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Metasurface-enhanced nanospectroscopy
Biomolecular spectroscopic imaging for living cells has attracted much attention as a way to understand biological systems and detect biological events on a cellular scale. For a label-free, non-destructive spectroscopic imaging method, plasmonic resonance energy transfer (PRET)-based molecular imaging using plasmonic nanoparticles as a probe has been proposed. We propose a metasurface-driven multiplexed nanospectroscopy based on PRET to overcome the limitation of the previous plasmonic nanoparticle based-PRET imaging. Our probing method of biological light-matter interactions in metasurfaces via multiplexed PRET nanospectroscopy will enable real-time monitoring of cellular communications, continuous tracking of chemicals or secretome profiling of live cells, real-time monitoring of exosomes, understanding systems biology, and precision molecular diagnostics.
Metasurface-enhanced molecular diagnostics
The global impact of the COVID-19 pandemic caused by SARS-CoV-2 has led to a need for quick and accurate pathogen detection. Therefore, developing inexpensive point-of-care devices is crucial to identifying infected individuals and preventing the spread of the disease. Polymerase chain reaction (PCR) is widely used in molecular diagnosis, genotyping, and gene expression analysis, and is considered the gold standard for nucleic acid amplification. We develop a low-cost photonic PCR device that uses a titanium nitride (TiN)-based meta-absorber to heat and cool the PCR mixture rapidly. With the help of a compact single infrared LED source, DNA amplification can be achieved within 5 minutes. This metasurface-enhanced photonic PCR platform has the potential to become a new molecular diagnostic tool for point-of-care testing devices.
Single molecule biophysics
Single molecule fluorescence spectroscopy is at the heart of molecular biophysics research and the most sensitive biosensing assays. The growing demand for precision medicine and environmental monitoring requires the creation of miniaturized and portable sensing platforms. However, the need for highly sophisticated objective lenses has precluded the development of single molecule detection systems for truly portable devices.Here,we propose a dielectric metalens device of submicrometer thickness to excite and collect light from fluorescent molecules instead of an objective lens. The unprecedented sensitivity of the metalens opens up various biomedical applications in portable single molecule systems. Because of their extremely small size, the proposed metalens can be integrated with available miniaturized microscope solutions, e.g., smartphone microscopes and 3D-printed FCS platforms. Metalens structures are compatible with silicon photonic chips making them viable candidates for integrating single molecule on-chip sensors for point-of-care testing.
Functional bioimaging with metasurfaces
Biological imaging techniques are indispensable for the exploration of biological processes, structures, and states. Advanced imaging techniques have been widely studied for various biological applications, such as diagnosis, biometrics, and fundamental biological research. As the importance of biological imaging has been highlighted, there has been an increased demand for advanced imaging techniques that are faster, wider, clearer, and more accurate. With multifunctional metasurfaces we are advancing biological imaging techniques such as super-resolution imaging, analog image processing, fluorescent imaging, photoacoustic imaging, medical imaging and biometrices. For example, the axially multifocal metalens can extend depth-of-field to enable 3D volumetric photoacoustic imaging for live organoid. We successfully monitor the melanogenesis in live brain organoids at various maturation stages and determine the distribution of neuromelanin content and its location in the organoid volumes. Since neuromelanin is selected as the target substance due to its key association with the pathology of Parkinson's Disease (PD), where the loss of dopaminergic neurons in the substantia nigra is closely correlated with decreased neuromelanin levels, we believe that our system can effectively monitor the progressive neurodegeneration observed in PD.
Quantum-enhanced molecular spectroscopy
Quantum mechanical perspective on light-matter interactions with specifically designed optical cavity, or cavity quantum electrodynamics, can offer insight into the relationship between atomic states of matter and electromagnetic modes in optical cavity. We are witnessing that the peculiar hybridized energy state between atom and photon, or partial matter and partial light at the same time, can be detected using general optical microscope at room temperature, though, relatively few applications of strong coupling effects have been reported. We develop quantum metasurfaces for plexcitonic and polaritonic strong coupling effects in chemical and biomedical applications. The strong coupling effect can be utilized as a tool to modify chemical reaction landscapes using the vibrational state of molecule and hot electron of plasmon in chemistry. In addition, strong coupling-induced quantum plasmonic biosensor not only can detect quantum coherence effects, but also improve detection sensitivity beyond the limit of classical sensors.
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