20.500.12556/RUL-156228 Ojačenje optodinamsko generiranih tlačnih valov globoko pod obsevano površino Amplification of Optodynamically Generated Pressure Waves Deep Below The Irradiated Surface V doktorskem delu smo raziskali metodo laserskega generiranja lokaliziranih tlačnih motenj globoko pod obsevano površino in tvorbo kavitacije. Eksperimentalni sistem je sestavljen iz laserskega vira Nd:YAG s preklopom kvalitete, ki omogoča generiranje večjega števila nanosekundnih bliskov do energije 900 mJ, ki si sledijo v intervalu med 50 µs in 400 µs. Z uporabo sferično oblikovane optoakustične leče, ki je izdelana iz titana s površinskim slojem črnega TiOx, smo tvorili tlačne motnje, katerih velikost v gorišču znaša približno 120 x 300 µm2 (dolžine x premer), amplituda tlačne motnje pa znaša ~100 MPa. S schlieren fotografijo in hitro kamero smo pokazali, da je možno doseči lokalizirano kavitacijo v gorišču optoakustične leče. Velikost kavitacijskega oblaka in njegovo nihanje v času narašča monotono z energijo laserskega vzbujanja. V primeru uporabe štirih zaporednih laserskih bliskov, ko je zamik med laserskimi bliski enak trajanju parnih mehurčkov nad optoakustično lečo, se velikost kavitacije poveča za 10-krat, medtem ko se amplituda tlačnega vala poviša za več kot 75 %. Na to ojačenje odločilno vplivajo trije medsebojno konkurenčni pojavi: zastiranje laserskega bliska zaradi prisotnosti oblaka parnih mehurčkov, povečanje temperature površine OL in resonančni učinek, ki se pojavi, kadar je naslednji laserski blisk sprožen ob kolapsu oblaka parnih mehurčkov. Doseženi rezultati so dobra osnova za prihodnji razvoj novih minimalno invazivnih medicinskih posegov, kjer je potrebno vplivati na tkivo globoko pod površjem kože (več mm), ki ga s svetlobo ni možno neposredno osvetliti. In the doctoral thesis, a method for amplification of high-intensity pressure waves generated deep below the irradiated surface with multi-pulsed Nd:YAG laser coupled with a black-TiOx optoacoustic lens in the water is presented and characterized. The experimental system consists of a quality-switched Nd:YAG laser source that enables the generation multiple nanosecond pulses up to an energy of 900 mJ with delays between 50 µs and 400 µs. Using a spherically shaped optoacoustic lens, which is made of titanium with a surface layer of black TiOx, we created high intensity focusing pressure waves. Size of generated pressure waves in the focus is about 120 x 300 μm2 (length x diameter), and the amplitude ~100 MPa. Using schlieren photography and a high-speed camera, we have shown that it is possible to achieve localized cavitation in the focus of an optoacoustic lens. The size of the cavitation cloud and its fluctuation in time increases monotonically with the laser excitation energy. In the case of using four consecutive laser pulses, when the delay between the laser flashes is equal to the duration of the vapor bubbles above the optoacoustic lens, the size of the cavitation increases by 10 times, while the amplitude of the pressure wave increases by more than 75%. This amplification is decisively influenced by three mutually competing phenomena: obscuration of the laser pulse due to the presence of a shroud cloud of vapor bubbles, an increase in the temperature of the OL surface, and the resonance effect that occurs when the next laser pulse is triggered upon the collapse of the cloud of vapor bubbles. The achieved results are a good basis for the future development of new minimally invasive medical interventions, where it is necessary to influence tissue deep below the surface of the skin (several mm), which cannot be directly illuminated with light. laser optoakustična leča kavitacija ablacija optodinamika laser optoacoustic lens cavitation ablation optodynamics true false false [B. Tašič Muc] Slovenski jezik Angleški jezik Doktorsko delo/naloga 2024-05-15 08:30:24 2024-05-15 08:30:29 2024-05-16 13:32:13 0000-00-00 00:00:00 2024 0 Ljubljana 0 XXVII, 114 str. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 535.3:621.375.826:620.193.16(043.3) 260116 195661827 33116.pdf 33116.pdf 1 CC8923DFB27CD7102C69D78A2B13F126 6cf4893dfa45467dc01503ab36c253893971e18e2719051efda72c13bb2c9f03 9ef52816-1284-11ef-af1f-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=183573 Fakulteta za strojništvo 0 0 0