Alexey P. Porfirev, Anna B. Dubman, and Denis P. Porfiriev
The rotation of optically trapped particles is used in many applications for the realization of different micromechanical devices, such as micropumps, microrotors, and microgyroscopes, as well as for the investigation of particle interactions. Although for transparent micro-objects in both liquid media and vacuum, the rotation can easily be realized by transfer of the spin angular or orbital angular momentum from the light to the object. In the case of light-absorbing micro-objects in gaseous media, such transfers are insignificant in comparison with the thermal effects arising from the photo- and thermo-phoresis phenomena initiating the movement of trapped particles in a laser beam. Currently, proposed methods using a single focused laser beam, tapered-ring optical traps, or single and multiple bottle beams (BBs) have various limitations—for example, the inability to control the direction of the revolution of trapped particles or the low revolution frequency and small revolution angles. Here we propose a simple method for the realization of the revolution of airborne light-absorbing particles. The method is based on a combination of a circular diaphragm and a rotating cylindrical lens, enabling the generation of linear optical BBs. Our results show the flexibility and reliability of the proposed technique, allowing such laser traps to be used in various optical systems for the manipulation of micro-objects with different dimensions and shapes.
DOI
Wednesday, August 26, 2020
Arrays of individually controllable optical tweezers based on 3D-printed microlens arrays
Dominik Schäffner, Tilman Preuschoff, Simon Ristok, Lukas Brozio, Malte Schlosser, Harald Giessen, and Gerhard Birkl
We present a novel platform of optical tweezers which combines rapid prototyping of user-definable microlens arrays with spatial light modulation (SLM) for dynamical control of each associated tweezer spot. Applying femtosecond direct laser writing, we manufacture a microlens array of 97 lenslets exhibiting quadratic and hexagonal packing and a transition region between the two. We use a digital micromirror device (DMD) to adapt the light field illuminating the individual lenslets and present a detailed characterization of the full optical system. In an unprecedented fashion, this novel platform combines the stability given by prefabricated solid optical elements, fast reengineering by rapid optical prototyping, DMD-based real-time control of each focal spot, and extensive scalability of the tweezer pattern. The accessible tweezer properties are adaptable within a wide range of parameters in a straightforward way.
DOI
We present a novel platform of optical tweezers which combines rapid prototyping of user-definable microlens arrays with spatial light modulation (SLM) for dynamical control of each associated tweezer spot. Applying femtosecond direct laser writing, we manufacture a microlens array of 97 lenslets exhibiting quadratic and hexagonal packing and a transition region between the two. We use a digital micromirror device (DMD) to adapt the light field illuminating the individual lenslets and present a detailed characterization of the full optical system. In an unprecedented fashion, this novel platform combines the stability given by prefabricated solid optical elements, fast reengineering by rapid optical prototyping, DMD-based real-time control of each focal spot, and extensive scalability of the tweezer pattern. The accessible tweezer properties are adaptable within a wide range of parameters in a straightforward way.
DOI
Rotation of Single-Molecule Emission Polarization by Plasmonic Nanorods
Tiancheng Zuo, Harrison J. Goldwyn, Benjamin P. Isaacoff, David J. Masiello, and Julie S. Biteen
The strong light–matter interactions between dyes and plasmonic nanoantennas enable the study of fundamental molecular-optical processes. Here, we overcome conventional limitations with high-throughput single-molecule polarization-resolved microscopy to measure dye emission polarization modifications upon near-field coupling to a gold nanorod. We determine that the emission polarization distribution is not only rotated toward the nanorod’s dominant localized surface plasmon mode as expected, but it is also unintuitively broadened. With a reduced-order analytical model, we elucidate how this distribution broadening depends upon both far-field interference and off-resonant coupling between the molecular dipole and the nanorod transverse plasmon mode. Experiments and modeling reveal that a nearby plasmonic nanoantenna affects dye emission polarization through a multicolor process, even when the orthogonal plasmon modes are separated by approximately 3 times the dye emission line width. Beyond advancing our understanding of plasmon-coupled emission modifications, this work promises to improve high-sensitivity single-molecule fluorescence imaging, biosensing, and spectral engineering.
