Energy harvesting techniques can exploit even subtle passive motion like that of plant leaves in wind as a consequence of contact electrification of the leaf surface. The effect is strongly enhanced by artificial materials installed as 'artificial leaves' on the natural leaves creating a recurring mechanical contact and separation. However, this requires a controlled mechanical interaction between the biological and the artificial component during the complex wind motion. Here, we build and test four artificial leaf designs with varying flexibility and degrees of freedom across the blade operating onNerium oleanderplants. We evaluate the apparent contact area (up to 10 cm2per leaf), the leaves' motion, together with the generated voltage, current and charge in low wind speeds of up to 3.3 m s-1and less. Single artificial leaves produced over 75 V and 1µA current peaks. Softer artificial leaves increase the contact area accessible for energy conversion, but a balance between softer and stiffer elements in the artificial blade is optimal to increase the frequency of contact-separation motion (here up to 10 Hz) for energy conversion also below 3.3 m s-1. Moreover, we tested how multiple leaves operating collectively during continuous wind energy harvesting over several days achieve a root mean square power of ∼6µW and are capable to transfer ∼80µC every 30-40 min to power a wireless temperature and humidity sensor autonomously and recurrently. The results experimentally reveal design strategies for energy harvesters providing autonomous micro power sources in plant ecosystems for example for sensing in precision agriculture and remote environmental monitoring.

A key challenge in designing soft continuum robotic arms is the realization of intelligent behavior while minimizing sensing, actuation, and control effort. This work investigates how soft continuum arms can benefit from mimicking the distribution of flexural rigidity of searcher stems in climbing plants to accomplish this goal. A modeling approach is presented to tune both the structural design and the tactile sensor design of a soft continuum arm inspired by the flexural rigidity distribution of Mandevilla cf. splendens’ searcher stems. The resulting soft continuum arm, named Mandy , can detect suitable supports along its length and twining around them using a single sensor and actuator. Through simulations and experiments, it is shown such behavior cannot be achieved with a soft continuum arm possessing uniform structural stiffness and a standard tactile sensor design. Thus, the significance of investing greater effort in structural design, leveraging biological data, to improve the design of soft continuum arms with more compact actuation and sensing hardware, is highlighted.

New devices inspired by flying seeds, or more technically by fruits with dispersal units, could have a significant impact for environmental monitoring and aerial seeding. Among the various types of dispersal units (e.g., winged, gliding), parachuted or plumed units offer the lowest vertical descent speed (i.e., 0.3-0.7 m s(-1)), making them an appealing solution for wind-driven distribution over large areas. Here, a biodegradable and porous parachute flier based on cellulose acetate, inspired by a Tragopogon pratensis fruit is presented. A micrometric-thick pappus is 3D printed and integrated with a porous colorimetric indicator or a porous beak, with micrometric pores, fabricated through injection molding and leaching techniques. Thanks to the bioinspired design and the lightweight porous structure, the artificial Tragopogon mimics the aerodynamics and descent speed of the natural species. Its feasibility is demonstrated in aerial seeding by integrating the beak with a mustard seed (as a model), and in environmental monitoring by coupling it with colorimetric indicators for rain pH and nitrate levels in soils. The proposed flier represents a significant advancement as it is the first parachute-like biodegradable solution, seamlessly integrated into natural ecosystems, thus contributing to moving a step forward in artificial solutions with zero impact.

Annulus cells of fern sporangia spontaneously deform driven by water transpiration and cavitation, resulting in the peculiar macroscale catapult-like movement of the sporangium. Annulus cells' behavior, if artificially replicated, can inspire a novel class of fast actuators composed of annulus-mimicking units. However, the transpiration and cavitation-driven dynamics observed in annulus cells is never reproduced. Here, prismatic microcavities are assembled with a polydimethylsiloxane (PDMS) microfilm to realize artificial microchambers that mimic the annulus cells, replicating for the first time their evaporation-driven collapse and their fast return triggered by the nucleation of bubbles. The microchambers, in turn, can be fabricated in adjacency, resulting in bending arrays driven by transpiration. Working with an artificial system allows this study to investigate the fluidic phenomena arising from the interplay of a soft, semi-permeable membrane with a micro-confined liquid bounded by rigid walls. First, the microchambers aspect ratio influences the membrane dynamics and the bubble shape (either spherical or non-spherical). Second, the growth rate of the bubble interplay with the membrane in the expansion dynamics. This study's results demonstrate the artificial replication of annulus cells' behavior, offering a plant-like solution to realize fast, microscale movements, and a novel tool to investigate complex fluidic mechanisms involving micro-confined cavitation.

