Morphing Behavior Research Articles

Manufacturing of electroactive morphing carbon fiber/glass fiber/epoxy composite: Process and structural monitoring by FBG sensors

The aim of this paper is to design and develop a new class of electroactive carbon fiber/glass fiber/epoxy hybrid morphing composite with ability to change its shape in response to external stimuli. Morphing composites are of a great interest for aerodynamic structures to minimize the energy consumption and control the overall system performance. The hybrid asymmetric carbon fiber/glass fiber/epoxy morphing composite developed in this study provides a fine morphing controllability compared to classical morphing and bistable composites. In the conventional morphing structures, morphing ability is bestowed by only directionality of fibers from the same material. Herein, the morphing behavior stems from a mismatch in the coefficient of thermal expansion (CTE) between carbon and glass fibers. Fiber Bragg grating (FBG) sensors are used to monitor the manufacturing process of composites and to shed light on the physics behind the morphing behavior. Direct thermal loads are applied to the composite structure by using a temperature-controlled oven, hence manipulating its shape and in turn studying its morphing performance. Moreover, benefiting from electrical conductivity of carbon fiber reinforcement, the composite structures are provided with self-heating functionality based on Joule heating, which is used as an external stimulus for adjusting the shape of the composite structure.

Development and Testing of a Shape Memory Alloy-Driven Composite Morphing Radiator

Future crewed deep space missions will require thermal control systems that can accommodate larger fluctuations in temperature and heat rejection loads than current designs. To maintain the crew cabin at habitable temperatures throughout the entire mission profile, radiators will be required to exhibit turndown ratios (defined as the ratio between the maximum and minimum heat rejection rates) as high as 12:1. Potential solutions to increase radiator turndown ratios include designs that vary the heat rejection rate by changing shape, hence changing the rate of radiation to space. Shape memory alloys exhibit thermally driven phase transformations and thus can be used for both the control and actuation of such a morphing radiator with a single active structural component that transduces thermal energy into motion. This work focuses on designing a high-performance composite radiator panel and investigating the behavior of various SMA actuators in this application. Three designs were fabricated and subsequently tested in a relevant thermal vacuum environment; all three exhibited repeatable morphing behavior, and it is shown through validated computational analysis that the morphing radiator concept can achieve a turndown ratio of 27:1 with a number of simple configuration changes.

Quantum delayed-choice experiment with a single neutral atom.

We present a proposal to implement a quantum delayed-choice (QDC) experiment with a single neutral atom, such as a rubidium or cesium atom. In our proposal, a Ramsey interferometer is adopted to observe the wave-like or particle-like behaviors of a single atom depending on the existence or absence of the second π/2-rotation. A quantum-controlled π/2-rotation on target atom is realized through a Rydberg-Rydberg interaction by another ancilla atom. It shows that a heavy neutral atom can also have a morphing behavior between the particle and the wave. The realization of the QDC experiment with such heavy neutral atoms not only is significant to understand the Bohr's complementarity principle in matter-wave and matter-particle domains but also has great potential on the quantum information process with neutral atoms.

Bifurcation of self-folded polygonal bilayers

Motivated by the self-assembly of natural systems, researchers have investigated the stimulus-responsive curving of thin-shell structures, which is also known as self-folding. Self-folding strategies not only offer possibilities to realize complicated shapes but also promise actuation at small length scales. Biaxial mismatch strain driven self-folding bilayers demonstrate bifurcation of equilibrium shapes (from quasi-axisymmetric doubly curved to approximately singly curved) during their stimulus-responsive morphing behavior. Being a structurally instable, bifurcation could be used to tune the self-folding behavior, and hence, a detailed understanding of this phenomenon is appealing from both fundamental and practical perspectives. In this work, we investigated the bifurcation behavior of self-folding bilayer polygons. For the mechanistic understanding, we developed finite element models of planar bilayers (consisting of a stimulus-responsive and a passive layer of material) that transform into 3D curved configurations. Our experiments with cross-linked Polydimethylsiloxane samples that change shapes in organic solvents confirmed our model predictions. Finally, we explored a design scheme to generate gripper-like architectures by avoiding the bifurcation of stimulus-responsive bilayers. Our research contributes to the broad field of self-assembly as the findings could motivate functional devices across multiple disciplines such as robotics, artificial muscles, therapeutic cargos, and reconfigurable biomedical devices.

