Fish Lateral Line Research Articles

Design of Piezo-Resistive Type Acoustic Vector Sensor using Graphene for Underwater Applications

In recent years as the level of radiated noise of submarine drastically got decreased, the requirement of underwater acoustic sensor has become essential for the detection of low frequency acoustic signal. The latest advancement in the field of underwater sensors is the Micro Electro Mechanical Systems (MEMS) sensor. The major advantage of this sensor being determination of directionality along with the measurement of pressure of an acoustic signal. The biological inspiration behind the design of the sensor was derived from fish lateral line sensing system, with piezoresistive transduction principle to obtain the objective of miniaturization and low frequency signal detection. In this paper, we are reporting the design, simulation of an underwater two-dimensional MEMS acoustic vector sensor which exhibits better sensitivity, flexibility when compared to the traditional acoustic vector sensor. In this work, thin film of piezoresistve material, Reduced Graphene Oxide (Rgo) is taken as pressure sensing element instead of traditional polysilicon material and its performance in terms of sensitivity and directivity is analysed. MEMS acoustic vector sensors using Reduced Graphene Oxide and polysilicon were simulated on flexible kapton and silicon substrate respectively using COMSOL Multiphysics 5.5 vesrion. The simulation results indicates that designed vector sensor based on MEMS technology and piezoresistive effect of rGO on flexible kapton substrate is feasible and possesses better sensitivity of -149.47 dB when compared to the sensitivity of -171.37 dB of polysilicon based traditional acoustic vector sensor. The simulated value of eigen frequency of the sensor is found as around 47Hz, which almost matches with the theoretical value of resonance frequency of the sensor as per the design considerations of the sensor and hence capable of detecting low frequency acoustic signals.

Design and implementation of anulus-shaped ciliary structure for four-unit MEMS vector hydrophone

Inspired from fish bionics, an anulus-shaped ciliary structure for four-unit MEMS vector hydrophone (AFUVH) is proposed in this paper. It replaces the previous bionic cilium-shaped structure and becomes a novel sensing structure in the four-unit MEMS vector hydrophone (FUVH), which realizes the complete simulation of the fish lateral line neuromasts structurally and functionally. It not only improves the sensitivity of FUVH, but also retains a sufficient bandwidth, which improves the overall performance of FUVH for monitoring remote ships noise. Meanwhile, this paper theoretically analyzes the performance of AFUVH for detecting acoustic signals. ANSYS 17.0 simulation is used to derive the parameters of effective structure and optimum dimension structure of annulus-shaped ciliary structure. Finally, the experimental results show that comparing with cilium-structured FUVH, the sensitivity of AFUVH with effective structure is increased by 3.92 dB, and the sensitivity of AFUVH with optimum dimension structure is increased by 5.87 dB, reaching up to −177.53 dB.

Diversity and sexual dimorphism in the head lateral line system in North Sea populations of threespine sticklebacks, Gasterosteus aculeatus (Teleostei: Gasterosteidae)

The mechanosensory lateral line of fishes is a flow sensing system and supports a number of behaviors, e.g. prey detection, schooling or position holding in water currents. Differences in the neuromast pattern of this sensory system reflect adaptation to divergent ecological constraints. The threespine stickleback, Gasterosteus aculeatus, is known for its ecological plasticity resulting in three major ecotypes, a marine type, a migrating anadromous type and a resident freshwater type. We provide the first comparative study of the pattern of the head lateral line system of North Sea populations representing these three ecotypes including a brackish spawning population. We found no distinct difference in the pattern of the head lateral line system between the three ecotypes but significant differences in neuromast numbers. The anadromous and the brackish populations had distinctly less neuromasts than their freshwater and marine conspecifics. This difference in neuromast number between marine and anadromous threespine stickleback points to differences in swimming behavior. We also found sexual dimorphism in neuromast number with males having more neuromasts than females in the anadromous, brackish and the freshwater populations. But no such dimorphism occurred in the marine population. Our results suggest that the head lateral line of the three ecotypes is under divergent hydrodynamic constraints. Additionally, sexual dimorphism points to divergent niche partitioning of males and females in the anadromous and freshwater but not in the marine populations. Our findings imply careful sampling as an important prerequisite to discern especially between anadromous and marine threespine sticklebacks.

