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Cell migration is an essential physiological process in the life cycle of cells, playing a crucial role in cancer metastasis, neural development, and cellular immune response. However, achieving precise control of cell migration at single‐cell level is challenging due to the intricate and diverse microenvironments of cells. Here, an optical technique is presented that utilizes light‐actuated micronavigators to guide the directional migration of individual cells both in vitro and in vivo. Employing high‐speed scanning optical tweezers, micronavigators near target cells are trapped and rotated at a rotation speed of up to 12 000 rpm, which, to the best of knowledge, represents the fastest rotation of light‐driven micromotors in a biological environment to date. The micronavigators generate a powerful fluid shear force (up to 40 pN) which can guide the migration of immune and nerve cells in a predetermined direction. Furthermore, micronavigators are employed to guide cell migration in various biological systems, including lab‐on‐a‐chip devices and blood vessels within living animals. This technique offers new opportunities for controlling cell migration, enabling precise immune activation, and neuron repair at the single‐cell level. [ABSTRACT FROM AUTHOR]

The visual perception of a moving target is not always true. Wheels turning rapidly, for instance, may look like rotating inversely. This phenomenon is known as the wagon‐wheel effect (WWE) and it is caused by the undersampling of visual information. Here, an analogous manifestation of the WWE concept is described in the scenario of light–matter interactions, by showing that the dynamic response of a particle, to an optical trap scanned at different rates, can be diametrically opposed. Further, such behaviors are modulated by the particle dimensions, which can be exploited for particle size selection. The results uncover a distinct paradigm of nontrivial optical manipulation and expand the bidirectional optical sorting range of dielectric particles to the sub‐200 nm scale. [ABSTRACT FROM AUTHOR]

The intensity gradient of light represents the most important property for optical tweezers to manipulate small particles, which is known to produce a conservative optical force that is either attractive or repulsive. Here, it is shown that Kerker interference, the interplay between electric and magnetic dipoles induced in nanoparticles, permits the intensity gradient to exert a nonconservative optical force, in the case of a standard optical trap created with linearly or elliptically polarized Gaussian beams. The Kerker‐type intensity‐gradient force has an "anisotropic" directionality, and it tends to repel particles away from the beam axis. Such repulsive effects can greatly sensitize the particle trapping behavior of optical tweezers to the particle size. Utilizing these peculiar properties, all‐optical sorting of Si nanoparticles is theoretically demonstrated, with tunable size‐selection criterion and accuracy. [ABSTRACT FROM AUTHOR]

Intensity-Gradient Force: Kerker-Type Intensity-Gradient Force of Light (Laser Photonics Rev. 14(4)/2020) In article number 1900265 by Yao Zhang and co-workers, a nontrivial optical intensity-gradient force is uncovered in conventional optical tweezers set-ups. Its non-conservative and anisotropic properties are in sharp contrast to the classical widespread picture of optical intensity-gradient forces. [Extracted from the article]