it travels, because it can cut the drag caused by air resistance in half. Now researchers at MIT are aiming to harness that same effect to reduce drag on a variety of surfaces -- including domes that sometimes crumple in high winds, or perhaps even vehicles.

Detailed studies of aerodynamics have shown that while a ball with a dimpled surface has half the drag of a smooth one at lower speeds, at higher speeds that advantage reverses. So the ideal would be a surface whose smoothness can be altered, literally, on the fly -- and that's what the MIT team has developed.

The new work is described in a paper in the journal Advanced Materials by MIT's Pedro Reis and former MIT postdocs Denis Terwagne (now at the Université Libre de Bruxelles in Belgium) and Miha Brojan (now at the University of Ljubljana in Slovenia).

Shrinking leads to wrinkling

The ability to change the surface in real time comes from the use of a multilayer material with a stiff skin and a soft interior -- the same basic configuration that causes smooth plums to dry into wrinkly prunes. To mimic that process, Reis and his team made a hollow ball of soft material with a stiff skin -- with both layers made of rubberlike materials -- then extracted air from the hollow interior to make the ball shrink and its surface wrinkle.

"Numerous studies of wrinkling have been done on flat surfaces," says Reis, an assistant professor of mechanical engineering and civil and environmental engineering. "Less is known about what happens when you curve the surface. How does that affect the whole wrinkling process?"

The answer, it turns out, is that at a certain degree of shrinkage, the surface can produce a dimpled pattern that's very similar to that of a golf ball -- and with the same aerodynamic properties.

The aerodynamic properties of dimpled balls can be a bit counterintuitive: One might expect that a ball with a smooth surface would sail through the air more easily than one with an irregular surface. The reason for the opposite result has to do with the nature of a small layer of the air next to the surface of the ball. The irregular surface, it turns out, holds the airflow close to the ball's surface longer, delaying the separation of this boundary layer. This reduces the size of the wake -- the zone of turbulence behind the ball -- which is the primary cause of drag for blunt objects.

When the researchers saw the wrinkled outcomes of their initial tests with their multilayer spheres, "We realized that these samples look just like golf balls," Reis says. "We systematically tested them in a wind tunnel, and we saw a reduction in drag very similar to that of golf balls."

Now you see it, now you don't

Because the surface texture can be controlled by adjusting the balls' interior pressure, the degree of drag reduction can be controlled at will. "We can generate that surface topography, or erase it," Reis says. "That reversibility is why this is pretty interesting; you can switch the drag-reducing effect on and off, and tune it."

As a result of that variability, the team refers to these as "smart morphable surfaces" -- or "smorphs," for short. The pun is intentional, Reis says: The paper's lead author -- Terwagne, a Belgian comics fan -- pointed out that one characteristic of Smurfs cartoon characters is that no matter how old they get, they never develop wrinkles.

Terwagne says that making the morphable surfaces for lab testing required a great deal of trial-and-error -- work that ultimately yielded a simple and efficient fabrication process. "This beautiful simplicity to achieve a complex functionality is often used by nature," he says, "and really inspired me to investigate further."

Many researchers have studied various kinds of wrinkled surfaces, with possible applications in areas such as adhesion, or even unusual optical properties. "But we are the first to use wrinkling for aerodynamic properties," Reis says.

The drag reduction of a textured surface has already expanded beyond golf balls: The soccer ball being used at this year's World Cup, for example, uses a similar effect; so do some track suits worn by competitive runners. For many purposes, such as in golf and soccer, constant dimpling is adequate, Reis says.

But in other uses, the ability to alter a surface could prove useful: For example, many radar antennas are housed in spherical domes, which can collapse catastrophically in very high winds. A dome that could alter its surface to reduce drag when strong winds are expected might avert such failures, Reis suggests. Another application could be the exterior of automobiles, where the ability to adjust the texture of panels to minimize drag at different speeds could increase fuel efficiency, he says.

