Dual-wavelength metalens enables Epi-fluorescence detection from single molecules

Area of Science:

• Molecular Biophysics
• Nanotechnology
• Optical Sensing

Background:

• Single molecule fluorescence spectroscopy is crucial for molecular biophysics and biosensing.
• Miniaturized, portable sensing platforms are needed for precision medicine and environmental monitoring.
• Traditional systems require bulky objective lenses, hindering portability.

Purpose of the Study:

• To develop a portable single-molecule detection system.
• To replace conventional objective lenses with a compact dielectric metalens.
• To enable sensitive fluorescence spectroscopy in miniaturized devices.

Main Methods:

• Fabrication of a submicrometer-thick dielectric metalens.
• Utilizing the metalens for excitation and light collection from fluorescent molecules.
• Implementing fluorescence correlation spectroscopy (FCS) and nanoparticle tracking analysis (NTA).

Main Results:

• Demonstrated single Alexa 647 molecule detection using FCS.
• Achieved real-time monitoring of fluorescent nanoparticle transitions.
• Successfully identified hydrodynamic diameters from nanometers to hundreds of nanometers.
• Metalens exhibited high numerical aperture, focusing efficiency, and dual-wavelength operation.

Conclusions:

• The dielectric metalens enables ultracompact single-molecule sensors.
• This technology advances portable biosensing for diverse applications.
• Metalens offer a viable alternative to traditional optics in miniaturized sensing platforms.