We have demonstrated a wireless hydrogen sensing system using commercially available wireless components and GaN Schottky diodes or AlGaN/GaN High Electron Mobility Transistors (HEMTs) as the sensing devices. GaN-based wide bandgap materials can be operated in high temperature, high power, high radiation or harsh environments. Platinum metal was used as the diode contact, which creates a catalytic surface for cracking molecular hydrogen. The resulting atomic hydrogen then diffuses to the metal-semiconductor interface and alters the device characteristics through its effect on surface charge. The HEMT structure shows increased sensitivity since it operates with an amplification effect, which is fundamentally different from the conventional sensing mechanism by detecting the conductivity change of the materials upon exposure to the hydrogen ambient. Our sensors have achieved ppm level detection, with the added advantages of a very rapid response time within a couple of seconds, and rapid recovery. The sensors have shown current stability for more than 6 weeks in an outdoor environment.

Our wireless network sensing system enables wireless monitoring of independent sensor nodes and transmits wireless signals. This is especially useful in manufacturing plants and hydrogen-fuelled automobile dealerships, where a number of sensors, possibly with each detecting different chemicals, would be required. The sensor data, along with each sensor's unique ID code, is transmitted wirelessly to a central station connected to a computer. The computer processes the sensor data and performs pre-programmed actions, such as triggering alarms or shutting off valves. If connected to the Internet, the computer can also send the data to a remote server.

We have also developed an energy-efficient transmission protocol to reduce the power consumption of the remote sensor nodes. This enables very long lifetime operation using batteries. Experimental results showed that a 150 meter transmission distance can be achieved with 10 mW total power consumption. Most of the power consumption is in the powering of the sensor device itself, which draws 5 mA when active. Efforts are underway to improve the design of the sensor to reduce power consumption, and 500 mA levels have been achieved. This will cut the power consumption in half. The entire sensor package can be built for less than $50, making it extremely competitive in today's market.