Lattice Slot Waveguide for Terahertz Microfluidics Biomedical Trace Analysis.

Electromagnetic metasurface integrated microfluidic chips enable a real-time, label-free platform for terahertz trace analysis of volume-limited biomedical samples with suppressed water absorption noise. However, conventional metal-insulator-metal (MIM) metasurface resonators exhibit inherently limited Q-factor and sensitivity due to radiative leakage through open side boundaries. Here, a lattice slot waveguide based on MIM configuration is designed to effectively confine energy within the microfluidic channel and mitigate radiative loss. This trapped mode achieves enhanced sensitivity and Q-factor through synergistic excitation of surface lattice resonance and guided mode resonance under propagation constant matching conditions. Leveraging this platform, an anisotropic detection strategy incorporating a patterned lattice structure is devised to achieve simultaneous polarization multiplexed responses, exhibiting a figure of merit of 135 in both polarizations. Experimental validation demonstrates a limit of detection of 625 pmol mL-1 and a Q-factor of 189 for this polarization multiplexing microfluidic platform. This work offers a unique avenue for enhanced accuracy and efficiency in terahertz biomedical trace analyzing via multidimensional sensing capabilities.