Belgium

Actuation has been identified as a significant limiting factor for turbulence mitigation of aircraft. Turning to nature for inspiration enables an understanding of how highly agile birds can articulate their aerodynamic surfaces during precision flight conditions such as wind hovering. Such understanding can inspire morphing actuation that enable higher control authority and rapidity, improving flight performance in challenging scenarios. This paper, therefore, explores the effects of specific kestrel morphing motions using a high-fidelity morphing robot of a kestrel, which replicates predominant motions seen in real wind-hovering kestrels. Through comprehensive wind tunnel testing, the aerodynamic effects and stability implications of wing extension, tail spread, and tail incidence mechanisms are examined. The findings illustrate redundancy in control axes, enabling the birds to trim for stability through their area changing degrees-of-freedom. The coupling of wing and tail extension, seen in real flight, not only facilitates improved lift generation but also effectively decouples lift and pitching moment axes, reflecting strategies observed in real kestrel flight. The remarkably low inertia of kestrels, extracted through CT scanning, is found to be an important contributor to the agility advantage of kestrels versus similar sized aircraft. This study highlights the significant potential of bio-inspired morphing, providing fresh perspectives on control strategies informed by nature&#39;s flight mechanisms.

SEB Conference 2025

Kestrel morphing reveals stability tailoring and aerodynamic benefits of wing-tail coupling in wind-hovering flight

morphing couplings in flight

kestrel kinematics

kestrel aerodynamics

Actuation has been identified as a significant limiting factor for turbulence mitigation of aircraft. Turning to nature for inspiration enables an understanding of how highly agile birds can articulate their aerodynamic surfaces during precision flight conditions such as wind hovering. Such understanding can inspire morphing actuation that enable higher control authority and rapidity, improving flight performance in challenging scenarios. This paper, therefore, explores the effects of specific kestrel morphing motions using a high-fidelity morphing robot of a kestrel, which replicates predominant motions seen in real wind-hovering kestrels. Through comprehensive wind tunnel testing, the aerodynamic effects and stability implications of wing extension, tail spread, and tail incidence mechanisms are examined. The findings illustrate redundancy in control axes, enabling the birds to trim for stability through their area changing degrees-of-freedom. The coupling of wing and tail extension, seen in real flight, not only facilitates improved lift generation but also effectively decouples lift and pitching moment axes, reflecting strategies observed in real kestrel flight. The remarkably low inertia of kestrels, extracted through CT scanning, is found to be an important contributor to the agility advantage of kestrels versus similar sized aircraft. This study highlights the significant potential of bio-inspired morphing, providing fresh perspectives on control strategies informed by nature's flight mechanisms.

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Flight tests were conducted on Nankeen kestrels (Falco cenchroides) hovering in a wind tunnel to investigate their responses to discrete gusts. Gusts were generated using downstream rotating louvres, which modulated the strength of an updraught in which the birds could hover with wings fixed. Motion capture cameras recorded the kestrels’ kinematic responses during gust encounters. These gust responses were replicated using a robotic morphing kestrel wing and tail with three degrees of freedom: wing extension, tail spread, and tail pitch. The model was pre-programmed with movements imitating the birds’ gust responses, which were actuated in coordination with the gust generator. Measurements of the aerodynamic loads showed that the gust loads were effectively mitigated in the lift axis for both upward and downward step gusts. These findings highlight key degrees of freedom that could inform bioinspired gust mitigation strategies for small UAVs.