In the framework of GrowBot project, Task 5.4 aims at developing a robotic searcher with sensing and actuation abilities.IIT has developed a modular continuum soft arm taking inspiration from the structural features of climbing plants investigated in WP3. The searcher module can explore the environment via circumnutation movements and tactile feedback. DS7 aims at collecting all the data related to the design and development of the soft searcher robot.

Biomimetic machines able to integrate with natural and social environments will find ubiquitous applications, from biodiversity conservation to elderly daily care. Although artificial actuators have reached the contraction performances of muscles, the versatility and grace of the movements realized by the complex arrangements of muscles remain largely unmatched. Here, we present a class of pneumatic artificial muscles, named GeometRy-based Actuators that Contract and Elongate (GRACE). The GRACEs consist of a single-material pleated membrane and do not need any strain-limiting elements. They can contract and extend by design, as described by a mathematical model, and can be realized at different dimensional scales and with different materials and mechanical performances, enabling a wide range of lifelike movements. The GRACEs can be fabricated through low-cost additive manufacturing and even built directly within functional devices, such as a pneumatic artificial hand that is fully three-dimensionally printed in one step. This makes the prototyping and fabrication of pneumatic artificial muscle-based devices faster and more straightforward.

This paper presents the results obtained during an experimental campaign on blast resistant wheels designed for a low-cost demining machine, derived from an agricultural tractor. Such wheels must fulfil two requirements: first, they have to be able to retain their mechanical integrity in case of blast and still work after one or more explosions, in order to be able to drive the machine out of the minefield without human intervention; second, they must reduce as much as possible the amount of energy transferred to the vehicle, to protect the on-board equipment from the effect of the detonation of a landmine. One of the goals of the experimental activity was to compare two wheels characterized by different designs. Mechanical performance and capacity of the wheels to reduce the energy transferred to the vehicle have been assessed to verify whether the wheels were suitable for the task and to identify which wheel performs best. Physical integrity of both wheels was assessed by visual inspection after each explosion. To evaluate the energy transferred to the vehicle, a measurement of the potential energy transferred, by means of a ballistic pendulum, equipped with an encoder, was performed together with a triaxial acceleration measurement in correspondence of the wheel hub. The triaxial accelerometer measurement was then also used to assess the behaviour of the wheels mounted on the vehicle after tests on the ballistic pendulum. Wheel performances have been quantified using specific features and frequency domain functions, related to the damage induced by the vibration at the interface between the hub and the demining machine. The obtained results suggest that the heaviest wheel performs better both in terms of mechanical integrity and of shock response.

High-tech sensors, energy harvesters, and robots are increasingly being developed for operation on plant leaves. This introduces an extra load which the leaf must withstand, often under further dynamic forces like wind. Here, we took the example of mechanical energy harvesters that consist of flat artificial "leaves" fixed on the petioles of N. oleander, converting wind energy into electricity. We developed a combined experimental and computational approach to describe the static and dynamic mechanics of the natural and artificial leaves individually and join them together in the typical energy harvesting configuration. The model, in which the leaves are torsional springs with flexible petioles and rigid lamina deforming under the effect of gravity and wind, enables us to design the artificial device in terms of weight, flexibility, and dimensions based on the mechanical properties of the plant leaf. Moreover, it predicts the dynamic motions of the leaf-artificial leaf combination, causing the mechanical-to-electrical energy conversion at a given wind speed. The computational results were validated in dynamic experiments measuring the electrical output of the plant-hybrid energy harvester. Our approach enables us to design the artificial structure for damage-safe operation on leaves (avoiding overloading caused by the interaction between leaves and/or by the wind) and suggests how to improve the combined leaf oscillations affecting the energy harvesting performance. We furthermore discuss how the mathematical model could be extended in future works. In summary, this is a first approach to improve the adaptation of artificial devices to plants, advance their performance, and to counteract damage by mathematical modelling in the device design phase.