John Rogers, a professor of materials research and engineering at the University of Illinois at Urbana-Champaign who was not involved in this work, says, "It represents a delightful example of how controlled processes of mechanical buckling can be used to create three-dimensional structures with interesting aerodynamic properties. The type of dynamic tuning of sophisticated surface morphologies made possible by this approach would be difficult or impossible to achieve in any other way."

Video: http://www.youtube.com/watch?v=_86mIMPbcDg

The research was supported by the National Science Foundation, MIT's Charles E. Reed Faculty Initiatives Fund, the Wallonie-Bruxelles International, the Belgian American Education Foundation, and the Fulbright Foundation.

Sweet, sweet straw: Scientists learn to produce sweetener from straw and fungi

 

June 24, 2014

Vienna University of Technology, TU Vienna

The calorie free sweetener erythritol is widely used in Asia; it is also gaining popularity in Europe and in the US. Now, a new cheap method has been developed to produce erythritol from straw with the help of mould fungi. Erythritol has many great advantages: it does not make you fat, it does not cause tooth decay, it has no effect on the blood sugar and, unlike other sweeteners, it does not have a laxative effect.

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Various Trichoderma strains.

The calorie free sweetener erythritol is widely used in Asia; it is also gaining popularity in Europe and America. At the Vienna University of Technology, a new cheap method has been developed to produce erythritol from straw with the help of mould fungi.

Erythritol has many great advantages: it does not make you fat, it does not cause tooth decay, it has no effect on the blood sugar and, unlike other sweeteners, it does not have a laxative effect. In Asia it is already widely used and it is becoming more and more common in other parts of the world too. Up until now, erythritol could only be produced with the help of special kinds of yeast in highly concentrated molasses. At the TU Vienna, a method has now been developed to produce the sweetener from ordinary straw with the help of a mould fungus. The experiments have been a big success, and now the procedure will be optimized for industry.

From Straw via Sugar to Erythritol

Straw is often considered to be worthless and is therfore burnt, but it can be a precious resource. Some of its chemical components can be made into valuable products. First, the finely chopped straw has to be "opened up": with the help of solvents, the cell walls are broken, the lignin is dissolved away. The remaining xylan and cellulose are then processed further. "Usually the straw has to be treated with expensive enzymes to break it down into sugar," says Professor Robert Mach (Vienna University of Technology). "In highly concentrated molasses, special strains of yeast can then turn the sugar into erythritol, if they are placed under extreme osmotic stress."

Mould Fungus Makes Intermediate Step Obsolete

The enzymes opening up the straw can be obtained with the help of the mould fungus Trichoderma reesei. This kind of mould also plays the leading role in the new production process developed at the Vienna University of Technology.

Two big advantages have been achieved by genetically modifying the fungus: the process of obtaining the enzymes from mould cultures and chemically cleaning them used to be cumbersome -- now the improved strain can be directly applied to the straw. Secondly, the mould can now produce erythritol directly from the straw. The intermediate step of producing molasses is not necessary any more and no yeast has to be used.

"We knew that the mould fungus Trichoderma reesei is in principle capable of producing erythritol, but usually only in tiny quantities," says Robert Mach. "By genetically modifying it, we managed to stimulate the production of an enzyme, which enables the large-scale production of the sweetener."

Erythritol is about 70 to 80 percent as sweet as sugar. Today, 23000 tons of erythritol are produced every year. This quantity could increase considerably if the trend of switching to erythritol spreads from Asia to Europe and the US. Astrid Mach-Aigner and Robert Mach from the Vienna University of Technology have already patented the new production process, together with the company ANNIKKI. "We have proven that the new production method works," says Robert Mach. "Now we want to improve it together with our industry partners so that it can be used for large-scale production."

Not everyone wants cheering up, new study suggests

 

June 24, 2014

You may want to rethink cheering up your friends who have low self-esteem because chances are they don't want to hear it. People with low self-esteem have overly negative views of themselves, and often interpret critical feedback, romantic rejections, or unsuccessful job applications as evidence of their general unworthiness. A new study found that they likely don't want you to try to boost their spirits.

