On‐Chip Microfluidic Lasers and Laser Arrays From Colloidal Quantum‐Dot Cement

Colloidal quantum dots (QDs) have emerged as promising gain media owing to their solution‐processability and broadband tunable emission. However, the practical deployment of QD lasers in demanding environments, such as microfluidic systems, has been hindered by their susceptibility to surface degradation and difficulties in device integration. Herein, we realize a new class of microfluidic lasers based on a QD‐in‐matrix architecture, termed QD cement, which achieves superior optical gain through a ligand‑mediated polymerization strategy. By virtue of the epitaxy‐like heterostructure via coordination bonding design, the QD cement exhibits robust stimulated emission featuring simultaneous triple state transitions, along with a record‐high saturation intensity. Notably, the malleability of QD cement enables the construction of microlasers and laser arrays with arbitrary geometries and resonant modes that perform reliably in both aqueous and organic solvents. Leveraging this platform, an optofluidic chip and its proof‐of‐concept application for in situ liquid monitoring are demonstrated, achieving a high sensitivity of 293 nm/RIU. This work marks a significant step toward practical QD lasers and opens a new avenue for integrated optofluidics and optoelectronics.