Scientists developing new materials can significantly improve the resolution of optical microscopes

Electrical engineers from the University of California, San Diego have developed a new technology that can greatly improve the resolution of ordinary light mirrors, allowing for direct observation of finer structures and details in living cells. After applying this new technology, traditional optical microscopes can be transformed into so-called super-resolution microscopes. This technology mainly uses a special engineering material that shortens the wavelength of light when illuminating the sample - this reduced light essentially enables the microscope to image at higher resolution.

Professor Zhaowei Liu from the Department of Electrical and Computer Engineering at the University of California, San Diego said, "This material converts low resolution light into high-resolution light. It is very simple and easy to use. Just place the sample on the material and then put the entire thing under a regular microscope - no fancy modifications are needed.".

This new technology, published in Nature Communications, overcomes a limitation of traditional optical microscopes - low resolution. Light mirrors are useful for imaging live cells, but they cannot be used to see smaller things. The resolution limit of traditional optical microscopes is 200 nanometers, which means that any object closer to this distance will not be observed. Although there are more powerful tools, such as electron microscopes, whose resolution allows for the visualization of subcellular structures, they cannot be used to image live cells because the samples need to be placed in a vacuum chamber.

Professor Liu said, "The main challenge is to find a technology with very high resolution that is also safe for live cells.". The technology developed by Liu's team combines these two characteristics. With it, traditional optical microscopes can be used to image subcellular structures in vivo, with a resolution of up to 40 nanometers.

This technology consists of a microscope slide coated with a light shrink material called hyperbolic metamaterial. It is composed of alternating layers of silver and silicon glass at the nanoscale. When light passes through, its wavelength shortens and scatters, producing a series of random high-resolution speckle patterns.

When a sample is installed on a glass slide, it is illuminated in different ways by this series of speckle patterns. This generates a series of low resolution images, all of which are captured and then pieced together by a reconstruction algorithm to produce a high-resolution image.

The researchers tested their technique using a commercial inverted microscope. They are able to image fine features (such as actin filaments) in fluorescent labeled Cos-7 cells - these features cannot be clearly distinguished using a microscope alone. This technology also enables researchers to clearly distinguish tiny fluorescent beads and quantum dots with intervals of 40 to 80 nanometers.

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