Anyone who’s been around a laboratory long enough will know a microscope like the back of their hand. Ever handy, the tool allows researchers and scientists to see the details of items at magnifications the human eye is simply incapable of seeing. However, there are limitations to the technology; as standard microscopes are reliant on visible light to see their subjects in greater detail, they are therefore limited by the wavelengths of visible light itself. Light microscopes are often limited to features not smaller than 200 nanometers; any features smaller in dimension than the wavelengths of visible light can simply not be seen with sufficient detail. This limitation led to the development of devices such as electron microscopes, which completely skip over the limitations set by visible light by skipping over using visible light altogether. This led to a conundrum; sample preparation for electron microscopes and other similar technologies demand that the specimen be treated with either resins or sputter-coated with conductive material under a vacuum—meaning that viewing biological specimens under these microscopes while alive prove to be a huge challenge.
A recent study published in Nature Communications aims to remove the limitations set by visible light to allow closer inspection of biological specimens, by using specially-engineered materials called hyperbolic metamaterial that shortens the wavelength of light as it passes through the material—allowing light microscopes to see in higher resolution, viewing structures with resolutions up to 40 nanometers.
The team, led by University of California San Diego electrical and computer engineering professor Zhaowei Liu, performed the feat by coating microscope slides with the hyperbolic metamaterial, composed of nanometer-thin alternating layers of silver and silica glass. Light passing through the slide is scattered by the metamaterial while its wavelength shortens, creating a series of high-resolution speckled patterns. Any sample mounted on the microscope slide is illuminated by these speckled patterns, creating a series of low-resolution images which are then captured then reconstructed by algorithms to produce a high-resolution image. Tests done by the team show that the technology is capable of viewing cellular structures that are otherwise impossible to see using an unmodified version of the microscope.
Liu’s team is hopeful that the technology can be further improved, with previous research by the team already showing it capable of viewing at ultra-high axial resolutions of 2 nanometers. In combining this with the current two-dimensional imagery, the team hopes they will be able to do high-resolution imaging in three dimensions.
Bibliography
- Labios, L. (2021, June 1). Light-shrinking material lets ordinary microscope see in super resolution. UC San Diego Jacobs School of Engineering. Retrieved August 19, 2021, from https://jacobsschool.ucsd.edu/news/release/3287
- ScienceDaily. (2021, June 1). Light-shrinking material lets ordinary microscope see in super resolution. ScienceDaily. Retrieved August 19, 2021, from https://www.sciencedaily.com/releases/2021/06/210601100729.htm
- Lee, Y.U., Zhao, J., Ma, Q. et al. Metamaterial assisted illumination nanoscopy via random super-resolution speckles. Nat Commun 12, 1559 (2021). https://doi.org/10.1038/s41467-021-21835-8
