Optical tweezers have emerged as a powerful tool for the non-invasive trapping and manipulation of colloidal particles and biological cells1,2. However, the diffraction limit precludes the low-power trapping of nanometre-scale objects. Substantially increasing the laser power can provide enough trapping potential depth to trap nanoscale objects. Unfortunately, the substantial optical intensity required causes photo-toxicity and thermal stress in the trapped biological specimens3. Low-power near-field nano-optical tweezers comprising plasmonic nanoantennas and photonic crystal cavities have been explored for stable nanoscale object trapping4,5,6,7,8,9,10,11,12,13. However, the demonstrated approaches still require that the object is trapped at the high-light-intensity region. We report a new kind of optically controlled nanotweezers, called opto-thermo-electrohydrodynamic tweezers, that enable the trapping and dynamic manipulation of nanometre-scale objects at locations that are several micrometres away from the high-intensity laser focus. At the trapping locations, the nanoscale objects experience both negligible photothermal heating and light intensity. Opto-thermo-electrohydrodynamic tweezers employ a finite array of plasmonic nanoholes illuminated with light and an applied a.c. electric field to create the spatially varying electrohydrodynamic potential that can rapidly trap sub-10 nm biomolecules at femtomolar concentrations on demand. This non-invasive optical nanotweezing approach is expected to open new opportunities in nanoscience and life science by offering an unprecedented level of control of nano-sized objects, including photo-sensitive biological molecules.
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The authors acknowledge financial support from the National Science Foundation (NSF ECCS-1933109) and Vanderbilt University. We thank A. Locke for providing the protein samples and K. Wang and C. Batista for help with the zeta potential measurements.
The authors declare no competing interests.
Peer review information Nature Nanotechnology thanks Reuven Gordon and the other, anonymous, reviewer(s) for their contribution to the peer review of this work
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Figs. 1–2, discussion and refs. 1–5.
Fast transport, trapping and release of a single BSA protein molecule.
Dynamic manipulation of a single BSA protein molecule.
Frequency-dependent tuning of trapping position.
Sorting 20 nm polystyrene particles from a mixture of 100 nm and 20 nm polystyrene particles by changing the a.c. frequency.
Excel data of particle positions for different a.c. frequencies.
Excel data of particle displacements from the edge of the nanohole array for different a.c. frequencies; simulation data for the fluid’s radial velocity as a function of position for different a.c. frequencies; and Excel data of particle positions for different a.c. frequencies.
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Hong, C., Yang, S. & Ndukaife, J.C. Stand-off trapping and manipulation of sub-10 nm objects and biomolecules using opto-thermo-electrohydrodynamic tweezers. Nat. Nanotechnol. (2020). https://doi.org/10.1038/s41565-020-0760-z