A power generating system includes an energy source coupled to a DC link through a first power converter and a second power converter to couple the DC link to a power grid. A preferential printing feature is selected from a group of preferential printing features. Returned ultrasound is sensed by an FBG sensor. Using the spatial and dynamic information the mobile device is further configured to generate a biometric identifier characterizing the user’s biometric features and which can be used to identifyauthenticate the user by comparing the biometric identifier to a previously generated biometric identifier. Moreover, the dynamic friction coefficient was decreased by adding fullerene to synovial fluid.