Photothermal metallic nanoparticles have attracted significant attention owing to their energy-conversion properties1-4. Here, we introduce an optofluidic application based on a direct optical-to-hydrodynamic energy conversion using suspended photothermal nanoparticles near the liquid-air interface. Using light beams with submilliwatt power, we can drive and guide liquid flow in microfluidic channels to transport biomolecules and living cells at controlled speeds and directions. Previously, a variety of methods for controlling microscale liquid flow have been developed owing to the increasing interest for microfluidics-based biochemical analysis systems5. However, our method dispenses with the need for complex pump and valve devices6-8, surface chemistry9,10 and electrode patterning11-14, or any other further effort towards substrate fabrication15,16. Instead, our optofluidic control method will allow the fabrication of all-optical large-scale integrated microfluidic circuits for biomolecular and cellular processing without any physical valve or mechanical pumping device.
Bibliographical noteFunding Information:
The authors gratefully acknowledge financial support from the Defense Science Office of the Defense Advanced Research Projects Agency, USA. J.K. was supported by a grant (05K1501-02810) from the Center for Nanostructured Materials Technology under the 21st Century Frontier R&D Programs of the Ministry of Science and Technology, Korea. Correspondence and requests for materials should be addressed to L.P.L. Supplementary Information accompanies this paper on www.nature.com/naturematerials.