Developing renewable energy technologies, especially solar energy-based, is of great importance to secure our energy future. Current solar thermal systems, however, have relatively low utilization efficiencies, limited not only by their low solar energy capture efficiency but also the auxiliary pumping power to circulate the working fluid. Here an innovative nanoparticle enabled pump-free direct absorption solar collector concept is presented, which combines the advantages of volumetric solar harvesting and oscillating heat pipes. Two different flow modes have been observed when the concentration of nanofluid is different. There is an optimum filling ratio when the thermal resistance reaches the minimum. Validation experiments show that the proposed concept can efficiently harvest solar energy and spontaneously transfer the heat into targeted areas, providing a novel approach for efficient solar energy utilization. (c) 2019 Elsevier Ltd. All rights reserved.