Plants translate wind energy into leaf fluttering and branch motion by reversible tissue deformation. Simultaneously, the outermost structure of the plant, i.e. the dielectric cuticula, and the inner ion-conductive tissue can be used to convert mechanical vibration energy, such as that produced during fluttering in the wind, into electricity by surface contact electrification and electrostatic induction. Constraining a tailored artificial leaf to a plant leaf can enhance oscillations and transient mechanical contacts and thereby increase the electricity outcome. We have studied the effects of wind-induced mechanical interactions between the leaf of a plant (Rhododendron) and a flexible silicone elastomer-based artificial leaf fixed at the petiole on power output and whether performance can be further tuned by altering the vibrational behavior of the artificial leaf. The latter is achieved by modifying a concentrated mass at the tip of the artificial leaf and observing plant-generated current and voltage signals under air flow. In this configuration, the plant-hybrid wind-energy converters can directly power light-emitting diodes and a temperature sensor. Detailed output analysis has revealed that, under all conditions, an increase in wind speed leads to nearly linearly increased voltages and currents. Accordingly, the cumulative sum energy reaches its highest values at the highest wind speed and resulting oscillations of the plant-artificial leaf system. The mass at the tip can, in most cases, be used to increase the voltage amplitude and frequency. Nevertheless, this behavior was found to depend on the individual configuration of the system, such as the leaf morphology. Analysis of these factors under controlled conditions is crucial for optimizing systems meant to operate in unstructured outdoor scenarios. We have established, in a first approach, that the artificial leaf-plant hybrid generator is capable of autonomously generating electricity outdoors under real outdoor wind conditions, even at a low average wind speed of only 1.9 m s−1.

In article number 2003380, Isabella Fiorello, Barbara Mazzolai, and co-workers develop innovative climbing plant-inspired flexible micro-patterned devices for reversible attachment using a two-photon lithography system. The microfabricated devices demonstrate strong interlocking over a wide range of rough surfaces, such as abrasive materials, fabrics with different textures, and soft skin tissues. Furthermore, the high shear-dependent microfabricated devices show great potential for climbing robot applications, especially in soft- and micro-robotics.

Climbing plants have evolved over millions of years and have adapted to unpredictable scenarios in unique ways. These crucial features make plants an outstanding biological model for scientists and engineers. Inspired by the ratchet‐like attachment mechanism of the hook‐climber Galium aparine , a novel micropatterned flexible mechanical interlocker is fabricated using a 3D direct laser lithography technique. The artificial hooks are designed based on a morphometric analysis of natural hooks. They are characterized in terms of pull‐off and shear forces, both in an array and as individual hooks. The microprinted hooks array shows high values of pull‐off forces (up to F ⊥ ≈ 0.4 N cm −2 ) and shear forces (up to F // ≈ 13.8 N cm −2 ) on several rough surfaces (i.e., abrasive materials, fabrics, and artificial skin tissues). The contact separation forces of individual artificial hooks are estimated when loads with different orientations are applied (up to F ≈ 0.26 N). In addition, a patterned tape with directional microhooks is integrated into a mobile platform to demonstrate its climbing ability on inclined surfaces of up to 45°. This research opens up new opportunities for prototyping the next generation of mechanical interlockers, particularly for soft‐ and microrobotics, the textile industry, and biomedical fields.

