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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 active delivery of nanodrugs has been a bottleneck problem in nanomedicine. While modification of nanodrugs with targeting agents can enhance their retention at the lesion location, the transportation of nanodrugs in the circulation system is still a passive process. The navigation of nanodrugs with external forces such as magnetic field has been shown to be effective for active delivery, but the existing techniques are limited to specific materials like magnetic nanoparticles. In this study, an alternative actuation method is proposed based on optical manipulation for remote navigation of nanodrugs in vivo, which is compatible with most of the common drug carriers and exhibits significantly higher manipulation precision. By the programmable scanning of the laser beam, the motion trajectory and velocity of the nanodrugs can be precisely controlled in real time, making it possible for intelligent drug delivery, such as inverse‐flow transportation, selective entry into specific vascular branch, and dynamic circumvention across obstacles. In addition, the controlled mass delivery of nanodrugs can be realized through indirect actuation by the microflow field. The developed optical manipulation method provides a new solution for the active delivery of nanodrugs, with promising potential for the treatment of blood diseases such as leukemia and thrombosis. [ABSTRACT FROM AUTHOR]

With high reconfigurability and swarming intelligence, programmable medical micromachines (PMMs) represent a revolution in microrobots for executing complex coordinated tasks, especially for dynamic routing of various targets along their respective routes. However, it is difficult to achieve a biocompatible implantation into the body due to their exogenous building blocks. Herein, a living microrouter based on an organic integration of endogenous red blood cells (RBCs), programmable scanning optical tweezers and flexible optofluidic strategy is reported. By harvesting energy from a designed optical force landscape, five RBCs are optically rotated in a controlled velocity and direction, under which, a specific actuation flow is achieved to exert the well‐defined hydrodynamic forces on various biological targets, thus enabling a selective routing by integrating three successive functions, i.e., dynamic input, inner processing, and controlled output. Benefited from the optofluidic manipulation, various blood cells, such as the platelets and white blood cells, are transported toward the damaged vessel and cell debris for the dynamic hemostasis and targeted clearance, respectively. Moreover, the microrouter enables a precise transport of nanodrugs for active and targeted delivery in a large quantity. The proposed RBC microrouter might provide a biocompatible medical platform for cell separation, drug delivery, and immunotherapy. [ABSTRACT FROM AUTHOR]

Serving as natural vehicles to deliver oxygen throughout the whole body, red blood cells (RBCs) have been regarded as important indicators for biomedical analysis and clinical diagnosis. Various diseases can be induced due to the dysfunction of RBCs. Hence, a flexible tool is required to perform precise manipulation and quantitative characterization of their physiological mechanisms and viscoelastic properties. Optical tweezers have emerged as potential candidates due to their noncontact manipulation and femtonewton‐precision measurements. This review aimed to highlight the recent advances in the multifunctional manipulation of RBCs using optical tweezers, including controllable deformation, dynamic stretching, RBC aggregation, blood separation and Raman characterization. Further, great attentions have been focused on the precise assembly of functional biophotonics devices with trapped RBCs, and a brief overview was offered for the growing interests to manipulate RBCs in vivo. [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]

Control of blood microflow is crucial for the prevention and therapy of blood disorders, such as cardiovascular diseases and their complications. Conventional control strategies generally implant exogenous synthetic materials into blood vessels as labeling markers or actuating sources, which are invasive and incompatible with biological systems. Here, a label‐free, noninvasive, and biocompatible device constructed from natural red blood cells (RBCs) for controlling blood microflow in vivo is reported. The RBCs, optically manipulated, arranged, and rotated using scanning optical tweezers, can function as an optofluidic switch for targeted switching, directional enrichment, dynamic redirecting, and rotary actuation of blood microflow inside zebrafish. The regulation precision of the switch is determined to be at the single‐cell level, and the response time is measured as ≈200 ms using a streamline tracking method. This in vivo optofluidic switch may provide a biofriendly device for exploring blood microenvironments in a noncontact and noninvasive manner. [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]

