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Contribution of individual legs to overall attachment in the adult ladybird Harmonia axyridis depends on the relative leg orientation to an external force

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ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA 2025年第3期173卷 232-245页

作者： Saitta, Valerio Rebora, Manuela Piersanti, Silvana Gorb, Elena Salerno, Gianandrea Gorb, Stanislav Univ Perugia Dipartimento Sci Agr Alimentari & Ambientali Perugia Italy Univ Perugia Dipartimento Chim Biol & Biotecnol Perugia Italy Univ Kiel Zool Inst Dept Funct Morphol & Biomech Kiel Germany

This study investigates the attachment ability of harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), focusing on the synergic action of opposite legs, the anisotropy of adhesive organs and sexual dimorphism. Contrary to expectations, experiments showed that beetles with fewer legs sometimes exhibited higher attachment forces, challenging the hypothesis that collective leg action enhances attachment. This result is attributed to differences in experimental set-ups, where our centrifugal method highlighted the importance of pad orientation relative to external forces. The anisotropy of adhesive pads, characterized by the directional dependence of adhesion and friction, significantly influenced attachment performance. Results demonstrated that inward-oriented legs enhanced attachment due to lower peeling angles, whereas outward orientation reduced effectiveness. Sexual dimorphism was evident in the structure of adhesive pads, with males possessing discoidal setae on fore- and midlegs. No significant difference in attachment was observed between intact males and females on smooth surfaces, although ablated males sometimes showed higher forces due to the presence of discoidal setae. These findings underscore that attachment strength in H. axyridis is not solely dependent on pad area but also on the orientation and anisotropic properties of adhesive organs, as well as the specific role of sexual dimorphism in leg morphology.

关键词： adhesive organs anisotropy behaviour centrifuge Coccinellidae Coleoptera friction force harlequin ladybird morphology sexual dimorphism

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Centennial Isomers: A Unique Fluorinated Azobenzene Macrocyclus with Dual Stability Over 120 Years

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ADVANCED FUNCTIONAL materialS 2024年第23期34卷 2313268-2313268页

作者： Schultzke, Sven Puylaert, Pim Wang, Henry Schultzke, Isabell Gerken, Jonas Staubitz, Anne Univ Bremen Inst Organ & Analyt Chem Leobener Str 7 D-28359 Bremen Germany Univ Bremen MAPEX Ctr Mat & Proc Bibliothekstr 1 D-28359 Bremen Germany Univ Bremen Inst Inorgan Chem & Crystallog Leobener Str 7 D-28359 Bremen Germany

A macrocyclic azobenzene with unique thermal stability, demonstrating potential for use in optical data storage material is presented: The Z-isomer of this novel photoswitch exhibits unparalleled thermal stability, with a thermal half-life surpassing 120 years at 25 degrees C. This stability is attributed to the strategic fluorination at two ortho- and both para-positions. Comparative analyses involving its non-fluorinated counterpart, ortho-only-fluorinated variant, and open-chain analog are performed. Employing NMR and UV-vis spectroscopy, X-ray diffraction, alongside Arrhenius, Eyring, and DFT calculations, revealed insights into its extraordinary stability. Furthermore, when incorporated into poly(methylmethacrylate), this material showcase efficient switching with visible light in the solid state, emphasizing its potential for optical data storage applications. A macrocyclic azobenzene is synthesized, demonstrating an exceptional half-life of 120 years at room temperature and above 14 000 years at 0 degrees C. Switching efficiencies with visible light are high in both directions and the material retains its switchability within a polymer film, underscoring its potential for optical data storage applications. image

关键词： azobenzene long half-life time macrocycle optical data storage visible light

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Numerical model of the locomotion of oscillating 'robots' with frictional anisotropy on differently-structured surfaces

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SCIENTIFIC REPORTS 2024年第1期14卷 1-16页

作者： Filippov, Alexander Gorb, Stanislav Univ Kiel Dept Funct Morphol & Biomech Zool Inst Bot Garten 1-9 D-24098 Kiel Germany Natl Acad Sci Donetsk Inst Phys & Engn Donetsk Ukraine

