Tag Archives: atomic force microscopy

strongest underwater glue

Underwater glue inspired by shellfish might help repair ships

strongest underwater glue

Shown here is the adhesion between the silica tip of an atomic force microscope and adhesive fibers made by fusing mussel foot proteins and curli amyloid fibers.(Photo : Pixabay)

Taking inspiration from nature, scientists at MIT have engineered a new sort of glue that acts like a powerful adhesive even in underwater conditions and can cling on to virtually any surface, be it metal or organic. The glue might prove to be useful to repair ships or seal wounds and surgical incisions.

The strongest underwater glue to date

Shellfish like mussels and barnacles are a familiar sight to seamen since they’re often found by the thousands clinging to rocks or ship hulls. They hold on tightly even through the worse of storms and can be very difficult to detach, much to the exasperation of the maintenance crew. This uncanny ability is made possible by very sticky proteins secreted by such animals, called mussle foot protein

[ALSO READ] Making a novel glue out of gold

Previously, scientists engineered E. coli bacteria to produce the same proteins, however the resulting matter wasn’t nearly as adhesive. This time, the MIT engineers took an alternate route; while they engineered the same E. coli bacteria to secret these proteins, they were also careful to add and activate genes that produce curli fibers. Curl fibers are fibrous proteins that can naturally join together and self-assemble into much larger, more complicated compounds. More familiarly, the fibers join to form a biofilm – slimy layers formed by bacteria growing on a surface.

Two experiments were made where curli fibers bonded to either mussel foot protein 3 or mussel foot protein 5.After purifying these proteins from the bacteria, the researchers let them incubate and form dense, fibrous meshes. The resulting material has a regular yet flexible structure that binds strongly to both dry and wet surfaces.

“The result is a powerful wet adhesive with independently functioning adsorptive and cohesive moieties,” says Herbert Waite, a professor of chemistry and biochemistry at the University of California at Santa Barbara who was not part of the research team. “The work is very creative, rigorous, and thorough.”

The team tested the resulting matter with atomic force microscopes – a technique for analyzing the surface of a rigid material all the way down to the level of the atom. AFM uses a mechanical probe – the tip – to magnify surface features up to 100,000,000 times, and it produces 3-D images of the surface.The researchers found that the adhesive bonded strongly to different types of materials, using three tips for the microscope: silica, gold, and polystyrene. Adhesives assembled from equal amounts of mussel foot protein 3 and mussel foot protein 5 formed stronger adhesives than those with a different ratio, or only one of the two proteins on their own.

The researchers report the resulting adhesive is actually stronger than naturally occurring mussel adhesives and that it’s the strongest protein-based glue designed to work underwater, reported to date. Findings appeared in the journal Nature Nanotechnology.

The team's small prototype neutron microscope is shown set up for initial testing at MIT's Nuclear Reactor Laboratory. The microscope mirrors are inside the small metal box at top right.

MIT readies neutron microscope – new kind of imaging

A cylindrical mirror of the type the MIT and NASA researchers have developed for a novel type of neutron microscope is shown on a test stage in the lab, with light reflected through it to test the precision polishing of its shape.  (c) NASA

A cylindrical mirror of the type the MIT and NASA researchers have developed for a novel type of neutron microscope is shown on a test stage in the lab, with light reflected through it to test the precision polishing of its shape. (c) NASA

A joint project between scientists at NASA and MIT is focusing on creating a new kind of microscope that uses neutrons instead of beams of light or electrons to create high-resolution images. Since the subatomic particles are electrically neutral, such a microscope would allow scientists to peer through places otherwise inaccessible today, like inside metals even if these are in motion.  Also, neutron instruments are also uniquely sensitive to magnetic properties and to lighter elements that are important in biological materials.

The concept of a neutron microscope isn’t entirely new, however other neutron instruments developed so far can be considered primitive to say the least.  These are crude imaging systems that simply let light through a tiny opening, resulting in low-resolution images.

The team of researchers at MIT want to build something that rivals in quality current atomic force microscopes or electron microscopes. With this in mind, MIT postdoc Dazhi Liu, research scientist Boris Khaykovich, professor David Moncton, and four others are currently exploring an innovative idea that’s been on the table for more than 60 years.

“For neutrons, there have been no high-quality focusing devices,” Moncton says. “Essentially all of the neutron instruments developed over a half-century are effectively pinhole cameras.” But with this new advance, he says, “We are turning the field of neutron imaging from the era of pinhole cameras to an era of genuine optics.”