Controllable organization and transport of cell chain in a fluid, which is of great importance in biological and medical fields, have attracted increasing attentions in recent years. Here we demonstrate an optofluidic strategy, by implanting the microfluidic technique with a large-tapered-angle fiber probe (LTAP), to organize and transport a cell chain in a noncontact and noninvasive manner. After a laser beam at 980-nm wavelength launched into LTAP, the E. coli cells were continuously trapped and then arranged into a cell chain one after another. The chain can be transported by adjusting the magnitudes of optical force and flow drag force. The proposed technique can also be applied for the eukaryotic cells (e. g., yeast cell) and human red blood cells (RBCs). Experiment results were interpreted by the numerical simulation, and the stiffness of cell chain was also discussed. [ABSTRACT FROM AUTHOR]

SUMMARY Practically, the maximum transmission power of transmission systems is limited. This power constraint causes the variable power control derived from no maximum power limitation suffering from performance degradation. In this paper, a constrained variable-power adaptive M-ary quadrature amplitude modulation scheme for MIMO systems with space-time coding is developed. Convex optimization is used to derive the switching thresholds of the instantaneous signal-to-noise ratio for power control (PC) and adaptive modulation under the constraints of maximum power, average power, and target BER. In the derivation of the relation between modulation and power, the exact BER expression of binary phase shift keying modulation and a tight bound for higher order quadrature amplitude modulation are used to make the PC scheme fulfill the target BER even at low signal-to-noise ratio where the previous PC schemes fail to meet the target BER. Numerical results show that the derived control scheme under the power constraints can obtain the spectrum efficiency and BER performance close to the previous control scheme without power limitation. Moreover, it can satisfy the requirements of power limitation and target BER and can effectively avoid the excessive power consumption of previous PC scheme in poor channel condition. Copyright © 2012 John Wiley & Sons, Ltd. [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]

The single‐cell screening has attracted great attentions in advanced biomedicine and tissue biology, especially for the early disease diagnosis and treatment monitoring. In this work, by using a specific‐designed fiber probe with a flat facet, we propose an "optical fan" strategy to screen K562 cells at the single‐cell level from a populations of RBCs. After the 980‐nm laser beam injected into the fiber probe, the RBCs were blown away but holding target K562 cells in place. Further, multiple leukemic cells can be screened from hundreds of red blood cells, providing an efficient approach for the cell screening. The experimental results were interpreted by the numerical simulation, and the stiffness of optical fan was also discussed. [ABSTRACT FROM AUTHOR]

Living Biosensors: Red-Blood-Cell Waveguide as a Living Biosensor and Micromotor (Adv. Funct. In article number 1905568, Yao Zhang, Baojun Li, and co-workers report a biocompatible biosensor and micromotor that are assembled with an in vivo red blood cell waveguide. The living biosensor is used for the diagnosis of pH-related disorders of the blood; the waveguide can rotate as a micromotor and transport microparticles to the target region. [Extracted from the article]

With great potential in intelligent sensing and actuating systems, biosensors and micromotors are expected to be powerful instruments for early diagnosis and drug delivery in precision medicine. However, it is difficult to ensure the synthetic biosensors and micromotors are compatible with biosystems because of their exogenous building blocks. Biocompatible biosensors and micromotors assembled are reported from living red blood cells (RBCs) optically bound into a waveguide using fiber probes. By monitoring light propagation of the RBC waveguide, the pH of blood solution is detected in real time with an accuracy of 0.05. This can be used for the diagnosis of pH‐related disorders of the blood. After diagnosis, optical torque is exerted on the RBC waveguide, allowing it to rotate as a micromotor and transport microparticles to a target region. The RBC waveguide is then constructed inside zebrafish blood vessels to validate in vivo application. The living biosensors and micromotors are expected to provide a "smart" platform for precise biosensing, medical analysis, and drug delivery. [ABSTRACT FROM AUTHOR]

Non‐contact optofluidic organization of cell chain were demonstrated by implanting a large‐tapered‐angle fiber probe (LTAP) into the microfluidic platform, and the organized cell chain can be transported via the adjustment of laser power and flow velocity. Further details can be found in the article by Xiaoshuai Liuet al. on pp. 1627–1635. [ABSTRACT FROM AUTHOR]