In engineering materials, surface anisotropy is known in certain textured patterns that appear during the manufacturing process. In biology, there are numerous examples of mechanical systems which combine anisotropic surfaces with the motion, elicited due to some actuation using muscles or stimuli-responsive materials, such as highly ordered cellulose fiber arrays of plant seeds. The systems supplemented by the muscles are rather fast actuators, because of the relatively high speed of muscle contraction, whereas the latter ones are very slow, because they generate actuation depending on the daily changes in the environmental air humidity. If the substrate has ordered surface profile, one can expect certain statistical order of potential trajectories (depending on the order of the spatial distribution of the surface asperities). If not, the expected trajectories can be statistically rather random. The same presumably holds true for the artificial miniature robots that use actuation in combination with frictional anisotropy. In order to prove this hypothesis, we developed numerical model helping us to study abovementioned cases of locomotion in 2D space on an uneven terrain. We show that at extremely long times, these systems tends to behave according to the rules of ballistic diffusion. Physically, it means that their motion tends to be associated with the "channels" of the patterned substrate. Such a motion is more or less the same as it should be in the uniform space. Such asymptotic behavior is specific for the motion in model regular potential and would be impossible on more realistic (and complex) fractal reliefs. However, one can expect that in any kind of the potential with certain symmetry (hexagonal or rhombic, for example), where it is still possible to find the ways, the motion along fixed direction during long (or even almost infinite) time intervals is possible.

关键词： Anisotropic friction Tribology Surfaces Locomotion robotics Biomimetics Animal Plant

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Singular-Perturbation Control of a Tendon-Driven soft Robot: Theory and Experiments

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IEEE TRANSACTIONS ON CONTROL systems TECHNOLOGY 2025年

作者： Ribeiro, Lucas Novaki Borja, Pablo Della Santina, Cosimo Deutschmann, Bastian German Aerosp Ctr DLR Inst Robot & Mechatron D-82234 Wessling Germany Univ Plymouth Sch Engn Comp & Math Plymouth PL4 8AA England

The existing model-based control strategies for tendon-driven continuum soft robots neglect the dynamics of the actuation system. Nevertheless, such dynamics have an important impact on the closed-loop performance. This work analyzes the influence of the actuation dynamics in tendon-driven continuum soft robots performing trajectory-tracking tasks. To this end, we use singular perturbation (SP) theory to design controllers that account for such dynamics. We provide the analytical formulation of the SP controllers and their in-depth experimental validation. Additionally, we use high-and low-stiffness tendons to experimentally compare the performance of the proposed SP controllers against traditional feedback control schemes that disregard the actuation dynamics. The experimental results show that SP controllers outperform the approaches that neglect the actuation dynamics by reducing oscillations and achieving lower errors without relying on high gains. Furthermore, it is shown that neglecting the actuation dynamics may lead to instability when the tendons have a low stiffness coefficient.

关键词： soft robotics Robots Tendons Vectors Aerodynamics Motors Actuators Trajectory Frequency modulation Jacobian matrices Continuum soft robots model-based control singular perturbation tendon-driven robots

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Passive and active acoustic sensing for soft pneumatic actuators

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INTERNATIONAL JOURNAL OF roboticS RESEARCH 2023年第3期42卷 108-122页

作者： Wall, Vincent Zoeller, Gabriel Brock, Oliver Tech Univ Berlin Robot & Biol Lab Berlin Germany Res Cluster Excellence Sci Intelligence Berlin Germany

We propose a sensorization method for soft pneumatic actuators that uses an embedded microphone and speaker to measure different actuator properties. The physical state of the actuator determines the specific modulation of sound as it travels through the structure. Using simple machine learning, we create a computational sensor that infers the corresponding state from sound recordings. We demonstrate the acoustic sensor on a soft pneumatic continuum actuator and use it to measure contact locations, contact forces, object materials, actuator inflation, and actuator temperature. We show that the sensor is reliable (average classification rate for six contact locations of 93%), precise (mean spatial accuracy of 3.7 mm), and robust against common disturbances like background noise. Finally, we compare different sounds and learning methods and achieve best results with 20 ms of white noise and a support vector classifier as the sensor model.

