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Shape transformation of polymeric materials, including hydrogels, liquid crystalline, and semicrystalline polymers, can be realized by exposing the shape-changing materials to the effect of a variety of stimuli such as temperature, light, pH, and magnetic and electric fields. Herein, we demonstrate a novel and different approach that allows a flat sheet or strip of a polymer to transform into a predesigned 3D shape or structure by simply stretching the polymer at room temperature and then releasing it from the external stress, that is, a 2D-to-3D shape change is activated by mechanical deformation under ambient conditions. This particular type of stimuli-controlled shape-changing polymers is based on suppressing plastic deformation in selected regions of the flat polymer sheet prior to stretching and release. We validated the design principle by using a polymer blend composed of poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA), and tannic acid (TA) whose plastic deformation can be locally inhibited by surface treatment using an aqueous solution of copper sulfate pentahydrate (Cu2+ ink) that cross-links PAA chains through a Cu2+-carboxylate coordination and, consequently, increases the material's Young's modulus and yield strength. After room temperature stretching and release, elastic deformation in the Cu2+ ink-treated regions leads to 3D shape transformation that is controlled by the patterned surface treatment. This facile and effective "stretch-and-release" approach widens the scope of preparation and application for shape-changing polymers.

P2-type Na2/3Ni1/3Mn2/3O2 is a promising cathode material for practical applications in Na-ion batteries, due to its high energy density, high volumetric capacity, excellent Na ion conductivity, ea...

Although shape-memory polymers (SMPs) can alter their shapes upon stimulation of environmental signals, complex shape transformations are usually realized by using advanced processing technologies (four-dimensional printing) and complicated polymer structure design or localized activation. Herein, we demonstrate that stepwise controlled complex shape transformations can be obtained from a single flat piece of SMP upon uniform heating. The shape-memory blends prepared by solution casting of poly(ethylene oxide) and poly(acrylic acid) (PAA) exhibit excellent mechanical and room-temperature shape-memory behaviors, with fracture strain beyond 800% and both shape memory and shape recovery ratio higher than 90%. After plastic deformation by stretching under ambient conditions, the material is surface-patterned to induce the formation of an Fe3+-coordinated PAA network with gradually altered cross-linking density along the thickness direction at desired areas. Upon subsequent heating for shape recovery, strain r...

A nanostructured protective structure, pillared by the copper nanoclusters and in situ filled with lithium oxide in the interspace, is constructed to efficiently improve the cyclic stability and lifetime of lithium metal electrodes. The porous structure of copper nanoclusters enables high specific surface area, locally reduced current density, and dendrite suppressing, while the filled lithium oxide leads to the structural stability and largely extends the electrode lifespan. As a result of the synergetic protection of the proposed structure, lithium metal could be fully discharged with efficiency ∼97% for more than 150 cycles in corrosive alkyl carbonate electrolytes, without dendrite formation. This approach opens a novel route to improve the cycling stability of lithium metal electrodes with the appropriate protective structure.