Tribological investigation of piezoelectric ZnO films for rolling contact-based energy harvesting and sensing applications

In this work we propose a rolling-sliding tribological harvester/sensor. Understanding the combination of tribological and piezoelectric output of ZnO films can lead towards the development of the next generation of harvesting and sensing applications that will be based on rolling-sliding contacts. We report on the mixed rolling-sliding characteristics and the piezoelectric output of sol-gel ZnO films deposited on Au-coated glass substrates when in contact with a rolling-sliding counterface electrode. By exposing ZnO surfaces to UV their frictional response, and therefore their response to rolling-sliding counterfaces, can be further studied. For this reason, the films' wetting behavior and frictional response are connected and investigated. We also report on the mechanical properties of the ZnO films using nanoindentation. The piezoelectric response of the films is measured in-situ using a reciprocating apparatus in mixed rolling-sliding conditions. We observe that the proposed device design exhibits response to external mixed sliding-rolling stimulus and remains functional for up to 7500 cycles. In addition, limited ZnO material transfer to the rolling cylinder electrode counterface is observed for the above amount of reciprocating cycles. (C) 2013 Elsevier B.V. All rights reserved.