关键词： Acoustic sensing force and tactile sensing computational sensor soft sensors pneumatic actuators soft robotics

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Design and build of small-scale magnetic soft-bodied robots with multimodal locomotion

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NATURE PROTOCOLS 2024年第2期19卷 441-486页

作者： Ren, Ziyu Sitti, Metin Max Planck Inst Intelligent Syst Phys Intelligence Dept Stuttgart Germany Swiss Fed Inst Technol Inst Biomed Engn Zurich Switzerland Koc Univ Sch Med Istanbul Turkiye Koc Univ Coll Engn Istanbul Turkiye

Small-scale magnetic soft-bodied robots can be designed to operate based on different locomotion modes to navigate and function inside unstructured, confined and varying environments. These soft millirobots may be useful for medical applications where the robots are tasked with moving inside the human body. Here we cover the entire process of developing small-scale magnetic soft-bodied millirobots with multimodal locomotion capability, including robot design, material preparation, robot fabrication, locomotion control and locomotion optimization. We describe in detail the design, fabrication and control of a sheet-shaped soft millirobot with 12 different locomotion modes for traversing different terrains, an ephyra jellyfish-inspired soft millirobot that can manipulate objects in liquids through various swimming modes, a larval zebrafish-inspired soft millirobot that can adjust its body stiffness for efficient propulsion in different swimming speeds and a dual stimuli-responsive sheet-shaped soft millirobot that can switch its locomotion modes automatically by responding to changes in the environmental temperature. The procedure is aimed at users with basic expertise in soft robot development. The procedure requires from a few days to several weeks to complete, depending on the degree of characterization required. The protocol describes a sheet-shaped millirobot with 12 locomotion modes for traversing different terrains, a jellyfish-inspired millirobot for manipulating objects in liquids, a zebrafish-inspired millirobot for efficient swimming and a dual stimuli-responsive millirobot that can switch locomotion modes automatically by responding to the environmental ***-bodied robots lack deformation capabilities, limiting them to specific functions, whereas soft-bodied millibots display sophisticated locomotion strategies similar to those adopted by small-scale organisms. The detailed design and fabrication of small-scale magnetic soft-bodied robots with

关键词： Actuators Mechanical engineering

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Energy-based modeling of rate-independent hysteresis and viscoelastic effects in dielectric elastomer actuators

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SMART materialS AND STRUCTURES 2024年第5期33卷 055027-055027页

作者： Rizzello, Gianluca Saarland Univ Dept Syst Engn Saarbrucken Germany

Dielectric elastomer (DE) transducers are known to exhibit a rate-dependent hysteresis in their force-displacement response, which is commonly attributed to the viscoelastic behavior of elastomer materials and compliant electrodes. In the case of DE materials characterized by low mechanical losses, such as silicone, the mechanical hysteresis often turns out to be practically rate-independent in the low frequency range (sub-Hz), whereas rate-dependent hysteretic effects only become relevant at higher deformation rates. Most of the existing literature focuses on describing DE hysteretic losses using viscoelasticity theory. This approach results in relatively simple dynamic models, which are not capable of describing rate-independent hysteretic behaviors. In this work, we propose a control-oriented modeling framework for both rate-dependent and rate-dependent hysteresis occurring in uniaxially loaded DE actuators. To this end, classic thermodinamically-consistent modeling approaches for DEs are combined with a new energy-based Maxwell-Lion formalization of the hysteretic losses. The resulting dynamic model comprises a set of nonlinear ordinary differential equations, and is capable of simultaneously describe geometric dependencies, large deformation nonlinearities, electro-mechanical coupling, and rate-independent and rate-dependent hysteretic effects. To deal with the large number of involved parameters, a novel systematic identification algorithm based on quadratic programming is also proposed. After presenting the theory, the model is validated based on experiments conducted on a silicone-based rolled DE actuator. Its superiority compared to classic DE viscoelastic models is quantitatively assessed.

