Behaviors of 3D-printed objects made of thermo-responsive hydrogels: motion in flow and molecule release ability

Abstract

Functional and intelligent soft materials are useful for controlled release of medicines and other molecules. Poly(N-isopropylacrylamide) (PNIPAm) gels are well known as thermo-responsive gels with large discontinuous volume change which is commonly called as the volume phase transition. PNIPAm gels are expected to be applied to controlled-releasable material for drug delivery systems. Furthermore, we can fabricate arbitrary shapes made of gels freely by using 3D hydrogel printing techniques. Here we report that the effect of capsule shapes on behaviors of the PNIPAm objects under water flow with Reynolds number 102. In addition, we compared the behaviors of 3D-printed PNIPAm gel objects with 3D-printed polylactic acid (PLA) objects. The velocity at the first period of 2 or 3 s from the beginning of movement is slower than that of second period in the case of PNIPAm objects with ellipsoidal and bullet shapes. In other words, the capsules are accelerated after the period of 2 or 3 s. For the bullet shape objects, the velocity of the PNIPAm gel is approximately three times faster than that of PLA. It is considered that the cause of the difference between the velocities of PLA and PNIPAm gel is the difference of their frictions. The hydrogels possess commonly low friction properties. Finally, it is demonstrated that the 3D-printed PNIPAm capsules can release the solution inside the capsules by shrinking the PNIPAm gels, caused by volume phase transition.