Through laser welding experiment using high speed camera, the dynamics of plasma plume and keyhole could be observed simultaneously due to two image output modes of the camera. One showed the plasma plume and the other showed the keyhole. The keyhole area, plasma area and angle was extracted by image processing. To improve accuracy, a modified image processing algorithm named multiple binarization algorithm was proposed. It was found the areas of keyhole and plasma varied with changes in welding speeds and laser powers. Increased energy density led to an increase in their areas and a decrease in their stability. In addition, the plasma angle decreased with the decreased speed and has no relationship with the power.

Statement of the Problem: Functional performance of optical lighting and illumination products and components critically depends on advanced technologies for cost-effective fabrication of tooling with strict surface quality and form geometry accuracy. Recent advancements in laser material processing have resulted in developing fundamentals of a novel unique no-material additive/removal technology known as a surface structuring by laser remelting (SSLRM) process [1-3]. During SSLRM, laser beam moves over a workpiece surface with a constant speed and synchronously controlled laser power while desired surface geometry is defined as a function of a laser power control algorithm. Consequently, new surface geometry is formed due to redistribution and relocation of molten workpiece material. It is a complex, highly non-linear thermo-dynamic process where material rapid melting, reallocation and rapid solidification is controlled by the parameters of the applied continuous wave laser irradiation. The purpose of this study is to advance preliminary developments of SSLRM towards optical tooling applications [4, 5]. Methodology: A wedged edge-lit light guide (WELLG) was chosen as a typical element of automotive rear lighting. Initially, sine-shape WELLG was optically designed where its geometry parameters (e.g. period of 500 µm, amplitude of 40 µm, wedge angle of 2°, made from PMMA plastic) were found to ensure a light delivery efficiency of >50% while covering >80% of the illuminated area. A metal insert from DIN 1.2343 (AISI H11) tooling steel was fabricated using SSLRM process (fig. a), replicated into PMMA plastic by hot embossing as a functional WELLG prototype (fig. c), and its optical performance was evaluated (fig. d). Findings: A period of 498.2±3.8 µm and amplitude of 40.0±2.0 µm were achieved for fabricated tooling insert. Plastic WELLG prototype has demonstrated highly efficient light delivery performance while fully covering the illuminated area. Conclusion & Significance: This study demonstrates high potentials in applicability of the SSLRM process for efficient fabrication of optical tooling for light guiding, distribution and illumination functions and products especially for automotive, solar energy and biomedical industry.

Narrow gap hybrid laser - arc welding is emerging joining technology that is very promising for the fabrication of thick sections in shipbuilding applications, but the matching performance of welded joint and base material has been seldom studied. This paper investigates the microstructure, microhardness and mechanical property of welded joints for 785 MPa high strength steel with 60 mm thickness with different welding materials. The results indicate that when the traditional welding material is used, the weld metal(WM) mainly contains lath martensite, its ultimate tensile strength and microhardness is 22% and 40% higher than those of base metal, respectively. While the low matching welding material is used, the microstructure of WM is predominately acicular ferrite and granular bainite, its ultimate tensile strength and microhardness is slightly higher than those of base metal, respectively. The impact energies under different welding materials are in the range of 88 to 96 J. The results indicating that equal strength matching is obtained with low matching welding material.

With observation of small objects, a precisely manipulation is also highly desirable, especially for a three-dimensional manipulation of nanoparticles or biomolecules with a size of less than 100 nm [1]. Although optical tweezers have become powerful tools to manipulate microparticles and cells, they have limits when extended to the nanoscale because of the fundamental diffraction limit of light. The emergence of near-field methods, such as plasmonic tweezers and photonic crystal resonators, have enabled surpassing of the diffraction limit. However, these methods are usually used for two-dimensional manipulation and may lead to local heating effects that will damage the biological specimens. Therefore, we propose a near-field technique that uses a photonic nanojet to perform the three-dimensional optical manipulation of sub-100-nm objects. With the photonic nanojet generated by a dielectric microlens bound to an optical fiber probe, three-dimensional manipulations were achieved for fluorescent nanoparticles as well as for plasmid DNA molecules [2]. Backscattering and fluorescent signals from the trapped targets were detected in real time with a strong enhancement. The demonstrated approach provides a potentially powerful tool for nanostructure assembly, biosensing and single-biomolecule studies.