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People with low self-esteem have overly negative views of themselves, and often interpret critical feedback, romantic rejections, or unsuccessful job applications as evidence of their general unworthiness. A new study from researchers at the University of Waterloo and Wilfrid Laurier University found that they likely don't want you to try to boost their spirits.

"People with low self-esteem want their loved ones to see them as they see themselves. As such, they are often resistant to their friends' reminders of how positively they see them and reject what we call positive reframing-expressions of optimism and encouragement for bettering their situation," said Professor Denise Marigold, from Renison University College at Waterloo, and lead author of the study.

These individuals usually prefer negative validation, which conveys that the feelings, actions or responses of the recipient are normal, reasonable, and appropriate to the situation. So a friend could express understanding about the predicament or for the difficulty of a situation, and suggest that expressing negative emotions is appropriate and understandable.

The researchers found no evidence that positive reframing helps participants with low self-esteem. And in fact, the people providing support to friends with low self-esteem often felt worse about themselves when they attempted to cheer up their friend.

Some study participants indicated that supporting friends with low self-esteem could be frustrating and tiring. The researchers found that when these support providers used positive reframing instead of negative validation in these situations, they often believed the interaction went poorly, perhaps because the friends with low self-esteem were not receptive and the efforts didn't work.

"If your attempt to point out the silver lining is met with a sullen reminder of the prevailing dark cloud, you might do best to just acknowledge the dark cloud and sympathize," said Professor Marigold.

The findings appear in the new issue of the Journal of Personality and Social Psychology.

Triggers, treatment of immediate-type allergic reactions

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Sudden allergic reactions can be fatal. The most common triggers of such reactions, also known as anaphylaxis, are wasp and bee venoms, legumes (pulses), animal proteins, and analgesics (painkillers). The incidence of anaphylaxis is age-dependent. In the current issue of Deutsches Ärzteblatt International, Margitta Worm (Berlin) and her co-authors describe the causes and treatment methods for anaphylaxis, based on data from the anaphylaxis registry of the German-speaking countries.

Worm and co-authors analyzed the data from the registry, which covers Germany, Austria, and Switzerland, for information on triggers, symptoms, and treatment from 2006 to 2013; they also evaluated data recorded from ADAC air rescue callouts in 2010 and 2011. A total of 4141 persons were affected by anaphylaxis (52.5% female, 47.5% male), 3168 adults and 973 children. Among children, boys were affected more often than girls (640 boys), whereas among adults, women were the more often affected. Most cases (85%) were classified as severity grade II or III. Grade IV reactions, which are very severe, were less frequently reported: 3% of adult cases and 0.9% of pediatric cases. Among children, foods were the most frequent triggers of allergic reactions; among adults, the most frequent triggers were insect venoms. Of these, wasp stings were reported most often (70%), bee stings more rarely (20%).

Analysis of medical emergency cases showed that epinephrine was used to treat only 14.5% of patients in the anaphylaxis registry with grade III reactions and 43.9% of those with grade IV reactions. Of the patients who had to be treated by air rescue personnel, 19% and 78% respectively received epinephrine. Epinephrine was not used often enough, even though it is recommended in the treatment guidelines for reactions from grade II upward.

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Story Source:

The above story is based on materials provided by Deutsches Aerzteblatt International. Note: Materials may be edited for content and length.

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Journal Reference:

1. Worm M, Eckermann O, Dölle S, Aberer W, Beyer K, Hawranek T, Hompes S, Koehli A, Mahler V, Nemat K, Niggemann B, Pföhler C, Rabe U, Reissig A, Rietschel E, Scherer K, Treudler R, Ruëff F. Triggers and treatment of anaphylaxis: an analysis of 4000 cases from Germany, Austria and Switzerland. Dtsch Arztebl Int, 2014; 111: 367%u201375 DOI: 10.3238/arztebl.2014.0367

Menthol cigarettes linked to increased smoking among teens

 

June 20, 2014

University of Waterloo

Teens who use menthol cigarettes smoke more cigarettes per day than their peers who smoke non-menthols, says a new study. The findings mark the first time that menthol cigarettes have been directly linked to elevated nicotine addiction among youth. "The appeal of menthol cigarettes among youth stems from the perception that they are less harmful than regular cigarettes. The minty taste helps mask the noxious properties, but the reality is that they are just as dangerous as any unflavoured cigarette," said the lead author of the paper.

