Compared with traditional electronic materials (metals and semiconductors), electrically conductive biopolymers have improved compatibility with biological cells and human biological tissues. This allows creating new bioelectronic devices, for example, biosensors, drug delivery devices, 3D tissue-engineering matrix et al. A new laser method has been developed for the 3D manufacturing of electrically conductive nanocomposites with a given architecture. The architecture may be similar to the microelectronic component base (for example, the creation of microchannels between nanocomposite regions for designing transistors). A pulsed ytterbium fiber laser connected to a galvanometric scanner (laser wavelength - 1064 nm, pulse duration - 100 ns, frequency - 100 kHz, irradiation power up to 10 W) was used to form nanocomposites. By the galvanometric scanner, the focused laser beam moved along the trajectory (XYZ) specified in the software. As a result, the samples had the desired geometric 3D shape. Homogeneous dispersions of carbon nanotubes and biopolymers (albumin, collagen and chitosan amino sugar) were used as raw materials on a flexible substrate. The phase transition of the liquid dispersion of nanotubes into a solid was the main mechanism for the nanocomposites formation process. With focused laser irradiation, the temperature in the region of defects in carbon nanotubes increased, in contrast to other regions of nanotubes. As a result, the nanotubes were connected in an electrically conductive scaffold. Nanocomposites had high conductivity values of ~10 S/m, as well as high hardness of 300-500 MPa. The biocompatibility of nanocomposites has been proven in vitro и in vivo.
The technology of modification of the CNT array on a silicon substrate using laser radiation of nanosecond duration has been developed. The energy regime of irradiation of the array is determined with the aim of aligning the nanotubes perpendicular to the substrate. Structuring of CNTs at a given area using impulse nanosecond radiation moving using a galvanometric scanner system is obtained. Patterning was carried out using pulsed laser radiation with a wavelength of 1064 nm, which was moved by means of galvanometric mirrors over the area of the CNT array. The spatial profile of the beam was Gaussian. The energy density of the pulse was in the range 0.4-2.2 J/cm2. In order to obtain a homogeneous region of the CNT array after irradiation, the following parameters were set: the pulse duration was 100 ns, the radiation frequency was 30 kHz, at which the overheating of CNTs was minimized. The diameter of the laser beam at the focus of the laser was 20 μm. The moving rate of the laser beam of 500 mm/s was chosen in such a way so that individual pulses formed a continuous line with a laser beam overlap to compensate the changing in laser spot power along the diameter. Thus, the processed square 5×5 mm was formed by parallel lines 5 mm long, consisting of individual pulses located at a distance of 17 μm from each other. It is shown that the following effects are possible: CNT ablation, the effect of CNT alignment (straightening), singling, and “splicing” of individual CNTs in a single structure, as well as changing the morphology of the array itself. Nanotubes are less defective after laser modification. This is proved by Raman spectroscopy. The effect of CNT array structuring can be used to create new sensitive elements of photodetectors, solar cells, chemical sensors, temperature and pressure sensors, probes in microscopy and emitters.
Laser radiation limiters can be made on the basis of working substances, which have strong nonlinear effects after reaching a certain critical value (threshold limiting). Thus, it becomes possible to obtain a high transmission for a safe beam and a sharply reduced transmission for a hazardous beam. To determine the nonlinear and linear optical properties of these materials there were carried out comprehensive spectroscopic studies, experiments by Z-scan methods with an open aperture and a fixed location of the limiter. Working substances was developed which is suspension of conjugates J-type phthalocyanine dimers Zn or Mg with single-walled carbon nanotubes (SWCNTs) in water. Created conjugates can be used not only for protecting eyes and light-sensitivity elements, but for forming three-dimensional tissueengineered structures. Using conjugates J-type phthalocyanine dimers Zn and Mg with SWCNTs will increase the optical absorption in the wavelength range of laser processing by reducing the thermal effect on other substances in the composition of this structure. The Nd:YAG laser was used as the laser radiation source for generating pulses of 16 ns duration at a wavelength of 532 nm with the linearly polarized laser beam in the horizontal plane and a shape of Gaussian type. The threshold of limiting, linear and nonlinear absorption coefficients were determined by output characteristic, that was obtained by fixed location of the limiter. Created working substances have values of the following order: linear absorption coefficient ~ 3 cm-1 for layer of 0.2 cm thickness, low limiting threshold ~ 1 MW·cm-2 and high value of the nonlinear absorption coefficient ~ 550 cm GW-1 . Knowing the nonlinear optical parameters, Z-scan data with an open aperture can be calculated for comparison with experimental data.
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