Magnetically-propelled hydrogel particle motors produced by ultrasound assisted hydrodynamic electrospray ionization jetting.

One of the most promising future applications of hydrogels is drug delivery. The hydrogels act as a biomedical cargo model to reach the target and release drugs to cure diseases. This application requires no side effects of the hydrogel and the ability to pass through porous media (e.g. membranes, interstitial tissue etc.) with nanoscaled channels. At the same time, the hydrogel must be mass-producible in an economic way. In this work, we show that hydrodynamic electrospray ionization jetting combined with ultrasound can fulfill these high requirements. This method can produce mucoadhesive micro-/nano-particles, which are small enough to pass through the gastrointestinal epithelium. The average size of the produced particles is exactly predictable by controlling the spraying distance, spraying mode, alginate concentration, ultrasound bath frequency and counter electrode shape. These micro-/nano-particles are loaded with biocompatible magnetite nanoparticles, and propelled by a rotating magnetic field between 5 to 20 m T and a frequency from 1 Hz to 100 Hz. These rotating micro-/nano-particle motors perform directional motion in solution, offering a promising possibility for magnetically controlled drug delivery.