Morph specific foraging behavior by a polymorphic raptor under variable light conditions

Colour polymorphism may be maintained within a population by disruptive-selection. One hypothesis proposes that different morphs are adapted to different ambient light conditions, with lighter morphs having a selective advantage in bright conditions and darker morphs having advantages in darker conditions. The mechanism for this advantage is proposed to be through enhanced crypsis via background-matching. We explore this hypothesis in a polymorphic raptor, the black sparrowhawk Accipiter melanoleucus, which exhibits a discrete dark and white-morph. We use GPS-tracking data to contrast the foraging behaviour and habitat selection of morphs. As predicted, we found that light-levels influenced foraging behaviour in different ways for morphs: Dark-morphs showed a decrease in foraging with increasing light-levels; whereas no relationship was found for white-morphs. Furthermore, we found differential-degrees of habitat selection, with dark-morphs selecting more enclosed habitats compared to white-morphs. This suggests that different morphs may be better adapted to foraging under different light-conditions, potentially playing a role in maintaining colour polymorphism in this species. Our results may also help explain why dark-morphs predominate in this study region, which experiences high rainfall and lower light-levels during the breeding-period. This study suggests that avian morphs may allocate/partition foraging activity by weather conditions/habitat, which maximise their concealment from prey.

Thermally Driven Morphing and Snap-Through Behavior of Hybrid Laminate Shells

Analytical and experimental results are presented regarding the nonlinear temperature-curvature relationship displayed by composite bimorph shells. Snap-through action, driven solely by temperature change, is demonstrated using fiber–metal hybrid laminates. These laminates exploit the high coefficient of thermal expansion mismatch between composites and metals to yield thermal bimorphs with tailorable properties. To predict the potentially nonlinear response of these laminates, an energy-based multistability model is developed and made available online. The model utilizes experimentally measured one-dimensional thermally induced curvatures as input parameters to predict a corresponding shell’s two-dimensional flexural behavior. Initial curvature is found to be a critical component in enabling snap-through behavior, especially when partnered with highly orthotropic internal moments. Interestingly, the class of unsymmetric laminates popular in the study of thermally induced bistability are shown to be inherently incapable of displaying thermally driven snap-through behavior, regardless of initial curvature. Modeling results compare well with experiments for a square-planform hybrid laminate. The potential impact of this work is the realization of passively controlled, variable geometry structures that can be triggered to change shape at certain temperatures or within specified temperature ranges. Applications include flow and cooling control of gas turbine engines, spacecraft passive thermal control systems, and bimorph-based micro-electromechanical systems.

Delayed-choice quantum control of light-matter interaction

Superposition is the fundamental signature of quantum behavior. A quantum system can exist in a superposition of different eigenstates of an observable. Only after the measurement process, the system will collapse on one of the eigenvalues of the measured observables. We propose the realisation of the counterintuitive superposition of On and Off strong light-matter interaction using an optical resonator and a generic three-level quantum system. Leaked cavity photons can be detected and collected in order to post-select the events and to choose if we want to observe interacting or non-interacting photons. Such proposal can be readily realised within the present technology. Finally we will show that the cavity field can have a morphing behavior between On and Off interaction, by changing the area of the control pulse.

Proposal for a Quantum Delayed-Choice Experiment

Gedanken experiments help to reconcile our classical intuition with quantum mechanics and nowadays are routinely performed in the laboratory. An important open question is the quantum behavior of the controlling devices in such experiments. We propose a framework to analyze quantum-controlled experiments and illustrate it by discussing a quantum version of Wheeler's delayed-choice experiment. Using a quantum control has several consequences. First, it enables us to measure complementary phenomena with a single experimental setup, pointing to a redefinition of complementarity principle. Second, it allows us to prove there are no consistent hidden-variable theories having "particle" and "wave" as realistic properties. Finally, it shows that a photon can have a morphing behavior between particle and wave. The framework can be extended to other experiments (e.g., Bell inequality).

Unexpected absence of behavioural differences between female damselfly colour morphs

Males are often selected for higher mating rates than females. As a consequence of this sexual conflict, unreceptive females may suffer fitness costs from excessive male sexual harassment. In a variety of vertebrate and invertebrate species, multiple female morphs coexist in natural populations which have been observed to differ in body colour, in behaviour and also in the amount of male harassment received. However, the degree of harassment on a female morph may depend on the frequency and density of males and female morphs in the population. We quantified harassment rate and subsequent refusal behaviour of males and female morphs of the polymorphic damselfly Nehalennia irene. Unexpectedly and contrary to previous work, female morphs received similar amounts of male harassment and showed mostly the same behaviour. We discuss why differences in morph behaviours may be lacking and how this compares to contemporary explanations for the maintenance and evolution of female-limited polymorphisms.

