This paper shows how to create a hydrogel that has many zones, each of which has different mechanical properties. The gel above has four zones, which stretch to different extents. The modulus of the stiffest zone is 100 times the modulus of the softest zone. Our approach could be used to build realistic mimics of the spinal discs present between our vertebrae, which have a soft core and a stiff shell.
Many molecules (‘gelators’) self-assemble into long fibers, which entangle to form molecular gels. Such gelation occurs in some organic solvents, but not in others. But is it possible to predict if gelation would occur beforehand? This paper provided a framework to predict molecular gelation using thermodynamic parameters of the various solvents. The same framework has now been used by many researchers.
This paper showed for the first time how one could easily create a ‘photorheological fluid‘ in the lab, i.e., a fluid whose viscosity could be dramatically altered by shining light. The fluid contained molecules that self-assembled into long chains initially. Irradiation with UV light altered the geometry of the molecules, which made them re-assemble into tiny spheres. This caused a 10,000-fold drop in viscosity.