Xiaobo Xing

Graphene oxide-deposited microfiber: a new photothermal device for various microbubble generation

This study makes a claim of utilizing the photothermal effect of graphene oxide nanosheets (GONs) to effectively produce various microbubbles in an optical microfiber system at infrared optical communications band. A low power continuous-wave light at wavelength of 1527-1566 nm was launched into the microfiber to form GONs-deposition which acted as a linear heat source for creating various microbubbles. Both thermal convection flow and optical gradient force were responsible for the driving force to assemble GONs onto the microfiber. This simple optical fiber system can be used for assembling other micro/nanoscale particles and biomolecules, which has prospective applications in sensing, microfluidics, virus detection, and other biochip techniques.

Dynamic behaviors of approximately ellipsoidal microbubbles photothermally generated by a graphene oxide-microheater

Thermal microbubbles generally grow directly from the heater and are spherical to minimize surface tension. We demonstrate a novel type of microbubble indirectly generated from a graphene oxide-microheater. Graphene oxides photothermal properties allowed for efficient generation of a thermal gradient field on the microscale. A series of approximately ellipsoidal microbubbles were generated on the smooth microwire based on heterogeneous nucleation. Other dynamic behaviors induced by the microheater such as constant growth, directional transport and coalescence were also investigated experimentally and theoretically. The results are not only helpful for understanding the bubble dynamics but also useful for developing novel photothermal bubble-based devices.

Subwavelength and Nanometer Diameter Optical Polymer Fibers as Building Blocks for Miniaturized Photonics Integration

© 2012 Xing et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Subwavelength and Nanometer Diameter Optical Polymer Fibers as Building Blocks for Miniaturized Photonics Integration

Optofluidic trapping and delivery of massive mesoscopic matters using mobile vortex array

The realization of directional and controllable delivery of massive mesoscopic matters is of great significance in the field of microfluidics. Here, the mobile thermocapillary vortex array has achieved the enrichment and transport of massive mesoscopic matters in free or limited space. The ability of the vortex array to confine objects in the center ensures the controllability of particle trajectory. We also simulated the delivery process to reveal the stability of the mobile vortex. Owing to the distance between the vortex center and the heat source, the method provides the ability to protect trapped matters, including organisms and living cells. The mobile vortex array has opened the exciting possibilities of realizing that bridges the gap between remote optofluidics and lab on a chip.

Hybrid optofluidics and three-dimensional manipulation based on hybrid photothermal waveguides

Despite enormous breakthroughs in lab-on-a-chip techniques, light-driven manipulation faces two long-standing challenges: the ability to achieve both multiform manipulation and tunable manipulation range and the means to avoid potential thermal damage to the targets. By harnessing the optical heating of hybrid photothermal waveguides (HPW), we develop a hybrid optofluidic technique involving buoyancy and thermocapillary convection to achieve fluid transport with controllable modes and tunable strength. Switching of the optofluidic mode from buoyancy to thermocapillary convection, namely, from vertical to horizontal vortices, is employed for three-dimensional manipulation. The strong confinement and torque in the vortices are capable of trapping and rotating/spinning particles at the vortex centers rather than the HPW. Buoyancy convection provides a trapping circle to achieve collective trapping and vertical rotation/spin, while thermocapillary convection offers a trapping lattice to achieve distributed trapping and horizontal rotation/spin. By integrating micro/nanoparticles with various properties and sizes, further investigations of the optofluidic arrangement, mixing, and synthesis will broaden the potential applications of the hybrid optofluidic technique in the fields of lab-on-a-chip, materials science, chemical synthesis and analysis, photonics, and nanoscience.Optofluidics: Adding another dimension to optical controlA method for manipulating tiny particles both vertically and horizontally using lasers has been developed by scientists in China. Intense beams of light create vortices in a fluid that can trap nanoscale objects. This concept is harnessed using so-called ‘optical tweezers’ for accurately positioning or sorting cells. The ideal optical manipulation set-up can transfer the target particle in any direction. Sailing He, Xiaobo Xing, and their colleagues at South China Normal University, Guangzhou, realized just such a system using micrometer-scale channels in graphene oxide. Vertical manipulation was achieved by using laser light to heat the fluid-carrying channel and generate buoyancy. Similarly, heat-induced capillary action drove horizontal motion. This approach could be used in lab-on-a-chip applications: portable compact devices that can sensitively and accurately analyze chemical or biological samples.A hybrid optofluidic technique was developed to achieve fluid transport with controllable modes and tunable strength. The switch of the optofluidic mode from buoyancy to thermocapillary convection is employed for three-dimensional manipulation. The strong confinement and torque in the convection are capable of trapping and rotating/spinning particles. The buoyancy convection provides a trapping circle to achieve collective trapping and vertical rotation/spin, while the thermocapillary convection offers a trapping lattice to achieve distributed trapping and horizontal rotation/spin. Further investigations in optofluidic arrangement, mixing, and synthesis will broaden its potential applications in the fields of lab-on-a-chip.

