An energy-generating device is provided for generating energy by device deformation in any of three orthogonal directions. The device includes a resilient wave-shaped substrate (10) comprising six ormore alternating wave structures extending along at least one axis. The resilient wave-shaped substrate (10) is capable of deformation and recovery in three orthogonal directions. Resilient, energy-generating components (20) are mounted on top and bottom surfaces of the resilient wave-shaped structure. The energy-generating components (20) are selected from piezoelectric and triboelectric energy-generating component and output a voltage and current in response to deformation in any of three orthogonal directions. In one aspect, the energy generating device is included in an energy harvester. In another aspect, the energy-generating device is included in a sensor, particularly a sensor for measuring strain. In one aspect a mat of randomly-oriented piezoelectric fibers comprises the energy-generating component. The energy-generation device is portable and responsive to vibration generated by human activity.