Unraveling the Molecular Players at the Cholinergic Efferent Synapse of the Zebrafish Lateral Line.

The lateral line (LL) is a sensory system that allows fish and amphibians to detect water currents. LL responsiveness is modulated by efferent neurons that aid in distinguishing between external and self-generated stimuli, maintaining sensitivity to relevant cues. One component of the efferent system is cholinergic, the activation of which inhibits afferent activity. LL hair cells (HCs) share structural, functional, and molecular similarities with those of the cochlea, making them a popular model for studying human hearing and balance disorders. Because of these commonalities, one could propose that the receptor at the LL efferent synapse is a α9α10 nicotinic acetylcholine receptor (nAChR). However, the identities of the molecular players underlying ACh-mediated inhibition in the LL remain unknown. Surprisingly, through the analysis of single-cell expression studies and in situ hybridization, we describe that α9, but not the α10, subunits are enriched in zebrafish HCs. Moreover, the heterologous expression of zebrafish α9 subunits indicates that homomeric receptors are functional and exhibit robust ACh-gated currents blocked by α-bungarotoxin and strychnine. In addition, in vivo Ca2+ imaging on mechanically stimulated zebrafish LL HCs show that ACh elicits a decrease in evoked Ca2+ signals, regardless of HC polarity. This effect is blocked by both α-bungarotoxin and apamin, indicating coupling of ACh-mediated effects to small-conductance Ca2+-activated potassium (SKs) channels. Our results indicate that an α9-containing (α9*) nAChR operates at the zebrafish LL efferent synapse. Moreover, the activation of α9* nAChRs most likely leads to LL HC hyperpolarization served by SK channels.SIGNIFICANCE STATEMENT The fish lateral line (LL) mechanosensory system shares structural, functional, and molecular similarities with those of the mammalian cochlea. Thus, it has become an accessible model for studying human hearing and balance disorders. However, the molecular players serving efferent control of LL hair cell (HC) activity have not been identified. Here we demonstrate that, different from the hearing organ of vertebrate species, a nicotinic acetylcholine receptor composed only of α9 subunits operates at the LL efferent synapse. Activation of α9-containing receptors leads to LL HC hyperpolarization because of the opening of small-conductance Ca2+-activated potassium channels. These results will further aid in the interpretation of data obtained from LL HCs as a model for cochlear HCs.

Interface Deformable, Thermally Sensitive Hydrogel–Elastomer Hybrid Fiber for Versatile Underwater Sensing

AbstractUnderwater sensing plays a vital role in perceiving various hydrodynamic stimuli for underwater operations, while fishes evolve an adaptable, durable, and multifunctional lateral line sensory system to feel mechanical deformations from nearly all sources as well as water temperature changes. Such perfect integration of multiple functions into one biological system poses a great challenge for artificial soft sensors. Here, by constructing a stretchable and water‐proof core‐cladding hydrogel–elastomer hybrid optical fiber, nearly all the underwater sensations of fish lateral lines can be realized with unprecedented sensing stability. High‐refractive‐index salt, LiBr, is introduced to the hydrogel core to enable long‐range light propagation with a low loss coefficient (≈0.32 dB cm−1), and the dissimilar yet tightly adhered hydrogel–elastomer interface is readily deformable, contributing to the ultrasensitive optical response to subtle environmental stimulations, induced by either motions, hydrostatic pressure variations, ultrasonic/audible sound waves, or water flows. Moreover, the optical loss of the hybrid fiber is linearly responsive to wide temperature changes (5–70 °C), caused by the altered light scattering from hydrogel chain clustering. The present elastomer–hydrogel hybrid optical fiber offers a new designing strategy in developing next‐generation underwater stretchable ray‐optic sensors.

A numerical study of target flow field detection by autonomous underwater vehicles

ABSTRACT Sideline is a key component of fish sensory system, which has been found to affect many behaviours of fish, including manoeuvring obstacle avoidance, prey tracking and environmental mapping in complex fluid environment. In this paper, based on the sensing flow field mechanism of fish lateral line system, a sphere obstacle model is established by using the CFD method and FLUENT software, and the flow field around it is simulated and calculated. The experiment controls two variables: water flow velocity and sphere size. In this paper, the influence of velocity and obstacle size on pressure distribution is analysed, and the rectangular coordinate system is established with the spherical centre as the origin, and the characteristics of pressure distribution in X and Y directions are summarised. This research plays an important role in promoting the development of autonomous underwater vehicles.

