Selective current collecting design for spring-type energy harvestersElectronic supplementary information (ESI) available. See DOI: 10.1039/c4ra16443a

Here we present a high performance spring-type piezoelectric energy harvester that selectively collects current from the inner part of a spring shell. We analyzed the main reason behind the low efficiency of the initial design using finite element models and proposed a selective current collecting design that can considerably improve the electrical conversion efficiency of the energy harvester. We found that the newly designed energy harvester increases the output voltage by 8 times leading to an output power of 2.21 μW under an impulsive load of 2.18 N when compared with the conventional design. We envision that selective current collecting design will be used in spring-based self-powered active sensors and energy scavenging devices. We designed and fabricated a high performance spring-type piezoelectric energy harvester that selectively collects current from the inner part of a spring shell.