Spontaneous Formation of Microgels for a 3D Printing Supporting Medium

In this work, a facile and low-energy-consuming method is developed to obtain packed dispersions of self-forming agar microgels. As the agar concentration is lower than the critical gelation concentration (0.4 wt %), the microgels are spontaneously formed from the solution with a concentration as low as 0.04 wt % upon cooling. The dispersions with a concentration greater than 0.08 wt % exhibit yield stress and a storage modulus exceeding the loss modulus (G′ > G″), revealing a gel-like behavior. After centrifugation, a highly jammed dispersion of self-forming microgels (1 wt %) can be acquired, and it behaves like a liquid-like solid with a rapidly self-healing ability. On the basis of the gelification tests (inverted tube and falling ball), its mechanical strength is shown to be significantly stronger than that of the fluid gel (1 wt %) fabricated from strong agitation. The highly jammed dispersion can be used as a supporting medium for 3D printing. All the UV-cured structures match their designed shapes perfectly without deformation. The supporting medium also shows good reusability.