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The morphology of the fruit of stork's bill (Erodium gruinum). (a) Two complete stork's bill-shaped fruits, about 4 days prior to ripening. Arrows indicate the location of the seed; arrowheads indicate the awns. Dashed red line indicates the part from which cross section (b) was taken. (b) Erodium gruinum fruit in cross section depicts five awns (indicated by arrowheads) connected by a central column. (c) Dry awned seed showing the coiling region (arrowhead) close to the seed (arrow). Scale bar, (b) 1 mm.
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The sessile nature of plants demands the development of seed-dispersal mechanisms to establish new growing loci. Dispersal strategies of many species involve drying of the dispersal unit, which induces directed contraction and movement based on changing environmental humidity. The majority of researched hygroscopic dispersal mechanisms are based on...
Contexts in source publication
Context 1
... stork's bill fruit consists of five seeds equipped with long tapering appendages (awns) attached to a central column ( figure 1). The awns display hygro- scopic coiling movement during fruit drying. ...
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Citations
... Another typical plant tissue with shape changes from flat to helix is the stork's bill (Erodium gruinum). [16,53] It was found that the cellulose microfibrils in the cell wall structure are arranged in a unique tilted helix, where the cellulose helix axis is angled to the cell's long axis, resulting in a spiral configuration of the cell in dry state. Then, these cells generate a macroscopic coil by spiraling collectively, forming a helix Figure 2 Structural basis and simplified physical models for shape morphing of motile plant tissues. ...
... Then, these cells generate a macroscopic coil by spiraling collectively, forming a helix Figure 2 Structural basis and simplified physical models for shape morphing of motile plant tissues. From top to bottom: wheat awn, [23] vascular bundles of pine cone, [1] Selaginella lepidophylla, [27] dandelion pappus, [25] ice plant seed capsule, [21] Bauhinia pods, [13] and stork's bill awn [53]. Wheat awn, reproduced from Ref. [23] with permission, Copyright 2007, The American Association for the Advancement of Science. ...
... Bauhinia pod, reproduced from Ref. [13] with permission, Copyright 2011, The American Association for the Advancement of Science. Erodium gruinum, reproduced from Ref. [53] with permission, Copyright 2011, The Royal Society. ...
Natural plant tissues provide potential strategies for the speed regulation of biomimetic actuators, ranging from ultrafast to ultraslow. Feilong Zhang, ABSTRACT Motile plant tissues can control their configurations and regulate their motion speed according to their specific requirement s, which offer various protypes for biomimetic actuators with controlled motion speed. In this perspective, we focus on the speed control of plant tissues and the bioinspired strategies for speed regulation of artificial actuators. We begin with a summary to the strategies and mechanisms of motile plant tissues for controlling motion speed, ranging from ultrafast to ultraslow. We then exemplify the models for fabricating bioinspired artificial actuators and briefly discuss current application scenarios of actuators with varying speeds from ultrafast to ult raslow. Finally, we proposed potential strategies for the speed regulation of actuators.
... On the contrary, the walls of cells serving as an inactive layer are tightly bound by inextensible cellulose microfibrils. [7][8][9][10] Although the hygroscopic actuators in nature have served their functions for survival and reproduction over millions of years, 11,12 several issues remain to be solved before the biological principle can be translated to practical applications including soft robotics and energy harvesters. First, most of the botanical actuators rely on changes of humidity over a long timescale as days or even seasons. ...
Hygroscopic soft actuators offer an attractive means to convert environmental energy to mechanical motions as they use water vapor, a ubiquitous substance in the atmosphere. To overcome the limits of existing hygroactuators, such as simplistic actuation mode, slow response, and low efficiency, here we present three kinds of humidity-powered soft machines adopting directionally electrospun hygroresponsive nanofibrous sheets. The wheels, seesaws, and vehicles developed in this work utilize spatial humidity gradient naturally established near moist surfaces such as human skin, so that they operate spontaneously, realizing energy scavenging or harvesting. We also constructed a theoretical framework to mechanically analyze their dynamics, which allowed us to optimize their design to obtain the highest motion speed physically possible.