Simulation Study for Obstacle Avoidance of Autonomous Underwater Vehicles

Li, Y. and Zhang, M., 2020. Simulation study for obstacle avoidance of autonomous underwater vehicles. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 104–108. Coconut Creek (Florida), ISSN 0749-0208.Fish can track their prey and detect their surroundings in a complex water environment because of their unique underwater perception advantage. In this paper, on the basis of the sensing flow-field environment mechanism of the fish lateral line system, by analyzing the sonar system of an autonomous underwater vehicle (AUV) and the sensing principle of the fish lateral line system, the obstacle model of two shapes is established by using ANSYS software with computational fluid dynamics (CFD) analysis method. Two characteristic variables of different flow velocity and obstacle size are combined to simulate the flow field. The flow field of the fluid through different shape obstacles is analyzed, and the variation of the flow velocity to the flow field around the obstacle is compared, with the aim to establish a method to actively perceive and analyze the surrounding flow-field information through the characteristic parameters (velocity, size, shape) of the underwater obstacle itself. This paper provides a novel idea and practical sensing means for underwater detection technology, which can fill the void left by sonar and vision systems in a chaotic water environment. Improving the adaptive ability of AUV flow field and providing the theoretical basis for realizing the bionic lateral line engineering in the future, this research has an important impetus to the development of AUVs.

Shape Classification Using Hydrodynamic Detection via a Sparse Large-Scale 2D-Sensitive Artificial Lateral Line

Artificial lateral lines are fluid flow sensor arrays, bio-inspired by the fish lateral line organ, that measure a local hydrodynamic environment. These arrays are used to detect objects in water, without relying on light, sound, or on an active beacon. This passive sensing method, called hydrodynamic imaging, is complementary to sonar and vision systems and is suitable for collision avoidance and near-field covert sensing. This sensing method has so far been demonstrated on a biological scale from several to tens of centimeters. Here, we present measurements using a large-scale artificial lateral line of 3.5 meters, consisting of eight all-optical 2D-sensitive flow sensors. We measure the fluid flow as produced by the motion of five different objects, towed across a swimming pool. This results in repeatable stimuli, whose measurements demonstrate a complementary aspect of 2D-sensing. These measurements are both used for constructing temporal hydrodynamic signatures, which reflect the object’s shape, and for flow-feature based near-field object classification. For the latter, we present a location-invariant feature extraction method which, using an Extreme Learning Machine neural network, results in a classification F1-score up to 98.6% with selected flow features. We find that, compared to the traditional sensing dimension parallel to the sensor array, the novel transverse fluid velocity component bears more information about the object shape. The classification of objects via hydrodynamic imaging thus benefits from 2D-sensing and can be scaled up to a supra biological scale of several meters.

BTO/P(VDF-TrFE) Nanofiber-based Artificial Lateral Line Sensor with Drag Enhancement Structures

A flexible Artificial Lateral Line (ALL) sensor is presented in this paper, featuring a barium titanate/polyvinylidene fluoride-trifluoroethylene [BTO/P(VDF-TrFE)] nanofiber mat, a hydrogel cupula, and a constriction structure in the canal.. The excellent piezoelectric performance of the BTO/P(VDF-TrFE) nanofiber, superior to that of a pristine P(VDF-TrFE) nanofiber, helps improve the sensitivity of the ALL sensor. The hydrogel cupula imitating the cupula in a fish lateral line system enhances the ALL sensitivity through a material-induced drag enhancement mechanism. The constriction mimics the diminution structure found in fish canal lateral line systems, endowing the canal ALL sensor with enhanced sensitivity through a structure-induced drag enhancement mechanism. The contributions of the hydrogel cupula and constriction structure in offering an enhanced sensing performance are studied experimentally, in comparison with conventional ALL sensors. The constriction structure in the canal helps modify the frequency response of the canal ALL sensor, i.e., attenuating low frequencies while amplifying high frequencies. The proposed biomimetic flow sensor is expected to aid in the development of smart skins for underwater robotics applications.

