The purpose of this work is to demonstrate that laser-induced conductive tracts in AlN ceramic can be applied for fabrication of an integrated resistive heating element. Nanosecond laser processing at a wavelength of 1064 nm of ceramic in vacuum is used for a formation of conductive areas. It is demonstrated that the applied laser fluence and the number of pulses influence strongly the electrical properties of the material in the irradiated zone. The resistance value of the produced tracks with a length of about 4 mm and width of about 1 mm may vary from 17 to about 2000 Ohms, depending on the processing conditions. The material in the processed zone is characterized by means of surface composition, morphology, and electric properties. It is found that the electrical conductivity of the formed structure is based on the ceramic decomposition and formation of aluminum layer. The analysis of the influence of the temperature on the electrical resistance value shows that the material’s conductivity could be preserved after annealing, as in the present study it is confirmed up to 300 °C. The ability of the formed tracks to serve as a basis element of ceramic integrated resistive heater is studied by applying DC voltage. It is found that the fabricated element can be used with a high reliability to about 90 °C without special requirements for contact design and encapsulation. Operation at higher temperatures is also demonstrated as the maximal one achieved is about 150 °C at 10V. The performance of the heater is investigated and discussed as the operation range is defined. The proposed element can be a basis for a design of an integrated heater in ceramic with high stability and applications in everyday life and research.

Abstract The weak magnetic fields generated by a current-carrying metallized traces are detected in view of their applications in bionic systems and neural-electrode interface technologies. The traces are formed by femtosecond laser processing of the surface of polydimethylsiloxane polymer substrate and further functionalization by electroless metallization. The measurements are performed by means of magneto-optical spectroscopy involving two optical beams, serving as pump and probe, where the magnetic field sensor is 87Rb atoms confined in a paraffin-coated optical cell. The experimental results show the feasibility of remote detection of the conductivity of metallized nickel traces.

Picosecond and Nanosecond Nd:YAG laser systems with a fundamental wavelength of 1064 nm are utilizedfor green synthesis of bimetallic nanocomposites based on metal combinations of Pt/Ti, Pd/Ti, Pt/Zn and Pd/Zn. The laser assisted method is based on pulsed laser ablation of metal targets, which are immersed consecutively in bidistilled water to obtain water colloids of the corresponding bimetallic nanostructures. Comparative study of the structural and optical properties of the nanocomposites is conducted by means of transmission electron microscopy in its corresponding main modes and by optical spectrometer measurements, respectively. Suspensions of water colloids of the nanocomposites and methylene blue dye prepared in 1 : 2.5 ratio, respectively, are exposed under sunlight irradiation for 3 h. Photocatalytic activity of the nanocomposites against methylene blue (MB) dye is tested by measuring the optical absorbance of the suspensions before and after the sunlight irradiation.

The method of pulsed laser ablation in liquids (PLAL) is applied for synthesis of composite nanostructures on the basis of TiO x and ZnO combined with noble metals like Au, Pt and Pd. The metallic plate immersed in water is laser ablated by nanosecond Nd:YAG pulsed laser irradiation. Its fundamental wavelength and the fourth harmonic are used, respectively, to produce and to modify the morphology and structure of the nano-objects. The synthesis procedure consists of two consecutive steps: laser ablation of the selected metal targets followed by unfocused laser beam irradiation of the initial colloids of nanostructures. The phase composition, structural and the shape and size morphological features were assessed by analytical method – transmission electron microscopy (TEM) in its main modes – Bright Field TEM (BF TEM), High Resolution TEM (HRTEM) and Selected Area Electron Diffraction (SAED). Formation of bimetallic polycrystalline alloys and Pt/Ti(Ti x O y ) and Pd/Ti(Ti x O y ) core-shell nanoparticles was founded.

Here we present experimental results on the modification of graphite suspensions in bi-distilled water by laser irradiation in a flow mode system. The fundamental wavelength of a Nd:YAG laser system (λ= 1064 nm) was used in our experiments. The morphology of the sedimented and dried powders was studied by transmission electron microscopy (TEM). Their phase composition and structure were explored by Raman spectroscopy, GIXRD, as well as TEM.

The study investigates the effect of the femtosecond laser pulse irradiation on the modification and activation effects of medical-grade polydimethylsiloxane (PDMS) polymer. The motivation of the research is based on the continuous interest and variety of applications of the PDMS material in medicine and implantable neural interface devices. The PDMS is the preferred material due to its exceptional properties such as high biocompatibility and biostability, mechanical flexibility and stability, optical transparency from UV to near IR spectral region, and cost-effectiveness. The experimental investigation is performed by a femtosecond laser system with a pulse duration of 35 fs operating at a repetition rate of 1 kHz. Consistent sets of measurements are performed to analyze and characterize the effect of the laser beam parameters on the optical absorption, and surface morphology concerning the laser-treated zones. The morphology and the optical properties of the PDMS are investigated to activate its surface for successful metallization of the modified tracks. The reported findings and observations specify favourable results of the implementation of the ultrafast laser-based method for micro- or nano-processing of optically transparent biopolymers for interface devices in bioengineering technologies such as neural implants and interface applications.

