Micromotors with Spontaneous Multipattern Motion and Microvortex for Enhanced "On-the-Fly" Molecule Enrichment

"On-the-fly" molecule enrichment by micro/nanomotors obviously improves heterogeneous catalysis, trace detection, and environmental monitoring, yet faces challenges of the trade-off between collection range and interaction time. Inspired by the versatile foraging process of predators, this work demonstrates that micromotors doing spontaneous multipattern motion with microvortex can greatly enhance "on-the-fly" enrichment, demonstrated by highly sensitive surface-enhanced Raman scattering detection. It leverages an axis-asymmetric bowl-shaped structure and the nonlinear Ag-AgCl reaction, realizing alternating low-velocity swinging forward and accelerated steering motions for prolonged interaction and large work area. Moreover, the bowl-shaped microstructure bestows a micro-vortex above the Ag side due to the competition of electric potential and pressure gradient, also extending interaction time during the acceleration. Consequently, it exhibits at least an order of magnitude larger enhancement of detection signals than the counterparts. This proof-of-concept study highlights the significance of motion mode and structure design in guiding flow field, offering substantial benefits for applications. Leveraging an axis-asymmetric bowl-shaped structure and Ag-AgCl nonlinear chemical reaction can produce a micromotor spontaneously doing switchable multipattern motion between swinging forward and accelerated steering with a microvortex. It demonstrates an enhanced "on-the-fly" molecule enrichment by an order of magnitude larger than the counterparts.image & COPY; 2023 WILEY-VCH GmbH