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Teens who use menthol cigarettes smoke more cigarettes per day than their peers who smoke non-menthols, says a new study. The findings from the Propel Centre for Population Health Impact at the University of Waterloo mark the first time that menthol cigarettes have been directly linked to elevated nicotine addiction among youth.

"The appeal of menthol cigarettes among youth stems from the perception that they are less harmful than regular cigarettes. The minty taste helps mask the noxious properties, but the reality is that they are just as dangerous as any unflavoured cigarette," said Sunday Azagba, a scientist at Propel and lead author on the paper.

Published in Cancer Causes and Control, the study found that menthol users smoked an average of 43 cigarettes a week, close to double the 26 smoked by non-menthol users. The study also found that menthol smokers were almost three times more likely to report that they intend to continue smoking in the next year.

Despite the well-documented health risks associated with tobacco use,  high school students from Grades  are current smokers. Research shows that the majority of long-term adult smokers start smoking during their adolescence. The national Youth Smoking Survey has found that 32 per cent of smokers in high school smoke menthols.

"There is a growing concern that the high popularity of menthol cigarettes among youth may hinder the recent progress in preventing other young people from smoking because many of them may experiment with menthol rather than unflavoured brands," said Azagba.

In July 2010, Canada implemented a ban on the sale of most flavoured cigarettes, little cigars and blunt wraps, but not menthol. Alberta is the only province to include a ban on menthol cigarettes in provincial legislation, though it is not yet in force. In April 2014, the European Union (EU) adopted a new Tobacco Products Directive that will see all 28 EU countries implement a ban on menthol cigarettes.

"Our findings indicate that youth smoking of menthol cigarettes is a serious concern," said Azagba. "It's clear moving forward that we need new laws to ban all added flavours in all tobacco products."

Many babies born before full-term without medical reason

 

June 20, 2014

University of Minnesota Academic Health Center

The first of its kind research is out showing who is having early elective deliveries between 37 and 39 weeks gestation, and whether these deliveries happen following labor induction or cesarean. Labor induction or cesarean delivery without medical reason before a baby is considered full-term at 39 weeks, or an 'early elective delivery,' is associated with health problems for mothers and babies.  

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New University of Minnesota research out this week is the first of its kind to show who is having early elective deliveries between 37 and 39 weeks gestation, and whether these deliveries happen following labor induction or cesarean.

Labor induction or cesarean delivery without medical reason before a baby is considered full-term at 39 weeks, or an "early elective delivery," is associated with health problems for mothers and babies.

The study, led by University of Minnesota School of Public Health Assistant Professor Katy Kozhimannil, Ph.D., M.P.A., in collaboration with Children's Hospital of Philadelphia researchers Michelle Macheras, M.A., and Scott A. Lorch, M.D., M.S.C.E., appears in this month's edition of the journal Medical Care.

The chance of early elective induction was higher among women:

• 35 years of age or older, white with higher education levels
• Who were privately insured
• Who gave birth at rural or nonteaching hospitals

Early elective cesareans were more likely for women:

• Less than 20 years old or over 35 years old
• Who were black
• Who had higher education levels
• Who gave birth at smaller-volume hospitals

"There are misunderstandings about when a baby is ready to be born," said Kozhimannil. "Since our findings show there are differences in who is having an early elective delivery, the importance of a full-term birth needs to be communicated to all women, not just those who may traditionally be considered high risk for elective procedure or high risk for poor outcomes."

