Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, Massachusetts 02155, USA.
Published: April 2003
AI Article Synopsis
Article Abstract
We demonstrate, what is to the best our knowledge, a new method for studying the motion of a particle trapped by optical tweezers; in this method the trapping beam itself is used as a confocal probe. By studying the response of the particle to periodic motion of the tweezers, we obtain information about the medium viscosity, particle properties, and trap stiffness. We develop the mathematical model, demonstrate experimentally its validity for our system, and discuss advantages of using this method as a new form of scanning photonic force microscopy for applications in which a high spatial and temporal resolution of the medium viscosity is desired.
In this Letter, we have proposed an all-optical scheme for chiral particle separation with a microcylinder-pair system (MCPS) with a micrometer scale channel, applicable in microfluidic environments. By illuminating the MCPS with two counter-incident plane waves of orthogonal polarization, the electromagnetic chirality gradient can be generated. The MCPS can also enhance chirality-dependent lateral optical forces of the coupled fields so that the setup can shift trapping equilibrium positions for opposite-handedness nanoparticles and make the sideways motion observable.
Light-matter interaction is a long-standing promising topic that can be dated back to a few centuries ago and has witnessed the long-term debate between the particle and wave nature of light. In modern condensed matter physics and materials science, light usually serves as a detection tool to effectively characterize the physical and chemical features of samples. The light modulation on intrinsic properties of materials, such as atomic geometries, electronic bands, and magnetic behaviors, is more intriguing for information control and storage.
Center of Single-Molecule Sciences, Institute of Modern Optics, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, Nankai University, Tianjin 300350, China.
Via conductance measurements of thousands of single-molecule junctions, we report that the π-π coupling between neighboring aromatic molecules can be manipulated by laser illumination. We reveal that this optical manipulation originates from the optical plasmonic gradient force generated inside the nanogaps, in which the gapped antenna electrodes act as optical tweezers pushing the neighboring molecules closer together. These findings offer a nondestructive approach to regulate the interaction of the molecules, deepening the understanding of the mechanism of π-π interaction, and open an avenue to manipulate the relative position of extremely small objects down to the scale of single molecules.
Nowadays, optical tweezers play a vital role not only in optical manipulation but also in bioassay. As principal optical trapping objects, microbeads can combine optical tweezers with suspension array technology, with amply focused laser beams and adequately concentrated tags contributing to highly sensitive detection. In view of the inefficiency of conventional single-trap optical tweezers, multitrap systems are developed.
The formation of biomolecular condensates in vitro and in vivo has become an increasingly important subject of studies. One particular area of interest is the phase separation of chromatin in the nucleus. However, the interplay of condensed chromatin and chromatin-binding enzymes has barely been studied as of now.
