The incorporation of bioactive compounds onto polymer fibrous scaffolds with further control of drug release kinetics is essential to improve the functionality of scaffolds for personalized drug therapy and regenerative medicine. In this study, polymer and hybrid microcapsules were prepared and used as drug carriers, which are further deposited onto polymer microfiber scaffolds [polycaprolactone (PCL), poly(3-hydroxybutyrate) (PHB), and PHB doping with the conductive polyaniline (PANi) of 2 wt % (PHB-PANi)]. The number of immobilized microcapsules decreased with increase in their ζ-potential due to electrostatic repulsion with the negatively charged fiber surface, depending on the polymer used for the scaffold's fabrication. Additionally, the immobilization of the capsules in dynamic mechanical conditions at a frequency of 10 Hz resulted in an increase in the number of the capsules on the fibers with increase in the scaffold piezoelectric response in the order PCL < PHB < PHB-PANi, depending on the chemical composition of the capsules. The immobilization of microcapsules loaded with different bioactive molecules onto the scaffold surface enabled multimodal triggering by physical (ultrasound, laser radiation) and biological (enzymatic treatment) stimuli, providing controllable release of the cargo from scaffolds. Importantly, the microcapsules immobilized onto the surface of the scaffolds did not influence the cell growth, viability, and cell proliferation on the scaffolds. Moreover, the attachment of human mesenchymal stem cells (hMSCs) on the scaffolds revealed that the PHB and PHB-PANi scaffolds promoted adhesion of hMSCs compared to that of the PCL scaffolds. Two bioactive compounds, antibiotic ceftriaxone sodium (CS) and osteogenic factor dexamethasone (DEXA), were chosen to load the microcapsules and demonstrate the antimicrobial properties and osteogenesis of the scaffolds. The modified scaffolds had prolonged release of CS or DEXA, which provided an improved antimicrobial effect, as well as enhanced osteogenic differentiation and mineralization of the scaffolds modified with capsules compared to that of individual scaffolds soaked in CS solution or incubated in an osteogenic medium. Thus, the immobilization of microcapsules provides a simple, convenient way to incorporate bioactive compounds onto polymer scaffolds, which makes these multimodal materials suitable for personalized drug therapy and bone tissue engineering.

We study, theoretically and experimentally, optical properties of different types of honeycomb photonic structures, known also as 'photonic graphene'. First, we employ the two-photon polymerization method to fabricate the honeycomb structures. In experiment, we observe a strong diffraction from a finite number of elements, thus providing a unique tool to define the exact number of scattering elements in the structure by a naked eye. Then, we study theoretically the transmission spectra of both honeycomb single layer and 2D structures of parallel dielectric circular rods. When the dielectric constant of the rod materials ε is increasing, we reveal that a twodimensional photonic graphene structure transforms into a metamaterial when the lowest TE01 Mie gap opens up below the lowest Bragg bandgap. We also observe two Dirac points in the band structure of 2D photonic graphene at the K point of the Brillouin zone and demonstrate a manifestation of the Dirac lensing for the TM polarization. The performance of the Dirac lens is that the 2D photonic graphene layer converts a wave from point source into a beam with flat phase surfaces at the Dirac frequency for the TM polarization.

Emission enhancement of quantum emitters is particularly relevant in the development of single-photon sources, which are key elements in quantum information and quantum communications. All-dielectric metasurfaces offer a route towards strong enhancement of local density of optical states via engineering of high quality factor optical modes. In particular, the recently proposed concept of quasi-bound states in the continuum (quasi-BIC) allows for precise control of such resonances in lattices with an asymmetric unit cell. Still, the spectral band of emission enhancement is usually fixed by the geometric parameters of the metasurface. Here, we propose to utilize phase change materials to tune the properties of light-emitting metasurfaces designed to support quasi-BIC states in the telecom wavelength range. In our design, a thin layer of a phase change material, which provides strong contrast of refractive index when switched from the amorphous to the crystalline state, is located on top of the resonators made of amorphous silicon (a-Si). Depending on the selected phase change material, we numerically demonstrate different functionalities of the metasurface, In particular, for low-loss Sb2Se3 we evidence spectral tuning effects, whereas for Ge2Sb2Te5, we report an “on”/“off” switching effect of the quasi-BIC resonance. Furthermore, we investigate the influence of the crystallization fraction and the asymmetry parameter of the metasurface on the results. This work provides concrete design blueprints for switchable metasurfaces, offering new opportunities for nanophotonics devices or integrated photonic circuits.

Tunable and ultracompact optical elements are highly important for the development of advanced nanophotonics. Such elements significantly expand the capabilities of photonic circuits and devices. Phase changing materials based on Ge-Sb-Te composition are very promising for tunable nanophotonic elements. This family of materials is excellent for the creation of tunable optical elements, since it has a non-volatile reversible phase transition and exhibits a strong modulation of the dielectric permittivity in broad spectral range. In this work, fabrication of Ge-Sb-Te nanoparticles by laser ablation as well as strong and repeatable changing of their optical properties by fs-laser irradiation are demonstrated. Beside the control of linear optical response, switchable second harmonic generation from Ge-Sb-Te nanoparticles over two orders of magnitude after the phase change is also demonstrated.