Convection- and bubble-assisted nanoaperture-based plasmonic tweezers are presented to overcome the diffusion-limited trapping. Opto-thermally generated convection and bubble-induced flows rapidly transported particles from large spatial extent to plasmonic nanoapertures without relying on diffusion. The trapping time was reduced by more than order of magnitude. Moreover, the trapping time was brought within practical time limits at ultralow particle concentrations for which it could take several hours to trap a single particle.
Nanoaperture based trapping has developed as a significant tool among the various optical tweezer systems for trapping of very small particles down to the single nanometer range. The double nanohole aperture based trap provides a method for efficient, highly-sensitive, label-free, low-cost, free-solution single molecule trapping and detection. We use the double nanohole tweezer to understand biomolecular phenomena like protein unfolding, binding, structural conformation of DNA, protein-DNA interactions, and protein small molecule interactions.
The nanoplasmonic properties of apertures in metal films have been studied extensively; however, we have recently
discovered surprising new features of this simple system with applications to super-focusing and super-scattering.
Furthermore, apertures allow for optical tweezers that can hold onto particles of the order of 1 nm; I will briefly
highlight our work using these apertures to study protein - small molecule interactions and protein - DNA binding.
In this paper we describe the double nanohole laser tweezer system used to trap single nanoparticles. We cover the basic theory behind the DNH and what makes it more powerful than traditional laser tweezers commonly used for larger particles. We outline the basic setup used to reliably trap several different types of particles ranging in size from 1 nm to 40 nm. Data from several experiments is shown which displays exactly how a particle is confirmed to be trapped. We will discuss the use of autocorrelation as well as other information that can be extracted from the optical transmission in our setup and how it has been applied to the identification of protein small molecule interactions and protein binding. Other uses of the data collected from our setup will be discussed including the observation of protein folding. Finally we discuss the current developments of the process and its possible uses as a drug discovery tool, a new type of single particle nanopipette and new bio-sensors.