关键词： dielectric elastomer DE hysteresis rate-independent hysteresis parameter identification modeling energy-based modeling

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Graphene/fabric-based sensors for low-to-mid-range acoustic signals

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SENSORS AND ACTUATORS A-PHYSICAL 2025年 382卷

作者： Chakraborthy, Aniket Oezer, Mehmet Sait Harija, H. Nuthalapati, Suresh Nag, Anindya Alahi, Md. Eshrat E. Altinsoy, M. Ercan Tech Univ Dresden Ctr Tactile Internet Human Inthe Loop CeTI D-01069 Dresden Germany Tech Univ Dresden Fac Elect & Comp Engn D-01062 Dresden Germany Tech Univ Dresden Dept Urol Suresh Nuthapati Life Res Hub 6G D-01069 Dresden Germany Walailak Univ Sch Engn & Technol 222 Thaiburi Nakhon Si Thammarat 80160 Thailand

The paper highlights the research on designing, developing and utilising low-cost graphene-based sensors for acoustic applications. Although commercial sensors are available to detect acoustic signals, some limitations are limited access, high cost, and difficulty in replicability. The work showcases the development of low-cost graphene/fabric sensors for acoustic applications. Due to the excellent electromechanical characteristics of graphene, it has been integrated with fabrics to form sensors with high integrity and flexibility. The rise and fall times for the PDMS-based sensors were 32.77 ms and 106.06 ms, respectively, and it was 35.1 ms and 135.02 for the PI-based substrates. The pressure-sensitive nature of these sensors has allowed them to respond to acoustic signals with varied nature, amplitude and frequency. A comparison has been made of their performances when they were attached to two different polymeric substrates, including polydimethylsiloxane and polyimide. The results shown here depict the high potentiality of these sensors and offer a podium towards low-cost acoustic sensing for wearable and industrial applications.

关键词： Graphene Acoustic Flexible Piezoresistive Fabric

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Investigating frictional contact behavior for soft material robot simulations

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MECCANICA 2023年第11期58卷 2165-2176页

作者： Berthold, Rebecca Burgner-Kahrs, Jessica Wangenheim, Matthias Kahms, Stephanie Leibniz Univ Hannover Inst Dynam & Vibrat Res Univ 1 D-30823 Hannover Germany Univ Toronto Dept Math & Computat Sci Continuum Robot Lab 3359 Mississauga Rd Mississauga ON L5L 1C6 Canada

The ability to interact safely with the environment is known as one of the major advantages of soft robots (SRs). Due to their low material stiffness, these continuously deformable robots offer inherent flexibility. These advantages make them suitable for application that involve human-robot collaboration in industrial settings as well as medical application such as minimally invasive surgery. To date only few research groups have analyzed the contact and frictional behavior of soft robots. In fact, the contact behavior is often oversimplified or neglected. Motivated by the idea to bridge this gap, this work presents measurements and the resulting coefficient of friction (COF) for silicone rubbers that are widely used in the field of SRs and different contact partners which depend on contact pressure and ambient temperature. From these measurements, a more representative contact model is established and used to more accurately simulate soft material robots' frictional contact behavior. Moreover the influence of friction and therefore the need to implement frictional behavior is demonstrated for a typical application of a SR.

关键词： soft robotics Elastomers Friction Contact modeling Friction measurement

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Task Space Trajectory Planning for an Articulated Dielectric Elastomer soft Robot with Input Saturation and Underactuation 20

Task Space Trajectory Planning for an Articulated Dielectric...

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20th IEEE/ASME International Conference on Mechatronic and Embedded systems and Applications (MESA)

作者： Soleti, Giovanni Cicali, Lorenzo Franci, Michael Pugi, Luca Rizzello, Gianluca Saarland Univ Dept Syst Engn Saarbrucken Germany Univ Florence Dept Elect & Automat Engn Florence Italy

ISBN: (纸本)9798331516246;9798331516239

In this paper we propose a new trajectory planning algorithm for an underactuated soft robot based on dielectric elastomer actuators. The planning of the dynamic trajectories is addressed by accounting for the constraints imposed by the underactuated nature of the robot, the physical limits of its operational space, as well as control input saturation. After deriving all the feasible equilibrium configurations of the robot, a trajectory planning algorithm is proposed to achieve a desirable motion in the configuration space of the system. The obtained trajectories provide a feasible reference for trajectory tracking motion control algorithms. The effectiveness of the approach is verified via numerical simulations conducted on an experimentally validated, physics-based model of the system.

关键词： Trajectory planning task-space control tracking control underactuated robot soft-robotics dielectric elastomer

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