All-Aqueous Soft Milli-swimmers.

Microscale swimmers are attractive for targeted drug delivery, noninvasive microsurgery and environmental remediation at different length scales, among which, Marangoni-based swimmers have garnered considerable attention due to their independence of external energy supply. However, applications of most existing chemical swimmers are limited by complex fabrication, high cost, utilization of organic (or even toxic) solvents, poor motility performance, and lack of controllability. To address these challenges, we propose an approach for all-aqueous soft milli-swimmers that utilizes biodegradable hydrogels and biocompatible fuels. This innovative method achieves swimmer body generation and fuel loading in one step by simply dripping one aqueous solution into another, saving fabrication time and minimizing fuel loss during transfer. These all-aqueous soft milli-swimmers have rove beetle-like self-propulsion, which stores low-surface-energy compounds within their body for propulsion on liquid surfaces. Isotropic and anisotropic all-aqueous soft milli-swimmers are formed with precise control over their dimension, morphology, and movement velocity. Through their motion within engineered channels, intricate labyrinths, dynamic air-liquid interfaces, and collective self-assemblies, their remarkable adaptability in complex aqueous environments is demonstrated. Furthermore, the integration of functional nanoparticles endows these all-aqueous milli-swimmers with multifunctionality, expanding their applications in cargo transportation, sensing, and environmental remediation.