From Polymer Gels to 3D Actuators: Transformation of Programmed 2D Structures to 3D Objects

After understanding the basic knowledge of polymer gels through the swelling test with organic solvents, students fabricated polymer gel actuators that can be reversibly transformed between two-dimensional (2D) structures and 3D objects. Two types of polymer films (acrylic polymer and polyimide) selected to fabricate 3D actuators exhibited strikingly different volume expansions due to the different chemical affinity between those polymers and solvents. Considering the polymer-solvent chemical affinity as well as breaking the structural symmetry of the 2D structures, students fabricated various 3D actuators such as roll, helical, cubic, and more complex actuators. They were obtained from the respective programmed 2D structures through bending, twisting, and folding transformations in solvent. From these systematic experiments, intermediate and undergraduate students beginning to study organic and polymer chemistry can learn the fundamental concepts about polymer gels and actuators, chemical affinity, and structural symmetry.