  The combination of multiple functionalities in a single material is an
appealing strategy for the de-velopment of smart materials with unique
features. In this work, we present the preparation of thermoresponsive magnetic
nanoparticles and their one-dimensional assembly into transient
micro-filaments. 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 {\deg}C and 28 {\deg}C, depending on the pH and
the ionic strength. When heated above the LCST in defined conditions, the
nanoparticles ag-gregate and respond to an external magnetic field. An
intrinsic characteristic of the thermorespon-sive 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 stimu-li, including temperature, magnetic
field, pH and ionic strength and its transformation into magneti-cally active
microfilaments that could find potential applications in remotely controlled
devices.
