Underwater shear-stress sensor

This paper reports the development of a micromachined, vacuum-cavity insulated, thermal shear-stress sensor for underwater applications. We focus on two major challenges for underwater shear-stress sensors: the waterproof coating and pressure sensitivity. It is found that thin-film CVD Parylene is a good waterproof material and sensors coated with 2 µm Parylene N can survive in water for at least one month at 55°C. It is also found that reducing the size and increasing the thickness of the sensor diaphragm are effective in minimizing the pressure sensitivity