Observation and analysis of diving beetle movements while swimming

The fast swimming speed, flexible cornering, and high propulsion efficiency of diving beetles are primarily achieved by their two powerful hind legs. Unlike other aquatic organisms, such as turtle, jellyfish, fish and frog et al., the diving beetle could complete retreating motion without turning around, and the turning radius is small for this kind of propulsion mode. However, most bionic vehicles have not contained these advantages, the study about this propulsion method is useful for the design of bionic robots. In this paper, the swimming videos of the diving beetle, including forwarding, turning and retreating, were captured by two synchronized high-speed cameras, and were analyzed via SIMI Motion. The analysis results revealed that the swimming speed initially increased quickly to a maximum at 60% of the power stroke, and then decreased. During the power stroke, the diving beetle stretched its tibias and tarsi, the bristles on both sides of which were shaped like paddles, to maximize the cross-sectional areas against the water to achieve the maximum thrust. During the recovery stroke, the diving beetle rotated its tarsi and folded the bristles to minimize the cross-sectional areas to reduce the drag force. For one turning motion (turn right about 90 degrees), it takes only one motion cycle for the diving beetle to complete it. During the retreating motion, the average acceleration was close to 9.8 m/s2 in the first 25 ms. Finally, based on the diving beetle's hind-leg movement pattern, a kinematic model was constructed, and according to this model and the motion data of the joint angles, the motion trajectories of the hind legs were obtained by using MATLAB. Since the advantages of this propulsion method, it may become a new bionic propulsion method, and the motion data and kinematic model of the hind legs will be helpful in the design of bionic underwater unmanned vehicles

Whirligig beetles as corralled active Brownian particles

We study the collective dynamics of groups of whirligig beetles Dineutus discolor (Coleoptera: Gyrinidae) swimming freely on the surface of water. We extract individual trajectories for each beetle, including positions and orientations, and use this to discover (i) a density-dependent speed scaling like v ∼ ρ−ν with ν ≈ 0.4 over two orders of magnitude in density (ii) an inertial delay for velocity alignment of approximately 13 ms and (iii) coexisting high and low-density phases, consistent with motility-induced phase separation (MIPS). We modify a standard active Brownian particle (ABP) model to a corralled ABP (CABP) model that functions in open space by incorporating a density-dependent reorientation of the beetles, towards the cluster. We use our new model to test our hypothesis that an motility-induced phase separation (MIPS) (or a MIPS like effect) can explain the co-occurrence of high- and low-density phases we see in our data. The fitted model then successfully recovers a MIPS-like condensed phase for N = 200 and the absence of such a phase for smaller group sizes N = 50, 100

Visual Adaptations and Behavioural Strategies to Detect and Catch Small Targets

Predatory behaviours are ideal for studying the limits of performance and control within animals. Predation naturally creates a competition between the sensors and physiology of predator and prey. Aerial predation demonstrates the greatest feats of physical performance, demanding the highest speeds and accelerations whilst both predator and prey are free to pitch, yaw, and roll. These high speeds and degrees of rotational freedom make control a complex problem. However, from the perspective of the researcher attempting to decipher the control laws that underpin predator guidance, the question is made more soluble by the predator’s fixation on its target. The goal of the pursuer is clear, to contact the target, and thus their systems are focused on the optimization of that action. This is as opposed to more mundane activities, where conflicting interests compete for the attention and behavioural response of the animal. In order to study the necessary trade-offs that underpin aerial predation, this thesis will focus on the hunting behaviour of two fly species. The first is a robber fly, Holcocephala fusca, on which the majority of the first two chapters focus. Secondarily, work with the killer fly Coenosia attenuata will be included in the latter two chapters as a direct contrast to results from Holcocephala. Both are miniature dipteran predators, but not closely related. The structure of this thesis is broken into six chapters, summarised in the following list: 1. Thecompoundeyeofinsectsgenerallyhasmuchpoorerresolutionthanthatofcameratype eyes. Poor resolution is exacerbated in smaller insects that cannot commit the resources required for eyes with large lenses that facilitate high spatial resolution. Holcocephala has developed a small number of facets into a forward-facing acute zone where the spatial acuity is reduced to ~0.28°, rivalling the very best resolution of any compound eye. The only compound eyes with a comparable spatial resolution belong to dragonflies, in excess of an order of magnitude larger than Holcocephala. 2. Numerous potential targets may be airborne within the visual range of a predator. Not all of these may be suitable. Chasing unsuitable targets may waste energy or result in direct harm should they turn out to be larger than the predator can overcome. It is thus a strong imperative for a predator to filter the targets it takes after. Targets silhouetted against the sky display a paucity of cues that a predator could use to determine their size. Holcocephala displays acute size selectivity towards smaller targets. This selectivity goes beyond heuristic rules and size/speed ratios. Instead, Holcocephala appears able to determine absolute size and distance of targets. 3. Both Holcocephala and Coenosia intercept targets, heading for where the target is going to be in the future rather than its current location. Both species plot trajectories in keeping with the guidance law of proportional navigation, an algorithm derived for modern guided missiles. There are key differences evident in the internal physiological constants applied to the control system between the species. These differences are likely linked to the specific environmental conditions and visual physiologies of the flies, especially the range at which targets are attacked. 4. Stemming from the use of the proportional navigational framework, this chapter dives into the intricacies of gain and the weighting of the navigational constant, and the geometric factors that underpin the control effort and eventual success of the control system. 5. “Falcon-diving” can be found in killer flies dropping from their enclosure ceiling, in which they miss targets after diving towards them. Through proportional navigation, it can be demonstrated that the navigational system combined with excessive speed results in acceleration demands the body cannot match. 6. Holcocephala is capable of evading static obstacle whilst intercepting targets. Application of proportional navigation and a secondary obstacle-evasive controller can demonstrate where the fly is combining multiple inputs to guide its heading.This work was funded by the United States Airforce Office of Scientific Research

