Stimuli-responsive assembly of iron oxide nanoparticles into magnetic flexible filaments

The combination of multiple functionalities in a single material is an appealing strategy for the development of smart materials with unique features. In this work, we present the preparation of thermoresponsive magnetic nanoparticles and their one-dimensional assembly into transient microfilaments. The material is based on 9.4 nm iron oxide nanoparticles grafted with poly(N-n-propylacrylamide) via multiphosphonic acid anchoring sites. The hybrid nanoparticles present a low critical solution temperature (LCST) transition between 21 degrees C and 28 degrees C, depending on the pH and the ionic strength. When heated above the LCST in defined conditions, the nanoparticles aggregate and respond to an external magnetic field. An intrinsic characteristic of the thermoresponsive particles is an asymmetric transition between cooling and heating cycles that was favorably exploited to build one-dimensional permanent microstructures, such as magnetic microfilaments and cilia. In summary, we present the development of a nanoplatform responsive to multiple stimuli, including temperature, magnetic field, pH, and ionic strength and its transformation into magnetically active microfilaments that could find potential applications in remotely controlled devices.

Automated summary

The study developed a nanoplatform responsive to multiple stimuli, including temperature, magnetic field, pH, and ionic strength, and transformed it into magnetically active microfilaments, which could potentially find applications in remotely controlled devices.