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Manipulation and Deposition of Complex, Functional Block Copolymer Nanostructures using Optical Tweezers
摘要： Block copolymer self-assembly has enabled the creation of a range of solution-phase nanostructures with applications from optoelectronics and biomedicine to catalysis. However, to incorporate such materials into devices a method that facilitates their precise manipulation and deposition is desirable. Herein we describe how optical tweezers can be used to trap, manipulate, and pattern individual cylindrical micelles and larger hybrid micellar materials. Through the combination of TIRF imaging and optical trapping we can precisely control the three-dimensional motion of individual cylindrical block copolymer micelles in solution, enabling the creation of customizable arrays. We also demonstrate that dynamic holographic assembly enables the creation of ordered customizable arrays of complex hybrid block copolymer structures. By creating a program which automatically identifies, traps and then deposits multiple assemblies simultaneously we have been able to dramatically speed up this normally slow process, enabling the fabrication of arrays of hybrid structures containing hundreds of assemblies in minutes rather than hours.
关键词： optical trapping,directed assembly,block copolymers,self-assembly,nanofibers
更新于2025-11-21 11:24:58
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Controlling the Dynamics and Optical Binding of Nanoparticle Homodimers with Transverse Phase Gradients
摘要： While transverse phase gradients enable studies of driven nonequilibrium phenomena in optical trapping, the behavior of electrodynamically interacting particles in a transverse phase gradient has not been explored in detail. In this Letter we study electrodynamically interacting pairs of identical nanoparticles (homodimers) in transverse phase gradients. We establish that the net driving force on homodimers is modulated by a separation-dependent interference effect for small phase gradients. By contrast, large phase gradients break the symmetry of the interaction between particles and profoundly change the electrodynamic interparticle energy landscape. Our findings are particularly important for understanding multiparticle dynamics during the self-assembly and rearrangement of optical matter.
关键词： nonequilibrium,optical trapping,optical microscopy
更新于2025-09-23 15:23:52
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Colloidal Rare Earth Vanadate Single Crystalline Particles as Ratiometric Luminescent Thermometers
摘要： Thulium/ytterbium-doped yttrium vanadate particles provide ratiometric thermal response as both colloids and powders via downshift or upconversion emissions. Here, we synthesized yttrium vanadates by controlled colloidal conversion of hydroxycarbonate precursors. A protected annealing process yielded single crystalline and readily dispersible particles that were manipulated individually by optical tweezers in water. Because individual particles displayed detectable emissions, this system has potential applications as a single-particle luminescent temperature sensor. Excitation on Yb3+ sensitizers (λexc=980 nm) or at vanadate groups (λexc=300 nm) resulted in Tm3+ emissions that effectively correlated with the temperature of the sample from 288 to 473 K with high relative thermal sensitivity (0.8-2.2% K-1), one of the highest reported for vanadate nanocrystals so far. Different pairs of Tm3+ transitions afford a ratiometric thermal response, which fitted common sensing requirements such as large [3F2,3→3H6 (λ=700 nm)/1G4→3H6 (λ=475 nm)] or small [3F2,3→3H6 (λ=700 nm)/1G4→3F4 (λ=650 nm)] spectral gaps, and emission wavelengths at the first near infrared biological window [3F2,3→3F4 (λ=700 nm)/3H4→3H6 (λ=800 nm)]. Our findings open new perspectives for the use of luminescent nanothermometers with controllable spatial localization, which is a remarkably interesting prospect to investigate microscopically-localized events related to changes in temperature.
关键词： Luminescence,Thermometry,Nanoparticles,Thermal Sensors,Vanadates,Optical Trapping,Rare Earth
更新于2025-09-23 15:23:52
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Optimized rotation of an optically trapped particle for micro mixing
摘要： The angular momentum transferred by circularly polarized photons is able to rotate an optically trapped microparticle. Here, the optically rotating particle is introduced as an active micromixer to reduce the mixing time in a microfluidic system. To optimize the system for microfluidic application, the effect of several optical parameters such as spherical aberration and the numerical aperture of the objective on the rotation rate of a trapped particle is investigated. The results show that the optimized depth for the rotation of a particle is located close to the coverslip and can be changed by a fine adjustment of the refractive index of the immersion oil. By applying the obtained optimized optical parameters on a trapped particle at the interface of two fluids in a microchannel, the mixing length is reduced by a factor of (cid:2)2.
