Tunable mechanical metamaterials in soft and biological matterMarinčič, Matevž (Avtor) Ravnik, Miha (Mentor) Humar, Matjaž (Komentor) numerical simulationsblue phase IIIchiral liquid crystalskyrmionswhispering gallery modesliquid inclusionselastocapillaritysoft biological mattermechanical metamaterialThis thesis numerically explores the mechanics of complex soft and biological materials along two lines of research. The first focuses on investigating the topological structures in blue phase liquid crystals (BP), stabilized by highly chiral anisotropic elasticity, and the second on using whispering gallery mode (WGM)-supporting microspheres as biosensors for probing local mechanical properties in soft elastic and biological materials. The first part of the thesis is devoted to the study and visualization of half-skyrmions and skyrmion filaments, also known as double-twist cylinders, in blue phases of chiral liquid crystals. Using a combination of Landau–de Gennes theory and surface anchoring, we investigate the effects of confinement to an experimentally relevant planar cell, focusing particularly on the less-studied blue phase III. Using advanced visualization techniques, the 3D structure of BPIII emerges as an amorphous tangle of quarter-skyrmions, stabilized by a connected network of topological defects. This structure transitions into an amorphous quasi-2D array of half-skyrmions bound by vertical disclination lines when confined to layers thinner than approximately half the chiral pitch. The full phase diagram of chiral structures is numerically calculated. Cubic BPI and BPII are also investigated, particularly the effect of stabilization by one-dimensional boundary patterns that impose specific orientations and monocrystallinity. The second part of the thesis introduces the theory and numerical simulations for a novel methodology for local measurement of mechanical properties in soft and biological materials, motivated as a minimally invasive technique with promising biomedical applications. We develop WGM-spectroscopy that utilizes WGM-resonances in dye-doped liquid droplets for high-precision spectral fitting to determine refractive indices, droplet size, and shape. Additionally, we develop finite element simulations to determine the deformation of a liquid inclusion in a soft elastic material, where elastocapillary effects influence the mechanical response of the droplet to local stress. The WGM-spectroscopy and simulations are complemented by experimental measurements to demonstrate the determination of local anisotropic stress and Young's modulus. Finally, the versatility and advantages of WGM spectroscopy are demonstrated through several additional biosensing applications, including ultra-precise microdroplet generation and barcoding, deep-tissue and intracellular localization of microbeads (unaffected by scattering), and simultaneous tracking and sensing. Local refractive indices were measured with high precision, demonstrating the ability to monitor intracellular changes during cellular processes. The work presented in this thesis will allow for a better understanding of the topology and structure of blue phases and advance WGM-based applications in biomedicine and the study of soft materials.20252025-10-24 08:15:23Doktorsko delo/naloga175317VisID: 155322COBISS_ID: 254889475sl