“The new mirror device acts like the image-forming lens of an optical microscope,” Liu adds.

The team's small prototype neutron microscope is shown set up for initial testing at MIT's Nuclear Reactor Laboratory. The microscope mirrors are inside the small metal box at top right.

The team’s small prototype neutron microscope is shown set up for initial testing at MIT’s Nuclear Reactor Laboratory. The microscope mirrors are inside the small metal box at top right.

The main challenge in developing a neutron optical device is that the particles minimally interact with matter, which makes it practically impossible to focus a beam of neutrons in the same way you would light or electrons. A basic means of manipulating neutron beams was expressed in the mid 1950s, even though the original idea was used for X-rays, involving concentric mirrors. Neutron beams interact weakly, much like X-rays, and can be focused by a similar optical system.

A neutron microscope

The instrument currently in development by the researchers uses several reflective cylinders nested one inside the other, so as to increase the surface area available for reflection. The resulting device could improve the performance of existing neutron imaging systems by a factor of about 50, the researchers say — allowing for much sharper images, much smaller instruments, or both.

So far, the team have digitized their concept, and have even created a small-version of the instrument as a proof of concept and demonstrated its performance using a neutron beam facility at MIT’s Nuclear Reactor Laboratory. Such a new instrument could be used to observe and characterize many kinds of materials and biological samples; other nonimaging methods that exploit the scattering of neutrons might benefit as well. Because the neutron beams are relatively low-energy, they are “a much more sensitive scattering probe,” Moncton says, for phenomena such as “how atoms or magnetic moments move in a material.”

 

Roger Pynn, a materials scientist at the University of California at Santa Barbara who was not involved in this research, says, “I expect it to lead to a number of breakthroughs in neutron imaging. … It offers the potential for some really new applications of neutron scattering — something that we haven’t seen for quite a while.”

The concept was outlined in a paper published in the journal Nature Communications.

Underwater Atomic Force Microscopy opens new frontiers for biologists

To fully understand the processes and mechanisms that work at a cellular level, biologists should study them in their native, watery environments. But how would you go on doing this? Well, leave it to engineers to solve everyone’s problems – they have now deviced a kind of atomic force microscopy that works on samples sitting in water and that is gentle enough to analyze fragile biological surfaces.

afm

An elevated silicon hexagon. The colors designate the relative height of the surface from high (red) to low (yellow). The image on the left is a scanning electron micrograph of the same silicon hexagon. Right is with new technique.

Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very high-resolution type of scanning probe microscopy, which works at incredibly large resolutions, on the order of fractions of a nanometer – there’s 1.000.000.000 nanometers in a meter.

In an AFM experiment, a sharp tip scans over a surface, producing an image based on the forces the tip experiences as it interacts with molecules or atoms on the surface. It then generates images which reveal information about the topographic and electrical properties of a surface. But AFM is not suitable for cells and proteins; cells and proteins are wet, squishy – not really what you want for this technique.

Seong H. Kim, a chemical engineer at Pennsylvania State University, wanted to develop something that works for those kinds of environments as well. He developed a method called scanning polarization force microscopy. Whoa! That sounds really fancy – and it is. In this method, which was first developed in the 90s, physical contact with the surface being imaged is not required. Instead, static charges on the surface either attract or repel the tip, creating a measurable force.

Most people working in the field thought this method wouldn’t work underwater – and they were right, initially; dissolved ions coated the AFM tip, interfering with how the tip interacted with a sample’s surface. But by oscillating the voltages, they were able to overcome this hurdle.

To prove that this method works, Kim’s group imaged a gold surface covered with self-assembled monolayers of charged polymers. With the AFM technique, the team could make a map of the surface’s topography and distinguish between positive and negative charges.

“The fact that you can truly operate in a liquid with this method could make it interesting for biological researchers,” says Adam Z. Stieg of the California NanoSystems Institute at the University of California, Los Angeles. If Kim’s group can demonstrate it with actual biological samples and can make a user-friendly version, he says, the method could offer something unique for biologists. No technique currently used could match the spatial resolution possible with AFM, Stieg says.