It is admitted that Liquid-Phase Pulsed Laser Ablation (LP-PLA) attracts more and more  much attention and has been presented as an effective and innovative method of synthesis of functional nanoparticle materials. In our previous study, we have shown that the concentration of produced nanoparticles is linear with time, meaning that the production of nanoparticles by Pulse Laser Ablation is a controllable and precise process. This paper completes the first study by carrying a particular attention on average size estimation of the generated nanoparticles. The study is based on the use of a simple Multi Angle Near-Infrared Light Scattering (MA N-IR LS) device, which in real time, estimates easily by transmissometry and dual angles nephelometry, the average size of copper and iron nanoparticles produced by LP-PLA process. The developed experimental setup, mounted on a simple electronic’s instrumentation board and a specialized software has shown that the method can be easily used to estimate size evolution of produced nanoparticles; justified by the fact that our experimental curves can be correlated to the size of  Cu and Fe nanoparticles, present in the aqueous medium. The software implements Beer-Lambert law and Rayleigh theory at two different angles which, after the nanoparticles concentration calculation, evaluates their average size, based on exploitation of the reverse equations correlated to the concentration after multi-angle observations. With our integrated device, only three angles of light scattering theorie are sufficient to evaluate judiciously the global size of the nanoparticles generated during a Femto-Second Laser Ablation process. The users would just have to correctly install our device in the laser ablation process plan.

A comprehensive analysis has been reported, based on localized surface plasmon resonance phenomenon on responses with the change in probe geometry of optical fiber. Plasmonic responses of noble metal nanoparticles such as AuNPs and AgNPs have been examined for the detection of methanol exclusively by adopting D-type and tapered optical fiber probe. With increase in concentration of methanol, absorbance characteristics of the NPs changes, results in the change in effective refractive index of the medium. Consequently, the change in effective RI leads to alter the output responses of the proposed sensor. A comparative study has been presented with respective change in geometrical shape of the probes to detect methanol. The sensitivity in case of D-type probe for detection of methanol is found to be ~0.09644 mV/ppm with AuNPs and ~0.03038 mV/ppm with AgNPs. On the other hand, the sensitivity for AgNPs coated probe is found to be ~0.00389 mV/ppm and 0.00379 mV/ppm for AuNPs in case of tapered probe.     

The present study invesitgated the fabrication of the periodic subwavelength structures on vairous material surfaces with femtosecond laser pulses. Through using the collinear propagation of two temporally delayed femtosecond laser beams with crossed linear polarizations, we have one-step produced the regular distribution of the periodic surface structures on different materials including bulk metals and thin films without any masks. During the double-pulsed irradiation experiment, the incident first laser pulse is to modulate the optical properties of the material surface into the transient nonequibrium situations, and consequently the surface polasmon excitation behavior of the incident second laser pulse is affected. As a result, the feature aspects and the quality of the structure formation, such as the geometric profiles, the dimeniosnal size and the spatial arrangement, can be well controlled by varying the laser parameters. Moreover, it is identified that the high speed fabrication of such structures can be perfomed by adopting the line-shaped focusing of a cylindrical lens. This provide new routes for the effective design and fabrication of nanodevices for many potential applications.

