Simulating the structures and behaviors of living organisms are of great significance to develop novel multi-functional intelligent devices. However, the development of biomimetic devices with ...complex deformable structures and synergistic properties is still on the way. Herein, we propose a simple and effective approach to create the multi-functional stimuli-responsive biomimetic devices with independently pre-programmable colorful visual patterns, complex geometries and morphable modes. The metal organic framework (MOF)-based composite film acts as a rigidity actuation substrate to support and mechanically guide the spatial configuration of the soft chiral nematic liquid crystal elastomer (CLCE) sheet. We can directly program the structural color of the CLCE sheet by adjusting the thickness distribution without tedious chemical modification. By using this coordination strategy, we fabricate an artificial flower, which exhibits a synergistic effect of both shape transformation and color change like paeonia ‘Coral Sunset’ at different flowering stages, and can even perform different flowering behaviors by bending, twisting and curling petals. The assembled bionic flower is innovatively demonstrated to respond to local stimuli of humidity, heat or ultraviolet irradiation. Therefore, the spatial assembly of CLCE combined with functional MOF materials has a wide range of potential application in multi-functional integrated artificial systems.
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A simple and effective approach was proposed to prepare the multi-functional stimuli-responsive biomimetic devices with independently pre-programmable colorful visual patterns, complex geometries and morphable modes. The assembled artificial flower exhibits synergistic responses in shape and color by employing swellable metal organic framework (MOF)-based composite film to act as a rigidity actuation substrate and mechanically guide the spatial configuration of the soft chiral nematic liquid crystal elastomer (CLCE) sheet.
Micrometer‐scale liquid crystal network (LCN) actuators have potential for application areas like biomedical systems, soft robotics, and microfluidics. To fully harness their power, a diversification ...in production methods is called for, targeting unconventional shapes and complex actuation modes. Crucial for controlling LCN actuation is the combination of macroscopic shape and molecular‐scale alignment in the ground state, the latter becoming particularly challenging when the desired shape is more complex than a flat sheet. Here, one‐step processing of an LCN precursor material in a glass capillary microfluidic set‐up to mold it into thin shells is used, which are stretched by osmosis to reach a diameter of a few hundred micrometers and thickness on the order of a micrometer, before they are UV crosslinked into an LCN. The shells exhibit radial alignment of the director field and the surface is porous, with pore size that is tunable via the osmosis time. The LCN shells actuate reversibly upon heating and cooling. The decrease in order parameter upon heating induces a reduction in thickness and expansion of surface area of the shells that triggers continuous buckling in multiple locations. Such buckling porous shells are interesting as soft cargo carriers with capacity for autonomous cargo release.
Thin spherical shells of radially aligned polymeric liquid crystal networks respond to temperature changes by programmed reversible buckling. The shell actuators are produced at high rate in a microfluidic pathway, employing osmosis for alignment, thinning, and ensuring a high degree of porosity. This gives them potential for controlled cargo delivery and localized mixing.
•A consistent plate model is proposed for nematic liquid crystal elastomers within the framework of finite elasticity.•The plate model is suitable for large deformations and has no ad hoc kinematic ...or scaling assumptions.•The accuracy of the proposed plate model is verified by a benchmark problem that an NLCE bonded to a substrate is subjected to finite bending.•The plate model can attain an accuracy of O(h2) where h is the ratio of the thickness to width.
Nematic liquid crystal elastomer, abbreviated as NLCE, combines many excellent features of liquid crystal and elastomer, which promote its potential applications in many areas. In most reported situations, the thickness of an NLCE is relatively small compared with the other two dimensions. In particular, an NLCE can undergo large elastic deformation subjected to various stimuli. It is therefore of fundamental importance to derive a plate model describing nonlinear behaviors of an NLCE. This paper develops such a consistent plate theory for an NLCE incorporating both the hyperelasticity and the anisotropy. The 3D governing system, which is composed of the deformational momentum balance and the orientational momentum balance, is presented within the framework of nonlinear elasticity using a variational approach. Series expansions for all independent unknowns in terms of the thickness variable are conducted on the bottom surface of the plate. Furthermore, systematic manipulations of the expanded governing system generate two 2D vector plate equations containing five unknowns. Meanwhile, the associated edge boundary conditions are proposed. It turns out that the derived plate theory guarantees a required asymptotic order for each term in the variation of a generalized potential energy functional. In order to verify the accuracy of the obtained 2D plate system, we specify an exact form of the strain-energy function for an NLCE and study the finite pure bending of an NLCE-substrate structure where the substrate is assumed to be composed of an incompressible neoHookean material. It is found that the plate model can offer second-order correct results through comparisons between approximate and exact solutions. Remarkably, we find that for this benchmark problem the current plate model still works for a thick substrate plate and extremely large bending angles.
