Thermoresponsive hydrogel with embedded magnetic nanoparticles for the implementation of shrinkable medical microrobots and for targeting and drug delivery applications

The paper describes the choice of a thermoresponsive material for the implementation of untethered medical microrobots and other microdevices. These entities can be propelled at a specific location in the body using a Magnetic Resonance Imaging (MRI) system while being actuated for various functions such as the release of drugs by a volume change induced by hyperthermia of nanoparticles embedded in the hydrogel. This paper presents some preliminary results showing that poly(N-isopropylacrylamide) (PNIPA) might be an interesting choice, because of the important volume decrease when temperature is increased of some degrees. Using PNIPA based microparticles could be an interesting choice because, according to our results, volume changes are more important when the volume is smaller, and shrinking rate is higher when there are nanoparticles embedded in the hydrogel.