Cavitation as a physical phenomenon occurs due to a local pressure drop in the liquid and represents small gas/vapour bubbles that grow and collapse at multiple locations and can release a large amount of energy in a short span of time. Bubble collapse can be accompanied by extreme conditions such as strong shear flows, microjet formation, shock waves and high local temperatures. This usually results in unwanted effects such as erosion, efficiency loss, noise and vibrations on mechanical machines/devices. However, cavitation can also serve for intensification of various physical and chemical processes that are important in a variety of applications, such as surface cleaning, enhanced chemistry, and wastewater treatment. To exploit this enormous potential of hydrodynamic cavitation, we are already investigating fundamental mechanisms of interaction between bubbles and contaminants (bacteria and viruses) within our ERC Consolidator Grant – CABUM.

Wastewater treatment and other processes that use hydrodynamic cavitation for decontamination require extreme cavitation conditions for efficient destruction of microorganisms. Consequently, a cavitation device that usually consists of a cavitation chamber, suffers from intense material loss, noise and vibrations. This problem is currently addressed by (i) modification of main geometry of the submerged body or flow tract or (ii) by selection of advanced materials with increased wear resistance. However, geometry modification results in decreased cavitation and is therefore not appropriate for inducing extreme cavitation conditions required for decontamination, while solely increased wear resistance does not allow controlling the cavitation intensity.

To fill this gap and develop a new approach to generate extreme cavitation conditions with minimized erosion effects on the cavitation device, the proposed eCATS project investigates the mechanisms of interaction between different types of cavitation and laser- functionalized surfaces. To achieve this, we will combine different body geometries with functionalized surfaces. We will perform surface functionalization by laser nano- and micro-processing that we have already developed within our ARRS project (No. J2-1741) and that has been proven as one of the most promising paramount methods in the field of surface engineering. Recent studies that exploit and implement cavitation as an advanced treatment method deal mostly with the effectiveness of the method itself. Thus, they usually follow a very simplistic principle – the more intense the cavitation, the more effective the process. Most of them intentionally discard the consequences such as material erosion and durability of the cavitation device, even though these side effects significantly affect applicability.

The overall eCATS objective is to improve the fundamental understanding of how surface micro-/nano-topography, chemistry, and wettability influence cavitation dynamics and cavitation erosion. This understanding will allow us to use advanced laser processing to control cavitation dynamics. We expect that the eCATS results will enable to create 3D surfaces that lead to extreme cavitation behind these surfaces, but do not lead to cavitation erosion of themselves. This is achieved in three steps, where we study the interaction between: (i) a single laser-induced bubble and flat functionalized surfaces; (ii) bubble clusters and flat functionalized surfaces; (iii) 3D laser-textured samples and hydrodynamic cavitation. In the final step, the results of the previous two steps are merged to find optimal surface functionalization techniques to control cavitation characteristics to either enhance or mitigate cavitation and its consequences.

The project will be implemented within six work packages (WP): (i) project management (WP1); (ii) R&D activities (WP2-WP5); and (iii) dissemination and exploitation of the results (WP6).

WP1: Project management (M1-M36)  
– T1.1 Progress and cost reporting (M1-M36)
– T1.2 Monitoring, control and quality management (M1-M36)

WP2: Development of functionalized surfaces (M1-M18)
– T2.1 Selection of the laser processing strategies (M1-M3)
– T2.2 Laser texturing of surfaces (M4-M12)
– T2.3 Modification of surface energy (M13-M18)

WP3: Interaction between cavitation and flat surfaces (M8-M27)
– T3.1 Single bubble interaction (M8-M14)
– T3.2 Bubble clusters interaction (M15-M21)
– T3.3 Study of cavitation erosion (M21-M27)

WP4: Hydrodynamic cavitation on 3D surfaces (M25-M36)
– T4.1 Development of 3D laser processing system (M25-M27)
– T4.2 Cavitation characterization in visible spectrum (M28-M32)
– T4.3 Study of cavitation erosion (M28-M32)
– T4.4 X-ray imaging (M30-M36)

WP5: Characterization (supporting activities; M4-M32)
– T5.1 Surface topography (supporting activity; M4-M27)
– T5.2 Surface chemistry and wettability (supporting activity; M4-M27)
– T5.3 Surface erosion (supporting activity; M21-M32)

WP6: Dissemination and exploitation of the results (M1-M36)
– T6.1 Presentation of the results to general public (M1-M36)
– T6.2 Presentation of the results to scientific audience (M1-M36)
– T6.3 Presentation of the results to professional public (M24-M36)