关键词： microfluidics,numerical aperture,micromixing,angular momentum,optical trapping,spherical aberration
更新于2025-09-23 15:21:21
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Confined whispering-gallery mode in silica double-toroid microcavities for optical sensing and trapping
摘要： We propose and theoretically study a silica double-toroid microcavity to confine the whispering-gallery mode (WGM) in an ultra-small space, which consists of two toroid-to-toroid coupled cavities separated by a nanoscale gap region with low refractive index, such as the air gap. Benefitting from the strong field localization of the “slot” effect, power enhancement of symmetric WGMs in the gap results in the ultra-small mode volume of 4.8 μm3, which is quite smaller than the conventional toroidal microcavity with mode volume of about hundreds of cubic micrometers. The confined modes hold the potential advantages over conventional photonic devices, especially in the applications of the sensing and optical trapping. In the application of refractometer, a high refractive index sensitivity of up to 468 nm per refractive index unit (nm/RIU) can be obtained in the 1000 nm wavelength band. In the optical trapping application, the double-toroid microcavity enables a significant field enhancement in the confined WGM, and the gradient force could reach as high as 22 pN/W for a single nanoparticle with the radius of 5 nm. As the potential advantages, this study of silica double-toroid microcavity provides a good reference for realizing the high-efficient photonic applications such as optical sensing and trapping.
关键词： optical sensing,refractometer,silica double-toroid microcavity,gradient force,optical trapping,whispering-gallery mode
更新于2025-09-23 15:21:01
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Optical Trapping of Nanoparticles Using All-Silicon Nanoantennas
摘要： The ability to optically trap nanoscale particles in a reliable and noninvasive manner is emerging as an important capability for nanoscience. Different techniques have been introduced, including plasmonic nanostructures. Nano-optical tweezers based on plasmonics face the problem of Joule heating however due to high losses in metals. Here we experimentally demonstrate the optical trapping and transport of nanoparticles using a non-plasmonic approach, namely a silicon nanoantenna. We trap polystyrene nanoparticles with diameters of 20 and 100 nm, and use fluorescence microscopy to track their positions as a function of time. We show that multiple nanoparticles can be trapped simultaneously with a single nanoantenna. We show that the infrared trapping laser beam also produces fluorescent emission from trapped nanoparticles via two-photon excitation. We present simulations of the nanoantenna that predict enhanced optical forces with insignificant heat generation. Our work demonstrates that silicon nanoantennas enable nanoparticles to be optically trapped without deleterious thermal heating effects.
关键词： Optical trapping,silicon nanoantenna,thermal effect,optical force,nanoparticle
更新于2025-09-23 15:21:01
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Convection Dynamics Forced by Optical Trapping with a Focused Laser Beam
摘要： Optical trapping dynamics of colloidal particles in solution is essential for understanding laser-induced assembling of molecules and nanomaterials, which contributes to nanofabrication, bioengineering, and microfluidics. In this paper, the importance of the surrounding fluid motion in optical trapping is investigated; that is, we reveal convection fluid dynamics forced by optical trapping with a focused laser beam. The fluid flow in optical trapping is evaluated by both experiments using the particle-image-velocimetry of fluorescent particles in solutions and theoretical consideration based on numerical analysis. A theoretical model consists of Navier?Stokes equations with the Boussinesq approximation that considers the temperature elevation induced by a photothermal effect. Furthermore, the effect of the particle motion induced by the optical force on fluid flow is also included in the analysis by developing a simple one-way homogeneous-type multiphase flow model. From both experimental and theoretical results, it turns out that the fluid flow in optical trapping is caused not only by thermal convection due to the temperature elevation but also by the collective particle motion induced by optical forces. Therefore, the optical forces can induce the large-scale fluid convection, which supports accumulating the target particles to the focal spot.