Proclivity and effectiveness in gall defence by soldiers in five species of gall-inducing thrips: benefits of morphological caste dimorphism in two species (Kladothrips intermedius and K. habrus)

The essence of eusociality is a trade-off between producing one’s own offspring and helping collateral kin via such activities as defence, foraging and brood rearing. This trade-off often involves morphological differences between “helper” and “reproductive” castes, but the advantages, correlates and phylogenetic context of morphological caste differentiation have seldom been analysed. Six species of Australian gall-inducing thrips on Acacia show morphological polymorphism. One morph, referred to as a soldier, has reduced wings and antennae but greatly enlarged fore-femora, which are thought to be adaptations for gall defence. The other, dispersing morph, has fully developed wings and relatively slight fore-femora. Here, we quantify the defensive behaviour of soldier morphs, and compare soldier and foundresses, using behavioural assays designed to measure proclivity to attack kleptoparasites (specialised invaders in the genus Koptothrips) and effectiveness in killing them. In all five species investigated, soldiers were able to kill Koptothrips. Moreover, the effectiveness of soldiers was relatively high in the more-derived species in the phylogeny of the clade, Kladothrips intermedius, K. habrus and K. waterhousei. Soldiers of K. intermedius and K. habrus also killed kleptoparasites more effectively than did foundresses, and K. habrus soldiers exhibited higher proclivity to attack than did foundresses. Data from naturally invaded galls demonstrate that soldiers in the field do kill Koptothrips, and vice versa. These results show that soldiers of Australian gall thrips are motivated and effective for gall defence.

Variation in propensity to defend by reproductive gall morphs in two species of gall-forming thrips

Six species of Australian phleaothripine gall forming thrips on Acacia have two morphs. One morph, referred to as a soldier, has reduced antennae and wings and greatly enlarged fore femora, which are thought to be adaptations for gall defence. For most species, female soldier morphs have reduced reproductive output relative to dispersing females and these species have been regarded as eusocial. We examine defensive behaviour of soldier morphs using in situ presentation of gall invading kleptoparasites. We show that the gall-morph of Oncothrips tepperi attack kleptoparasites more often (N=87 interactions, n = 11 attacks) than does the gall-morph of Oncothrips morrisi (N = 231, n = 1). This difference in proclivity for defence is coincident with a lower reproductive output by the gall-morph in O. tepperi compared to O. morrisi. Our results also show an almost complete absence of attack behaviour by the gal l-morph of O. morrisi. Lastly, we show that there is no difference in proclivity for defence between soldier and foundress morphs of O. tepperi. These observations taken together call into question the suitability of the term 'soldier' as applied to the gall-morph of the gall-forming thrips of Australia.

Difference in habitat selection by different morphs of the land snail Arianta arbustorum

The behaviour of morphs of Arianta arbustorum has been investigated using a new technique involving a paint which fades in daylight. The technique was used to study the response of different morphs to exposure to sunlight at a homogeneous woodland habitat and a heterogeneous open habitat. The yellow morph showed a significantly higher rate of fading than the brown morph. A mark, release and recapture programme was used to analyse the association between frequencies of different morphs recaptured and not recaptured. In both habitats, there was a general tendency for the frequency of recapture to increase with increasing age in both morphs. Habitat selection resulting from different behaviour of different morphs of A. arbustorum is discussed. Morph frequencies can be related to habitat, the brown morphs of A. arbustorum are significantly less frequent in the open habitat. The behavioural responses of Cepaea hortensis, present with A. arbustorum in two other populations, to the exposure of sunshine were also studied. Climatic selection by solar energy associated with different morphs, species and habitat are also discussed.

An experimental investigation of the behaviour and mortality of artificial and natural morphs of Cepaea nemoralis (L.)

Two population cage experiments which examined the mortality and behaviour of artificial and natural morphs of the landsnail C. nemoralis (L.) are described. In the first experiment artificial ‘morphs’ were manufactured from one genetically homogeneous founder group of snails by painting the shells black or white. Differences in behaviour and mortality between these two ‘morphs’ were observed during the course of the experiment. Daylight and weather conditions were important in determining the activity patterns of the two types of snail. In the second experiment naturally occurring brown and yellow colour morphs were used. These exhibited very similar behaviour patterns to those of their artificial ‘mimics’ and it is concluded that phenotype must play an important role in determining the behavioural responses of the snails to their environment. Thermal relationships are suggested as causal factors for the differences between the experimental morphs.