... Some other seeds also spread from the parent plant and can be buried for germination and survival. Their self-burial feature can be achieved by hygroscopic expansiveness awns (Abraham et al., 2012;Geer et al., 2020), drilling into the soil, twisting and untwisting with respect to changing in humidity, and modified hygroscopically powered helical shape. The rotational penetration movement caused by this cyclic ...
It has been found that certain biological organisms, such as Erodium seeds and Scincus scincus, are capable of effectively and efficiently burying themselves in soil. Biological Organisms employ various locomotion modes, including coiling and uncoiling motions, asymmetric body twisting, and undulating movements that generate motion waves. The coiling-uncoiling motion drives a seed awn to bury itself like a corkscrew, while sandfish skinks use undulatory swimming, which can be thought of as a 2D version of helical motion. Studying burrowing behavior aims to understand how animals navigate underground, whether in their natural burrows or underground habitats, and to implement this knowledge in solving geotechnical penetration problems. Underground horizontal burrowing is challenging due to overcoming the resistance of interaction forces of granular media to move forward. Inspired by the burrowing behavior of seed-awn and sandfish skink, a horizontal self-burrowing robot is developed. The robot is driven by two augers and stabilized by a fin structure. The robot's burrowing behavior is studied in a laboratory setting. It is found that rotation and propulsive motion along the axis of the auger's helical shape significantly reduce granular media's resistance against horizontal penetration by breaking kinematic symmetry or granular media boundary. Additional thrusting and dragging tests were performed to examine the propulsive and resistive forces and unify the observed burrowing behaviors. The tests revealed that the rotation of an auger not only reduces the resistive force and generates a propulsive force, which is influenced by the auger geometry, rotational speed, and direction. As a result, the burrowing behavior of the robot can be predicted using the geometry-rotation-force relations.
... Some other seeds also spread from the parent plant and can be buried for germination and survival. Their self-burial feature can be achieved by hygroscopic expansiveness awns (Abraham et al., 2012;Geer et al., 2020), drilling into the soil, twisting and untwisting with respect to changing in humidity, and modified hygroscopically powered helical shape. The rotational penetration movement caused by this cyclic ...
It has been found that certain biological organisms, such as Erodium seeds and Scincus scincus, are capable of effectively and efficiently burying themselves in soil. Biological Organisms employ various locomotion modes, including coiling and uncoiling motions, asymmetric body twisting, and undulating movements that generate motion waves. The coiling-uncoiling motion drives a seed awn to bury itself like a corkscrew, while sandfish skinks use undulatory swimming, which can be thought of as a 2D version of helical motion. Studying burrowing behavior aims to understand how animals navigate underground, whether in their natural burrows or underground habitats and to implement this knowledge in solving geotechnical penetration problems. Underground horizontal burrowing is challenging due to overcoming the resistance of interaction forces of granular media to move forward. Inspired by the burrowing behavior of seed-awn and sandfish skink, a horizontal self-burrowing robot is developed. The robot is driven by two augers and stabilized by a fin structure. The robot's burrowing behavior is studied in a laboratory setting. It is found that rotation and propulsive motion along the axis of the auger's helical shape significantly reduce granular media's resistance against horizontal penetration by breaking kinematic symmetry or granular media boundary. Additional thrusting and dragging tests were performed to examine the propulsive and resistive forces and unify the observed burrowing behaviors. The tests revealed that the rotation of an auger not only reduces the resistive force and generates a propulsive force, which is influenced by the auger geometry, rotational speed, and direction. As a result, the burrowing behavior of the robot can be predicted using the geometry-rotation-force relations.
... The gripper design needs to ensure appropriate grasping strength, enough to hold a sensing unit (≈ 5 g). To achieve maximum contact area with the tree branch, we opted to look at helical curling, found in nature [5], [30], [31]. Helical curling allows the gripper to maximize the contact area with large deformation and multiple turns. ...