Kozhimannil explained that contrary to the commonly-held belief that babies born after 37 weeks are considered "term," the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine say a pregnancy is full term only after 39 weeks.

The study found that infants born by early elective cesareans were 60 percent more likely to stay longer in the hospital and more than twice as likely to have respiratory distress compared to infants born on or after 39 weeks. Infants born via early elective induction were also more likely to stay in the hospital longer than expected.

"While prior work has shown that early elective delivery policies can be highly effective within particular healthcare systems, there is a need to address this issue at the population level," said Kozhimannil. "It is our hope that this study will add fuel to the ongoing efforts to educate pregnant women and influence clinical and policy environments to facilitate healthy, full-term deliveries whenever possible."

Antidepressant use during pregnancy may lead to childhood obesity, diabetes

 

June 21, 2014

McMaster University

Maternal use of a class of antidepressants called selective serotonin reuptake inhibitors, or SSRIs, resulted in increased fat accumulation and inflammation in the liver of the adult offspring, researchers have demonstrated for the first time in an animal model. This raises new concerns about the long-term metabolic complications in children born to women who take SSRI antidepressants during pregnancy.

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Women who take antidepressants during pregnancy may be unknowingly predisposing their infants to type 2 diabetes and obesity later in life, according to new research from McMaster University.

The study finds a correlation between the use of the medication fluoxetine during pregnancy and an increased risk of obesity and diabetes in children.

Currently, up to 20 per cent of woman in the United States and approximately seven per cent of Canadian women are prescribed an antidepressant during pregnancy.

"Obesity and Type 2 diabetes in children is on the rise and there is the argument that it is related to lifestyle and availability of high calorie foods and reduced physical activity, but our study has found that maternal antidepressant use may also be a contributing factor to the obesity and diabetes epidemic," said the study's senior investigator Alison Holloway, associate professor of obstetrics and gynecology at McMaster University.

Previous studies have found that pregnant women are particularly vulnerable to depression and it is estimated that up to one in five pregnant women have symptoms of depression during pregnancy.

"While it is known that these drugs can increase the risk of obesity in adults, it is unknown whether a woman's antidepressant use during pregnancy increases the risk of metabolic disturbances in her children," Holloway says, adding the goal of their project was to determine whether maternal exposure to a commonly used antidepressant is related to the development of fatty liver, an outcome commonly seen with obesity, in the offspring.

"We have demonstrated for the first time in an animal model that maternal use of a class of antidepressants called selective serotonin reuptake inhibitors, or SSRIs, resulted in increased fat accumulation and inflammation in the liver of the adult offspring, raising new concerns about the long-term metabolic complications in children born to women who take SSRI antidepressants during pregnancy," says PhD student Nicole De Long, who presented this research on June 22nd at the joint meeting of the International Society of Endocrinology and The Endocrine Society.

Their study does not suggest women should avoid taking antidepressants during pregnancy, only that there may be risks associated with antidepressants that haven't been previously identified, Holloway says.

"The benefit of the study is it may help in the identification of a high-risk group of children who may require specific interventions to prevent obesity and type 2 diabetes later in life," she says.

The next stage of their research will be to understand the mechanistic pathways behind why these drugs pose a risk. "If we can understand how the antidepressant causes adverse metabolic outcomes in the offspring than we can design therapeutic strategies to prevent the damage while allowing women who require these drugs to be treated but reduce the potential harm to the offspring.

New mobile app provides faster, more accurate measurement of respiratory rate

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A new mobile app developed by researchers at the Child & Family Research Institute (CFRI) at BC Children's Hospital and the University of British Columbia can measure respiratory rate in children roughly six times faster than the standard manual method.

According to findings published this month in PLOS One, RRate can reliably measure respiratory rate in an average of 9.9 seconds. Currently, health care workers typically measure respiratory rate by counting a patient's breaths for 60 seconds using a stop watch.

