MEMS (Micro Electro Mechanical Systems) pressure sensor for water flow velocity and flow direction sensing

• Main Author: Goh, Joshua Hui Mun.
• Other Authors: Miao Jianmin
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Nanotechnology; DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/54183
• Institution: Nanyang Technological University

Autonomous Underwater Vehicles are robotic vehicles that travel underwater without requiring real time input from operators. Their usages have been previously limited by technology, but now with unprecedented technology progression, AUVs now have greater processing capabilities and higher durability. Getting employed in various applications that are often requires tedious manning and traveling onto hard to reach regions of the oceans is no longer a mean feat for them. As such, they have been used by oil and gas industry to conduct offshore surveys by mapping out seafloors before the installation of subsea infrastructures such as pipelines. This way helps the companies to be cost effective as well as minimize disturbances to the environment[1]. AUVs are used in military navies to survey seafloors for mines and threats as well as deployment to areas to protect from trespassers such as submarines. They are also used by researches for the study of lakes, oceans and seabed for composition, concentration of substances as well as detection of life forms be it planktonic or marine. The vehicles are also used for transportation of merchandises, tools, stock to various locations with the use of GPS navigation. As such, various drug traffickers have capitalised on this vehicle to bypass customs. Many robot enthusiasts build AUVs as a form of hobby and compete in objective or design based competitions[2]. Current AUVs survey their environments with either sonar or optical sensors. These environments are often murky, corrosive and cluttered in nature. As such, the sensors employed will have to be tough and effective against these conditions in order for the AUVs to obtain acceptable results to accomplish the objectives. Sonar sensors have been widelyused and accepted as a common technology for AUVs. However, under murky and cluttered conditions, they do not produce fine resolution and thus requiring additional surveillance efforts before actions or decisions could be made. Moreover, they have been reported to cause lethal disruptions to marine animals exposed to the waves[3]. In wartime, sonar waves can also allow the enemy to detect the user’s location from tracing the waves[4]. Optical sensors have also failed to work in murky and cluttered environments. The presence of light in these environments is critical for the optical sensors to function. Thus we can see that there is a need for a different kind of sensor that can achieve reasonable resolution in conditions that does not permit light and sound waves to work. Sometimes, nature can provide us with the simplest yet most effective solution. Even the most advance technology may pale out to a simple creation that nature has to offer. We see this from spider web silks that are 10 times stronger than Kevlar and scientists are trying to synthesize these silk. Looking back at murky and cluttered water, we find fishes that are able to navigate and swim within these waters at a fast speed. They depend on arrays of sensors on their skin known as lateral-line. The blind cave fish is one of these fishes that has the capability to manuever efficiently in unlit conditions that have lots of obstacles[5]. It is discovered that their capability was granted by two kinds of sensors on their lateral-line. One being the Superficial Neuromast while the other is the Canal Neuromast. These neuromasts are extremely small yet effective, at around 80x50 micrometres in size. If we were to mimic these sensors, we have to consider Microelectronic mechanical sensors (MEMS) as they are also similar in terms of size[6].