Biological adhesion in wet environments: adaptations and mechanisms

Physiochemical conditions in water are fundamentally different to those in air; hence, organisms require special adaptations to adhere in wet environments. In my thesis, I have investigated three study systems to elucidate mechanisms for adhesion under wet conditions. In Chapters 2 and 3, I explore an aquatic insect (Diptera: Blephariceridae) that uses suction organs to attach to rocks in raging alpine torrents. Suction-based attachment is driven by physical processes requiring a pressure difference and a seal to maintain it. Through my investigations, I have identified several key principles for biological suction attachments to wet and rough surfaces. Using three-dimensional reconstructions of blepharicerid suction organs and in vivo visualisation of the adhesive contact zone, I found several internal and external morphological adaptations that are important for strong adhesion under water. Moreover, I characterised a mechanism for rapid detachment which is the first detailed account of an actively controlled detachment system in biological suction organs. In Chapter 4, I investigate the contribution of physical and chemical mechanisms to the powerful attachment of common limpets (Patella vulgata) to rocks in the intertidal zone. I demonstrate that suction is not the primary contributor to their attachment forces; rather, it is their adhesive pedal mucus that is responsible. This adhesive mucus comprises of a complex mixture of glycans and proteins, many of which share homology with adhesive secretions from other marine invertebrates, such as sea stars, sea anemones, and flatworms. In Chapters 5 and 6, I study the physical and chemical properties of sticky secretions from carnivorous pitcher plants (Nepenthes) that help to capture, retain, and digest insects. I show that the viscoelastic pitcher fluid readily adheres to but not easily dewets from insect cuticle, and forms stable filaments as the insect attempts to escape that require significant work to overcome. In addition, the surface tension is reduced in pitcher fluid compared to water, making insects sink more easily into the former and facilitating further wetting of the cuticle. Chemical characterisation of the pitcher fluid revealed that its sticky filamentous property is caused by a polysaccharide with a glucurono-mannan backbone structure, which is chemically stable and contains carboxylic groups for strong interactions. Glucurono-mannan are an understudied group of plant polysaccharides that are present in mucilaginous secretions from across the plant kingdom, including sticky capture fluids from other carnivorous plants. My findings show that pitcher plant fluid can be used as a study system for future investigations into the origins and functional role of glucurono-mannan in carnivorous plants. In summary, my thesis has identified novel adaptations and principles for biological adhesion under wet conditions using three selected study systems, hence expanding our understanding of the underlying physical and chemical mechanisms and providing inspiration for biomimetic adhesives with improved performance in wet environments.EU Horizon 2020 under Marie Skłodowska-Curie grant agreement No. 64286

Bio-Inspired Robotics

Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field

2011, UMaine News Press Releases

This is a catalog of press releases put out by the University of Maine Division of Marketing and Communications between January 3, 2011 and December 30, 2011

2013, UMaine News Press Releases

This is a catalog of press releases put out by the University of Maine Division of Marketing and Communications between January 2, 2013 and December 31, 2013