关键词： thermal convection,fluid dynamics,colloidal particles,photothermal effect,Boussinesq approximation,optical trapping,multiphase flow model,Navier?Stokes equations,particle-image-velocimetry
更新于2025-09-23 15:21:01
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Electro-Optical Ion Trap for Experiments with Atom-Ion Quantum Hybrid Systems
摘要： In the development of atomic, molecular, and optical (AMO) physics, atom-ion hybrid systems are characterized by the presence of a new tool in the experimental AMO toolbox: atom-ion interactions. One of the main limitations in state-of-the-art atom-ion experiments is represented by the micromotion component of the ions’ dynamics in a Paul trap, as the presence of micromotion in atom-ion collisions results in a heating mechanism that prevents atom-ion mixtures from undergoing a coherent evolution. Here, we report the design and the simulation of a novel ion trapping setup especially conceived of for integration with an ultracold atoms experiment. The ion con?nement is realized by using an electro-optical trap based on the combination of an optical and an electrostatic ?eld, so that no micromotion component will be present in the ions’ dynamics. The con?ning optical ?eld is generated by a deep optical lattice created at the crossing of a bow-tie cavity, while a static electric quadrupole ensures the ions’ con?nement in the plane orthogonal to the optical lattice. The setup is also equipped with a Paul trap for cooling the ions produced by photoionization of a hot atomic beam, and the design of the two ion traps facilitates the swapping of the ions from the Paul trap to the electro-optical trap.
关键词： atom-ion mixtures,atom-ion interactions,Paul traps,ion optical trapping
更新于2025-09-23 15:21:01
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Optical counting of guided particles in a vortex beam as an optical tube by laser-two-focus method
摘要： In this study, microscopic particles such as aerosols were counted by Laser-Two-Focus method, L2F, after being trapped and guided by an optical tube. This prevents particles diffusivity as they pass through the Gaussian beam in the L2F method by optical forces such as radiation pressure and photophoretic forces. In optical tube, particles can guid to the center of the beam where the intensity gets zero. A single-charged Bessel Gaussian beam, BG01, is used as the particle guidance beam in this method, which is generated by passing the first-order Laguerre-Gaussian beam, LG01, from an axicon lens. LG01 beam are also produced by using holographic interference grid mask. The results of the theory and simulations showed that by optical guiding of particles in the L2F-method measurement, their transverse turbulence can be reduced by about 60% and then the probability of measuring all particles to be increased by about 30%. Measurements of in-laboratory aerosols less than 3.5 μm with this method showed a 20% increase in their condensation of them compared to the conventional L2F method.
关键词： Photophoretic force,Laser-two-focus,Optical trapping,Optical particle counter,Optical tube,Radiation force
更新于2025-09-23 15:19:57
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Generation and modulation of terahertz gradient force in the interactions of two-color laser pulses with magnetized plasmas
摘要： Terahertz (THz) waves, as far-infrared light, offer new opportunities for the optical trapping and manipulation of single cells, in contrast to the other light sources. We present an efficient scheme to flexibly control multiple THz field distribution patterns generated by the laser–plasma interaction in a magnetized plasma. An analytical THz radiation field and two-dimensional particle-in-cell simulation are constructed to verify the feasibility of the scheme. Modulation of the THz gradient force and the energy flux by an asymmetrical THz field is investigated for the purpose of trapping and manipulating particles and cells. In particular, the stabilities of flexibly controlled THz radiation are investigated carefully in the form of the strong and short laser and super-strong magnetic field induced significant spatial structure instabilities and frequency instabilities of terahertz radiation.
关键词： Terahertz waves,laser–plasma interaction,optical trapping,magnetized plasmas,THz gradient force
更新于2025-09-23 15:19:57