The present study investigates the possibility of obtaining graphene-like phases (defected graphene, graphene oxide, and reduced graphene oxide) as fine suspensions by applying a novel pulsed laser ablation (PLA) approach in flow mode. Two types of suspensions of microcrystalline graphite in aqueous suspensions and two types of microcrystalline graphite in suspensions of 6% hydrogen peroxide solution were irradiated in a quartz tube through which they flow. The third (λ = 355 nm) and fourth harmonics (λ = 266 nm) of an Nd:YAG laser system (15 ns pulse duration and 10 Hz pulse repetition rate) were used. The morphology of the obtained particles was studied by transmission electron microscopy (TEM). Their phase composition and structure were explored by X-ray photoelectron spectroscopy, X-ray diffractometry, and Raman spectroscopy.

In this work, the surface modifications are studied of aluminium nitride (AlN) and silicon nitride (Si3N4) ceramics irradiated by nanosecond laser pulses. The laser processing is performed by a Nd:YAG laser system at four wavelengths - 266 nm, 355 nm, 532 nm, and 1064 nm. It is found that the average ablation rate per pulse is in the order of few hundreds of nanometers, as the laser treatment leads to the appearance of a variety of micro- and nanostructures on the surface of the material. In the case of AlN, a conductive layer is formed on the surface whose resistance can be modified by varying the processing conditions. Using a model based on the heat-conduction equation, the temperature evolution, ablation depth and temporal dynamics of the ablation process are followed.

The present research aims to investigate the modification and activation effects on medical-grade polydimethylsiloxane (PDMS) polymer irradiated by ultrashort laser pulses. The motivation of the current study is based on the wide use of the PDMS material in medicine and, more specifically, in implantable neural interface applications. Systematic measurements are carried out to characterize the effect of the laser beam parameters on the optical absorption and the surface morphology with respect to the laser-treated zones. The PDMS polymer is modified by surface tracks after the femtosecond laser processing. The optical properties of the PDMS are investigated to prove the effective laser activation of the surface, which ensures further successful metallization of the modified tracks. It is seen that defective transformations occur in the entire laser-treated area when the number of pulses is increased. The preliminary observation indicates promising results regarding the implementation of such a laser-based method for micro-or nano-processing of optically transparent biopolymers for interface devices in bioengineering technologies, such as neural implants and interface applications.

A pump – probe configuration is used to register zero-field level-crossing resonances in Rb vapour contained in a cell with antirelaxation coated walls. The scheme is applied to detect the weak magnetic field generated by a current-carrying micro-wire (metallised track). Such micro-wires can be employed in neural prostheses and hybrid bionic systems as micro-electrode arrays. More specifically, the operation of such live micro-wire belonging to a neuronal – electrode interface is demonstrated, which indicates the possibility of remote testing of the operation (conducting/nonconducting) of micro-wires for in neural implants.

The aim of this work was to obtain graphene-like phases (defected graphene, graphene oxide and reduced graphene oxide) as fine suspensions by applying pulsed laser ablation (PLA) of micro-crystalline graphite suspension in water medium. The fundamental (λ = 1064 nm), second (λ = 532 nm), third (λ = 355 nm) and fourth harmonics (λ = 266 nm) of a Nd:YAG laser system (15-ns pulse duration and 10-Hz pulse repetition rate) were used. The morphology of the particles was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Their phase composition and structure were explored by Raman and X-ray photoelectron spectroscopies, grazing incidence X-ray diffractometry (GIXRD) and TEM. The specimens were prepared by drop-casting on a glass substrate (for Raman and GIXRD studies) and on a standard TEM copper mesh for SEM and TEM examination.

Pulsed laser ablation in liquids is utilized for preparation of composite nanostructures on the basis of TixO2x-1 and Ag. Plates of bulk Ti and Ag immersed in the corresponding liquid serve as targets in the ablation procedure. A nanosecond Nd:YAG pulsed laser is employed as a source of irradiation. Its fundamental wavelength and the third and fourths harmonic are used both to fabricate and to change the chemical composition and the morphology of the nanostructures considered. The procedure for synthesis of complex nanostructures is performed following a specific sequence, namely, the consecutive laser ablation of the selected targets is followed by a post-ablation irradiation of the colloid obtained of the complex nanostructures. The changes in the characteristics of the complex nanostructures are indirectly evaluated based on the profile of the optical transmission spectra of the as-obtained colloids. The colloids' properties are controlled by varying the laser beam parameters. Transmission electron microscopy (TEM) is applied for direct visualization of their shape. The chemical composition and the morphology were assessed by high-resolution TEM and SAED analyses.

