Artificial lateral line canal system for underwater disturbance sensing.

摘要

The lateral line is a primitive sensory organ commonly found in fish. It plays a vital role in the normal activities of fish including schooling, station holding, prey capture and predator avoidance. The lateral line is a good source of information when visibility is limited or impossible. For instance, a blind cave fish can "see" by imaging the distortion of a self-generated flow field with 1 mm resolution. Functionality of the lateral line has been actively studied by biologists. A type of canal-like lateral line is of particular interest. It consists of flow sensing neuromasts embedded in a canal structure that contains pores. Outside disturbances cause pressure differences between pores and hence induce flow inside the canal. Studies show that fish use this type of canal structure as a mechanical filter to enhance disturbance sensing under noisy flow conditions, such as in running water.;This dissertation describes a new mode of hydrodynamic sensing using a micromachined artificial lateral line canal system. As a potential alternative to sonar, it offers a passive mode of detection, which could allow for the realization of stealth monitoring capabilities. An example would be for the real-time autonomous detection and tracking of underwater targets. In order to create an artificial lateral line canal, flow sensors are needed to detect the flow inside the canal. A microfabricated artificial haircell flow sensor has been developed for this purpose. The sensor utilizes a piezoresistive transduction mechanism. It consists of a silicon cantilever with doped piezoresistors at the fixed end and an out-of-plane, high-aspect-ratio SU-8 hair structure attached to the free end. The design, fabrication, theoretical modeling and experimental characterization of the sensor will be presented. The sensor exhibits good sensitivity down to the submm/s range for underwater oscillatory flow. It can also distinguish between flows from different directions. However, the sensor becomes saturated by low frequency noise under strong background flow. In order to detect disturbances under these conditions, the sensors are embedded in an artificial canal structure. The fabrication of the first prototype artificial lateral line canal device will be presented, followed by the fluid-mechanics modeling and experimental validation. Measurements conducted in running water have clearly demonstrated the advantage of using a canal structure for disturbance sensing under noisy flow conditions.