“Qin Zhou and A. Zettl of the University of California at Berkeley realized the newly discovered material graphene could make a great electrostatic [diaphragm] material...  
…Thin, conductive, and strong with a high spring constant, graphene could prove to be the material diaphragms of the future are made of, not gel. Due to the combination of properties, graphene speakers could be several magnitudes more energy efficient than current speaker design, leading to some great new applications.”
— The HeadPhoneList.com 1/16/14
 

Graphene

The Holy Grail of Micro Speaker Diaphragm Material