Multiplexed Immunoassays Enabled by Pixelated High-Quality Factor Metasurfaces and Acoustic Bioprinting

Nanophotonic biosensors hold the promise of early disease identification and continuous treatment monitoring due to their high sensitivity, fast response time, and possibility for label-free detection. Here, we leverage ultra-densely-pixelated high-quality factor (high-Q) metasurfaces in conjunction with acoustic bioprinting surface chemistry to enable scalable multiplexed immunoassays. Our platform capitalizes on a 2D array of finite-size all-dielectric metasurfaces supporting quasi-bound state in the continuum (qBIC) resonances to significantly enhance light-matter interaction with high spatial resolution. Unlike conventional metasurfaces, where sharp resonances are generally generated via the interference of sub- and super-radiant modes in a large 2D arrangement of metaunits, our high-Q metasurface exploits photonic mirrors to highly confine the collective qBIC mode of a 1D array of broken-symmetry resonators. Without comprising the optical performance, such small-scale (i.e., 15×3 um²) metasurfaces provide high Q-factors (~3000) with a mode volume below (λ/n_eff)³. We demonstrate an ultradense array of pixelated biorecognition elements by introducing an acoustic bioprinting approach for the local functionalization of each metasurface resonator. In contrast to conventional surface functionalization approaches, which expose all sensing elements at once, our approach facilitates the realization of multiplexed biodetection by addressing individual elements at Khz rate. In combination with hyperspectral imaging, this sensitive label-free sensing platform allows for the simultaneous quantitative detection and kinetic analysis of multiple antibodies (e.g., SARS-CoV, Influenza A, and Influenza B) on a single chip. Further, we demonstrate how a single chip can also allow simultaneous detection of proteins and the associated gene fragments. Our AI-enhanced technique can capture two-dimensional spatially resolved images across contiguous spectral bands revealing subtle differentiation of spectral signatures associated with each linked bioanalyte, without relying on bulky and expensive spectrometers. The capability of our multiplexed immunoassay platform for parallel measurement of several biological targets of interest opens the door for easy-to-use and portable diagnostics.