Reproduction of kestrel gust-mitigation kinematics with a robotic morphing wing

Landing precisely is vital for flying animals. However, disturbances in outdoor environments always complicate the process. For bumblebees, dynamic gusts cause both unpredictable flower movements and displacements of foraging bumblebees, which necessitate a rapid compensation of perturbations with their sensory-motor control system. Here, we study how rapid flower movements affect the landing behavior of bumblebees (Bombus terrestris). Using stereoscopic high-speed videography, we track bumblebees landing on an oscillating flower mimic and model their landing kinematics with control theory. The result shows that bumblebees land on moving flower with rapid motor actions controlled using visual perception of the moving target. The proposed visual-motor control model shows that optical perception signals facilitate bumblebees tracking the moving flower and gaze control while landing. The model also suggests a surprisingly low sensory-motor delay (median 57.1 ms). Moreover, by examining in-flight time histories of roll angle and sideway-acceleration, the helicopter model for aerodynamics force production proposed based on fruit flies is proved as valid for bumblebee flights. These results lead to a more thorough understanding of insect flight control system and could facilitate bio-inspired tracking and landing algorithms for flying robots.

How bumblebees land on rapidly-moving flowers: Sensory-motor flight control of landing on sideway moving flowers

Fastening barbules are hook-like microstructures on the surface of a bird’s primary flight feathers which prevent separation of adjacent feathers during wing extension. As a result, they are thought to be important for improving bird flight performance at high angles of attack by helping to maintain a smooth aerodynamic surface. This ability would be very useful for morphing-wing uncrewed aerial vehicles (UAVs) which can adjust the shape of their wing to suit a variety of flight conditions. Some of these UAV wings are comprised of multiple feather-like segments which slide over one another. However, they lack this between-feather fastening. Because of this, they struggle in gusty flight conditions and when flying at high angles of attack; their wing segments flap apart creating gaps that air can pass through which prevents the wings from producing sufficient aerodynamic force to maintain flight. Taking inspiration from fastening barbules, we investigate an electro-adhesive mechanism with the aim to enable controllable fastening between wing segments. Electro-adhesion involves the application of high voltage to electrodes which causes them to adhere together, but as soon as this voltage is removed, adhesion is lost. This study measures maximum adhesion strength between two electrodes in multiple directions. Results from these tests will enable application of this mechanism to future morphing wing UAVs.

A feather-inspired, electro-adhesive mechanism to improve flight capabilities of morphing wing UAVs

Fast motions play a crucial role in many biological processes, allowing organisms to capture elusive prey, escape predators, or navigate challenging environments with remarkable speed and precision. These rapid movements are especially vital in predator-prey interactions, often requiring a performance that exceeds the limits of pure muscle contraction alone, to fulfil the particularly high demands placed on the associated musculature and skeletal system. To overcome these limitations, specialized anatomical structures and biomechanical mechanisms are employed, often involving elastic energy storage, rapidly released through latch-mediated spring actuation (LaMSA) systems combined with optimized musculoskeletal gearing. These biological catapults are widespread in nature, enabling animals to achieve speeds and accelerations far beyond what muscle power alone could produce. Although commonly known for their grasping-like predatory strike, which was until now reported to be purely muscle driven, a small group of mantodeans (praying mantises) reveals strong morphological and behavioural deviations. The highly transformed raptorial forelegs of Haania orlovi are moved in a ballistic high-speed motion (~1,6 ms), utilizing the spear-like reinforced distal spines of the tibia to impale their prey item. The system is mainly based on elastic energy storage in the deformed cuticle of the trochanter, presumably caused by co-activated contraction of the large extensor and flexor muscles of the coxa, with a calculated mechanical power output of more than 100.000 W/kg. It presents a very simple and compact power amplification system. Understanding the principles behind such high-speed movements provides insights into evolutionary adaptations of biological systems and may inspire new technological innovations.

A striking difference: Biomechanics of a specialized predatory strike - the impaling hunting strategy of the moss mantis Haania orlovi (Insecta: Mantodea)

Seahorses possess a unique tail muscle architecture that enables efficient grasping and anchoring onto objects. This prehensile ability is crucial for their survival, as it allows them to resist currents, cling to mates during reproduction, and remain camouflaged to avoid predators. Unlike in any other fish, the muscles of the seahorse tail form long, parallel sheets that can span up to eleven vertebral segments. Our study investigates how this distinctive muscle arrangement influences the mechanics of prehension. Through in-silico simulations validated by a 3D-printed prototype, we reveal the complementary roles of these elongated muscles alongside shorter, intersegmental muscles. Furthermore, we show that muscles spanning more segments allow greater contractile forces and provide more efficient force-to-torque transmissions. Our findings confirm that the elongated muscle-tendon organisation in the seahorse tail provides a functional advantage for grasping, offering insights into the evolutionary adaptations of this unique tail structure.

