Ústav fyzikálního inženýrství

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Apparent Young´s modulus of human cranial cancellous bone
(Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, 2024-05-14) Votava, Tomáš; Marcián, Petr; Borák, Libor; Fuis, Vladimír; Zikmund, Tomáš; Kaiser, Jozef; Wolff, Jan
This study investigates the biomechanical behavior of cancellous bone in the os occipitale through finite element modeling. Utilizing micro-computed tomography scans, 47 bone segments were analyzed, and their apparent Young's moduli of each segment were determined in three orthogonal directions. The results revealed strong directional dependencies of Young’s modulus on bone volume fractions. In contrast, nondirectional dependency exhibited a weaker correlation, indicating an orthotropic elasticity. The derived correlation equations offer an efficient means to describe cancellous bone in cranial biomechanical simulations, especially when a detailed trabecular representation is impractical.
Raman microspectroscopy and laser-induced breakdown spectroscopy for the analysis of polyethylene microplastics in human soft tissues
(CELL PRESS, 2024-09-30) Parobková, Viktória; Holub, Daniel; Kizovský, Martin; Kalčíková, Gabriela; Rozman, Ula; Urík, Milan; Novotný, Karel; Samek, Ota; Zikmund, Tomáš; Pořízka, Pavel; Kaiser, Jozef
People are exposed to microplastics (MPs) on a large scale in everyday life. However, it is not clear whether MPs can also be distributed and retained in certain tissues. Therefore, the development of analytical methods capable of detecting MPs in specific human organs/tissues is of utmost importance. In this study, the use and combination of spectroscopic techniques, namely Raman microspectroscopy and laser-induced breakdown spectroscopy (LIBS), was tested for the detection of polyethylene (PE) MPs in human tonsils. Preliminary results showed that Raman microspectroscopy was able to detect MPs down to 1 mu m in size and LIBS down to 10 mu m. In the next step, human tonsils were spiked with PE MPs, and digested. The filtered particles were analyzed using Raman microspectroscopy and LIBS, and complemented by X-ray fluorescence (XRF). The results showed that Raman microspectroscopy could reliably detect PE MPs in spiked human tonsils, while LIBS and XRF served as a reference analytical method to characterize particles that could not be classified by Raman microspectroscopy for their non-organic origin. The results of this study, supported by a current feasibility study conducted on clinical samples, demonstrated the reliability and feasibility of this approach for monitoring MPs in biotic samples.
Investigating the effects of laser wavelengths and other ablation parameters on the detection of biogenic elements and contaminants in hydroxyapatite
(ROYAL SOC CHEMISTRY, 2024-08-28) Fazlić, Aida; Faruzelová, Anna; Buday, Jakub; Michlovská, Lenka; Vojtová, Lucy; Modlitbová, Pavlína; Pořízka, Pavel; Kaiser, Jozef
The main purpose of this work is to thoroughly describe sensitivity and resolution enhancement by systematically optimizing key parameters in laser-induced breakdown spectroscopy analysis. Simultaneous analysis of biogenic (C, P, Mg, and Ca) and contaminating (Pb) elements, which are commonly detected in selected biotic matrices (mammal teeth), was performed. Hydroxyapatite reference pellets were utilized as model matrices, which successfully reflect human dental tissue. The optimization involved precise adjustments of the used laser wavelengths (1064, 532, and 266 nm), relative defocus of the laser pulse, ablation pulse energies, and gate delays for collecting characteristic spectra. In addition, for Ca analysis, the signals of different ionization line types (Ca I 364.44 nm; Ca II 370.60 and 396.85 nm) were compared; in the case of Pb analysis, the limits of detection were established for each used laser wavelength, and the revealed differences were discussed in detail. We intend to demonstrate the benefits of rapid, low-cost analysis and also the importance of measurement parameters used in biotic sample testing. A comparison of laser ablation measurement parameters (laser wavelength, energy, gate delay, defocus, and spot size) to determine optimal settings for the detection of heavy metals and biogenic elements in a hard tissue matrix (hydroxyapatite).
Fabrication of customized open-cell titanium foams by direct foaming for biomedical applications
(ELSEVIER, 2024-11-01) Oliver Urrutia, Carolina; Casas Luna, Mariano; Koledová, Zuzana; Slámečka, Karel; Zikmund, Tomáš; Kaiser, Jozef; Čelko, Ladislav; Montufar Jimenez, Edgar Benjamin
Titanium (Ti) foams offer a promising alternative for bone reconstruction and repair due to their high porosity and lower stiffness compared to solid metals, which improves in vivo osseointegration by reducing the stress shielding effect and allowing bone ingrowth. In this work, customized Ti foams were successfully fabricated for the first time at room temperature using a direct foaming method. Ti powder suspension with a water-soluble surfactant and environmentally friendly thickener was foamed by mechanical stirring. Then, 3D-printed moulds were utilized to achieve near-net shape foams, which were subsequently consolidated by sintering, thus avoiding the need for complex processing of molten Ti. The resulting Ti foams exhibited a cancellous-like open-cell structure, high porosity (> 80%), and a five times higher effective surface area than a 3D Ti mesh with a primitive cubic-based cell fabricated by additive manufacturing. In addition, the Ti foams exhibited similar mechanical properties to cancellous bone and facilitated the adhesion, proliferation, and maturation of human osteoblasts in vitro.
Engineering of Active and Passive Loss in High-Quality-Factor Vanadium Dioxide-Based BIC Metasurfaces
(AMER CHEMICAL SOC, 2024-08-27) Aigner, Andreas; Ligmajer, Filip; Rovenská, Katarína; Holobrádek, Jakub; Idesová, Beáta; Maier, Stefan A.; Tittl, Andreas; Menezes, Leonardo de S.
Active functionalities of metasurfaces are of growing interest in nanophotonics. The main strategy employed to date is spectral resonance tuning affecting predominantly the far-field response. However, this barely influences other essential resonance properties like near-field enhancement, signal modulation, quality factor, and absorbance, which are all vital for numerous applications. Here we introduce an active metasurface approach that combines temperature-tunable losses in vanadium dioxide with far-field coupling tunable symmetry-protected bound states in the continuum. This method enables exceptional precision in independently controlling both radiative and nonradiative losses. Consequently, it allows for the adjustment of both the far-field response and, notably, the near-field characteristics like local field enhancement and absorbance. We experimentally demonstrate continuous tuning from under- through critical- to overcoupling, achieving quality factors of 200 and a relative switching contrast of 78%. Our research marks a significant step toward highly tunable metasurfaces, controlling both near- and far-field properties.

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