"Inverse" shape memory effect in energetic electron crosslinked methylcellulose hydrogels: Programming, demonstration and quantification

Shape memory hydrogels constitute a highly attractive materials class that bears enormous potential within a broad range of areas - from engineering to medicine. Within the present contribution we demonstrate that energetic electron crosslinked methylcellulose-only hydrogels exhibit an "inverse" shape memory effect that transforms from a secondary shape to its primary shape upon cooling. The primary shape can conveniently be "programmed" by application of energetic electrons. This intrinsically sterilizing processing approach promises to preserve the excellent FDA-approved biocompatibility of methylcellulose, particularly as it does not involve potentially hazardous crosslinkers or other reagents with medically adverse effects. While we observe the transformation behavior in a systematic study as function of synthesis parameters, we also address functional fatigue and quantify fixity, strain recovery as well as attainable actuator forces. With the latter being in the range of 0.1 N, our actuator elements might prove useful for biomedical applications.