Three-dimensional multi-source localization of underwater objects using convolutional neural networks for artificial lateral lines.

This research focuses on the signal processing required for a sensory system that can simultaneously localize multiple moving underwater objects in a three-dimensional (3D) volume by simulating the hydrodynamic flow caused by these objects. We propose a method for localization in a simulated setting based on an established hydrodynamic theory founded in fish lateral line organ research. Fish neurally concatenate the information of multiple sensors to localize sources. Similarly, we use the sampled fluid velocity via two parallel lateral lines to perform source localization in three dimensions in two steps. Using a convolutional neural network, we first estimate a two-dimensional image of the probability of a present source. Then we determine the position of each source, via an automated iterative 3D-aware algorithm. We study various neural network architectural designs and different ways of presenting the input to the neural network; multi-level amplified inputs and merged convolutional streams are shown to improve the imaging performance. Results show that the combined system can exhibit adequate 3D localization of multiple sources.

Optimal sensor placement for artificial swimmers

Natural swimmers rely for their survival on sensors that gather information from the environment and guide their actions. The spatial organization of these sensors, such as the visual fish system and lateral line, suggests evolutionary selection, but their optimality remains an open question. Here, we identify sensor configurations that enable swimmers to maximize the information gathered from their surrounding flow field. We examine two-dimensional, self-propelled and stationary swimmers that are exposed to disturbances generated by oscillating, rotating and D-shaped cylinders. We combine simulations of the Navier–Stokes equations with Bayesian experimental design to determine the optimal arrangements of shear and pressure sensors that best identify the locations of the disturbance-generating sources. We find a marked tendency for shear stress sensors to be located in the head and the tail of the swimmer, while they are absent from the midsection. In turn, we find a high density of pressure sensors in the head along with a uniform distribution along the entire body. The resulting optimal sensor arrangements resemble neuromast distributions observed in fish and provide evidence for optimality in sensor distribution for natural swimmers.

Constriction canal assisted artificial lateral line system for enhanced hydrodynamic pressure sensing

With the assistance of mechanosensory lateral line system, fish can perceive minute water motions in complex underwater environments. Inspired by the constriction within canal nearby canal neuromast in fish lateral line system, we proposed a novel canal artificial lateral line (CALL) device with constriction in canal nearby the sensing element. The designed CALL device consisted of a poly(vinylidene fluoride-trifluoroethylene)/polyimide cantilever as the sensing element and a polydimethylsiloxane (PDMS) microfluid canal. Two types of CALL devices, i.e., CALL with straight canal (S-CALL) and CALL with constriction canal (C-CALL), were developed and characterized employing a dipole source. Experimental results showed that the proposed C-CALL device achieved a pressure gradient detection limit of 0.64 Pa m−1, which was much lower than the S-CALL device. It indicates that the constriction in the canal nearby the sensing element could enhance the hydrodynamic pressure sensing performance of the CALL device. In addition, the constriction could modify the frequency response of the CALL device, and the C-CALL device achieved higher voltage output than S-CALL in high-frequency domain.

Underwater Robot Detection System Based on Fish’s Lateral Line

This paper introduces the near-field detection system of an underwater robot based on the fish lateral line. Inspired by the perception mechanism of fish’s lateral line, the aim is to add near-field detection functionality to an underwater vehicle. To mimic the fish’s lateral line, an array of pressure sensors is developed and installed on the surface of the underwater vehicle. A vibrating sphere is simulated as an underwater pressure source, and the moving mechanism is built to drive the sphere to vibrate at a certain frequency near the lateral line. The calculation of the near-field pressure generated by the vibrating sphere is derived by linearizing the kinematics and dynamics conditions of the free surface wave equation. Structurally, the geometry shape of the detection system is printed by a 3D printer. The pressure data are sent to the computer and analyzed immediately to obtain information of the pressure source. Through the experiment, the variation law of the pressure is generated when the source vibrates near the body, and is consistent with the simulation results of the derived pressure calculation formula. It is found that the direction of the near-field pressure source can distinguished. The pressure amplitude of the sampled signals are extracted to be prepared for the next step to estimate the vertical distance between the center of the pressure source and the lateral line.