"Mobile phones are changing how we administer health care, especially in rural settings and developing countries where access to medical devices is limited," says Dr. Walter Karlen, who co-led the study with Dr. Heng Gan. "With this app, we can give health care workers with few resources faster and more accurate measurements, help them make better decisions, and give them more time with their patients."

Dr. Karlen is a UBC Postdoctoral Fellow. At the time of this study, Dr. Gan was a Clinical Research Fellow. Both are working with Dr. Mark Ansermino and Dr. Guy Dumont at CFRI, UBC and BC Children's.

Researchers say this simple, but innovative piece of technology is a big step towards better diagnoses for children with pneumonia and other respiratory illnesses. Pneumonia is the leading cause of death of children worldwide according to the World Health Organization. With timely and accurate diagnosis, children with pneumonia can often be saved with simple interventions such as antibiotics.

RRate allows workers to measure respiratory rate by tapping the touch screen every time the child inhales. In addition to calculating the rate of inhalations during a given time, the app also provides an animation of a breathing baby, allowing for a direct comparison with the breathing patient. A free, non-study version of the app is available online.

"We are leveraging the phone's capabilities of computing, touch screen, and vibrational feedback to measure respiratory rate faster and with more confidence," says Dr. Karlen.

Researchers collected data from 30 subjects who used the app while watching videos of children breathing at different rates. Using these findings, they developed an algorithm that enabled the app to produce accurate measurements in the least amount of time.

The next stage of this research is to further improve the diagnosis of pneumonia in low-resource settings by combining this app with the Phone Oximeter. Developed by CFRI and UBC researchers, the Phone Oximeter provides non-invasive measurements of blood oxygen levels using a light sensor and a mobile phone.

New ultrastiff, ultralight material developed

 

This microscope image shows a single unit of the structure developed by the team, called a stretch-dominated octet truss unit cell, made from a polymer using 3-D microstereolithography.

What's the difference between the Eiffel Tower and the Washington Monument? Both structures soar to impressive heights, and each was the world's tallest building when completed. But the Washington Monument is a massive stone structure, while the Eiffel Tower achieves similar strength using a lattice of steel beams and struts that is mostly open air, gaining its strength from the geometric arrangement of those elements.

Now engineers at MIT and Lawrence Livermore National Laboratory (LLNL) have devised a way to translate that airy, yet remarkably strong, structure down to the microscale -- designing a system that could be fabricated from a variety of materials, such as metals or polymers, and that may set new records for stiffness for a given weight.

The new design is described in the journal Science by MIT's Nicholas Fang; former postdoc Howon Lee, now an assistant professor at Rutgers University; visiting research fellow Qi "Kevin" Ge; LLNL's Christopher Spadaccini and Xiaoyu "Rayne" Zheng; and eight others.

The design is based on the use of microlattices with nanoscale features, combining great stiffness and strength with ultralow density, the authors say. The actual production of such materials is made possible by a high-precision 3-D printing process called projection microstereolithography, as a result of the joint research collaboration between the Fang and Spadaccini groups since 2008.

Normally, Fang explains, stiffness and strength declines with the density of any material; that's why when bone density decreases, fractures become more likely. But using the right mathematically determined structures to distribute and direct the loads -- the way the arrangement of vertical, horizontal, and diagonal beams do in a structure like the Eiffel Tower -- the lighter structure can maintain its strength.

A pleasant surprise

The geometric basis for such microstructures was determined more than a decade ago, Fang says, but it took years to transfer that mathematical understanding "to something we can print, using a digital projection -- to convert this solid model on paper to something we can hold in our hand." The result was "a pleasant surprise to us," he adds, performing even better than anticipated.

"We found that for a material as light and sparse as aerogel [a kind of glass foam], we see a mechanical stiffness that's comparable to that of solid rubber, and 400 times stronger than a counterpart of similar density. Such samples can easily withstand a load of more than 160,000 times their own weight," says Fang, the Brit and Alex d'Arbeloff Career Development Associate Professor in Engineering Design. So far, the researchers at MIT and LLNL have tested the process using three engineering materials -- metal, ceramic, and polymer -- and all showed the same properties of being stiff at light weight.

