Trapping and assembling of particles and live cells on large-scale random gold nano-island substrates

Abstract

We experimentally demonstrated the use of random plasmonic nano-islands for optical trapping and assembling of particles and live cells into highly organized pattern with low power density. The observed trapping effect is attributed to the net contribution due to near-field optical trapping force and long-range thermophoretic force, which overcomes the axial convective drag force, while the lateral convection pushes the target objects into the trapping zone. Our work provides a simple platform for on-chip optical manipulation of nano- and micro-sized objects, and may find applications in physical and life sciences.

Thermal gradient induced tweezers for the manipulation of particles and cells

“…Our results show that typical power density of our METH tweezers is in the range of 10−100 μW/μm 2 , which is lower than the optical power density of plasmonic assisted trapping (≥100 μW/μm 2 )11. We expect a relatively lower chance of sample damage914151622 when trapping is performed with METH. This can be explained by the fact that plasmonic optical trapping results in temperature increase in the trapped object due to (i) radiation absorption by the object itself and (ii) conductive thermal energy from plasmonic absorption in the gold nanostructure.…”

“…In the optical case, the trapping potential well takes a Gaussian shape because of the Gaussian intensity profile of the laser focal spot. Consequently, the time evolution plot of particle count increases exponentially1416. While the METH trapping potential well is likely to take a square shape, i.e.…”

“…1). The final METH device structure, which typically contains a narrow current constriction, readily produces localised electrical heating akin to that due to absorption of a focused laser spot141516. Figure 1(b) shows two parallel insulating lines of exposed glass with a width of 2.1-μm, and the endpoints separated by 5 μm.…”

“…In spite of this, it is also exciting to see that optical thermal effect can be utilized to facilitate trapping. Plasmonic bowtie nano-antenna arrays11, single plasmonic nano-antenna assisted with an AC electric field12, thermal absorption medium13, random plasmonic absorption structures1415, and continuous gold films16, have been reported to perform manipulation and transportation of small colloid particles through the assistance of plasmon-induced thermal convection and diffusion. In addition, fibre-optic based tweezer systems1718192021, which are readily integrated into lab-on-a-chip devices, can also reduce the exposure intensities and eliminate the necessity of bulky optics.…”

Insight into plasmonic hot-electron transfer and plasmon molecular drive: new dimensions in energy conversion and nanofabrication

“…66 Using Au nanoisland substrates, another study demonstrated the optical trapping and assembly of PS microspheres and living cells into highly organized patterns with low laser power density (~10 4 W cm − 2 at 785 nm). 68 The observed trapping is attributed to the net contribution from a near-field optical trapping force and a long-range thermophoretic force that overcomes the axial convective drag force. In this case, the thermophoretic force was assumed to have dragged the PS particles from cold to hot, the opposite direction to that suggested by other studies.…”