High Stability and Low Power Nanometric Bio-Objects Trapping through Dielectric-Plasmonic Hybrid Nanobowtie

Abstract

Micro and nano-scale manipulation of living matter is crucial in biomedical applications for diagnostics and pharmaceuticals, facilitating disease study, drug assessment, and biomarker identification. Despite advancements, trapping biological nanoparticles remains challenging. Nanotweezer-based strategies, including dielectric and plasmonic configurations, show promise due to their efficiency and stability, minimizing damage without direct contact. Our study uniquely proposes an inverted hybrid dielectric-plasmonic nanobowtie designed to overcome the primary limitations of existing dielectric-plasmonic systems, such as high costs and manufacturing complexity. This novel configuration offers significant advantages for the stable and long-term trapping of biological objects, including strong energy confinement with reduced thermal effects. The metal's efficient light reflection capability results in a significant increase in energy field confinement (EC) within the trapping site, achieving an enhancement of over 90% compared to the value obtained with the dielectric nanobowtie. Numerical simulations confirm the successful trapping of 100 nm viruses, demonstrating a trapping stability greater than 10 and a stiffness of 2.203 fN/nm. This configuration ensures optical forces of approximately 2.96 fN with an input power density of 10 mW/μm² while preserving the temperature, chemical-biological properties, and shape of the biological sample.

Keywords: nanomanipulation; optical trapping; virus.

Figure 1

Schematic workflow diagram of the research article.

Figure 2

Schematic of the investigated nanobowtie in SOI platform with a metal layer.

Figure 3

(a) Electric field intensity distribution at the trapping site in the middle plane of the nanostructure at z = 200 nm + t_Ag for the bowtie with t_Ag = 50 nm by considering P_in = 10 mW/μm². (b) Zoom-in of (a).

Figure 4

(a) ΔEC (%) vs. metal layer thickness (nm) with gold and (b) silver layer.

Figure 5

Steady-state temperature rise distributions ∆T(K) = T − T₀, T₀ = 293.15 K for the silver layer configuration at z = 200 nm + t_Ag for P_in = 10 mW/μm².

Figure 6

(a) Temperature increase ∆T in the trapping area as a function of the input optical power for nanocavity with gold layer; (b) silver layer.

Figure 7

Schematic and lateral view of the nanocavity (z–y directions) with a trapped particle (d = 100 nm).

Figure 8

(a) Representation of the intensity of electric field along the trapping site of the nanocavity. (b) Optical force trend vs. displacement of nanoparticle in configuration with gold layer (c) and silver layer.

Figure 9

(a) Stability trapping vs. ∆T for nanobowtie with gold layer; (b) for nanobowtie with silver layer.

Figure 10

(a) Stability trapping by varying the input power P_in for nanobowtie with a gold layer; (b) for nanobowtie with a silver layer.

Figure 11

Trapping stability as a function of the particle diameter and the thickness of two dielectric layers for nanobowtie with a silver layer with P_in = 10 mW/μm².