Hybrid Metasurface for On-Chip Enrichment and Quantification of Biological Samples

This work reports a 3D-printed metasurface as a biosensing device that combines the functions of sample enrichment and quantification. The device consists of a nanoplasmonic sensing element surrounded by a biomimetic hydrophobic structure. The hydrophobic structure serves as a sample concentrator that can enrich analyte, which is subsequently quantified by the nanoplasmonic biosensor. Both the nanoscale biosensor and microscale hydrophobic sample concentrator were fabricated using two-photon polymerization lithography (TPL). The hydrophobic microstructure was inspired by natural patterns found on surfaces like lotus leaves, which are known for their water-repellent properties. The TPL-based 3D printing approach enables the integration of two functions into one chip with a high-resolution and simple fabrication process. The device was employed to detect swine influenza A virus within a droplet initially containing 20 μL of liquid. During testing, the droplet's volume decreased due to evaporation driven by plasmonic heating. As a result, the droplet's diameter can shrink from 3.4 mm to 0.1 mm in 15 min. The volume reduction corresponds to a virus concentration increase of over 4 × 10⁴ times. Integrating superhydrophobic sample concentration with the nanoplasmonic biosensor significantly improves analyte immobilization dynamics, enhances sensitivity, and reduces assay time.