The unique muscle architecture of the seahorse tail demystified

This study examines the impact of climate variability on garlic (Allium sativum L.) cultivation in Buzau, Romania, focusing on agricultural drought and breeding strategies for stress resilience. Between October 2023 and September 2024, precipitation remained below the multiannual average, with severe drought conditions affecting the southern and eastern regions. The Combined Drought Indicator (CDI) and Aridity Index confirmed increased drought severity, while heatwaves in July–August further stressed crops. Phenological observations indicated an earlier onset of developmental stages by 7–10 days due to rising temperatures, negatively affecting vegetable yields. A total of 26 garlic genotypes were evaluated against the registered cultivars 'Benone' and 'Ramniceanu' for productivity, stress tolerance, and morphological traits. Using Agglomerative Hierarchical Clustering (AHC), three distinct genotype groups were identified based on leaf morphology, bulb weight, and dry matter content. Preliminary results highlight significant phenotypic variability and potential for selecting drought-tolerant lines. The findings emphasize the importance of breeding programs in developing climate-resilient cultivars. Future research will refine genotype selection and enhance adaptation strategies for sustainable garlic production in Romania.

Phenotypic evaluation of garlic (Allium sativum L.) genotypes under open-field conditions

Resurrection or desiccation tolerant plants are characterized by a remarkable ability to survive extreme desiccation, losing more than 90% of the cellular water in their vegetative tissues, and then recover normal physiological activity after only few hours of rehydration.  Plants release many different Volatile Organic Compounds (VOCs) to cope with environmental stresses. The VOC emission capacity have been investigated only in few resurrection species and most of these studies has shown the leaf emission of isoprene and other VOCs (C6 green leaf volatiles), and oxygenated compounds (acetone, and methanol). In the present study, the leaf emission of VOCs was assessed in the resurrection angiosperm Haberlea rhodopensis Friv. (Gesneriaceae) that belongs to the homoiochlorophyllous type species that are characterized to retain the photosynthetic apparatus and pigments, which allows a quicker recovery following rehydration. However, the high concentration of chlorophyll during desiccation is a source for the production of harmful reactive oxygen specie. Therefore, H. rhodopensis needs better antioxidant protection against free radical attack experienced either during dehydration or immediately upon rehydration. Our study aims to understand the role of leaf VOCs emission in the desiccation tolerance strategy of H. rhodopensis. The temporal dynamic of VOC emission during dehdyration and rehydration was monitored continuously by applying proton transfer reaction – time of flight-mass spectrometry (PTR-MS) and gas chromatography-mass spectrometry (GC-MS). Our study on the VOC emission, together with parallel analysis of the photosynthetic activity and photoprotective mechanisms, provides new insights into the potential role of VOCs for the “drying without dying” ability.

Resurrection plants: the unsolved mystery of Volatile Organic Compounds (VOCs) emissions under extreme physiological desiccation