Hydrogel is a kind of hydrophilic soft material with a three-dimensional network structure and has a broad application prospect in the field of medicine. The wound dressings to meet the clinic needs are the seeking goals of scientists. Natural biological materials have excellent biocompatibility ^{1, 2}. In our study, Human-like collagen-hyaluronic acid-carboxylated chitosan (HLC-HA-CCS) complex hydrogels crosslinked with glutamine aminotransferase (TG) are prepared for wound dressing. HA elevates the compressive stress, CCS increases the anti-deformation, HA and CCS together contribute to improve the porosities, swelling and water retention properties. Full thickness skin defect experiments show that HLC-HA-CCS hydrogels can promote wound healing in comparison with traditional ones.However, the mechanical properties of hydrogels made from natural materials are poor ² , and the antimicrobial, moisturizing performance as well as bacteria resistance fail to meet the requirements of wound healing. Therefore, a double-layer polyvinyl alcohol-polyethylene glycol-sodium carboxymethyl cellulose (PVA-CMC-PEG) hydrogel are prepared to solve the above problems. The double-layer hydrogels present a tight upper layer with smaller pore size and a loose lower layer with larger pore size, which can meet the absorption of seepage and bacteria resistance at the same time. The pore size at the longitudinal section presents a trend of gradual reduction and the two layers are bonded tightly. Furthermore, the double-layer hydrogels have a suitable water vapor transmission rate, excellent moisturizing effect, bacteria resistance ability and are non-sticky to the wound. Besides, the hydrogel have no toxic effects on cells. Full-thickness skin defect experiment shows that the double-layer PVA-CMC-PEG hydrogels canenhance wound healing greatly and would be ideal wound dressings.

This study is an investigation of a hybrid hierarchical electrode produced by electrospinning and chemical vapor deposition methods. The binderless hybrid hierarchical electrode is composed by carbon nanofibers with carbon nanotubes inside and outside the fibers. Single- walled or multi-walled carbon nanotubes are present inside the nanofiber as a dopant and they are incorporated during the carbon nanofiber electrospun production. After that, multi-walled carbon nanotubes are grown onto the surface of the carbon nanofiber using chemical vapor deposition method.The suitability of carbon nanofibers for lithium storage applications was investigated by electrochemical methods using charge and discharge curves, cyclic voltammetry and impedance spectroscopy. The morphology of the flexible binderless hybrid hierarchical electrodes was investigated by scanning electron microscopy. The additional incorporation of oxide nanoparticles (manganese, zinc or both) by electrodeposition method are responsible to improve the specific capacitance of the electrode, showing new perspectives to use this electrode configuration to produce lightweight, flexible and conductive electrode for lithium ion batteries without binder addition.

L-Cysteine (abbreviated as L-Cys) is an important thiol containing amino acid which is found in human plasma and is known as the primary building block of protein. This amino acid is involved in many essential and important biological processes in our physiological system. Although the presence of L-Cys in our body has number of health benefits, but excess amounts of this amino acid in human plasma or urine causes several health problems such as neurotxicity¹, urinary stones² etc. So, it is of prime importance to detect L-Cys selectively and more accurately in order to prevent our body from various diseases. In this present study we address a mechanism for selective and sensitive sensing platform utilizing the interaction of colloidal gold nanoparticles and cationic dye Rhodamine B (RhB) towards the detection of L-Cys from the fluorometric change of the dye molecules in an aqueous environment. Initially the presence of Au NPs causes the drastic reduction of fluorescence signal of RhB molecules in their mixed solution due to some non-radiative energy transfer process. But the addition of L-Cys solution to Au/RhB mixed solution recovers the fluorescence signal and is found to be linear within the concentration range of 0.01 µL – 1000 µL of L-Cys. The experimental limit of detection (LOD) was 0.01 µL and may be comparable to that present in human blood plasma. Also the recovery of fluorescence of RhB due to the selective interaction of L-Cys with Au NPs is accompanied with a colour change from wine to bluish black. The interference of all other amino acids including some thiol (-SH) containing amino acids along with some neurotransmitters (Na+, K+ etc.) present in our body have been tested in the same aqueous environment. The proposed mechanism for sensing of L-Cys is also tested with human urine sample to confirm its applicability to the real biological sample in vitro. UV-vis absorption and Transmission electron microscopy have been employed to characterize the as synthesized Au NPs. Our proposed fluorometric assay method for L-Cys detection may have great potential for biomedical applications with high degree of accuracy.