1,721,218 research outputs found
Lessons from Animals and Plants: The Symbiosis of Morphological Computation and Soft Robotics
No full textMeasuring Triboelectric Energy Conversion in Leaves of Living Plants
No full textContact electrification or triboelectric charging is a long-known ubiquitous phenomenon which occurs on almost all material surfaces. It comprises the generation of longer- or shorter-lived static charges on the surface of a material upon contact with another material. The classical example is the charging of hairs with a rubber balloon. The effect is receiving increased attention as a possible mechanism to convert mechanical energy into electricity for energy harvesting. It is required that an electrode is installed near the charged surface (often a dielectric polymer) into which the generated charges can be electrostatically induced. Multiple artificial energy harvesters have been developed in the last decade to exploit this mechanism. Interestingly, also in nature, configurations exist that allow structures to convert mechanical energy into electricity by the triboelectric effect. These are especially the leaves of all living plants. Indeed, living plants have recently been used as triboelectric energy converters and for harvesting energy from leaf motion in the wind [1]–[5]. Here, we describe in detail how to measure triboelectric charges in the tissue of living plants, the particularities of measuring such signals in the organisms, and what is essential when using them for energy harvesting
Design of a compact bistable mechanism based on dielectric elastomer actuators
No full textBistable mechanisms are widely used in the applications where two stable positions must be held for long time without energy consumption. The main advantage of bistable mechanisms is a sensible reduction in bulkiness and energy cost. Among the possible active triggering systems, dielectric elastomer actuators (DEAs) are gaining attention, for their efficiency and strain rate, as a viable alternative to traditional technologies. In the present work, a novel design of a bistable system is proposed, counting on a cross-like shape bistable element coupled with two axially arranged conical DEAs. Analytical and FEM models have been used to implement and analyze the behavior of the single components and the final coupled system. The obtained results confirm the feasibility of the switching process between the equilibrium points and the capability to capture and numerically describe the interactions between the actuators and the bistable beams. A specific device has been finally envisaged to exemplify the possibility to develop a light-weight and compact system able to sustain and passively maintain a linear displacement which equals the 46 % of its own total length
Lightweight soft sensor for droplets on plant leaves and other surfaces
No full textDroplet sensing has crucial applications across many fields. For example, the effective arrival of droplets on plant leaves plays a vital role in representing the local conditions in plant ecosystems, ranging from rain and irrigation monitoring to analysis of agricultural spraying. Here, we present a soft, transparent, lightweight, and self-powered sensor that can be installed on plant leaves to measure impinging droplets of different sizes. The structure is fabricated by multilayer stacking of selected materials. The top layer contains an embroidered, patterned surface electrode that can be used to measure electrical signals due to liquid-solid surface charging when the droplet hits the device surface. Each droplet creates a characteristic current spike during interaction with the sensor materials and can be either directly read out in high frequency to obtain dynamic information on single droplets or analyzed in terms of average charges transferred to a sensing capacitor over larger periods. The devices allow to obtain droplet rates and information on the droplet size and could serve as sensors in smart and precision agriculture, spraying, and local, plant-level meteorology
Soft robotic arm inspired by the octopus: I. From biological functions to artificial requirements
No full textOctopuses are molluscs that belong to the group Cephalopoda. They lack joints and rigid links, and as a result, their arms possess virtually limitless freedom of movement. These flexible appendages exhibit peculiar biomechanical features such as stiffness control, compliance, and high flexibility and dexterity. Studying the capabilities of the octopus arm is a complex task that presents a challenge for both biologists and roboticists, the latter of whom draw inspiration from the octopus in designing novel technologies within soft robotics. With this idea in mind, in this study, we used new, purposively developed methods of analysing the octopus arm in vivo to create new biologically inspired design concepts.
Our measurements showed that the octopus arm can elongate by 70% in tandem with a 23% diameter reduction and exhibits an average pulling force of 40 N. The arm also exhibited a 20% mean shortening at a rate of 17.1 mm/s and a longitudinal stiffening rate as high as 2 N/(mms). Using histology and ultrasounds, we investigated the functional morphology of the internal tissues, including the sinusoidal arrangement of the nerve cord and the local insertion points of the longitudinal and transverse muscle fibres. The resulting information was used to create novel design principles and specifications that can in turn be used in developing a new soft robotic arm
Device for Simultaneous Wind and Raindrop Energy Harvesting Operating on the Surface of Plant Leaves
Full text linkSoft (bio)hybrid robotics aims at interfacing living beings with artificial technology. It was recently demonstrated that plant leaves coupled with artificial leaves of selected materials and tailored mechanics can convert wind-driven leaf fluttering into electricity. Here, we significantly advance this technology by establishing the additional opportunity to convert kinetic energy from raindrops hitting the upper surface of the artificial leaf into electricity. To achieve this, we integrated an extra electrification layer and exposed electrodes on the free upper surface of the wind energy harvesting leaf that allow to produce a significant current when droplets land and spread on the device. Single water drops create voltage and current peaks of over 40V and 15μA and can directly power 11 LEDs. The same structure has the additional capability to harvest wind energy using leaf oscillations. This shows that environment-responsive biohybrid technologies can be tailored to produce electricity in challenging settings, such as on plants under motion and exposed to rain. The devices have the potential for multisource energy harvesting and as self-powered sensors for environmental monitoring, pointing at applications in wireless sensor networks (WSNs), the Internet of Things (IoT), smart agriculture, and smart forestry
Wind dynamics and leaf motion: Approaching the design of high-tech devices for energy harvesting for operation on plant leaves
Full text linkHigh-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
A Plant Tendril-Like Soft Robot That Grasps and Anchors by Exploiting its Material Arrangement
Full text linkSome climbing plants use tendrils as efficient strategies to anchor and support their weights while they move in unstructured environments. In this letter, we mimic the essential functions of tendrils that wrap around the support in a soft state by a spiral winding (coiling) and then lignify or stiffen to strengthen the attachment. We implement a simple hierarchical pre-programmed functionality at the material level using off-the-shelf materials and easy fabrication methods to achieve coiling and stiffening and incorporate an electrical control. The resulting robots hence consist of a bilayer of silicone elastomers that encapsulate a thermoplastic core and a heating element. The bilayer that spontaneously forms a helically coiled configuration in its equilibrium state is controlled by a solid-to-liquid phase transition of the thermoplastic core upon resistive heating. Integrating these mechanisms into a single structure allows mimicking the basic tendril functions. Our realization is a straightforward assembly with electrical control that offers the perspective to be a building block for soft robots that require controllable attachment solutions such as growing artifacts and devices that operate in unstructured environments, e.g., operating in vegetation
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