RA A: Mechanical Materials focuses on developing 3D hybrid nanomaterials for mechanical functions driven by water interaction. Two main directions are considered: actuation/sensing and active acoustics. The objectives include creating materials with autonomous sensing, shape-changing abilities, and switchable acoustic transmission. The long-term vision is to achieve local control of functionality through patterning for programmable actuation, spatially resolved contact sensing, and tunable acoustic wave guidance. This area envisions new acoustic devices like switchable resonators and lenses, alongside bioinspired materials that can autonomously respond to various stimuli, paving the way for 4D programmable materials.