Self-oscillation absorbs energy from a steady environment to maintain its own continuous motion, eliminating the need to carry a power supply and controller, which will make the system more ...lightweight and promising for applications in energy harvesting, soft robotics, and microdevices. In this paper, we present a self-oscillating curling liquid crystal elastomer (LCE) beam-mass system, which is placed on a table and can self-oscillate under steady light. Unlike other self-sustaining systems, the contact surface of the LCE beam with the tabletop exhibits a continuous change in size during self-sustaining curling, resulting in a dynamic boundary problem. Based on the dynamic LCE model, we establish a nonlinear dynamic model of the self-oscillating curling LCE beam considering the dynamic boundary conditions, and numerically calculate its dynamic behavior using the Runge-Kutta method. The existence of two motion patterns in the LCE beam-mass system under steady light are proven by numerical calculation, namely self-curling pattern and stationary pattern. When the energy input to the system exceeds the energy dissipated by air damping, the LCE beam undergoes self-oscillating curling. Furthermore, we investigate the effects of different dimensionless parameters on the critical conditions, the amplitude and the period of the self-curling of LCE beam. Results demonstrate that the light source height, curvature coefficient, light intensity, elastic modulus, damping factor, and gravitational acceleration can modulate the self-curling amplitude and period. The self-curling LCE beam system proposed in this study can be applied to autonomous robots, energy harvesters, and micro-instruments.
Some atrial contractile assist devices applied on the heart surface can be regarded as a laminated Liquid crystal elastomer (LCE) plate under steady temperature loads and a contact mechanical force. ...An exact solution for the deformation of the laminated LCE plate under combined thermal and mechanical loads is derived by solving the three-dimensional (3D) equilibrium equations including heat conduction and thermoelastic theory. The validity of mathematical formula and computer programming is proved by convergence and comparison examples with finite element method (FEM). In order to simplify the complex calculation of exact solution, a back propagation neural network (BPNN) is further trained with a database containing 9504 sets of thermo-mechanical load conditions and their corresponding deformation which is solved by the exact solutions. Then the deformations of LCE plate subject to combined thermo-mechanical load can be predicted by this BP neural network instead of complex numerical calculation. Moreover, it is also applied to inverse the contact mechanical force at the bottom surface of LCE plate with a given deformation and temperature conditions. The results show that: (1) The results from the exact theoretical solution are in consistence with that from FEM but have a higher computational efficiency and stability; (2) The deformation of the laminated plate is more sensitive to the layered thickness of LCE than the variation of the temperature; (3) 3-D elasticity solutions of a laminated LCE plate under the combined thermos-mechanical load can be effectively predicted by a trained BP neural network.
•Exact deformation of simply supported laminated LCE plate under thermo-mechanical loads are presented.•BP neural network technique is used to predict the mechanical solutions of a laminated LCE plate.•Effects of layer thickness and temperature on deformation of the LCE plate are analyzed.•Highly accurate prediction of deformation or inversing mechanical load can be achieved.
Chaotic systems exhibit distinctive characteristics, including sensitivity to initial conditions and ergodicity within the domain of attraction. These features offer significant potential for ...applications in biomimetic machinery, medical instruments, and other domains. This paper focuses on exploring and analyzing a distinct class of a chaotic jumping systems composed of a liquid crystal elastomer (LCE) ball and an elastic substrate. By periodic illumination, the light-responsive LCE ball can be converted from a stationary state to a motion state. The coupled motion process of contact-expansion and jump of the LCE ball under periodic illumination is described, and the mechanism of the contact-expansion work compensating for the damping dissipation of the system and maintaining the sustained motion of the LCE ball is revealed. The numerical results show that the jumping behavior of the LCE ball is affected by system parameters, such as period and intensity of illumination, gravitational acceleration, elastic modulus, contraction coefficient and damping coefficient. The bifurcation diagram illustrates that by manipulating the system parameters, the LCE ball can transition between periodic motion and chaotic motion. The present research results can deepen the understanding of active materials based on the dynamics of chaotic systems, and provide guidance for the research on chaotic encryption communication, chaotic self-cleaning, chaotic agitation and so on.
Liquid crystal elastomers (LCEs) are programmable deformable materials that can respond to physical fields such as light, heat, and electricity. Photothermal-driven LCE has the advantages of accuracy ...and remote control and avoids the requirement of high photon energy for photochemistry. In this review, we discuss recent advances in photothermal LCE materials and investigate methods for mechanical alignment, external field alignment, and surface-induced alignment. Advances in the synthesis and orientation of LCEs have enabled liquid crystal elastomers to meet applications in optics, robotics, and more. The review concludes with a discussion of current challenges and research opportunities.
Additive manufacturing using liquid crystal elastomers (LCEs) has recently been explored for fabricating structures with stimuli-responsiveness and tunable mechanical behavior. Such structures show ...promising potential in the fields of soft robotics, haptic devices, and energy-absorbing materials. Herein, we study the processing-structure-property relationships of LCE sheets printed using direct ink writing (DIW) additive manufacturing. The printed sheets show anisotropic and temperature-dependent mechanical behaviors. We show that by tailoring the liquid crystal orientation patterns, the stress-strain relationship, as well as the strain distribution in the sheets (when subjected to a mechanical load), can be programmed. This work provides foundational material property and processing data for the design of additively manufactured LCE-based devices.
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