Direct imaging-based gradient metasurface sensor enabling spectrometer-free ultrasensitive biomolecule detection.

Area of Science:

• Nanotechnology
• Optical Engineering
• Biomedical Diagnostics

Background:

• Biosensors are vital for rapid, on-site diagnostics.
• Current optical biosensors often require complex spectroscopic instrumentation.
• There is a need for simplified, portable, and cost-effective biosensing solutions.

Purpose of the Study:

• To introduce a direct imaging-based biosensor that eliminates the need for a spectrometer.
• To demonstrate a novel metasurface design for spatial encoding of wavelengths.
• To enable sensitive, label-free molecular detection with a simplified optical setup.

Main Methods:

• Fabrication of a dielectric metasurface with a continuous geometry gradient.
• Spatially encoding distinct resonance wavelengths across the metasurface.
• Reconstructing spectral shifts from transmission images using a single camera.

Main Results:

• Achieved a high-quality factor and 0.1 nm spectral step size over a 30 nm window.
• Demonstrated a compact 300 µm footprint without spectroscopic instrumentation.
• Exhibited high sensitivity (FOM = 67.2 RIU) and label-free detection of proteins and DNA down to 388 pM.

Conclusions:

• The spectrometer-free biosensor offers a compact and sensitive platform for molecular testing.
• The direct imaging approach simplifies optical architecture, paving the way for cost-effective diagnostics.
• This technology facilitates molecular testing outside specialized laboratory settings.