Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NIST puts the optical microscope under the microscope to achieve atomic accuracy

23.05.2018

Over the last two decades, scientists have discovered that the optical microscope can be used to detect, track and image objects much smaller than their traditional limit--about half the wavelength of visible light, or a few hundred nanometers.

That pioneering research, which won the 2014 Nobel Prize in Chemistry, has enabled researchers to track proteins in fertilized eggs, visualize how molecules form electrical connections between nerve cells in the brain, and study the nanoscale motion of miniature motors.


This illustration shows an array of apertures with a spacing of 5000 nanometers (nm) ± 1 nm. The apertures pass light through a metal film on a glass slide. Imaging the aperture array with an optical microscope results in apparent errors in the spacing between apertures. Knowledge of the true spacing allows correction of these imaging errors. This calibration process enables accurate measurements of position across a large image.

Credit: NIST

Usage Restrictions: Please credit NIST when using this image.

Now, research developments at the National Institute of Standards and Technology (NIST) enable the microscopes to measure these nanometer-scale details with a new level of accuracy.

"We put the optical microscope under a microscope to achieve accuracy near the atomic scale," said NIST's Samuel Stavis, who served as the project leader for these efforts.

Because optical microscopes have not traditionally been used to study the nanometer scale, they typically lack the calibration--comparison to a standard to check that a result is correct--necessary to obtain information that is accurate at that scale.

A microscope may be precise, consistently indicating the same position for a single molecule or nanoparticle. Yet, at the same time, it can be highly inaccurate--the location of the object identified by the microscope to within a billionth of a meter may, in fact, be millionths of a meter off due to unaccounted-for errors. "Precision without accuracy can be very misleading," said Jon Geist, a NIST co-author of the study.

To address the problem, NIST has developed a new calibration process that closely examines and corrects these imaging errors. The process uses reference materials--objects with characteristics that are well-known and stable--that have the potential for mass production and widespread distribution to individual laboratories.

This is important because optical microscopes are common laboratory instruments that can easily magnify different samples, ranging from delicate biological specimens to electrical and mechanical devices. As well, optical microscopes are becoming increasingly capable and economical as they incorporate scientific versions of the lights and cameras in smartphones.

The NIST team relied on nanometer-scale fabrication processes to develop the reference material. The researchers used electron beams and ion milling to form an array of pinhole apertures through a thin film of platinum on a glass slide. The process enabled the team to space the apertures 5,000 nanometers apart, to within an accuracy of about 1 nanometer. In this way, the researchers built a measure of accuracy into the aperture positions.

Shining light through the array of apertures creates an array of points for imaging. But because all microscope lenses have imperfections, errors inevitably occur during imaging that change the apparent positions of the points, making the spacing between the apertures appear to be larger or smaller than the actual spacing engineered by the team. Knowledge of the true spacing allows correction of the imaging errors and calibration of the microscope for measurements of position with high accuracy across a wide field of view.

Even a small error can lead to a large problem. Consider, for example, a microscope having an actual magnification of 103 times when the expected magnification, as specified by the manufacturer, is 100 times. The resulting error of 3 percent adds up over large distances across a microscope image. Because of lens imperfections, a subtler problem also occurs--the microscope magnification changes across the image, causing image distortion. To solve this problem, the NIST team designed aperture arrays and calibration processes that worked across large fields of view.

The aperture arrays, which would enable individual researchers to perform calibrations in their own laboratories, could improve by a factor of 10,000 the ability of optical microscopes to accurately locate the position of single molecules and nanoparticles.

Stavis and his colleagues, including first author Craig Copeland of NIST and the Maryland NanoCenter at the University of Maryland, reported their findings in a recently posted article in Light: Science & Applications.

"We have identified and solved an underappreciated problem," said Copeland.

Having calibrated their optical microscope using the arrays, the team reversed the process, using their microscope to identify imperfections in the prototype arrays from the nanofabrication process. "We tested the limits of nanofabrication to control the aperture spacing," noted co-author Rob Ilic, manager of NIST's NanoFab. The ease and speed of optical microscopy could facilitate quality control of aperture arrays in a production process.

Finally, the team exploited the inherent stability of the aperture arrays to evaluate whether fluorescent nanoparticles, often used as fixed points of reference in optical microscopy, actually remained fixed to a particular point or if they moved around. The researchers found that while unintentional motions of their optical microscope made views of the nanoparticles blurry, using the aperture array showed that the nanoparticles were not actually moving at atomic scales.

###

Paper: Craig R. Copeland, Jon Geist, Craig D. McGray, Vladimir A. Aksyuk, J. Alexander Liddle, B. Robert Ilic and Samuel M. Stavis. Subnanometer localization accuracy in widefield optical microscopy. Light: Science & Applications. Accepted article posted online 16 May 2018. DOI: 10.1038/s41377-018-0031-z

Media Contact

Ben P. Stein
bstein@nist.gov
301-975-2763

 @usnistgov

http://www.nist.gov 

Ben P. Stein | EurekAlert!

More articles from Physics and Astronomy:

nachricht An ultrafast glimpse of the photochemistry of the atmosphere
15.10.2019 | Ludwig-Maximilians-Universität München

nachricht Putting quantum bits into the fiber optic network: Launching the QFC-4-1QID project
15.10.2019 | Fraunhofer-Institut für Lasertechnik ILT

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: An ultrafast glimpse of the photochemistry of the atmosphere

Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...

Im Focus: Shaping nanoparticles for improved quantum information technology

Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.

Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...

Im Focus: Novel Material for Shipbuilding

A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.

The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...

Im Focus: Controlling superconducting regions within an exotic metal

Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).

Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...

Im Focus: How Do the Strongest Magnets in the Universe Form?

How do some neutron stars become the strongest magnets in the Universe? A German-British team of astrophysicists has found a possible answer to the question of how these so-called magnetars form. Researchers from Heidelberg, Garching, and Oxford used large computer simulations to demonstrate how the merger of two stars creates strong magnetic fields. If such stars explode in supernovae, magnetars could result.

How Do the Strongest Magnets in the Universe Form?

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

International Symposium on Functional Materials for Electrolysis, Fuel Cells and Metal-Air Batteries

02.10.2019 | Event News

NEXUS 2020: Relationships Between Architecture and Mathematics

02.10.2019 | Event News

Optical Technologies: International Symposium „Future Optics“ in Hannover

19.09.2019 | Event News

 
Latest News

Shipment tracking for 'fat parcels' in the body

15.10.2019 | Life Sciences

An ultrafast glimpse of the photochemistry of the atmosphere

15.10.2019 | Physics and Astronomy

Unlocking the biochemical treasure chest within microbes

15.10.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>