H. T. Zhao

Nanoparticle sorting in silicon waveguide arrays

This paper presents the optical fractionation of nanoparticles in silicon waveguide arrays. The optical lattice is generated by evanescent coupling in silicon waveguide arrays. The hotspot size is tunable by changing the refractive index of surrounding liquids. In the experiment, 0.2-μm and 0.5-μm particles are separated with a recovery rate of 95.76%. This near-field approach is a promising candidate for manipulating nanoscale biomolecules and is anticipated to benefit the biomedical applications such as exosome purification, DNA optical mapping, cell-cell interaction, etc.

Parallel alignment of bacteria using near-field optical force array for cell sorting

This paper presents a near-field approach to align multiple rod-shaped bacteria based on the interference pattern in silicon nano-waveguide arrays. The bacteria in the optical field will be first trapped by the gradient force and then rotated by the scattering force to the equilibrium position. In the experiment, the Shigella bacteria is rotated 90 deg and aligned to horizontal direction in 9.4 s. Meanwhile, ~150 Shigella is trapped on the surface in 5 min and 86% is aligned with angle <; 5 deg. This method is a promising toolbox for the research of parallel single-cell biophysical characterization, cell-cell interaction, etc.

Particle separation under the co-action of Brownian motion and optical force in near-field speckle patterns

Continuous separation of nano-sized molecules has great importance in biomedical applications. This paper represents a near-field optical approach to separate nanoparticles using speckle patterns. Near-field random light patterns (speckle pattern) are generated by the repeated coupling and interference of light in nano-waveguide arrays. The movements of 2-μm and 0.5-μm particles are studied under the co-action of Brownian motion and the exerted optical force. The experimental results show that the 2-μm particle has an average lateral displacement of 10 μm, which is considerably larger than that of the 0.5-μm particle. This method avoids the stringent optical systems and broadens the perspectives of optical manipulation in real-life applications.

Optofluidics: Guiding the Nanoparticles and Biomolecules with Light

Optofluidics has recently gained huge research attentions because of its synergic manipulations of light and liquids. Several optofluidic components and devices have been demonstrated in the last 10 years, leading to its applications in guiding nanoparticles and biomolecules in the microchannel.