Fig. 6. Demonstration of the fusion of sparse particle localization and miniaturized mass sensing.

a, b Localization of scattered sparse PS beads on the small TPoS resonator area by acoustic actuation. c, d Closeup view of the resonator area prior to and after acoustic localization. After the water droplet evaporates, none of the particles are found on the resonator, while almost all the particles are localized on the resonator area. e Comparison of the measured S₂₁ of the TPoS resonator (Chip A) in air with no particles added and after acoustically localized PS particles (9 μm in diameter) are loaded on the resonant sensor. The addition of the localized particles results in a clear shift in the resonant frequency along with an attenuation and broadening of the peak. The broken lines are model curve fits based on a series resonant equivalent circuit model that describes the lumped electrical characteristics of the TPoS resonator (Fig. S3 of the Supplementary information).