Existing mechanical metamaterials are typically designed to either withstand loads as a stiff structure, shape morph as a floppy mechanism, or trap energy as a multistable matter, distinct behaviours that correspond to three primary classes of macroscopic solids. Their stiffness and stability are sealed permanently into their architecture, mostly remaining immutable post-fabrication due to the invariance of zero modes. Here, we introduce an all-in-one reprogrammable class of Kagome metamaterials that enable the in-situ reprogramming of zero modes to access the apparently conflicting properties of all classes. Through the selective activation of metahinges via self-contact, their architecture can be switched to acquire on-demand rigidity, floppiness, or global multistability, bridging the seemingly uncrossable gap between structures, mechanisms, and multistable matters. We showcase the versatile generalizations of the metahinge and remarkable reprogrammability of zero modes for a range of properties including stiffness, mechanical signal guiding, buckling modes, phonon spectra, and auxeticity, opening a plethora of opportunities for all-in-one materials and devices.

Snap‐through instability has been widely leveraged in metamaterials to attain non‐monotonic responses for a specific subset of applications where conventional monotonic materials fail to perform. In the remaining more plentiful set of ordinary applications, snap‐through instability is harmful, and current snapping metamaterials become inadequate because their capacity to snap cannot be suppressed post‐fabrication. Here, a class of topology‐transformable metamaterials is introduced to enable in situ activation and deactivation of the snapping capacity, providing a remarkable level of versatility in switching between responses from monotonic to monostable and bistable snap‐through. Theoretical analysis, numerical simulations, and experiments are combined to unveil the role played by contact in the topological transformation capable of increasing the geometry incompatibility and confinement stiffness of selected architectural members. The strategy here presented for post‐fabrication reprogrammability of matter and on‐the‐fly response switching paves the way to multifunctionality for application in multiple sectors from mechanical logic gates, and adjustable energy dissipators, to in situ adaptable sport equipment.

Power‐free shape retention enables soft pneumatic robots to reduce energy cost and avoid unexpected collapse due to burst or puncture. Existing strategies for pneumatic actuation cannot attain motion locking for trajectories combining extension and bending, one of the most common modes of operation. Here, a design paradigm is introduced for soft pneumatic actuators to enable zero‐power locking for shape retention in both extension and bending. The underpinning mechanism is the integration of a pneumatic transmitter and a multistable guider, which are programmed to interact for balanced load transfer, flexural and extension steering, and progressive snapping leading to state locking. Through theory, simulations, and experiments on proof‐of‐concept actuators, the existence of four distinct regimes of deformation is unveiled, where the constituents first interact during inflation to attain locking in extension and bending, and then cooperate under vacuum to enable fully reversible functionality. Finally, the design paradigm is demonstrated to realize a soft robotic arm capable to lock at desired curvature states at zero‐power, and a gripper that safely operates with puncture resistance to grasp and hold objects of various shapes and consistency. The study promises further development for zero‐power soft robots endowed with multiple deformation modes, sequential deployment, and tunable multistability.

As an effective means to manipulate elastic wave energy, the defect mode of phononic crystals (PCs) has recently been employed to implement vibration energy harvesting by localizing waves within certain areas at defect frequencies. Prior research has indicated that the thermal environment affects the defect behavior and energy harvesting of single defects. However, the dynamic characteristics of multi-defect phononic crystals have not yet been discussed. This paper presents an investigation of the coupling behavior and energy harvesting of double defects in heated PC beams. The frequencies and mode shapes of defect modes are studied for different defect pairs within the first bandgap. Results indicate that the difference in the single-defect frequency between the two defects plays a dominant role in determining the intensity of the defect interaction which splits the defect modes. Meanwhile, the influence of the energy distribution around the defects on the coupling behavior becomes prominent when the two defects are quite close to each other. These two factors could cause degeneration of the defect modes. As an external factor, thermal load could enhance the defect coupling intensity, and may reactivate the degenerated defect modes. This effect would increase as the initial defect interaction gets stronger. For vibration energy harvesting, temperature rise may lead to a significant reduction in defect-based harvested energy, even though the number of defect-induced resonance peaks could be increased in the thermal environment. The thermosensitivity of harvesting performance varies greatly for different combinations of defects. Thermal effects should be considered in the design of defect-based harvesters.

Mechanical instability is often harnessed in mechanical metamaterials to generate a diverse range of functionalities, and can be triggered by either a mechanical or a field stimulus, such as temperature. Existing field‐responsive metamaterials with snap‐through instability, however, need to rely on a mechanical input to realize functional reversibility, a limitation depriving them of the capacity to operate solely via the applied field. This work demonstrates reversible snap‐through instability in a bi‐material framework that is exclusively driven by environmental temperature. The need for mechanical intervention is bypassed by leveraging the thermally induced contact and mismatched thermal expansion of the constituent materials. A combination of experiments, theory and simulations, unveils the physics underpinning the thermally driven snapping undergoing four successive regimes of deformation: noncontact, full contact, partial contact, and release. The advantages of the concept are showcased in two applications. The first is the development of thermal switches with ternary operation (OFF‐ON‐OFF) and logic functions, going beyond the capabilities of current binary switches. The second is reversible temporal morphing in deployable structures programmed to snap sequentially in multiple locked configurations at predefined values of temperature, opening the door to applications across sectors, such as deployable antennas, soft robots, and self‐reconfigurable medical devices.