Biohybrid approaches harnessing living systems and biological tissue to accumulate electrical energy have potential to contribute green and autonomous power sources. We recently discovered that the cuticle-cellular tissue bilayer in higher plant leaves functions as an integrated triboelectric generator that is capable of converting mechanical stimuli into electricity. In this manner, living plants can be used to transduce mechanical energy such as wind energy into electricity. Here, we report on two essential components of the plant-biohybrid energy harvesting prototypes studied in Ficus microcarpa and Rhododendron yakushimanum, which are 1) the electrodes at the plant tissue that are used to harvest the electrical signals and 2) the wind-induced mechanical interactions between plants and an artificial leaf based on a silicone rubber/indium tin oxide/polyethylene terephthalate multilayer that is installed at the plant’s leaf to enhance the power output. We show moreover that in the same manner a Nerium oleander plant can directly power 50 LEDs and a digital thermometer under wind excitation. The results reveal design strategies for biohybrid energy harvesters on the basis of living plants that could become autonomous energy sources for sensor networks and environmental monitoring.

Exploring complex, unstructured environments requires a large set of information acquired by several sensors. Besides, a high level control is necessary to transfer and elaborate the whole data. Taking inspiration from plants, we aim at developing a system that is able to explore its surrounding environment paying a very low cost in terms of computation and data processing. Here, we demonstrate how a soft manipulator can identify the presence of an obstacle, or of a supporting structure, by means of a single sensor used together with a simplified mathematical model. The model can compute the configuration of the system only if no other forces other than the actuation are applied on it, while the sensor readings alone are not sufficient to infer the configuration. Exploiting the limitation of the model, an occurring mismatch between the expected position (computed by the model) and the measured one (by the sensor) provide sufficient information to identify the contact with a possible supporting structure. We validated the proposed methods in different scenarios in which we considered free motion without any obstacles, and in the presence of possible supports and impassable structures. To avoid false detection, we also considered the frequency of the discrepancy. In all the test cases the result is promising and this can pave the way toward a simplified approach for plant-inspired, non-vision-based navigation for soft devices.

Advanced MaterialsVolume 31, Issue 51 1970358 Cover PictureFree Access Actuators: Remotely Light-Powered Soft Fluidic Actuators Based on Plasmonic-Driven Phase Transitions in Elastic Constraint (Adv. Mater. 51/2019) Fabian Meder, Fabian Meder Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this authorGiovanna Adele Naselli, Giovanna Adele Naselli Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this authorAli Sadeghi, Ali Sadeghi Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this authorBarbara Mazzolai, Barbara Mazzolai Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this author Fabian Meder, Fabian Meder Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this authorGiovanna Adele Naselli, Giovanna Adele Naselli Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this authorAli Sadeghi, Ali Sadeghi Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this authorBarbara Mazzolai, Barbara Mazzolai Istituto Italiano di Tecnologia, Center for Micro-BioRobotics, Viale Rinaldo Piaggio 34, Pontedera, 56025 Pisa, ItalySearch for more papers by this author First published: 17 December 2019 https://doi.org/10.1002/adma.201970358AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract In article number 1905671, Fabian Meder, Ali Sadeghi, Barbara Mazzolai, and Giovanna Adele Naselli describe a light-driven soft pump that is based on a phase-transition-induced pressure generation of plasmonic nanoparticles constrained in an elastomer. The mechanism combines light-powering with fluidic actuation for soft actuators in microfluidics and soft robotics. Volume31, Issue51December 20, 20191970358 RelatedInformation

Modeling soft robots is not an easy task owing to their highly nonlinear mechanical behavior. So far, several researchers have tackled the problem using different approaches, each having advantages and drawbacks in terms of accuracy, ease of implementation, and computational burden. The soft robotics community is currently working to develop a unified framework for modeling. Our contribution in this direction consists of a novel dimensionless quantity that we call the softness distribution index (SDI). The SDI for a given soft body is computed based on the distribution of its structural properties. We show that the index can serve as a tool in the choice of a modeling technique among multiple approaches suggested in literature. At the moment, the investigation is limited to bodies performing planar bending. The aim of this work is twofold: (i) to highlight the importance of the distribution of the geometrical and material properties of a soft robotic link/body throughout its structure; and (ii) to demonstrate that a classification based on this distribution provides guidelines for the modeling.

