Transmission Electron Microscope Can Now See Nanoparticles In 4D

  • A new type of electron microscope can capture how nanoparticles transform in real time.
  • It provides dynamic, high-resolution, multi-frame videos of nanoparticles as they evolve.
  • This could change how scientists design paints, lubricants, coating and even future drug-delivery systems.

The Transmission Electron Microscopy was developed in the 1933. It can image at significantly higher resolution than conventional light microscopes, allowing scientists to peer inside nano-sized particles.

For decades, these advanced equipments had been limited to capturing only static pictures of microorganisms or cells, which doesn’t tell a complete story. However, researchers at the University of Florida and Northwestern University have come with a new type of microscopy that allows us to see the evolution of nanomaterials in real time.

They have developed a technique called Liquid Cell Transmission Electron Microscopy that captures, dynamic, high-resolution, multi-frame videos of nanoparticles as they evolve. This gives a picture of how particles change in four dimensions (space and time).

How It’s Made?

The novel technique consists of 3 key components –

  1. PISA (short for Polymerization-induced self assembly)
  2. Experiment assembling robotic system
  3. Camera that takes pictures of nanoparticles as they change.

PISA is used to produce well-defined soft materials in large quantities. In this case, researchers used PISA to create a special type of nanomaterial, called micelles, which has a wide range of applications, from targeted drug delivery to soaps.

Although micelles have several useful functions, we don’t know how exactly they form. Researchers wondered if they could use their technology to observe the process of formation of micelles.

They used the robotic system –with high accuracy and reproducibility — to assemble all the chemicals required to create micelles. Then, an electron beam of microscope started a reaction, which ultimately formed micelles.

The camera system attached to the microscope was unable to capture the complete transformation of micelles. However, it allowed them to observe some part of the process.

According to the researchers, they’ve added a crucial element to transmission electron microscopy – time. Further optimizing the system would enable them to observe the full trajectory of the reaction.

How growth of micelles was determined? 

Micelles form in a solution through PISA | Credit: Northwestern University

Growth profiles of spherical micelles were determined by a background subtraction algorithm that detects low-contrast particles against a solvent background, and by multi-object tracking analysis that automatically tracks multiple particles over picture frames.

Researchers determined that the imaging samples are necessary at low electron fluxes in thin liquid layers – 100 to 500 nanometers — within the liquid cell. Also, pulsed imaging conditions are very useful to control radical chemistry.

Reference: ACS Central Science | doi:10.1021/acscentsci.8b00148 | Northwestern University

What’s Next?

Researchers plan to further improve their technology and make it capable of observing the complete formation of spherical micelles in the solution cell by electron microscope. Also, to realize the full potential of dynamic videographic characterization of other nanomaterials, they will continue innovating new liquid cell design, imaging condition, experimental design and data analysis algorithm.

Read: Super-Resolution Microscopy Can See Cells In Both Space & Time

The detailed knowledge of transformation of nanoparticles could change how scientists design a wide range of materials, including paints, lubricants, coating and future drug-delivery systems.

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