This work reports on the production of Ag nanoparticles (AgNPs) in water solution based upon two-phase pulsed laser procedure for ophthalmological therapeutic approaches. In this case, the AgNPs should be less then 10 nm and have a narrow size distribution. Nanoparticles of this sized-scale are capable to penetrate the complex ocular barriers, ensuring effective non-invasive drug delivery to retina. In the first phase, AgNPs larger than 20 nm were fabricated via laser ablation of a Ag target under water by irradiation with a fundamental wavelength of 1064 nm generated by a Nd:YAG laser. During the second phase, to reduce the mean size of the as-obtained nanoparticles and properly adjust the size distribution, the water colloids were additionally irradiated by ultraviolet harmonics (355 nm and 266 nm) from the same laser source. The effect of the key laser parameters - wavelength, fluence and laser exposure time - upon the nanoparticles morphology was studied. The most suitable post-ablation treatment of initial colloids was obtained by consecutive irradiation with the third (355 nm) and the fourth (266 nm) harmonics of the fundamental laser wavelength. By using this approach synergistic effect between two mechanisms of light absorption by AgNPs was induced. As a result contaminant-free colloids of AgNPs with a size inferior to 10 nm and a quite narrow size distribution with a standard deviation of 1.6 nm were fabricated. The toxic effect of the as-produced AgNPs on Gram-positive and Gram-negative bacteria and Candida albicans was explored. The most efficient action was reached against Pseudomonas aeruginosa and Escherichia coli. Potential application of the synthesized AgNPs colloidal aqueous solutions with antimicrobial action as a non-invasive method for ocular infections prevention and treatment was proposed.

We report on a new approach toward a laser-assisted modification of biocompatible polydimethylsiloxane (PDMS) elastomers relevant to the fabrication of stretchable multielectrode arrays (MEAs) devices for neural interfacing technologies. These applications require high-density electrode packaging to provide a high-resolution integrating system for neural stimulation and/or recording. Medical grade PDMS elastomers are highly flexible with low Young’s modulus < 1 MPa, which are similar to soft tissue (nerve, brain, muscles) among the other known biopolymers, and can easily adjust to the soft tissue curvatures. This property ensures tight contact between the electrodes and tissue and promotes intensive development of PDMS-based MEAs interfacing devices in the basic neuroscience, neural prosthetics, and hybrid bionic systems, connecting the human nervous system with electronic or robotic prostheses for restoring and treating neurological diseases. By using the UV harmonics 266 and 355 nm of Nd:YAG laser medical grade PDMS elastomer is modified by ns-laser ablation in water. A new approach of processing is proposed to (i) activate the surface and to obtain tracks with (ii) symmetric U-shaped profiles and (iii) homogeneous microstructure This technology provides miniaturization of the device and successful functionalization by electroless metallization of the tracks with platinum (Pt) without preliminary sensitization by tin (Sn) and chemical activation by palladium (Pd). As a result, platinum black layers with a cauliflower-like structure with low values of sheet resistance between 1 and 8 Ω/sq are obtained.

The aim of our work was to obtain graphene-like phases (defected graphene, graphene oxide and reduced graphene oxide) as fine suspensions by applying pulsed laser ablation (PLA) to microcrystalline graphite suspension in water medium. The fundamental (lambda = 1064 nm), second (lambda = 532 nm), third (lambda = 355 nm) as well as the fourth harmonic (lambda = 266 nm) of a Nd:YAG laser system, 15 ns pulse duration and 10 Hz pulse repetition rate were used in PLA processes. The morphology of the particles was studied by transmission electron microscopy (TEM). Their phase composition and structure were explored by Raman and X-ray Photoelectron spectroscopies, grazing incidence X-ray diffractometry (GIXRD) and high temperature powder X-ray diffraction (HTXRD) and TEM. It can be assumed, in accordance to the XPS, TEM and Raman studies, that the colloids obtained by all experiments contain predominantly rGO and defected graphene, but also some GO, graphite micro-particles, and graphene-like phases. Amorphous carbon is frequently observed in by PLA at lambda = 355 nm as well as at lambda = 266 nm at high laser beam fluences but it can be found in very small quantities in all specimens. The XPS analysis of the samples revealed a significant increment in the quantity of different oxygen-containing radicals as a function of the fluence, which is a result of the quantity of the sp(3)-hybridized carbon. Finally, the established PLA procedures have been found to be highly reproducible.