Moving in complex and unstructured environments is still an open challenge in the robotic community. However, if we look at the plant kingdom, it is possible to find different promising solutions to overcome the problem. The continuum structure of the climbing plants allows to efficiently move in different environment by adapting and exploiting the surroundings. Similar to climbing plants, continuum robots proved to be very versatile. Their structure allows them to be inherently compliant, and to move in complex environments. However, due to their complex mechanical structure, and to their application as manipulators or inspections tools, the strategies to control such robots are not straightforward. In this work, we propose and prove a novel approach for identifying the location of a possible supporting structure for a continuum arm inspired by vines. Differently from the common approaches, our solution uses a simplified control strategy and an array of sensors for the detection of only the occurrence of contact. The position of the contact point is computed by means of a kinematic model of the manipulator. Results are still preliminary but encouraging for the development of novel strategies for adaptive exploration. The work serves as a basis for the development of a vine-inspired robot able to coil around supporting structures.

Materials capable of actuation through remote stimuli are crucial for untethering soft robotic systems from hardware for powering and control. Fluidic actuation is one of the most applied and versatile actuation strategies in soft robotics. Here, the first macroscale soft fluidic actuator is derived that operates remotely powered and controlled by light through a plasmonically induced phase transition in an elastomeric constraint. A multiphase assembly of a liquid layer of concentrated gold nanoparticles in a silicone or styrene-ethylene-butylene-styrene elastic pocket forms the actuator. Upon laser excitation, the nanoparticles convert light of specific wavelength into heat and initiate a liquid-to-gas phase transition. The related pressure increase inflates the elastomers in response to laser wavelength, intensity, direction, and on-off pulses. During laser-off periods, heating halts and condensation of the gas phase renders the actuation reversible. The versatile multiphase materials actuate-like soft "steam engines"-a variety of soft robotic structures (soft valve, pnue-net structure, crawling robot, pump) and are capable of operating in different environments (air, water, biological tissue) in a single configuration. Tailored toward the near-infrared window of biological tissue, the structures actuate also through animal tissue for potential medical soft robotic applications.

Imitating natural living beings remains a perpetual curiosity of human beings. The pursuit of replicating biological systems led humans to develop contemporary machines—the robots with diverse range of shapes, sizes, capabilities and applications. Such systems may exhibit strength, control and operation sustainability; however, rigidness of the hard underlying mechanical structures is one of the major constraints in achieving compliance like that of natural organisms and species. This constraint is required to be softened to create biological duos with enhanced structural compliance. This demarcation has led to a new corridor to craft biological mockups, and has made doors opened to exploit new materials, novel design methodologies and innovative control techniques. This paper is an exclusive appraisal to bio-inspired state-of-the-art developments conferring their design specific importance. The methodical study and survey of corresponding structural designs, actuation techniques, sensors, and materials is potentially useful to demonstrate the novelty of bio-inspired robotic developments. Keywords: Soft robotics, bio-inspiration, novelty, flexibility, softness and compliance.

. Innovation is considered as key to ensure continuous advancement and firm progress in any field. Robotics, with no exception, has gained triumph and approval based on its strength to address divers range of applications as well as its capacity to adapt new ways and means to enhance its applicability. The core of novelty in robotics technology is the perpetual curiosity of human beings to imitate natural systems. This desire urges to continuously explore and find new feet. In the past, contemporary machines, in different shapes, sizes and capabilities, were developed that can perform variety of tasks. The major advantage of these developments was the ability to exhibit superior control, strength and repeatability than the corresponding systems they were replicating. However, these systems were rigid and composed of hard an underlying structure, which is a constraint in bringing into being the compliance that exists in natural organisms. Inspiration of achieving such compliance and to take the full advantage of the design scheme of biological systems compelled researchers and scientists to develop systems avoiding conventional rigid structures. This ambition, to produce biological duos, needs soft and more flexible materials and structures to realize innovative robotic systems. This new footpath to craft biological mockups facilitates further to exploit new materials, novel design methodologies and new control techniques. This paper presents an appraisal on such innovative comprehensions, conferring to their design specific importance. This demonstration is potentially useful to prompt the novelty of soft robotics.