Using fish lateral line sensing to improve seismic acquisition and processing.

Bioengineering, which studies the principles and design of biological systems, is a field that has inspired the development of several technologies that are currently in use. In this work, we use concepts from the fish lateral line sensing mechanism and apply them to seismic imaging processing. The lateral line is a sensory system composed of an integrated array of mechanical sensors spanning along the fish body. We compare the array of sensors along body fish with the seismic acquisition, which employs an array of equally spaced identical mechanical sensors to image the Earth’s subsurface. In both situations, the mechanical sensors capture and process mechanical vibrations from the environment to produce useful information. We explore the strategy of using the low-pass and high-pass sensors schema of fish lateral line to improve the seismic technique. We use the full-wave inversion method to compare the conventional acquisition procedure of identical sensors with alternative sets of different sensors, which mimics the fish lateral line. Our results show that the alternate sensors arrangement surpasses the performance of the conventional acquisition method, using just half of the input information. The results point at an image processing technique that is computationally more efficient and economical than the usual seismic processing method.

Canal neuromasts enhance foraging in zebrafish (Danio rerio)

Aquatic animals commonly sense flow using superficial neuromasts (SNs), which are receptors that extend from the body’s surface. The lateral line of fishes is unique among these systems because it additionally possesses receptors, the canal neuromasts (CNs), that are recessed within a channel. The lateral line has inspired the development of engineered sensors and concepts in the analysis of flow fields for submersible navigation. The biophysics of CNs are known to be different from the SNs and thereby offer a distinct submodality. However, it is generally unclear whether CNs play a distinct role in behavior. We therefore tested whether CNs enhance foraging in the dark by zebrafish (Danio rerio), a behavior that we elicited with a vibrating rod. We found that juvenile fish, which have only SNs, bite at this rod at about one-third the rate and from as little as one-third the distance of adults for a high-frequency stimulus (50 < f < 100 Hz). We used novel techniques for manipulating the lateral line in adults to find that CNs offered only a modest benefit at a lower frequency (20 Hz) and that foraging was mediated entirely by cranial neuromasts. Consistent with our behavioral results, biophysical models predicted CNs to be more than an order of magnitude more sensitive than SNs at high frequencies. This enhancement helps to overcome the rapid spatial decay in high-frequency components in the flow around the stimulus. These findings contrast what has been previously established for fishes that are at least ten-times the length of zebrafish, which use trunk CNs to localize prey. Therefore, CNs generally enhance foraging, but in a manner that varies with the size of the fish and its prey. These results have the potential to improve our understanding of flow sensing in aquatic animals and engineered systems.

Bidirectional biomimetic flow sensing with antiparallel and curved artificial hair sensors.

Background: Flow stimuli in the natural world are varied and contain a wide variety of directional information. Nature has developed morphological polarity and bidirectional arrangements for flow sensing to filter the incoming stimuli. Inspired by the neuromasts found in the lateral line of fish, we present a novel flow sensor design based on two curved cantilevers with bending orientation antiparallel to each other. Antiparallel cantilever pairs were designed, fabricated and compared to a single cantilever based hair sensor in terms of sensitivity to temperature changes and their response to changes in relative air flow direction.Results: In bidirectional air flow, antiparallel cantilever pairs exhibit an axially symmetrical sensitivity between 40 μV/(m s−1) for the lower air flow velocity range (between ±10–20 m s−1) and 80 μV/(m s−1) for a higher air flow velocity range (between ±20–32 m s−1). The antiparallel cantilever design improves directional sensitivity and provides a sinusoidal response to flow angle. In forward flow, the single sensor reaches its saturation limitation, flattening at 67% of the ideal sinusoidal curve which is earlier than the antiparallel cantilevers at 75%. The antiparallel artificial hair sensor better compensates for temperature changes than the single sensor.Conclusion: This work demonstrated the successive improvement of the bidirectional sensitivity, that is, improved temperature compensation, decreased noise generation and symmetrical response behaviour. In the antiparallel configuration, one of the two cantilevers always extends out into the free stream flow, remaining sensitive to directional flow and preserving a sensitivity to further flow stimuli.

