Magnetically propelled soft microrobot navigating through constricted microchannels

• Soft helical microrobots were fabricated using a microfluidic strategy. • Mechanical property can be tuned by adjusting material composition and post ion solution treatment. • The soft microrobot can actively pass through narrow and sinuous microchannels by adaptive deformation. • The soft microrobot exhibits unique tightening when swimming in viscous liquids. Recent strides in microfabrication technologies offer important possibilities for developing microscale robotic systems with enhanced power, functionality and versatility. Previous microrobots fabricated by lithographic techniques usually lack the ability to adaptively deform in confined and constricted spaces and navigate through, therefore hindering their applications in complex biological environments. Here, a microfluidic strategy is combined with a dip-coating process for continuous fabrication of soft helical structures with controllable mechanical property as magnetically propelled microrobots, capable of actively propelling through narrow and sinuous microchannels. Because of their self-adaptive deformation capability, the magnetically propelled soft microrobots can actively navigate through a narrow opening, 2.21 times smaller than the sectional area of the microrobot, and a U-shape-bent capillary, directed by a programmed magnetic field. Additionally, the soft microrobot demonstrates increased swimming speed in a fluid of high viscosity, because of the adaptive tightening deformation of the helix when swimming. This new magnetically propelled soft microrobot and its attractive performance will open up new possibilities for biomedical operation at the micro and nanoscale.