Contact‐Driven Snapping in Thermally Actuated Metamaterials for Fully Reversible Functionality

Abstract

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.

Finding transition state and minimum energy path of bistable elastic continua through energy landscape explorations

“…Li et al, 2021aLi et al, , 2021b or differential swelling (Li et al, 2023). Such a characteristic enables the search for the energy barrier and transition path of bistable structures made of stimuli-responsive materials, which can facilitate their applications in controllable shape change (Ma et al, 2023;Shao et al, 2018;Zhao et al, 2016), fast actuation (Wani et al, 2017), etc.…”

Thermal Computing with Mechanical Transistors

“…Utilizing Kirigami mechanics, we harness significant vertical displacement (≈ 5 mm for ΔT = 40 °C), induced by a horizontal thermomechanical reaction force, a design pioneered by our group and others. [35][36][37][38] We enhance the vertical displacement by intentionally breaking a mirror symmetry about the vertical centerline of the Kirigami structure (details in Supplementary Materials "Thermomechanical deformation of Compliant Porous Structure (CPS)"). To construct the Kirigami thermomechanical sensor, we selected two materials with a marked discrepancy in thermal expansion: an invar alloy for the metal component and polycarbonate (PC) for the polymer, as illustrated in Figure 1a.…”

Reprogrammable Metamaterial Processors for Soft Machines

“…To address this challenge, a potential solution is to endow metamaterials with reprogrammable logical computation abilities, enabling them to perform various combinatorial and sequential logic operations. [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] However, the execution of these mechanical logic computations depends on specific inputs, such as sliding switches, [ 40 ] applying compressive forces, [ 41 , 42 , 43 , 46 ] or exposing to specific solvents, [ 44 ] which are difficult to generate autonomously. Moreover, the logic outputs of these computations cannot directly act as the actuation stimuli for soft robots.…”