4-D electron microscopy used to visualize the nanodrumming phenomenon.

More than a century ago, the development of the earliest motion picture technology made what had been previously thought “magical” a reality: capturing and recreating the movement and dynamism of the world around us. A breakthrough technology based on new concepts has now accomplished a similar feat, but on an atomic scale by allowing, for the first time, the real-time, real-space visualization of fleeting changes in the structure and shape of matter barely a billionth of a meter in size.

The new technique, dubbed four-dimensional (4D) electron microscopy, was developed in the Physical Biology Center for Ultrafast Science and Technology, directed by Ahmed Zewail, the Linus Pauling Professor of Chemistry and professor of physics at Caltech, and winner of the 1999 Nobel Prize in Chemistry.

Zewail was awarded the Nobel Prize for pioneering the science of femtochemistry, the use of ultrashort laser flashes to observe fundamental chemical reactions–atoms uniting into molecules, then breaking apart back into atoms–occurring at the timescale of the femtosecond, or one millionth of a billionth of a second. The work “captured atoms and molecules in motion,” Zewail says, akin to the freeze-frame stills snapped by 19th-century photographer Eadweard Muybridge of a galloping horse (which proved for the first time that a horse does indeed lift all four hooves off the ground as it gallops) and other moving objects.

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This schematic shows how a TSOM image is acquired. Using an optical microscope, several images of a 60 nanometer gold particle sample (shown in red) are taken at different focal positions and stacked together.

A technique under development at the National Institute of Standards and Technology (NIST) uses a relatively inexpensive optical microscope to quickly and cheaply analyze nanoscale dimensions with nanoscale measurement sensitivity. Termed “Through-focus Scanning Optical Microscope” (TSOM) imaging, the technique has potential applications in nanomanufacturing, semiconductor process control and biotechnology.

Optical microscopes are not widely considered for checking nanoscale (below 100 nanometers) dimensions because of the limitation imposed by wavelength of light—you can’t get a precise image with a probe three times the object’s size. NIST researcher Ravikiran Attota gets around this, paradoxically, by considering lots of “bad” (out-of-focus) images. “This imaging uses a set of blurry, out-of-focus optical images for nanometer dimensional measurement sensitivity,” he says. Instead of repeatedly focusing on a sample to acquire one best image, the new technique captures a series of images with an optical microscope at different focal positions and stacks them one on top of the other to create the TSOM image. A computer program Attota developed analyzes the image.

While Attota believes this simple technique can be used in a variety of applications, he has worked with two. The TSOM image can compare two nanoscale objects such as silicon lines on an integrated circuit. The software “subtracts” one image from the other. This enables sensitivity to dimensional differences at the nanoscale—line height, width or side-wall angle. Each type of difference generates a distinct signal.

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The black portion shows a shallow pit that has “healed” on a coated sample.

Put steel under a powerful microscope, revealing its microstructure, and prepare to be surprised. Known for its strength, the metal will appear pitted and pocked.

“It is intrinsic to the material,” says Carolyn Aita, a Wisconsin Distinguished Professor at the University of Wisconsin–Milwaukee (UWM). “A pit can begin to develop from a physiochemical defect in the steel itself.”

The pitting is cause for concern for industry because it can progress and lead to corrosion. But Aita’s research can help.

In her state-of-the-art lab at the College of Engineering and Applied Science, she has developed a host of coatings that heal shallow pits and fractures on almost any material – from metal to glass to silicon. The coatings also prevent further degradation.

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Researchers at the California Institute of Technology have developed a super-compact high-resolution microscope, small enough to fit on a finger tip. The ‘microscopic microscope’ operates without lenses, but has the magnifying power of a top quality optical microscope.

The new instrument combines traditional computer-chip technology with microfluidics – the channelling of flow fluid flow at incredibly small scales. An entire optofluidic chip is about the size of a quarter, although the part of the device that images objects is only size of Washington’s nose on that quarter.

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