• MALEKI, Mohammadamin, TALABAZAR, Farzad Rokhsar, DAVOUDIAN, Salar Heyat, DULAR, Matevž, KOŞAR, Ali, PETKOVŠEK, Martin, ŠMID, Alenka, ZUPANC, Mojca, GHORBANI, Morteza. The formation of hydroxyl radicals during hydrodynamic cavitation in microfluidic reactors using salicylic acid dosimetry. Chemical engineering journal. [Online ed.]. 2025, vol. , no. , [article no.] 161976, 42 str., ilustr. ISSN 1873-3212. https://www.sciencedirect.com/science/article/pii/S1385894725028025, DOI: 10.1016/j.cej.2025.161976. [COBISS.SI-ID 230634243]
• BOČEK, Žan, PETKOVŠEK, Martin, CLARK, Samuel J., FEZZAA, Kamel, DULAR, Matevž. Kelvin-Helmholtz instability as one of the key features for fast and efficient emulsification by hydrodynamic cavitation. Ultrasonics sonochemistry. Aug. 2024, vol. 108, [article no.] 106970, str. 1-9, ilustr. ISSN 1350-4177. https://www.sciencedirect.com/science/article/pii/S1350417724002189, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.ultsonch.2024.106970. [COBISS.SI-ID 201951491]
• ZUPANC, Andraž, PETKOVŠEK, Martin, ZDOVC, Blaž, ŽAGAR, Ema, ZUPANC, Mojca. Degradation of hydroxypropyl methylcellulose (HPMC) by acoustic and hydrodynamic cavitation. Ultrasonics Sonochemistry. [Online ed.]. Oct. 2024, vol. 109, art. 107020, str. 1-9, ilustr. ISSN 1873-2828. https://www.sciencedirect.com/science/article/pii/S1350417724002682, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.ultsonch.2024.107020. [COBISS.SI-ID 204078851]
• ZUPANC, Mojca, PRIMC, Gregor, DULAR, Matevž, PETKOVŠEK, Martin, ROŠKAR, Robert, ZAPLOTNIK, Rok, TRONTELJ, Jurij. Proof-of-concept for removing micropollutants through a combination of sub-atmospheric-pressure non-thermal plasma and hydrodynamic (super)cavitation. Ultrasonics Sonochemistry. [Online ed.]. Dec. 2024, vol. 111, [art. no.] 107110, str. 1-12, ilustr. ISSN 1873-2828. https://www.sciencedirect.com/science/article/pii/S1350417724003584, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.ultsonch.2024.107110. [COBISS.SI-ID 212810499]
• ZUPANC, Mojca, BRAJER HUMAR, Barbara, DULAR, Matevž, GOSTIŠA, Jurij, HOČEVAR, Marko, KOLBL REPINC, Sabina, KRZYK, Mario, NOVAK, Lovrenc, ORTAR, Jernej, PANDUR, Žiga, STRES, Blaž, PETKOVŠEK, Martin. The use of hydrodynamic cavitation for waste-to-energy approach to enhance methane production from waste activated sludge. Journal of environmental management. Dec. 2023, vol. 347, str. 1-11, ilustr. ISSN 0301-4797. https://www.sciencedirect.com/science/article/pii/S0301479723018625, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.jenvman.2023.119074. [COBISS.SI-ID 167876867]
• SENEGAČNIK, Matej, GREGORČIČ, Peter. Diffraction-driven laser surface nanostructuring : towards patterning with curved periodic surface structures = Matej Senegačnik, Peter Gregorčič. Applied Surface Science. [Print ed.]. Feb. 2023, vol. 610, str. 1-10, ilustr. ISSN 0169-4332. https://www.sciencedirect.com/science/article/pii/S0169433222030148, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.apsusc.2022.155486. [COBISS.SI-ID 129205507]
• PETKOVŠEK, Martin, KRŽAN, Andrej, ŠMID, Alenka, ŽAGAR, Ema, ZUPANC, Mojca. Degradation of water soluble poly(vinyl alcohol) with acoustic and hydrodynamic cavitation : laying foundations for microplastics. npj Clean water. 2023, vol. 6, [art. no.] 35, str. 1-11, ilustr. ISSN 2059-7037. https://www.nature.com/articles/s41545-023-00248-8, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1038/s41545-023-00248-8. [COBISS.SI-ID 150832899]
• ZUPANC, Mojca, ZEVNIK, Jure, FILIPIĆ, Arijana, GUTIÉRREZ-AGUIRRE, Ion, JEŠELNIK, Meta, KOŠIR, Tamara, ORTAR, Jernej, DULAR, Matevž, PETKOVŠEK, Martin. Inactivation of the enveloped virus phi6 with hydrodynamic cavitation. Ultrasonics sonochemistry. May 2023, vol. 95, str. 1-8, ilustr. ISSN 1350-4177. https://www.sciencedirect.com/science/article/pii/S1350417723001128, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.ultsonch.2023.106400. [COBISS.SI-ID 148619523]
• BOČEK, Žan, PETKOVŠEK, Martin, CLARK, Samuel J., FEZZAA, Kamel, DULAR, Matevž. Dynamics of oil–water interface at the beginning of the ultrasonic emulsification process. Ultrasonics sonochemistry. Dec. 2023, vol. 101, str. 1-20, ilustr. ISSN 1350-4177. https://www.sciencedirect.com/science/article/pii/S1350417723003693, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.ultsonch.2023.106657. [COBISS.SI-ID 170581251]
• KOZMUS, Gregor, ZEVNIK, Jure, HOČEVAR, Marko, DULAR, Matevž, PETKOVŠEK, Martin. Characterization of cavitation under ultrasonic horn tip : proposition of an acoustic cavitation parameter. Ultrasonics sonochemistry. 2022, vol. 89, str. 1-10, ilustr. ISSN 1350-4177. https://www.sciencedirect.com/science/article/pii/S1350417722002553, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.ultsonch.2022.106159. [COBISS.SI-ID 121319171]