... Nature utilizes the hygroscopic effect to induce shape changes in bi-layer structures. To do so, one layer is hygroscopically active and features volumetric swelling or shrinkage, while the other layer is hygroscopically inactive [30], [33]. Similarly, our gripper design also utilizes a multilayered structure as seen in Fig. 2a. ...
... Hygroscopic seeds of various natural grass species are known for their self-burial behaviours, in which the awns respond to variations in external humidity, causing the seed tip to self-bury [10][11][12][13][14]19 . These behaviours are advantageous, allowing seeds to avoid fire 20 , and reducing both exposure to high temperature 21 and sensitivity to precipitation. ...
... in which σ w is the stress in the wet state and described in equations (8) and (15) It is interesting to note that the non-uniform shrinkage strain only adds one constant term to the existing equations. The dry curvature can be solved from equation (13) as ...
Aerial seeding can quickly cover large and physically inaccessible areas¹ to improve soil quality and scavenge residual nitrogen in agriculture², and for postfire reforestation3–5 and wildland restoration6,7. However, it suffers from low germination rates, due to the direct exposure of unburied seeds to harsh sunlight, wind and granivorous birds, as well as undesirable air humidity and temperature1,8,9. Here, inspired by Erodium seeds10–14, we design and fabricate self-drilling seed carriers, turning wood veneer into highly stiff (about 4.9 GPa when dry, and about 1.3 GPa when wet) and hygromorphic bending or coiling actuators with an extremely large bending curvature (1,854 m⁻¹), 45 times larger than the values in the literature15–18. Our three-tailed carrier has an 80% drilling success rate on flat land after two triggering cycles, due to the beneficial resting angle (25°–30°) of its tail anchoring, whereas the natural Erodium seed’s success rate is 0%. Our carriers can carry payloads of various sizes and contents including biofertilizers and plant seeds as large as those of whitebark pine, which are about 11 mm in length and about 72 mg. We compare data from experiments and numerical simulation to elucidate the curvature transformation and actuation mechanisms to guide the design and optimization of the seed carriers. Our system will improve the effectiveness of aerial seeding to relieve agricultural and environmental stresses, and has potential applications in energy harvesting, soft robotics and sustainable buildings.
... When layers are combined that have variable cell wall architecture or cell orientation, and thus variable preferred directions of contraction, the dehydration of a tissue can lead to bending, twisting, or coiling [45]. Even dehydration of a specialized single homogeneous layer can induce coiling, as has been shown for Erodium awns [46]. As all these movements merely rely on humidity, they occur passively, i.e., without requiring metabolic energy. ...
Tendrils of climbing plants coil along their length and thus form a striking helical spring and generate tensional forces. We have found that, for tendrils of the passion flower Passiflora caerulea , the generated force lies in the range of 6-140 mN, which is sufficient to lash the plant tightly to its substrate. Further, we revealed that the generated force strongly correlates with the water status of the plant. By combining force measurements with anatomical investigations and dehydration-rehydration experiments on both entire tendril segments and isolated lignified tissues, we are able to propose a two-phasic principle of spring formation: First, during the free coiling phase, the tendril coiling is based on the active contraction of a fiber ribbon in interaction with the surrounding parenchyma as resistance layer. Second, in a stabilization phase, the entire center of the coiled tendril lignifies, stiffening the spring and securing its function independent of hydration status.
... Stimuli-responsive deformation is an important seed dispersal strategy for many natural organisms [1][2][3][4][5][6] , and clarifying the underlying mechanisms has become increasingly non-trivial for designing stimuli-responsive materials [7][8][9][10][11][12][13][14] . The pine cone, a typical natural organism with hygroscopic deformation character, has gained a good reputation as a bionic model for constructing artificial actuators [15][16][17][18][19][20] . ...
