Cell identification and sorting have been hot topics recently. However, most conventional approaches can only predict the category of a single target, and lack the ability to perform multitarget tasks to provide coordinate information of the targets. This limits the development of high-throughput cell screening technologies. Fortunately, artificial intelligence (AI) systems based on deep-learning algorithms provide the possibility to extract hidden features of cells from original image information. Here, we demonstrate an AI-assisted multitarget processing system for cell identification and sorting. With this system, each target cell can be swiftly and accurately identified in a mixture by extracting cell morphological features, whereafter accurate cell sorting is achieved through noninvasive manipulation by optical tweezers. The AI-assisted model shows promise in guiding the precise manipulation and intelligent detection of high-flux cells, thereby realizing semi-automatic cell research.

Mechanical forces play an important role in the behaviour of cells, from differentiation to migration and the development of diseases. Optical tweezers provide a quantitative tool to study these forces and must be combined with other tools, such as phase contrast and fluorescence microscopy. Detecting the retro-reflected trap beam is a convenient way to monitor the force applied by optical tweezers, while freeing top access to the sample. Accurate in situ calibration is required especially for single cells close to a surface where viscosity varies rapidly with height. Here, we take advantage of the well contrasted interference rings in the back focal plane of the objective to find the height of a trapped bead above a cover slip. We thus map the viscous drag dependence close to the surface and find agreement between four different measurement techniques for the trap stiffness down to 2 μm above the surface. Combining this detection scheme with phase contrast microscopy, we show that the phase ring in the back focal plane of the objective must be deported in a conjugate plane on the imaging path. This simplifies implementation of optical tweezers in combination with other techniques for biomechanical studies.

Nonlinear responses of nanoparticles induce enlightening phenomena in optical tweezers. With the gradual increase in optical intensity, effects from saturable absorption (SA) and reverse SA (RSA) arise in sequence and thereby modulate the nonlinear properties of materials. In current nonlinear optical traps, however, the underlying physical mechanism is mainly confined within the SA regime because threshold values required to excite the RSA regime are extremely high. Herein, we demonstrate, both in theory and experiment, nonlinear optical tweezing within the RSA regime, proving that a fascinating composite trapping state is achievable at ultrahigh intensities through an optical force reversal induced through nonlinear absorption. Integrated results help in perfecting the nonlinear optical trapping system, thereby providing beneficial guidance for wider applications of nonlinear optics.

悬浮光力传感技术利用真空环境的光阱实现对微纳尺度机械振子的悬浮和囚禁，将待测物理量转换为光悬浮机械振子运动参数的变化，理论上该振子与外部环境热噪声和振动完全隔绝，具有极高的测量分辨率潜力和易于小型化的独特优势。该技术在精密测量、微观热力学研究、暗物质观测、宏观量子态操控等领域具有广阔的应用前景。首先，阐述了悬浮光力系统中光力与光阱的基础概念和力学测量等基本理论；其次，介绍了其中初始起支、光力增强、位移测量、输出信号标定和等效反馈冷却等关键技术的研究进展，对比分析各子技术的特点，随后列举了悬浮光力传感技术在极弱力、加速度、微观质量、电学量、力矩等物理量测量中的典型应用；最后，总结了该技术的发展趋势，并提出相关建议。

光镊采用聚焦的激光束束缚微米、纳米级的粒子，具有亚皮牛级的力分辨率和亚毫秒级的时间响应，在单分子生物物理中具有广泛的应用。通过化学耦链将生物大分子连接到高分子微球上，光镊可以测量大分子的伸长以及受力，进而研究DNA‐蛋白质相互作用、蛋白质折叠及分子马达机械化学性质等动态过程。简要介绍光镊的基本原理和常见的单分子光镊几何构型，并以双光镊为例，介绍如何设计和搭建光镊设备、所涉及的技术原理、稳定性与降噪处理方法以及分辨率测试方法。以国家蛋白质科学研究（上海）设施的双光镊实验装置为例，论述双光镊在单分子生物物理中的应用及进展。最后，对单分子光镊技术的发展前景作出展望。

面向生物粒子操控方法的研究，在生物医学和生命科学等领域具有重要意义。光镊操控具有无接触与高精度的特点，已被广泛应用于多个领域的研究中。然而，传统光镊的光热效应以及衍射极限都制约着光镊在生物医学领域的更广泛应用和发展。近十年来，研究者们将光热效应化劣势为优势，利用光与热的耦合效应实现了多种粒子的精确捕获及操控，即光致温度场光镊（OTFT）。由于此种新型光镊对光能的利用率极高，能量密度低于传统光镊近3个数量级，并可实现颗粒的大范围操控，极大地拓展了光镊可操控粒子的种类，已经成为纳米技术以及生命科学领域的重要研究工具。温度场光镊仍面临诸多问题，例如对于颗粒界面调控的依赖性以及三维捕获受限等，尤其是在生物光子学的研究中，还需要进一步发展和优化。本文对光致温度场光镊操控基本原理及其在生物医学中的应用两个方面进行了系统阐述，并对其今后的发展与挑战进行了展望。

提出了一种用于生物细胞多路捕获与操纵的单光纤光镊。基于两种不同模式的光纤错位拼接，实现了LP₀₁和LP₁₁模式共存。该光镊的输出光场具有多个聚焦光斑，能够在多个支路上同时捕获和操纵多个生物细胞。仿真和实验结果表明，该光镊能够在三个支路上同时捕获和操纵多个小球藻细胞，在光镊移动速度约为14 μm/s时仍能保持捕获稳定。该光镊结构简单，为生物传感和直接检测生物信号提供了更多可能。

结合光束塑形技术、坐标变换技术、傅里叶相移定理，成功产生了霍曼转移结构光束，其具备相位梯度，从而拥有在微观世界中输运粒子的能力，并且大小、结构、相位梯度，均可任意调控，在应用中可依据实际需求对光束进行相应的调整。搭建光镊实验光路，并使用霍曼转移结构光束对聚苯乙烯粒子进行了操控，其实验结果与理论相符，可以使粒子完美的沿着轨道进行输运。该研究在光学微操纵特别是粒子的变轨运输领域具有重要的意义。

We present and demonstrate a multifunctional single-fiber optical tweezer for particle trapping and transport. The fiber probe of fiber optical tweezers is constructed as a planar structure. Laser sources with wavelengths of 650 nm and 980 nm in a single-mode fiber excite the linearly polarized LP11 mode and LP01 mode beams, respectively. These two laser beams can achieve non-contact trapping and long-distance transport of particles after passing through a flat-facet fiber probe, respectively. This structure makes it possible to perform non-contact trapping and transport of particles by combining multiple wavelengths and multiple modes.