Hye Jung Cho, Young Jae Kim, Young Soo Joung, Jae Yong Lee, US Patent # US8349487
A fuel cell cartridge includes a fuel pouch to store fuel, the fuel pouch including a fuel outlet; a pressing unit to press the fuel pouch; a variable resistor provided near the fuel pouch; a sensor provided on the pressing unit to read a resistance value of the variable resistor; and a contact pad to transmit an output voltage determined by the resistance value outside the fuel cell cartridge.
http://www.google.ch/patents/US20080070069