We modified carbon black (CB) with a large surface area (ENSACO 350 GRANULAR) by acetone and further thermal treatment. The pristine and the modified CB were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Raman spectroscopy. The acetone treatment increases the content of oxygen-containing radicals in CB. The thermal annealing was performed at temperatures ranging from 250 °C to 1080 °C for three hours in air atmosphere. The powder XRD patterns revealed that the broad complex peak centered at about 2θ = 24.7 – 24.8°, which arises from graphitic-ordered sp 2 -hybridized carbon, shifts to its usual position at 2θ = 26.2° as the annealing temperature is increased. We concluded that the above results pointed to a relative decrease in the number of 3D graphitic nano-crystals and an increase in the predominantly 2D ones. The Raman studies confirmed the above conclusions.

In this work, results on a new laser-induced mechanism of microstructures formation on the surface of borosilicate glass are presented. The samples are fabricated by melt quenching method and consist of 50% SiO2, 20% Al2O3, 20% B2O3, 5% CaO, 2% Li2O, 3% MgO (in wt.%). Irradiation at 266 nm delivered by Nd:YAG nanosecond system is used to modify the glass surface. It is found that this processing may result in the formation of voids in the irradiated area that have submicron mean diameter. The effect is observed at fluences below the ablation threshold. Different laser fluences and pulse number are applied to estimate their role on the induced surface morphology. It is observed that voids are also observed in the remaining material after ablation of the irradiated zone at high fluences. In this regime, glass structure modifications can also be observed under the glass surface at depths that may reach 100 µm. Based on measurements by differential thermal analysis equipped by mass spectrometer is concluded that the void formation is related to emission of gas phase from the glass induced by the laser heating.

The paper presents results on femtosecond laser irradiation-induced modification of the optical properties of a composite material – gold nanoparticles embedded into a borosilicate glass host. The process is initiated by laser pulses delivered by a Ti:sapphire laser system with pulse duration of 35 fs. The glass samples are prepared by melt quenching with gold added as hydrogen tetrachloroaurate (III) hydrate to the initial composition. Post-fabrication annealing leads to a homogeneous formation of nanoparticles in the glass; varying the annealing parameters results in producing nanoparticles with different sizes and shapes. The laser irradiation of the samples induces significant modification of the optical spectra of the glass through changes of the nanoparticles characteristics. The effects are studied of the laser fluence, laser wavelength and laser pulses number. The heat diffusion equation is applied to estimate the temperature evolution and explain the modifications observed. The results demonstrate this technique’s efficiency in modifying the nanoparticles properties with a high 3D spatial resolution, which can be useful in fabrication of integrated optical systems.

Noble metal nanoparticle composed glasses attract significant attention due to the unique optical properties that they express in the near UV and visible spectral range. These are related to the high values of the extinction cross section and nonlinear optical characteristics. In this work we study the ability of laser irradiation to induce modification of the optical properties of borosilicate glasses that contain gold nanoparticles. The process is investigated by application of laser pulses of nanosecond Nd:YAG system on glasses that consist of nanoparticles with different size and shape. The results show that at certain conditions the glass optical properties can be modified as a change of the nanoparticles plasmon resonance wavelength is observed. The influence of the laser fluence and pulse number on this effect is studied. Two fluence regimes are defined: (i) at low fluences, close to the optical properties modification threshold the increase of the laser fluence results in a blue shift of the resonance wavelength; (ii) further increase of the laser fluences induces a red shift. Similar behavior is observed by changing the number of the applied pulses. Here after application of several thousand laser pulses additional, third regime of blue shift is realized. Theoretical models based on multiparticle Mie scattering theory and heat conduction equation are applied to explain the observed modifications. On their basis and performed analyses can be concluded that the induced optical properties variations are related to modification of the nanoparticles size and shape by melting, fragmentation and coalescence. The obtained results indicate an ability of nanoparticle size and shape modifications with a high spatial resolution in 3D and can be used for fabrication of integrated optical systems.

This work represents results on the response of noble metal-doped borosilicate glass to laser radiation with femto- and nanosecond pulse duration. The material under study is obtained by conventional melt quenching method as samples with noble metal concentration varied up to 10 wt% are fabricated. Optical and morphology changes of the glass samples induced by application of laser pulses with a wide range of parameters are studied. Below the permanent modification threshold, defects associated with formation of color centers in the material are observed and their properties as a function of the processing conditions are discussed. It is found that at certain conditions laser irradiation may induce direct formation of noble metal nanoparticles in the glass. When permanent morphology modifications are induced, different micro-and nanostructures are observed depending on the laser parameters. The morphology of the ablated area is studied as function of the laser fluence and number of the applied pulses. It is found that the presence of noble metal in the glass at concentrations up to 10 wt% (the maximal used) does not influence the ablation rate at both femto- and nanosecond ablation. The formation of defects and the composition of the material in the vicinity of the ablated zone are also discussed.