Stimuli-responsive polymers with sophisticated functionalities have found numerous applications as soft robots and actuators, responsive medical devices, sensors, drug delivery agents, artificial muscles, and implants. Hydrogels have been widely used as smart materials due to their stimuli-responsive swelling and shrinking. Controllable transformation of shape can be achieved in response to various chemical and physical stimuli. Most of the current forming techniques to fabricate hydrogels with stimuli-responsive shape morphing are primarily limited to simple 2D film structures and impose huge limitations while fabricating complex 3D structures. 4D printing can overcome the limitations of fabricating hydrogels with enhanced flexibility and shape-morphing characteristics, along with complex and rapid deformation requirements. However, 4D printing of hydrogel structures is challenging due to the poor printability of hydrogels and the poor shape fidelity of printed patterns when direct-ink writing (DIW) 3D printers are used. To overcome these challenges, a highly printable bio-based hydrogel with shape-morphing ability is developed. Intricate 3D architectures with variable spacing, angles, and hinges are achieved on these printed structures using hydrophobic coating by the DIW technique. The solvent-responsive actuation mechanism of these printed structures is analysed with a chitosan-water system and reported in the first part of the work. A 4D-printed soft gripper is demonstrated as an application that is capable of lifting an object seven times its weight. The second part of the work is focused on developing 4D-printed bi-directional actuators with two different hydrogel systems. A chitosan-carboxymethyl cellulose system is used to make a bilayer pH-responsive printable hydrogel ink by systematic modification of the rheological properties. The deformation mechanism of the bilayer-printed structures is studied in extreme pH conditions (i.e., acidic and basic medium) with strong interlayer adhesion in the bilayer material system. The bi-directional actuation of these 4D-printed pH-responsive structures is demonstrated as a potential application in artificial valves, smart textiles, and smart vents.