We design and fabricate a simple micro-system to collect analyte molecules in the fluids for surface-enhanced Raman scattering detection.The system is based on catalytic Au/SiO/Ti/Ag microengines by employing roll-up nanotechnology.[1] The bubble-propelled microengines are gathered towards the center of the droplet on a silicon wafer by convex meniscus effect [2],absorbing analyte molecules on passage at the same time.Pronounced SERS is observed on the swarmed microengines with more attached molecules.Furthermore,finite-difference time-domain method is employed to illustrate the excitation of localized surface plasmon modes by calculating the electromagnetic field on the microengine surface.Optimized collection efficiency of the system is obtained by controlling the fuel concentration.This facile system for molecule collection and detection could spur expanding applications in bioanalysis and lab-on-a-chip research.