The Morphology and Adhesion Mechanism of Octopus vulgaris Suckers

The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology) and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa). In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species

Design and Characterization of Tri-axis Soft Inductive Tactile Sensors

Tactile sensors are essential for robotic systems to safely and effectively interact with the environment and humans. In particular, tri-axis tactile sensors are crucial for dexterous robotic manipulations by providing shear force, slip or contact angle information. The Soft Inductive Tactile Sensor (SITS) is a new type of tactile sensor that measures inductance variations caused by eddy-current effect. In this paper, we present a soft tri-axis tactile sensor using the configuration of four planar coils and a single conductive film with hyperelastic material in between them. The working principle is explained and design methods are outlined. A 3D finite element model was developed to characterize the tri-axis SITS and to optimize the target design through parameter study. Prototypes were fabricated, characterized and calibrated, and a force measurement resolution of 0.3 mN is achieved in each axis. Demonstrations show that the sensor can clearly measure light touch (a few mN normal force) and shear force pulses (10 to 30 mN) produced by a serrated leaf when it is moved across the sensor surface. The presented sensor is low cost, high performance, robust, durable, and easily customizable for a variety of robotic and healthcare applications

Micromechanical Analysis of Soft Tactile Sensors

NP is supported by the European Research Council PoC 2015 “Silkene” No. 693670 and by the European Commission H2020 under the Graphene Flagship Core 1 No. 696656 (WP14 “Polymer Nanocomposites”) and under the FET Proactive “Neurofibres” No. 732344

A plant-inspired robot with soft differential bending capabilities

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Origin of Polar Order in Dense Suspensions of Phototactic Micro-Swimmers

A main question for the study of collective motion in living organisms is the origin of orientational polar order, i.e., how organisms align and what are the benefits of such collective behaviour. In the case of micro-organisms swimming at a low Reynolds number, steric repulsion and long-range hydrodynamic interactions are not sufficient to explain a homogeneous polar order state in which the direction of motion is aligned. An external symmetry-breaking guiding field such as a mechanism of taxis appears necessary to understand this phonemonon. We have investigated the onset of polar order in the velocity field induced by phototaxis in a suspension of a motile micro-organism, the algae Chlamydomonas reinhardtii, for density values above the limit provided by the hydrodynamic approximation of a force dipole model. We show that polar order originates from a combination of both the external guiding field intensity and the population density. In particular, we show evidence for a linear dependence of a phototactic guiding field on cell density to determine the polar order for dense suspensions and demonstrate the existence of a density threshold for the origin of polar order. This threshold represents the density value below which cells undergoing phototaxis are not able to maintain a homogeneous polar order state and marks the transition to ordered collective motion. Such a transition is driven by a noise dominated phototactic reorientation where the noise is modelled as a normal distribution with a variance that is inversely proportional to the guiding field strength. Finally, we discuss the role of density in dense suspensions of phototactic micro-swimmers

Modeling of a propulsion mechanism for swimming microrobots inspired by ciliate metachronal waves

The envisioned applications of microrobots in bodily fluids have raised the demand for effectively swimming microdevices. Microorganisms have become a source of inspiration because their mechanisms of propulsion are effective at low-Re. We investigated the theoretical performance of swimming microrobots implementing propulsion inspired by metachronal waves. These come from the spontaneous coordination of cilia and are responsible for the high swimming speeds of ciliates. We found that microrobots of typical length below the millimeter could self-propel at speeds of several bodylengths per second. The microrobots were assumed to have a continuous active surface exhibiting traveling-wave deformations that mimic metachronal waves. We developed an FE model for analyzing the performance of propulsion of such bio-inspired microrobots in water. In particular we evaluated how velocity is affected by various parameters, such as the shape and size of the microrobot, and the frequency, wavelength and amplitude of the surface deformations. We believe that the proposed mechanism is advantageous over other methods of propulsion because it does not need external thin and fragile appendages. The results of this analysis could thus guide us towards the design of effective self-propelling microrobots. © 2012 IEEE

Novel smart concepts for designing swimming soft microrobots

The development of mobile un-tethered microscale robots could revolutionize the future of medicine, since they can be conceived to move in micro-structured liquid environments, such as in inaccessible districts of the human body for performing in vivo diagnosis and therapy. However, power supply and actuation are still open issues in microrobotics, because of the lack of power sources and actuators at these scales. Considering the amazing levels of functionality exhibited by microorganisms, bioinspiration is an attractive approach to address the development of innovative solutions. The demonstration of efficient methods for building, powering and steering microscale robots are thus the first crucial steps towards such advanced systems. © Selection and peer-review under responsibility of FET11 conference organizers and published by Elsevier B.V

Bioinspired design and energetic feasibility of an autonomous swimming microrobot

A mobile microrobot is an untethered robotic device with typical size ranging from few micrometres to few millimetres. Endowing such a microrobot with autonomy-oriented capabilities, e.g. self-propulsion and self-powering, represents a scientific and technological challenge that requires innovative approaches. Bioinspiration provides fundamental cues for designing microrobots, enabling the development of working devices. Here we present the conceptual design of an autonomous swimming microrobot relying on biomimetic glucose-based powering, reporting a preliminary analysis on its energetic feasibility. © 2013 Springer-Verlag Berlin Heidelberg