Biocompatible Direct Deposition of Functionalized Nanoparticles using Shrinking Surface Plasmonic Bubble

Functionalized nanoparticles (NPs) are the foundation of diverse applications, such as photonics, composites, energy conversion, and especially biosensors. In many biosensing applications, concentrating the higher density of NPs in the smaller spot without deteriorating biofunctions is usually an inevitable step to improve the detection limit, which remains to be a challenge. In this work, we demonstrate biocompatible deposition of functionalized NPs to an optically transparent surface using shrinking surface plasmonic bubbles. Leveraging the shrinking bubble can enable to mitigate any potential biomolecules degradation by strong photothermal effect, which has been a big obstacle of bridging plasmonic bubbles with biomolecules. The deposited NPs are closely packed in a micro-sized spot (as small as 3 μm), and the functional molecules are able to survive the process as verified by their strong fluorescence signals. We elucidate that the contracting contact line of the shrinking bubble forces the NPs captured by the contact line to a highly concentrated island. Such a shrinking surface bubble deposition (SSBD) is low temperature in nature as no heat is added during the process. Using a hairpin DNA-functionalized gold NP suspension as a model system, SSBD is shown to enable much stronger fluorescence signal compared to the optical pressure deposition and the conventional steady thermal bubble contact line deposition. The demonstrated SSBD technique capable of directly depositing functionalized NPs may benefit a wide range of applications, such as the manufacturing of multiplex biosensors.