"This material is among the lightest in the world," LLNL's Spadaccini says. "However, because of its microarchitected layout, it performs with four orders of magnitude higher stiffness than unstructured materials, like aerogels, at a comparable density."

Light material, heavy loads

This approach could be useful anywhere there's a need for a combination of high stiffness (for load bearing), high strength, and light weight -- such as in structures to be deployed in space, where every bit of weight adds significantly to the cost of launch. But Fang says there may also be applications at smaller scale, such as in batteries for portable devices, where reduced weight is also highly desirable.

Another property of these materials is that they conduct sound and elastic waves very uniformly, meaning they could lead to new acoustic metamaterials, Fang says, that could help control how waves bend over a curved surface.

Others have suggested similar structural principles over the years, such as a proposal last year by researchers at MIT's Center for Bits and Atoms (CBA) for materials that could be cut out as flat panels and assembled into tiny unit cells to make larger structures. But that concept would require assembly by robotic systems that have yet to be developed, says Fang, who has discussed this work with CBA researchers. This technique, he says, uses 3-D printing technology that can be implemented now.

Martin Wegener, a professor of mechanical engineering at Karlsruhe Institute of Technology in Germany who was not involved in this research, says, "Achieving metamaterials that are ultralight in weight, yet stiffer than you would expect from usual scaling laws for elastic solids, is of obvious technological interest. The paper makes an interesting contribution in this direction."

The work was supported by the U.S. Defense Advanced Research Projects Agency and LLNL.

Microscope maps surfaces at resolutions below 100 nanometers: Microparticles get the whole picture

 

June 19, 2014

The Agency for Science, Technology and Research

Microscopes are conventionally used to image tiny features. However, their resolution is inherently limited by the wavelength of light. This limitation means that they can resolve only structures larger than a few hundred nanometers. Now scientists have demonstrated an alternative optical approach capable of mapping surfaces at resolutions below 100 nanometers.

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Now, Leonid Krivitsky and Boris Luk'yanchuk at the A*STAR Data Storage Institute in Singapore and co-workers have demonstrated an alternative optical approach capable of mapping surfaces at resolutions below 100 nanometers.

Diffraction is the tendency for all waves, including light, to spread out when they pass near an object or through a gap. This effect means that optical imaging systems cannot resolve objects smaller than roughly half the wavelength of the illuminating light. Thus, for red light with a wavelength of about 600 nm, the resolution will be approximately 300 nanometers.

Luk'yanchuk and his colleagues previously showed that a micrometer-scale transparent bead placed on a surface can circumvent this so-called diffraction limit. They demonstrated that light passing through the bead, when collected by a conventional microscope, can create an image of the surface beneath it with a resolution of 50 nanometers. However, generating a complete two-dimensional map requires scanning the bead across the surface -- not easy to perform in a controlled way when the sphere is only 6 micrometers across. "We have now improved this superresolution technique by developing a method to controllably move the imaging microspheres," says Krivitsky.

Krivitsky and his team accomplished such spatial scanning using a tiny pipette with a tip just 1 or 2 micrometers wide. Computer simulations confirmed that the presence of the pipette would not adversely affect the superresolution capability of the microspheres. To fasten the pipette to the bead, they sucked the air out from within its cavity.

The team then connected the other end of the pipette to a mechanical stage, which could move in steps as small as 20 nanometers. Importantly, the vacuum inside the pipette created a bond tight enough to ensure that the bead did not disconnect as it was dragged across a surface. The researchers demonstrated the effectiveness of their system by successfully imaging trial samples with features as small as 75 nanometers.

While other techniques, such as near-field scanning microscopy, can perform sub-diffraction-limit imaging, they require very expensive systems. "The real advantages of our technique are its simplicity and its price," says Krivitsky. "The idea could be applied to a variety of superresolution applications such as sample inspection, microfabrication and bioimaging."