Asymmetric microstructure of hydrogel: two-photon microfabrication and stimuli-responsive behavior

We propose an asymmetric three-dimensional (3D) multiphoton polymerization microfabrication method, and successfully demonstrate it through fabricating the size-and shape-controlled stimuli-responsive asymmetric hydrogel microcantilevers. The reversible ion-responsive hydrogel microcantilevers exhibit attractive and controllable bending behavior due to their asymmetric deformation to external ions. The reversible bending direction of microcantilevers completed within only 0.133 s when the surrounding environment was alternated from water to 1 M NaCl solution. Furthermore, the microcantilevers exhibited large total bending angles theta(T) up to 32.9 degrees. The bending behavior can be also strongly influenced by increasing the length of the microcantilevers. The 3D stimuli-responsive hydrogels were demonstrated to be promising for the application of microactuators and micromanipulators. This designable microfabrication technique and the stimuli-responsive behavior of asymmetric microstructure of hydrogel with versatility in the shape would be prospective for developing biomedical microdevices.