Phase Segregation of Colloidal Quantum Dots Driven by Marangoni Vortex Flow for Multi-Component Microfabrication.

The deterministic integration of multiple materials is the cornerstone of the semiconductor industry, traditionally accomplished through complex microfabrication techniques, such as lithography, transfer, and wafer bonding. Inspired by biological systems that precisely form intricate intracellular structures, self-assembly offers an efficient, bottom-up pathway for monolithic integration. The challenge, however, lies in controlling the transport of multiple components within the inherently chaotic and confined fluidic environments of microfabrication, which typically induces mixed phases and structural disorder. Herein, we utilize capillary bridges with Marangoni vortex flow to guide the segregation of colloidal quantum dots (CQDs) by size, enabling the efficient self-assembly of multicomponent microstructures. The fluid flow in our system establishes a regulated concentration gradient. This gradient drives the diffusiophoresis of larger CQDs away from the evaporation front, inducing a "small-at-front" segregation. The versatility and robustness of our platform are demonstrated by the various phase-segregated microstructures with customizable morphologies and diverse compositions. To showcase its practical application, we leverage this technique to integrate dual-wavelength lasers within a single photonic circuit, achieving the on-chip propagation of coherent light for optical communications. Our work introduces a novel approach to multicomponent microfabrication.