The final morphology of a plant is determined by the activity of the shoot apical meristem (SAM), a group of pluripotent cells responsible for the generation of above-ground aerial plants’ organs. The identity and differentiation of SAM cells are under a strict hormonal and transcriptional regulatory network, involving epigenetic modifications and different signalling molecules. Among these, Reactive Oxygen Species (ROS) play an important role in cell cycle regulation, thus contributing to plant growth. Overall, plant hormones and ROS create a complex interplay of connections that can be modulated to boost plant development and productivity. Biogenic Volatile Organic Compounds (BVOCs) are a large variety of molecules produced by different plant tissues. There is increasing evidence that BVOCs participate in the regulation of signalling pathways involving ROS production and hormone synthesis. For this reason, application of BVOCs may represent a novel strategy to enhance plant meristematic activity, with a positive impact on plant productivity. Our project investigates the effects of exposure to BVOCs (i.e. isoprenoids) on rice, with the aim of exploring the possibility to increase rice yield through modulation of hormone signalling, gene activation and plant redox state. Experiments are currently ongoing to evaluate changes in cell redox mechanisms, hormones synthesis and gene expression at different plant levels: (i) on undifferentiated and regenerating rice callus, (ii) on rice seedlings exposed to exogenous isoprene. Preliminary results suggest that isoprene is able to modulate the rice redox machinery and positively affects the expression of auxin-responsive genes, possibly impacting plant growth and development.

Biogenic Volatile Organic Compounds (BVOCs) For Plant Growth Promotion: A Preliminary Study On Rice Callus and Seedlings

Global temperatures are rising, putting pressure on our wheat production systems. Predictions indicate that for every 1°C increase in temperature, wheat yields have the potential to decrease by 6%. This represents an approximate one million metric tonne loss in the UK yearly. Furthermore, regions experiencing the largest temperature shifts align with some of the world’s most food-insecure communities. Wild relatives of wheat offer a solution for enhancing yields under elevated temperatures. One such wild relative is Aegilops umbellulata, which can be found in Iran, Iraq, Turkey, and Syria—areas that frequently experience temperatures exceeding 40°C. Consequently, these conditions have influenced the development of Ae. umbellulata to withstand high temperatures compared to bread wheat. We measured chlorophyll fluorescence to determine Tcrit (the temperature at which Fv/Fm shifts from a steady decline in efficiency to a rapid decline, indicating severe damage to photosynthetic apparatus due to high temperatures) in a collection of Ae. umbellulata accessions and Ae. umbellulata/hexaploid wheat addition and substitution lines. Furthermore, we recorded plant yields and assessed seed morphology and elemental composition through imaging, ICP-MS, and carbon-nitrogen analysis. Our findings suggest that chromosome 7U of Ae. umbellulata may possess the ability to enhance the thermotolerance of bread wheat, therefore protecting yields under high-temperature stress.

Aegilops umbellulata: A wheat wild relative giving heat tolerance to hexaploid wheat

Low-temperature (LT) stress poses a serious threat to rice seed germination under direct sowing in rice production. Germination under LT therefore constitutes an important agronomic trait for such rice cultivation system. In this study, we identified a trehalose synthesis pathway gene, trehalose-6-phosphate phosphatase 3 (OsTPP3), involved in the regulation of LT germination in rice, as well as its upstream regulatory factor, the ABA signaling pathway gene OsbZIP23. LT stress induced the accumulation of ABA by upregulating the expression of OsNCED3. Consistently, overexpression of OsNCED3 significantly inhibited seed germination under LT conditions. RT-qPCR experiments found that the expression of OsbZIP23, a key component of ABA signaling pathway, was also significantly induced under LT stress and ABA treatment. Overexpressing OsbZIP23 increased the sensitivity to LT stress, resembling the phenotype of OsNCED3 overexpressing seeds. Furthermore, both LT stress and exogenous ABA treatment increased the trehalose content in WT seeds, by upregulating the expression of OsTPP3. Enhancing the expression of OsTPP3 or application of exogenous trehalose significantly increased the sensitivity to LT stress during seed germination. Transcriptional activation assays demonstrated that OsbZIP23 bound to the promoter of OsTPP3 and activated its expression, which was intensified by LT stress or application of ABA. Our study revealed an ABA-dependent OsbZIP23-OsTPP3 molecular module that responds to LT stress and inhibits seed germination under LT conditions. The regulated trehalose accumulation then balances growth and stress resistance under different temperature conditions.

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