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The paper detailing the "intelligent molecule" research has been chose as the cover article for ACS Nano, in combination with a 3D graphic of the NIM-media designer. (c) ACS Nano

Intelligent molecules that fold and change shape demonstrated for the first time

The new results demonstrate at the single-molecule level how solvent-induced collapse of an environmentally responsive copolymer modulates surface adhesion forces and bridging length distributions in a controllable way. (c) (Credit: Michael A. Nash, and Hermann E. Gaub/ACS Nano)

The new results demonstrate at the single-molecule level how solvent-induced collapse of an environmentally responsive copolymer modulates surface adhesion forces and bridging length distributions in a controllable way. (c) (Credit: Michael A. Nash, and Hermann E. Gaub/ACS Nano)

In an amazing breakthrough, scientists at Ludwig-Maximilians-Universität (LMU) have for the first time demonstrated an extremely appealing, yet still obscure concept – intelligent molecules. By definition intelligence is the ability to learn and understand or deal with new situation and the latter is exactly what the researchers’ polymer molecules can do, namely  react to external stimuli and reversibly change their shape.

The applications for such a smart molecule could be numerous. For instance, as nanoswitches: hot-cold, light-dark, altered salt concentrations or some other stimuli factors could be toggled or switched, in the process becoming stimulus generator by itself. Also, these could also be used in biosensors, drugs, chromatography procedures, and other applications, the researchers suggest.

The paper detailing the "intelligent molecule" research has been chose as the cover article for ACS Nano, in combination with a 3D graphic of the NIM-media designer. (c) ACS Nano

The paper detailing the “intelligent molecule” research has been chose as the cover article for ACS Nano, in combination with a 3D graphic of the NIM-media designer. (c) ACS Nano

The physicists demonstrated the concept by successfully making a reaction with a single polymer molecule visible for the first time. The researchers engineered a synthesized polymer which they then placed on a gold surface, very carefully, with an atomic force microscope (AFM). One of the ends of the polymer adhered to the surface, while the other to the tip of the AFM. Once the scientists increased the salt concentration of the surrounding medium, they were able to observe how the molecule collapsed gradually. Back in a weak salt solution, the molecule unfolds again

“We have observed both processes in our study for the first time for a single polymer molecule,” write the researchers.

The findings were reported in the journal ACS Nano.

source: press release

Atomic Bond

Incredible molecular imaging shows individual chemical bonds for first time

Atomic level imaging has come a long way in the past decade, and after scientists first managed to image molecular structure and even electron clouds, now a group of researchers at IBM Research Center Zurich have visually depicted how chemical bonds differentiate in individual molecules using a technique called non-contact atomic force microscopy (AFM).

In the image below one can clearly see detailed chemical bonds between individual atoms of a nanographene molecule or C60. In 3-D the molecule resembles a buckyball thanks to its football shape.

Atomic Bond

If you look closely you can see that some C-C chemical bonds are more highlighted than others. This is because in reality and practice, the  bonds between individual atoms differ slightly and subtly in length and strength, and for the first time we’ll now able to distinguish the different types of bonds from one another, visually.  The bright and dark spots correspond to higher and lower densities of electrons.

“In the case of pentacene, we saw the bonds but we couldn’t really differentiate them or see different properties of different bonds,” said lead author of the study Dr.  Leo Gross.

“Now we can really prove that… we can see different physical properties of different bonds, and that’s really exciting.”

Atomic Bond

The nanographene molecule imaged through the ATF versus the schematic of the molecule. (c) IBM Research Zurich

The nanographene molecule imaged through AFM versus the schematic of the molecule. (c) IBM Research Zurich

To create the images, the IBM researchers used an atomic force microscope with a tip that ended with a single carbon monoxide molecule. The CO molecule traces the image by oscillating between the tip and the sample. By measuring its wiggle and inter-molecular force  the AFM can slowly build up a very detailed image. The technique made it possible to distinguish individual bonds that differ by only three picometers, which is one-hundredth of an atom’s diameter.

“We found two different contrast mechanisms to distinguish bonds. The first one is based on small differences in the force measured above the bonds. We expected this kind of contrast but it was a challenge to resolve,” said IBM scientist Leo Gross. “The second contrast mechanism really came as a surprise: Bonds appeared with different lengths in AFM measurements. With the help of ab initio calculations we found that the tilting of the carbon monoxide molecule at the tip apex is the cause of this contrast.”

The findings were reported in the journal Science.

