MEMS-based Humidity Sensor Research Articles

Measurement of Hydrogen Fuel Cell Car Using MEMS Sensor

In today’s world, with increasing price of fuels, depletion of natural resources and pollution levels mounting up, an eco friendly and cheap alternative fuel in automobiles can be implemented. A hydrogen fuel cell makes it possible by converting the hydrogen to electricity that powers the vehicle. The proposed green fuel is hydrogen which is combined with oxygen inside the fuel cell. The byproduct is water which can be used for purposes like irrigation, domestic and industrial uses after treatment. The fuel cell efficiency is dependent on its moisture content and so a MEMS based humidity sensor is proposed for measuring the humidity

MEMS Based Humidity Sensor with Integration of Temperature Sensor

Humidity and temperature are one of the basic weather parameters that play a significant role in human life and its environment. This study utilizes finite element analysis for the optimization of temperature sensor The temperature sensor utilizes platinum RTD with a meander shape as a sensing element and parallel plate capacitive humidity sensor with array of hole at the upper electrode made of aluminum was design to operate in the range of -70°C to 70°C, 0% to 100% respectively. The humidity sensor gives a higher capacitance value of 120pF and sensitivity of 22pF/%RH. Moreover, the average temperature coefficient of resistances was found 5×10-4C-1. The results were compared based on analytical method and simulation in COMSOL Multiphysics. In future, atmospheric pressure sensor and wind velocity will be integrated with the above-mentioned sensor design.

MEMS based humidity sensor using Si cantilever beam for harsh environmental conditions

Sensing and controlling of humidity is a major issue in various industries. Many of the equipments in industries require monitoring and controlling humidity for its efficient and reliable operation. This paper presents the design, fabrication and complete characterization of a micro cantilever based humidity sensor for harsh environmental conditions. A Si cantilever humidity sensor based on capacitive principle is designed and displacement analysis is performed on the sensor. The polyimide, acts as a sensing material for this sensor. The polyimide is coated over the beam to sense the humidity. If the humidity absorbed by the polyimide material increases, the mass of the beam is also increased. The deflection of the beam causes the change in capacitance. The relative humidity can be calculated using the change in capacitance. The beam had an appreciable deflection causing a notable change in capacitance. The variation of capacitance is in the order of picofarads. The sensor is designed in a structure that can tolerate the harsh environmental conditions like pressure, temperature, etc.

MEMS-based humidity sensor with integrated temperature compensation mechanism

This study applies conventional micro-electro-mechanical systems (MEMS) techniques to develop a novel low-cost humidity sensor comprising a silicon substrate, a freestanding cantilever and an integrated resistive thermal sensor. The cantilever has a composite structure comprising a thin layer of platinum (Pt) deposited on a silicon nitride layer and then covered with a polyimide sensing layer. The cantilever deflected in the upward direction as water molecules absorbed by the polyimide sensing layer. The humidity sensor chip caused a measurable change in the resistance of the platinum layer. By compensating the change in the measured resistance by the ambient temperature, the absolute value of the relative humidity can be directly derived. The experimental results show that the sensor has a time-response of 0.9 s when exposed to a sudden humidity change of 65%RH to 95%RH. The sensitivity of the sensors decreases as the temperature increases. Furthermore, the sensor with the longest Pt resistor has the greatest sensitivity. In additions, the temperature-calibrated resistance signal generated by the sensor varies linearly with the ambient humidity.