Spatially Confined Microreactors via Evaporation-Induced Liquid-Liquid Phase Separation for Integrated Bacterial Detection and Elimination.

Molecular interactions in dilute and heterogeneous systems are limited by the lack of spatial confinement, resulting in low reaction probability, weak signal generation, and inefficient functional response. Here, we report an evaporation-driven liquid-liquid phase separation (LLPS) microreactor that generates confined liquid domains for local enrichment of targets, probes, and nanoagents. This confinement increases local concentrations and accelerates reaction processes within confined domains. An entropy-driven DNA circuit enables sensitive detection with a limit of 1.41 CFU/mL. Fluorescence patterns generated within the microdomains enable accurate identification of multiple bacteria using a lightweight deep learning model. The confined environment also supports localized photothermal heating by RhCoAu trimetallene/Au nanocrystals, leading to efficient bacterial elimination. By organizing recognition, signal generation, and functional response within phase-separated domains, the system integrates detection and treatment within a single process. This work shows that LLPS provides a general strategy for controlling reaction environments at the microscale, improving the performance of bioanalytical systems in complex conditions.