Olympicene

Scientists synthesize and image 5-ring graphite molecule in tribute to Olympics symbol

Olympicene

The 2012 London summer Olympic games are just a few weeks away, and as millions are set to flock to the city and other hundreds of millions will rejoice on the web and TV at the world’s grandest spectacle of athletic performance, it’s pretty clear this is one of the most anticipated events of the year. Every four-years people all over the world offer their tribute to the competition, including scientists too, of course.

“When doodling in a planning meeting, it occurred to me that a molecular structure with three hexagonal rings above two others would make for an interesting synthetic challenge,” says Professor Graham Richards, an RSC Council member.

“I wondered: could someone actually make it, and produce an image of the actual molecule?”

A joint collaborative scientific effort comprised of scientists at the Royal Society of Chemistry (RSC), the University of Warwick, and IBM Research Zurich, have  imaged the smallest possible five-ringed structure. The researchers employed synthetic organic chemistry to build the Olympicene molecule, while scanning tunneling microscopy was used to reveal a first glimpse of the molecule’s structure. To image the 1.2 nanometres in width molecule, about 100,000 times thinner than a human hair, at an unprecedented resolution, like captioned above, scientists at IBM Zurich made use of a complex technique known as noncontact atomic force microscopy.

“Alongside the scientific challenge involved in creating olympicene in a laboratory, there’s some serious practical reasons for working with molecules like this,” says Fox.

“The compound is related to single-layer graphite, also known as graphene, and is one of a number of related compounds which potentially have interesting electronic and optical properties.

“For example these types of molecules may offer great potential for the next generation of solar cells and high-tech lighting sources such as LEDs.”


source: Futurity

single molecule electric charge imaging

IBM images electric charge distribution in a SINGLE molecule – world’s first!

Part of a the recent slew of revolutionary technological and scientific novelties coming off IBM‘s research and development lab, the company has just announced that it has successfully managed to  measure and image for the first time how charge is distributed within a single molecule. The achievement was made possible after a new technique, called Kelvin probe force microscopy (KPFM), was developed. Scientists involved in the project claim that the research introduces the possibility of imaging the charge distribution within functional molecular structures, which hold great promise for future applications such as solar photoconversion, energy storage, or molecular scale computing devices. Until now it has not been possible to image the charge distribution within a single molecule.

single molecule electric charge imaging The team, comprised of scientists Fabian Mohn, Leo Gross, Nikolaj Moll and Gerhard Meyer of IBM Research, Zurich, imaged the charge distribution within a single naphthalocyanine molecule using what’s called Kelvin probe force microscopy at low temperatures and in ultrahigh vacuum – these conditions were imperative, as a high degree of thermal and mechanical stability and atomic precision of the instrument was required over the course of the experiment, which lasted several days.

Derived off the revolutionary atomic force microscopy (AFM), the KPFM measures the potential difference between the scanning probe tip and a conductive sample, in our case the naphthalocyanine molecule – a cross-shaped symmetric organic molecule. Therefore, KPFM does not measure the electric charge in the molecule directly, but rather the electric field generated by this charge.

“This work demonstrates an important new capability of being able to directly measure how charge arranges itself within an individual molecule,” says Michael Crommie, professor for condensed matter physics at the University of Berkeley.

“Understanding this kind of charge distribution is critical for understanding how molecules work in different environments. I expect this technique to have an especially important future impact on the many areas where physics, chemistry, and biology intersect.”

The potential field is stronger above areas of the molecule that are charged, leading to a greater KPFM signal. Furthermore, oppositely charged areas yield a different contrast because the direction of the electric field is reversed. This leads to the light and dark areas in the micrograph (or red and blue areas in colored ones).

The new KPFM technique promises to offer complementary information about a studied molecule, providing valuable electric charge data, in addition to those rendered by scanning tunneling microscopy (STM) or atomic force microscopy (AFM). Since their introduction in 1980′, STM, which images electron orbitals of a molecule, and ATM, which resolves molecular structure, have become instrumental to any atomic and molecular scale research today, practically opening the door to the nanotech age. Maybe not that surprisingly, the STM was developed in the same IBM research center in Zurich, 30 years ago.

“The present work marks an important step in our long term effort on controlling and exploring molecular systems at the atomic scale with scanning probe microscopy,” Gerhard Meyer, a senior IBM scientist who leads the STM and AFM research activities at IBM Research – Zurich.

The findings were published in the journal Nature Nanotechnology. 

Source / image via IBM