Controllable Microfluidic Fabrication of Magnetic Hybrid Microswimmers with Hollow Helical Structures

Controllable magnetic hybrid microswimmers with hollow helical structures are fabricated, by a facile strategy based on microfluidic template synthesis and biosilicification, to achieve enhanced rotation-based locomotion for cargo transport. The magnetic hybrid microswimmers are fabricated by first synthesizing Fe 3 O 4 -nanoparticles-containing helical Ca-alginate microfibers from microfluidics, followed with biosilicification and controllable dicing to engineer their rigid hollow helical structures. The microswimmers show hollow helical structures consisting of a rigid, biocompatible alginate/protamine/silica shell embedded with Fe 3 O 4 nanoparticles. Their helical structures can be engineered into open tubular structures or closed compartmental structures by using microfibers or diced microfibers as templates for biosilicification. Powered by a simple rotating magnet, the microswimmers can achieve enhanced rotation-based locomotion and provide good mechanical strength for supporting cargo for transportation. This work provides a simple and efficient strategy for fabricating controllable magnetic hybrid microswimmers with hollow helical structures to achieve enhanced rotation-based locomotion for cargo transport, encapsulation, and delivery.