Most energy generation systems consist of two components: a generator and a battery. Georgia Tech researcher Zhong Lin Wang thinks this is one too many. Along with his team, Wang has developed pocket-calculator-battery-sized fuel cells that is "self-charging." In other words, the device is both the generator and the battery all at once. At the heart of this tiny devices is a piezoelectric membrane which converts mechanical energy into chemical potential energy. The membrane does the job that a generator normally would by forcing lithium ions across the membrane from the cathode to the anode. "People are accustomed to considering electrical generation and storage as two separate operations done in two separate units," said Wang, "We have put them together in a single hybrid unit to create a self-charging power cell, demonstrating a new technique for charge conversion and storage in one integrated unit."