Photonic Nanojet Array for Fast Detection of Single Nanoparticles in a Flow

Abstract

ABSTRACT:We detect by optical microscopy Au and fluorescent nanoparticles (NPs) during their motion in water-based medium, using an array of dielectric microspheres that are patterned in a microwell array template. The microspheres act as lenses focusing the light originating from a microscope objective into so-called photonic nanojets that expose the medium within a microfluidic channel.When a NP is randomly transported through a nanojet, its back-scattered light (for a bare Au NP) or its fluorescent emission is instantaneously detected by video microscopy. Au NPs down to 50 nm in size, as well as fluorescent NPs down to 20 nm in size, are observed by using a low magnification/low numerical aperture microscope objective in bright-field or fluorescence mode, respectively. Compared to the NPs present outside of the photonic nanojets, the light scattering or fluorescence intensity of the NPs in the nanojets is typically enhanced by up to a factor ~40.The experimental intensity is found to be proportional to the area occupied by the NP in the nanojet. The technique is also used for immunodetection of biomolecules immobilized on Au NPs in buffer and, in future, it may develop into a versatile tool to detect nanometric objects of environmental or biological importance, such as NPs, viruses or other biological agents.

Super-Resolution Imaging and Microscopy by Dielectric Particle-Lenses

“…For example, Yang et al demonstrated a microfluidic device with an integrated microsphere-lens-array, as shown in Fig. 20(a-c) [98]. The microspheres are patterned in a microwell array template, acting as lenses focusing the light originating from a microscope objective into photonic nanojets that expose the medium within a microfluidic channel.…”

Optical Trapping and Manipulation Using Optical Fibers

“…The produced parallel photonic nanojets can be used to trap cells with high throughput and high selectivity. Interestingly, researchers found they can also help enhance the backscattering, fluorescence and Raman signal [83][84][85]. The strong confinement of trapping/ excitation field provides new opportunities for trapping and in situ characterization of particles.…”

Process engineering study of photonic nanojet from highly intense to higher propagation using FDTD method

“…Therefore the selection of the proper shape of microstructure depends on the field of various applications. Photonic nanojet is having wide range of applications such as imaging (microscopy [18,19] and Raman spectroscopy [20]), optical tweezing [21], micro etching [22], detection and sensing [23][24][25], laser surgery [17], optical data storage and switching [26,27] etc..…”

“…Theoretical investigations are mainly employed to know the behavior of change in light due to the desired structure. There are several methods employed to compute the solution of electromagnetic waves propagated from a finite structure such as transfer matrix method (TMM) [28], plane wave expansion (PWE) method [29], finite element method (FEM) [30], Boundary element method (BEM) [31], multiple multipole method (MMP) [7,8], finite difference time domain (FDTD) method [1][2][3][4][5][6][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] etc. Though there are several methods adopted for computation purpose, however FDTD method is frequently used because of user friendly simulation packages available in the market and to avoid empirical calculations [32].…”