In COVID-19 therapy with artificial lungs such as extracorporeal membrane oxygenation (ECMO) machines, platelets in the extracorporeal circulation are often activated by their contact with the artificial materials, leading to the formation of blood clots followed by serious complications such as stroke and heart attack. However, anticoagulation and antithrombotic management is challenging due to the lack of testing tools to evaluate the circulation. Here we demonstrate real-time monitoring of thrombogenesis in the circulation of an ECMO-equipped goat with an intelligent platelet aggregate characterizer (iPAC), which is based on imaging flow cytometry and deep-learning-based analysis of numerous platelet aggregates in blood.
In the near future, single-molecule surface-enhanced Raman spectroscopy (SERS) is expected to expand the family of popular analytical tools for single-molecule characterization. We provide a roadmap for achieving single molecule SERS through different enhancement strategies for diverse applications. We introduce some characteristic features related to single-molecule SERS, such as Raman enhancement factor, intensity fluctuation, and data analysis. We then review recent strategies for enhancing the Raman signal intensities of single molecules, including electromagnetic enhancement, chemical enhancement, and resonance enhancement strategies. To demonstrate the utility of single-molecule SERS in practical applications, we present several examples of its use in various fields, including catalysis, imaging, and nanoelectronics. Finally, we specify current challenges in the development of single-molecule SERS and propose corresponding solutions.
The chiroptical effect is a property that describes distinct response of matter to light with opposite handedness, which is extensively utilized in stereochemistry, analytical chemistry, metamaterials, and spin photonics. Conventionally, metallic nanostructures have been harnessed to generate a strong chiroptical effect with the assistance of surface plasmon resonance, but they usually suffer from low energy efficiency and large photothermal heat generation due to the high ohmic loss of metallic materials, which severely restricts their practical applications. Here we present a dielectric spiral nanoflower with a giant chiroptical effect produced by magnetic resonance. We theoretically predicted the giant chiroptical effect of the spiral nanoflower by numerical simulations and analyzed its underlying physics by combination of a multipole expansion method. Based on the theoretical design, we experimentally fabricated the spiral nanoflower and demonstrated its strong chiroptical effect by characterizing its circular intensity difference (CID). The largest-to-date CID of 35% is demonstrated. The magnetic quadrupole interference within the spiral nanoflower was also clarified by experimentally tailoring its magnetic quadrupole interference. Our work is expected to overcome the limitation of conventional metallic platforms and pave the way toward the development of various highly efficient and thermostable chiroptical devices and applications.
Mid-infrared (MIR) resonators with high quality (Q) factors play crucial roles in a variety of applications in nonlinear optics, lasing, biochemical sensing, and spectroscopy by virtue of their features of long photon lifetime as well as strong field confinement and enhancement. Previously, such devices have been mainly studied on silicon integration platforms while the development of high-Q germanium resonators is still in its infancy due to quality limitations of current germanium integration platforms. Compared with silicon, germanium possesses a number of advantages for MIR applications, such as a wider transparency window (2 - 15 µm), a higher refractive index (~4), and a higher third-order nonlinear susceptibility. Here we present our experimental demonstration of two types of MIR high-Q germanium resonators, namely, a microring resonator and a photonic crystal nanobeam cavity. A maximum Q factor of ~57,000 is experimentally realized, which is the highest to date on germanium platforms. Moreover, we demonstrate a monolithic integration of the high-Q germanium resonators with suspended-membrane waveguides and focusing subwavelength grating couplers. Our resonators pave a new avenue for the study of on-chip light-germanium interactions and development of on-chip MIR applications in sensing and spectroscopy.