Design and simulation of artificial fish lateral line

Fishes can avoid colliding with obstacles and track baits depending on the lateral distributed sense nodes which can sense the pressure variances of the surrounding flow field. Fish often uses the lateral-line system as their only means for navigation, especially under poor visual conditions. This sensing mechanism provides a new perspective for researchers and engineers to build such a sensing system that could be applied to control and near field navigation for underwater robots and vehicles. In this article, a pressure-sensing-based is proposed, with 10 pressure sensors acting as lateral line and use the three-dimensional printer to print the fish structure and install the artificial lateral line on it. Through preliminary experiments and numerical simulation, we obtain the pressure sensor data. By comparing the experimental data with the numerical simulation data, it can be verified that the pressure variation of the pressure sensor in the numerical simulation data is consistent with that in the experimental data. The artificial lateral line provides a new sense to man-made underwater vehicles and marine robots, so that they can sense like fish.

Research on Flow Field Perception Based on Artificial Lateral Line Sensor System.

In nature, the lateral line of fish is a peculiar and important organ for sensing the surrounding hydrodynamic environment, preying, escaping from predators and schooling. In this paper, by imitating the mechanism of fish lateral canal neuromasts, we developed an artificial lateral line system composed of micro-pressure sensors. Through hydrodynamic simulations, an optimized sensor structure was obtained and the pressure distribution models of the lateral surface were established in uniform flow and turbulent flow. Carrying out the corresponding underwater experiment, the validity of the numerical simulation method is verified by the comparison between the experimental data and the simulation results. In addition, a variety of effective research methods are proposed and validated for the flow velocity estimation and attitude perception in turbulent flow, respectively and the shape recognition of obstacles is realized by the neural network algorithm.

Bio-inspired all-optical artificial neuromast for 2D flow sensing

We present the design, fabrication and testing of a novel all-optical 2D flow velocity sensor, inspired by a fish lateral line neuromast. This artificial neuromast consists of optical fibres inscribed with Bragg gratings supporting a fluid force recipient sphere. Its dynamic response is modelled based on the Stokes solution for unsteady flow around a sphere and found to agree with experimental results. Tuneable mechanical resonance is predicted, allowing a deconvolution scheme to accurately retrieve fluid flow speed and direction from sensor readings. The optical artificial neuromast achieves a low frequency threshold flow sensing of 5 mm s−1 and 5 μm s−1 at resonance, with a typical linear dynamic range of 38 dB at 100 Hz sampling. Furthermore, the optical artificial neuromast is shown to determine flow direction within a few degrees.

Apparent sixth sense in theropod evolution: The making of a Cretaceous weathervane.

ObjectiveTwo separate and distinctive skills are necessary to find prey: Detection of its presence and determination of its location. Surface microscopy of the dentary of albertosaurines revealed a previously undescribed sensory modification, as will be described here. While dentary “foramina” were previously thought to contain tactile sensory organs, the potential function of this theropod modification as a unique localizing system is explored in this study.MethodDentary surface perforations were examined by surface epi-illumination microscopy in tyrannosaurine and albertosaurine dinosaurs to characterize their anatomy. Fish lateral lines were examined as potentially comparable structures.ResultIn contrast to the subsurface vascular bifurcation noted in tyrannosaurines (which lack a lateral dentary surface groove), the area subjacent to the apertures in albertosaurine grooves has the appearance of an expanded chamber. That appearance seemed to be indistinguishable from the lateral line of fish.ConclusionDentary groove apertures in certain tyrannosaurid lines (specifically albertosaurines) not only have a unique appearance, but one with significant functional and behavior implications. The appearance of the perforations in the dentary groove of albertosaurines mirrors that previously noted only with specialized neurologic structures accommodating derived sensory functions, as seen in the lateral line of fish. The possibility that this specialized morphology could also represent a unique function in albertosaurine theropods for interacting with the environment or facilitating prey acquisition cannot be ignored. It is suggested that these expanded chambers function in perceiving and aligning the body relative to the direction of wind, perhaps a Cretaceous analogue of the contemporary midwestern weathervane.