Heterogeneous nanoscale extracellular vesicles (EVs) are of significant interest for disease detection, monitoring, and therapeutics. However, trapping these nano-sized EVs using optical tweezers has been challenging due to their small size. Plasmon-enhanced optical trapping offers a solution. Nevertheless, existing plasmonic tweezers have limited throughput and can take tens of minutes for trapping for low particle concentrations.
Vanderbilt University researchers have developed an innovative approach called geometry-induced electrohydrodynamic tweezers (GET) that overcomes these limitations. GET generates multiple electrohydrodynamic potentials, allowing parallel transport and trapping of single EVs within seconds. By integrating nanoscale plasmonic cavities at the center of each GET trap, single EVs can be placed near plasmonic cavities, enabling instant plasmon-enhanced optical trapping upon laser illumination without detrimental heating effects. These non-invasive scalable hybrid nanotweezers open new horizons for high-throughput tether-free plasmon-enhanced single EV trapping and spectroscopy. Other potential areas of impact include nanoplastics characterization, and scalable hybrid integration for quantum photonics.
GET with superimposed plasmonic trapping potential and electrohydrodynamic potential
a Illustration of the GET system with a plasmonic cavity at the center of the void region. b SEM image of the GET trap with a plasmonic double nanohole aperture antenna at the center. The inset illustrates the SEM image of a double nanohole aperture antenna. c Temperature field distribution at the surface of the plasmonic double nanohole aperture antenna on the sapphire substrate under the trapping intensity of 3.2×109 W/m2 (6.3 mW laser power). The result shows that the temperature rise is negligible when the plasmonic cavity is on the high thermal conductivity sapphire substrate. d Simulated optical trapping potential on a 100 nm exosome. The inset shows the electromagnetic field distribution and enhancement near the double nanohole plasmonic aperture. e Frame-by-frame sequence exosome trapping and release using the superposition of electrohydrodynamic and plasmon-enhanced optical trapping potential upon laser illumination (second panel). The laser spot size is 1.6 μm. f Scatter plot showing the trapping stability for a single trapped exosome when either the a.c. field is ON (electrohydrodynamic trapping mode), both laser and a.c field are ON, and when only the laser is ON (i.e. plasmonic trapping mode). Results from microfluidic simulation presented in Fig. S2 show the outwards ACEO flow created by the center plasmonic aperture.