Size-tunable capture of mesoscopic matters using thermocapillary vortex

The hydrodynamics in lab-on-a-chip provides an efficient and tunable platform for manipulating mesoscopic particles. Current capture-tunable technology has been mainly focused on inertial flow with little attention on a thermocapillary vortex. The boundary condition is one of the most important factors on particle manipulation in a microvortex. By integrating a photothermal waveguide with a triangular channel in lab-on-a-chip, we present a tunable microvortex array for achieving size-tunable capture. Ellipticity of the temperature field and intensity of vortices are continuously adjustable by moving the photothermal waveguide along the triangular channel, resulting in tunable particle trajectories. Particles can be trapped in a vortex center and driven out of the vortex along with external flow. The detailed theoretical results reveal that a threshold size of trapped particles can be adjustable by the channel width. We believe that the approach, the thermocapillary vortex on chip, will provide a facile way for seamless connection between photonics and microfluidics.The hydrodynamics in lab-on-a-chip provides an efficient and tunable platform for manipulating mesoscopic particles. Current capture-tunable technology has been mainly focused on inertial flow with little attention on a thermocapillary vortex. The boundary condition is one of the most important factors on particle manipulation in a microvortex. By integrating a photothermal waveguide with a triangular channel in lab-on-a-chip, we present a tunable microvortex array for achieving size-tunable capture. Ellipticity of the temperature field and intensity of vortices are continuously adjustable by moving the photothermal waveguide along the triangular channel, resulting in tunable particle trajectories. Particles can be trapped in a vortex center and driven out of the vortex along with external flow. The detailed theoretical results reveal that a threshold size of trapped particles can be adjustable by the channel width. We believe that the approach, the thermocapillary vortex on chip, will provide a facile wa...

Microbubble-assisted optofluidic control using a photothermal waveguide

A convenient and easily controllable microfluidic system was proposed based on a photothermal device. Here, graphene oxide was assembled on an optical waveguide, which could serve as a miniature heat source to generate a microbubble and to control dynamic behaviors of flow by adjusting optical power at the micrometer scale. Micro/nanoparticles were used to demonstrate the trace of fluid flow around the microbubble, which displayed the ability of the flow to capture, transmit, and rotate particles in thermal convection. Correspondingly, three-dimensional theoretical simulation combining thermodynamics with hydrodynamics analyzed the distribution of the velocity field induced by the microbubble for collection and driving of particles. Furthermore, the photothermal waveguide would be developed into a microbubble-based device in the manipulation or transmission of micro/nanoparticles.

An improved one-pot aqueous phase synthesis of CdTe QDs

An improved one-pot synthesis of water soluble CdTe quantum dots (QDs) using sodium tellurite (Na2TeO3) as the Te sources and 3-mercaptopropionic acid (MPA) as thiolligands reactant via a facile direct-heating route. CdTe QDs concerning multiple series parameters can be synthesized just like being baked and picked up when needed. At the same conditions of Cd : MPA = 1 : 1.4, 90°C, pH = 10.5 and excess NaBH4, different Te : Cd molar ratio of 0.25, 0.45 and 0.65 of precursors were half filled into screw-cap-glass-bottles and then heated directly in an oven at 90°C. Samples with different growth time at 70, 100, 130, 160 and 200 min were picked up and their luminescence emission colors change from green to red if the growth time was long enough. By optimization of experimental parameters, the direct-heating route is highly effective, convenient, free of vacuum and inert gas protection, and environmentally friendly.

Linear dependence of absorbance of CdTe quantum dots on the ratio of Te:Cd in the aqueous phase synthesis

A simplified one-pot reflux heating synthesis of CdTe quantum dots (QDs) is introduced. As a result, the absorbance of CdTe QDs has a linear dependence on the Te:Cd molar ratio. Both the absorption intensities and the first absorption peaks increase linearly as the reaction time increases. The concentration of as-prepared CdTe QDs increases slower and the photoluminescence brightness decreases when the Te:Cd molar ratio is more than 0.5. It is concluded that the best Te:Cd ratio is less than 0.5 corresponding to lower Te content. Based on the excellent linear properties, a designed absorption peak or excitation peak of QDs can be obtained by controlling the reaction time, reactant concentration controlling, or other experimental parameters.