DOI
The strong light–matter interactions between dyes and plasmonic nanoantennas enable the study of fundamental molecular-optical processes. Here, we overcome conventional limitations with high-throughput single-molecule polarization-resolved microscopy to measure dye emission polarization modifications upon near-field coupling to a gold nanorod. We determine that the emission polarization distribution is not only rotated toward the nanorod’s dominant localized surface plasmon mode as expected, but it is also unintuitively broadened. With a reduced-order analytical model, we elucidate how this distribution broadening depends upon both far-field interference and off-resonant coupling between the molecular dipole and the nanorod transverse plasmon mode. Experiments and modeling reveal that a nearby plasmonic nanoantenna affects dye emission polarization through a multicolor process, even when the orthogonal plasmon modes are separated by approximately 3 times the dye emission line width. Beyond advancing our understanding of plasmon-coupled emission modifications, this work promises to improve high-sensitivity single-molecule fluorescence imaging, biosensing, and spectral engineering.
DOI
Advances in Fiber‐Optic Technology for Point‐of‐Care Diagnosis and In Vivo Biosensing
Shawana Tabassum, and Ratnesh Kumar
Development of reliable, sensitive, selective, and miniaturized sensing technologies is critical for health assessment and early diagnosis and treatment of diseases/anomalies while simultaneously mitigating the challenges associated with in vivo measurements. Some critical constraints to the realization of in vivo measurements include the necessity to fabricate the sensor on a tightly constrained footprint while ensuring acceptable biocompatibility, accuracy, and reliability. The inherent light‐guiding properties of optical fibers over long distances, their microscopic cross‐section that can be structured at the nanoscale to manipulate the light transmittance/reflectance spectrum, excellent biocompatibility enabling their efficient integration with biorecognition molecules, immunity to electromagnetic interference, mechanical flexibility, and low cost have been inviting research attention to utilize these unique features for in vivo and label‐free point‐of‐care diagnostics. Hence, fiber‐optic biosensing has become a promising research thrust, with a plethora of emerging methodologies to develop ultrasensitive and selective sensing probes. A unified presentation of the research trends on biosensors incorporated into optical fibers is presented.
DOI
Development of reliable, sensitive, selective, and miniaturized sensing technologies is critical for health assessment and early diagnosis and treatment of diseases/anomalies while simultaneously mitigating the challenges associated with in vivo measurements. Some critical constraints to the realization of in vivo measurements include the necessity to fabricate the sensor on a tightly constrained footprint while ensuring acceptable biocompatibility, accuracy, and reliability. The inherent light‐guiding properties of optical fibers over long distances, their microscopic cross‐section that can be structured at the nanoscale to manipulate the light transmittance/reflectance spectrum, excellent biocompatibility enabling their efficient integration with biorecognition molecules, immunity to electromagnetic interference, mechanical flexibility, and low cost have been inviting research attention to utilize these unique features for in vivo and label‐free point‐of‐care diagnostics. Hence, fiber‐optic biosensing has become a promising research thrust, with a plethora of emerging methodologies to develop ultrasensitive and selective sensing probes. A unified presentation of the research trends on biosensors incorporated into optical fibers is presented.
DOI
Blog on Optical Tweezers returning back to normal.
Blog on Optical Tweezers returning back to normal.
Friday, March 13, 2020
Opto-thermoelectric pulling of light-absorbing particles
Linhan Lin, Pavana Siddhartha Kollipara, Abhay Kotnala, Taizhi Jiang, Yaoran Liu, Xiaolei Peng, Brian A. Korgel & Yuebing Zheng
Optomechanics arises from the photon momentum and its exchange with low-dimensional objects. It is well known that optical radiation exerts pressure on objects, pushing them along the light path. However, optical pulling of an object against the light path is still a counter-intuitive phenomenon. Herein, we present a general concept of optical pulling—opto-thermoelectric pulling (OTEP)—where the optical heating of a light-absorbing particle using a simple plane wave can pull the particle itself against the light path. This irradiation orientation-directed pulling force imparts self-restoring behaviour to the particles, and three-dimensional (3D) trapping of single particles is achieved at an extremely low optical intensity of 10−2 mW μm−2. Moreover, the OTEP force can overcome the short trapping range of conventional optical tweezers and optically drive the particle flow up to a macroscopic distance. The concept of self-induced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-a-chip devices.
