A new mechanical energy harvester has been proposed, which can harvest, store and deliver energy in mechanical form. This harvester can be exploited in bioimplantable devices. The structure composed of three individual parts, namely actuator, storage and latch, accumulates mechanical energy in a conventional spiral spring in terms of stepwise rotation. A ratchet mechanism latches the spring and releases it when energy delivery is required. Various cells are defined and their performances are compared under sequential mechanical forces of up to 7 N amplitude, which models heart vein vibration force. The storage part will store 3.21 mJ energy in a single-step rotation. The total area of the structure was 30.06 mm2 with a thickness of 0.7 mm. The proposed mechanical microstructure shows an effective solution in bioimplantable energy harvesters.