Hydrogen Sensors That Are Impervious to Water but Sensitive to Gas

PMMA Encapsulation of Semiconductor-Based Hydrogen Sensor Effectively Increases Accuracy of Hydrogen Gas Detection by Blocking Water Molecules while Permitting the Penetration of the Hydrogen Molecules

This poly(methyl methacrylate) (PMMA)-encapsulated Schottky diode protects hydrogen sensors from humidity without affecting their ability to detect hydrogen. Hydrogen is a source of energy that powers different forms of transportation, buildings and industrial processes making it a valuable resource. However, hydrogen can become problematic because it is highly reactive, flammable, has low ignition energy, and has a high tendency to leak. Hence, it is crucial that efficient detection technologies are available to ensure the safe use of hydrogen. One of the biggest issues with GaN-based hydrogen sensors is their sensitivity to humidity. Exposure to ambient humidity significantly decreases the sensitivity because water molecules block the active sites of the sensor. Researchers at the University of Florida have enclosed hydrogen sensing diodes with PMMA to effectively mitigate the effects of water. This enables the sensors to work in a variety of humid environments and allows them to be modified to detect other gases.

Application

Encapsulation of Pt-AlGaN/GaN Schottky diodes with water-blocking polymer layer provide a moisture barrier for gas sensors

Advantages

• Has the ability to detect hydrogen as low as 100 ppm level
• Bars against water but allows hydrogen to permeate barrier, preserving the functionality of the gas sensor in humid conditions
• Able to function at temperatures up to 100 °C, allowing sensors to operate in a larger variety of environments
• Can be used to detect other volatile organic compounds (VOCs) and halogenides, providing a broad use for sensors

Technology

This Schottky diode is completely enclosed in PMMA, which creates a barrier between the sensor and any source of water or moisture, preventing excess background noise and corrosion. The PMMA coating allows hydrogen molecules to diffuse through and reach the sensor while preventing water molecules from reaching the diode. By eliminating this problem, the hydrogen sensor has an increased range of environments in which it can be used and provides more precise measurement.