Most robots and mobile machines are made of hard materials. However, movements in existing micro devices are in general not as dexterous and skillful as macro scale robots, because basic moving principles such as translation and rotation using mechanical components are no longer simple to realize on micro scale. These challenges can be addressed by employing soft active materials and biologically inspired design principles. For example, given 3D fabrication capability of PµSL, I have demonstrated simple and reversible shape transformation in micro polymer devices. By embedding microfluidic network, solvent is directly transported to control polymer swelling locally, mimicking the exquisite motions of sensitive plants such asVenus flytrap. In this manner, complex 3D motion can be programmed by appropriate design of the microvascular network. Based on the insights from solid mechanics, elastic instability has been successfully incorporated into the actuation to enhance actuation speed which would been otherwise limited by poroelasticity. Full control over the pattern transformation via buckling has also been demonstrated. Using responsive hydrogels, environmentally abundant energy sources such as humidity, temperature, and light can be utilized to generate mechanical work for energy harvesting applications.