Hydrogen sensors and switches from electrodeposited palladium mesowire arrays

Hydrogen sensors and hydrogen-activated switches were fabricated from array s of mesoscopic palladium wires. These palladium "mesowire" arrays were pre pared by electrodeposition onto graphite surfaces and were transferred onto a cyanoacrylate film. Exposure to hydrogen gas caused a rapid (less than 7 5 milliseconds) reversible decrease in the resistance of the array that cor related with the hydrogen concentration over a range from 2 to 10%. The sen sor response appears to involve the closing of nanoscopic gaps or "break ju nctions" in wires caused by the dilation of palladium grains undergoing hyd rogen absorption. Wire arrays in which all wires possessed nanoscopic gaps reverted to open circuits in the absences of hydrogen gas.