• PETKOVŠEK, Martin, ROSSELLÓ, Juan Manuel, HOČEVAR, Matej, GREGORČIČ, Peter. Cavitation bubble manipulation by laser-functionalized surfaces : [prispevek na] 12th International Cavitation Symposium – CAV2024, 2-5 June 2024, Chania, Greece. [COBISS.SI-ID 228854275]
• PETKOVŠEK, Martin, ROSSELLÓ, Juan Manuel, HOČEVAR, Matej, GREGORČIČ, Peter. Laser-functionalized surfaces for cavitation bubble manipulation. V: Akademija strojništva 2024 : inženirstvo – inovativen trajnostni razvoj z visoko dodano vrednostjo : Ljubljana, Cankarjev dom ter prek spleta, 10. december 2024. Ljubljana: Zveza strojnih inženirjev Slovenije – ZSIS, 2024. Letn. 13, št. 1/6, str. 88-89, ilustr. Svet strojništva, letn. 13, št. 1/6. ISSN 1855-6493. https://www.zveza-zsis.si/2024/11/30/svet-strojnistva-akademija-strojnistva-2024-december-2024/, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.62020/svet.str.as2024023. [COBISS.SI-ID 222224131]
• GREGORČIČ, Peter, SENEGAČNIK, Matej. Laser surface patterning with curved periodic nanostructures using cavitation bubbles : invited paper. V: Laser-based Micro- and Nanoprocessing XVIII : 29 January – 1 February 2024, San Francisco, California, United States : conference 12873. [Bellingham]: SPIE, 2024. Str. [1]. https://spie.org/photonics-west/presentation/Laser-surface-patterning-with-curved-periodic-nanostructures-using-cavitation-bubbles/12873-15#_=_. [COBISS.SI-ID 184176131]
• SENEGAČNIK, Matej, KUNIMOTO, Kohei, YAMAGUCHI, Satoshi, KIMURA, Koki, SAKKA, Tetsuo, GREGORČIČ, Peter. Primary and secondary cavitation effects induced by optical breakdown near sharp-edge geometry. V: COLA 2021/2022 : 16th International Conference on Laser Ablation, Hybrid format, Kunibiki Messe in Matsue, Japan & online 24 – 29 April, 2022 : conference program and abstracts. [S. l.: s. n., 2022]. Str. 52, ilustr. [COBISS.SI-ID 107173123]
• SENEGAČNIK, Matej, GREGORČIČ, Peter. Investigation of lipss structures fabricated in different surrounding media using focused-ion beam etching. V: LIPSS : book of abstracts : 10th International Workshop, Orléans, Val de Loire, France, 21-23 September 2022. [S. l.: s. n.], 2022. Str. 29, ilustr. https://lipss10.sciencesconf.org/data/Book_LIPSS10_Online.pdf. [COBISS.SI-ID 126867203]