Nearly all underwater vehicles and surface ships today use sonar and vision for imaging and navigation. However, sonar and vision systems face various limitations, e.g., sonar blind zones, dark or murky environments, etc. Evolved over millions of years, fish use the lateral line, a distributed linear array of flow sensing organs, for underwater hydrodynamic imaging and information extraction. We demonstrate here a proof-of-concept artificial lateral line system. It enables a distant touch hydrodynamic imaging capability to critically augment sonar and vision systems. We show that the artificial lateral line can successfully perform dipole source localization and hydrodynamic wake detection. The development of the artificial lateral line is aimed at fundamentally enhancing human ability to detect, navigate, and survive in the underwater environment.dipole localization ͉ hot wire anemometer ͉ micromachining ͉ wake detection ͉ neuromast A lateral line is a spatially distributed system of flow sensors found on the body surface of fish (1) and aquatic amphibians (2). It is comprised of arrays of neuromasts, which can be classified into two types: superficial neuromasts and canal neuromasts (Fig. 1). A superficial neuromast is situated on the surface of the fish and responds in proportion to fluid velocity (3, 4). In contrast, a canal neuromast is packaged in fluid-filled canals located beneath the surface of the skin and are commonly described as a detector of outside water acceleration that is proportional to the pressure gradient (1, 3-6). As an integrated flow sensing system, such lateral lines form spatial-temporal images of nearby sources based on their hydrodynamic signatures (1, 3, 5) and provide mechanosensory guidance for many different behaviors, including synchronized swimming in schools, predator and obstacle avoidance, prey detection and tracking, rheotaxis, and holding station behind immersed obstacles in streams (4,7,8). This ''distant touch'' sense complements other sensory modalities, including vision and hearing, to increase survivability in unstructured environments. To date, there has never been an engineering equivalent of the fish lateral line system for underwater vehicles and platforms. The goal of the present research is to build an artificial lateral line that mimics the functional organization and imaging capabilities of the biological one. The artificial lateral line can facilitate fundamental studies of biological systems and provide unprecedented sensing and control functions to underwater vehicles and platforms. Specifically, we envision that the distant touch hydrodynamic imaging capability of the artificial lateral line can provide a new sense in addition to sonar and vision. In this article, we demonstrate the functions of an artificial lateral line under two biologically relevant scenarios: (i) localizing a moving target with flapping part (7, 9, 10) and (ii) imaging a hydrodynamic trail for prey capture (11,12). Development of the Artificial Lateral LineThe artificial lateral line ...

A hydrogel‐capped hair‐cell flow microsensor, which closely mimics a superficial neuromast of a fish, is introduced. By encapsulating the hair sensor into the artificial hydrogel cupula a dramatic increase in hair‐sensor sensitivity to the oscillating and the steady flow is achieved. It opens the way toward the remote monitoring of the underwater environment by autonomous, unmanned microvehicles with self‐navigating capability.

Hydrodynamic imaging using the lateral line plays a critical role in fish behavior. To engineer such a biologically inspired sensing system, we developed an artificial lateral line using MEMS (microelectromechanical system) technology and explored its localization capability. Arrays of biomimetic neuromasts constituted an artificial lateral line wrapped around a cylinder. A beamforming algorithm further enabled the artificial lateral line to image real-world hydrodynamic events in a 3D domain. We demonstrate that the artificial lateral line system can accurately localize an artificial dipole source and a natural tail-flicking crayfish under various conditions. The artificial lateral line provides a new sense to man-made underwater vehicles and marine robots so that they can sense like fish.

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