**Acknowledgements**

concentration of microsized Fe3

Fe3 O4

174 Hydrogels

can be applied for drug release system.

different concentrations of Fe<sup>3</sup>

O4

O4

particles as fillers. The solid lines are for the eye guidance.

be narrower and smaller with decreasing magnetic filler concentration. This is attributed to the different magnetic response of ferrogel to be deformed and returned to its original length and position. This behavior is also associated with a magnetic remnant of the ferrogels. A higher magnetic concentration leads to a higher ferrogel ability to deform even under a low external magnetic field. Moreover, a wider hysteresis loop for ferrogel with microsized filler was observed, indicating a stronger magnetic saturation. This is in a good agreement with the previous paper [27] that the ferrogel with large particle size has the best magnetosensitive effect, so it

**Figure 10.** (a) Elongation and (b) deflection of ferrogels under 329 mT versus the concentration of micro- and nano-sized

**Figure 11.** Hysteresis loops of the deflection versus electric current (proportional to the magnetic field) for ferrogels with

microparticles: 2.5 wt%, 7.5 wt%, and 15 wt%.

particles from 2.5 to 15%. The hysteresis loops are found to

This chapter is based on research funded by several schemes of research grants, provided by LPPM ITS, DP2M—Ministry of National Education, and DRPM—Ministry of Research, Technology and Higher Education, Republic of Indonesia, 2006−2016.