DOI
Optomechanics arises from the photon momentum and its exchange with low-dimensional objects. It is well known that optical radiation exerts pressure on objects, pushing them along the light path. However, optical pulling of an object against the light path is still a counter-intuitive phenomenon. Herein, we present a general concept of optical pulling—opto-thermoelectric pulling (OTEP)—where the optical heating of a light-absorbing particle using a simple plane wave can pull the particle itself against the light path. This irradiation orientation-directed pulling force imparts self-restoring behaviour to the particles, and three-dimensional (3D) trapping of single particles is achieved at an extremely low optical intensity of 10−2 mW μm−2. Moreover, the OTEP force can overcome the short trapping range of conventional optical tweezers and optically drive the particle flow up to a macroscopic distance. The concept of self-induced opto-thermomechanical coupling is paving the way towards freeform optofluidic technology and lab-on-a-chip devices.
DOI
Nematic Liquid-Crystal Necklace Structure Made by Microfluidics System
Yoshiko Takenaka, Miha Skarabot, Igor Musevic
We report a necklace structure made of liquid crystal dispersed in polyvinyl alcohol (PVA) aqueous solution, which is fabricated by a microfluidics device. In the necklace structure, liquid crystal droplets of tens of micrometer diameter are connected by micro-tethers, which are birefringent, are not penetrating the droplets, and can be elastically stretched by applying external force. The necklace structure was analyzed by fluorescent confocal microscopy, and the tethers are made of liquid crystal and PVA composite. The elastic constant of the tether was determined by using laser tweezers to stretch the tether. The Whispering Gallery Modes (WGM) circulating inside individual droplets in the necklace structure were also observed.
DOI
We report a necklace structure made of liquid crystal dispersed in polyvinyl alcohol (PVA) aqueous solution, which is fabricated by a microfluidics device. In the necklace structure, liquid crystal droplets of tens of micrometer diameter are connected by micro-tethers, which are birefringent, are not penetrating the droplets, and can be elastically stretched by applying external force. The necklace structure was analyzed by fluorescent confocal microscopy, and the tethers are made of liquid crystal and PVA composite. The elastic constant of the tether was determined by using laser tweezers to stretch the tether. The Whispering Gallery Modes (WGM) circulating inside individual droplets in the necklace structure were also observed.
DOI
Study on the chemodrug-induced effect in nasopharyngeal carcinoma cells using laser tweezer Raman spectroscopy
Sufang Qiu, Miaomiao Li, Jun Liu, Xiaochuan Chen, Ting Lin, Yunchao Xu, Yang Chen, Youliang Weng, Yuhui Pan, Shangyuan Feng, Xiandong Lin, Lurong Zhang, and Duo Lin
To explore the effect in nasopharyngeal carcinoma (NPC) cells after treatment with chemodrugs, Raman profiles were characterized by laser tweezer Raman spectroscopy. Two NPC cell lines (CNE2 and C666-1) were treated with gemcitabine, cisplatin, and paclitaxel, respectively. The high-quality Raman spectra of cells without or with treatments were recorded at the single-cell level with label-free laser tweezers Raman spectroscopy (LTRS) and analyzed for the differences of alterations of Raman profiles. Tentative assignments of Raman peaks indicated that the cellular specific biomolecular changes associated with drug treatment include changes in protein structure (e.g. 1655 cm−1), changes in DNA/RNA content and structure (e.g. 830 cm−1), destruction of DNA/RNA base pairs (e.g. 785 cm−1), and reduction in lipids (e.g. 970 cm−1). Besides, both principal components analysis (PCA) combined with linear discriminant analysis (LDA) and the classification and regression trees (CRT) algorithms were employed to further analyze and classify the spectral data between control group and treated group, with the best discriminant accuracy of 96.7% and 90.0% for CNE2 and C666-1 group treated with paclitaxel, respectively. This exploratory work demonstrated that LTRS technology combined with multivariate statistical analysis has promising potential to be a novel analytical strategy at the single-cell level for the evaluation of NPC-related chemotherapeutic drugs.
