New hyperlenses are giving scientists the ability to capture images of living cells in great detail.
A team from Vanderbilt University has created a new hyperlens that can resolve objects much smaller than the wavelength of light using hexagonal boron nitride (hBN)—a natural crystal with hyperlensing properties.
Previously, the best resolution using hBN was an object about 36 times smaller than the infrared wavelength used—the size of the smallest bacteria. Improvements in the quality of the crystal has enhanced the potential imaging capability by about a factor of ten.
The researchers enhanced the hBN crystals by using isotopically purified boron. Natural boron contains two isotopes that differ in weight by about 10 percent, a combination that significantly degrades the crystal’s optical properties in the infrared.
The researchers believe that a lens made from the purified crystal can, in principle, capture images of objects as small as 30 nanometers in size.
“We have demonstrated that the inherent efficiency limitations of hyperlenses can be overcome through isotopic engineering,” Alexander Giles, a research physicists at the U.S. Naval Research Laboratory, said in a statement. “Controlling and manipulating light at nanoscale dimensions is notoriously difficult and inefficient.
“Our work provides a new path forward for the next generation of materials and devices.”
The level of detail that optical microscopes can image is limited by the wavelength of light and the index of refraction of the lens material.
At infrared wavelengths the diffraction limit is about 3,250 nanometers, which can be surpassed by using hBN due to its ability to support surface phonon polaritons, hybrid particles made up of photons of light coupling with vibrating, charged atoms in a crystal that have wavelengths much shorter than the incident light.
While scientists have developed several instruments capable of producing images with nanoscale resolution, they are incompatible with living organisms.
This is because they either operate under a high vacuum, expose samples to harmful levels of radiation, require lethal sample preparation techniques like freeze-drying or remove samples from their natural, solution-based environment.
However, hyperlens can provide highly detailed images of living cells in their natural environments using low-energy light that does not cause harm. Using infrared light to perform the imaging also provides spectroscopic information about the objects it images.
The new technology could have a range of applications for biological and medical science, as well as in communications and for nanoscale optical components.
Researchers from the University of California, Sand Diego, Kansas State University, Oak Ridge National Laboratory and Columbia University also contributed to the study.