Engineered Glass Slide Enables Microscopic Thermal Mapping

Using a coating of an optical exceptional point structure, researchers demonstrated a multifunctional microscope slide that supports real-time monitoring and mapping of temperature distribution and heat transport, in addition to conventional microscopic imaging. The integration of optical sensing technologies with a conventional glass slide could lead to improved experimental control at the microscale.

The coating is made of a layer of acrylic glass. The glass layer is sandwiched between two layers of gold. Each gold layer is just 20 nm thick.

The illustration depicts the three-layered coating, in which acrylic glass (PMMA) is sandwiched between extremely thin layers of gold. Courtesy of University of Buffalo.

Exception points (EPs) develop within this trilayered structure.

Researchers from the University of Buffalo and the University of Pennsylvania used the enhanced sensitivity associated with the topology of non-Hermitian EPs to design and coat the multilayer EP structure on a conventional microscope slide. Under ambient thermal perturbation, the polymer layer in the EP structure was found to deform due to the transferred heat, causing the lifting of EP degeneracy and, consequently, the increase of reflection. Through the reflection measurements at the initial EP wavelength, the temperature distribution on the glass slide could be gauged with high spatial resolution, facilitating efficient thermography in addition to conventional topographic imaging in an intact microscope system.

A monochromatic laser light at the EP wavelength was applied to map the reflection variation. A He–Ne laser at the wavelength of 632.8 nm, which according to researchers can be seamlessly integrated with most microscopes, was used to probe the optical-thermal signal transduction.

A photo of the experiment using a glass slide with the new coating. Courtesy of University at Buffalo.
The thermo-sensitive microscope slide could facilitate simultaneous microscopic mapping and monitoring of temperature distribution and thermal variation. Researchers believe that the microscope-integrated sensing technology could lead to improved controllability of multiple environmental parameters, streamlining scientific research.

“We have instruments that magnify incredibly small objects. And we have tools that measure heat, like infrared thermometers,” said professor Ruogang Zhao. “But we haven’t been able to combine them in a low-cost and reliable manner. This new coating takes a big step in that direction.”

According to researchers, the method is low-cost and efficient. Zhao said that the new coating would likely add a few cents to the cost of a common slide, which typically costs around five cents.

The research was published in Nature Communications (doi: 10.1038/s41467-018-04251-3).