DOI
To explore the effect in nasopharyngeal carcinoma (NPC) cells after treatment with chemodrugs, Raman profiles were characterized by laser tweezer Raman spectroscopy. Two NPC cell lines (CNE2 and C666-1) were treated with gemcitabine, cisplatin, and paclitaxel, respectively. The high-quality Raman spectra of cells without or with treatments were recorded at the single-cell level with label-free laser tweezers Raman spectroscopy (LTRS) and analyzed for the differences of alterations of Raman profiles. Tentative assignments of Raman peaks indicated that the cellular specific biomolecular changes associated with drug treatment include changes in protein structure (e.g. 1655 cm−1), changes in DNA/RNA content and structure (e.g. 830 cm−1), destruction of DNA/RNA base pairs (e.g. 785 cm−1), and reduction in lipids (e.g. 970 cm−1). Besides, both principal components analysis (PCA) combined with linear discriminant analysis (LDA) and the classification and regression trees (CRT) algorithms were employed to further analyze and classify the spectral data between control group and treated group, with the best discriminant accuracy of 96.7% and 90.0% for CNE2 and C666-1 group treated with paclitaxel, respectively. This exploratory work demonstrated that LTRS technology combined with multivariate statistical analysis has promising potential to be a novel analytical strategy at the single-cell level for the evaluation of NPC-related chemotherapeutic drugs.
DOI
Synergy of Intensity, Phase, and Polarization Enables Versatile Optical Nanomanipulation
Fan Nan, and Zijie Yan
Micromanipulation by optical tweezers mainly relies on the trapping force derived from the intensity gradient of light. Here we show that the synergy of intensity, phase, and polarization in structured light allows versatile optical manipulation of nanostructures. When a metal nanoparticle is confined by a linearly polarized laser field, the sign of optical force depends on the particle shape and the laser intensity, phase, and polarization profiles. By tuning these parameters in optical line traps, optical trapping, transporting, and sorting of silver nanostructures have been demonstrated. These findings inspired us to control the motion of nanostructures with designed intensity, phase, and polarization of light using holographic optical tweezers with advanced beam shaping techniques. This work provides a new perspective on active colloidal nanomanipulation in fully controlled optical landscapes, which largely expands the existing optical manipulation toolbox.
DOI
Micromanipulation by optical tweezers mainly relies on the trapping force derived from the intensity gradient of light. Here we show that the synergy of intensity, phase, and polarization in structured light allows versatile optical manipulation of nanostructures. When a metal nanoparticle is confined by a linearly polarized laser field, the sign of optical force depends on the particle shape and the laser intensity, phase, and polarization profiles. By tuning these parameters in optical line traps, optical trapping, transporting, and sorting of silver nanostructures have been demonstrated. These findings inspired us to control the motion of nanostructures with designed intensity, phase, and polarization of light using holographic optical tweezers with advanced beam shaping techniques. This work provides a new perspective on active colloidal nanomanipulation in fully controlled optical landscapes, which largely expands the existing optical manipulation toolbox.
DOI
Single-particle spectroscopy for functional nanomaterials
Jiajia Zhou, Alexey I. Chizhik, Steven Chu & Dayong Jin
Tremendous progress in nanotechnology has enabled advances in the use of luminescent nanomaterials in imaging, sensing and photonic devices. This translational process relies on controlling the photophysical properties of the building block, that is, single luminescent nanoparticles. In this Review, we highlight the importance of single-particle spectroscopy in revealing the diverse optical properties and functionalities of nanomaterials, and compare it with ensemble fluorescence spectroscopy. The information provided by this technique has guided materials science in tailoring the synthesis of nanomaterials to achieve optical uniformity and to develop novel applications. We discuss the opportunities and challenges that arise from pushing the resolution limit, integrating measurement and manipulation modalities, and establishing the relationship between the structure and functionality of single nanoparticles.
DOI
Tremendous progress in nanotechnology has enabled advances in the use of luminescent nanomaterials in imaging, sensing and photonic devices. This translational process relies on controlling the photophysical properties of the building block, that is, single luminescent nanoparticles. In this Review, we highlight the importance of single-particle spectroscopy in revealing the diverse optical properties and functionalities of nanomaterials, and compare it with ensemble fluorescence spectroscopy. The information provided by this technique has guided materials science in tailoring the synthesis of nanomaterials to achieve optical uniformity and to develop novel applications. We discuss the opportunities and challenges that arise from pushing the resolution limit, integrating measurement and manipulation modalities, and establishing the relationship between the structure and functionality of single nanoparticles.
DOI
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