The hygroscopic deformation of pine cones, featured by opening and closing their scales depending on the environmental humidity, is a well-known stimuli-responsive model system for artificial actuators. However, it has not been noted that the deformation of pine cones is an ultra-slow process. Here, we reveal that vascular bundles with unique parallelly arranged spring/square microtubular heterostructures dominate the hygroscopic movement, characterized as ultra-slow motion with the outer sclereids. The spring microtubes give a much larger hygroscopic deformation than that of the square microtubes along the longitudinal axis direction, which bends the vascular bundles and consequently drives the scales to move. The outer sclereids with good water retention enable the vascular-bundle-triggered deformation to proceed ultra-slowly. Drawing inspiration, we developed soft actuators enabling controllable yet unperceivable motion. The motion velocity is almost two orders of magnitude lower than that of the same-class actuators reported, which made the as-developed soft actuators applicable in camouflage and reconnaissance.
... 5 Erodium tail have been a source of inspiration for the design of novel soft pneumatic actuators [47]. Exploring the material characteristics, Abraham et al. (2012) [40] have reproduced the induced spiraling mechanism in a simplified physical model made from a thread embedded in an isotropic foam matrix. ...
Envisioning a rethink of the design of robotic systems is necessary for a step-change in developing more sustainable and efficient artificial machines. Recent trends in robotics have embraced the idea of taking inspiration from plants to create energy-efficient components, self-morphing growing robots, biodegradable robots, and the definition of novel models of embodied intelligence and morphological computation. Plants can move and grow in air, soil, and water. They can sense and explore the surrounding environment, continuously grow and adapt their shape, and even communicate with each other and with other organisms. Their role for us and our planet is fundamental: for the oxygen we breathe, the food we eat, and to preserve the equilibrium of biodiversity and global climate. Understanding their functioning is of paramount importance and represents an opportunity not only for scientific advancements but also for rethinking the design of artificial technologies that can better integrate with our ecosystems. With a specific focus on the aspects of plants’ embodied intelligence, this contribution highlights some of the features of plants that have been investigated for engineering design and introduces new research lines currently at the forefront of the field. A perspective for innovation in science and robotics inspired by plants is also discussed, with a vision toward a new generation of sustainable robots.
... The comparative analyses of reaction time and movement duration of stalked glands in different temperature regimes (Figure 4) revealed that the movement is indeed strongly dependent on physiological processes. From this result, a purely physical actuation scenario similar to the coiling of stork's bill (Erodium) awns [32] can be excluded with certainty. ...
Carnivorous rainbow plants (Byblis, Byblidaceae, Lamiales) possess sticky flypaper traps for the capture, retention, and digestion of prey (mainly small insects). The trapping system is based on a multitude of millimeter-sized glandular trichomes (also termed stalked glands), which produce adhesive glue drops. For over a century, the trapping system of Byblis was considered passive, meaning that no plant movement is involved. Recently, a remarkable discovery was made: the stalked glands of Byblis are indeed capable of reacting to chemical (protein) stimuli with slow movement responses. This prompted us to investigate this phenomenon further with a series of experiments on the stimulation, kinematics, actuation, and functional morphology of the stalked glands of cultivated Byblis gigantea plants. Measured stalked gland lengths and densities on the trap leaves are similar to the data from the literature. Motion reactions could only be triggered with chemical stimuli, corroborating the prior study on the stalked gland sensitivity. Reaction time (i.e., time from stimulation until the onset of motion) and movement duration are temperature-dependent, which hints towards a tight physiological control of the involved processes. The stalked gland movement, which consist of a sequence of twisting and kinking motions, is rendered possible by the components of the stalk cell wall and is furthermore anatomically and mechanically predetermined by the orientation of cellulose microfibrils in the cell wall. Successive water displacement processes from the stalk cell into the basal cells actuate the movement. The same kinematics could be observed in stalked glands drying in air or submersed in a saturated salt solution. Stimulated and dried stalked glands as well as those from the hypertonic medium were capable of regaining their initial shape by rehydration in water. However, no glue production could be observed afterwards. The long-time overlooked chemonastic movements of stalked glands may help Byblis to retain and digest its prey; however, further research is needed to shed light on the ecological characteristics of the rainbow plant’s trapping system.
