Thrombolysis is essential for treating vascular conditions such as pulmonary embolism and deep vein thrombosis, yet current thrombolytic drug-based approaches have notable limitations in efficacy and safety. Hydrodynamic cavitation (HC) offers drug-free clot degradation through mechanical disruption. In this study, the effects of HC exposure on thrombolysis were investigated using a clot-on-a-chip (CoC) platform. In this regard, the thrombolytic potential of HC exposure was evaluated by analyses involving hemolysis and fibrinolysis. Furthermore, the results were compared with acoustic cavitation (AC), a widely studied alternative. According to the obtained results, HC exposure (482 kPa, 120 s) resulted in 12.1% released hemoglobin and a 53.4% reduction in clot mass. In contrast, AC exposure (24 kHz, 50% nominal output power, 30 s) led to a 1.3-fold greater mass reduction with 26.8% released hemoglobin, likely due to additional thermal effects. Morphological analyses revealed that HC treatment significantly reduced red blood cell density in a pressure- and time-dependent manner. Notably, HC treatment effectively eroded blood clots by hemolysis with slight fibrinolysis, whereas clot erosion in AC was primarily due to hemolysis. HC achieved thrombolysis comparable to or better than AC, offering a safer, more targeted strategy, especially for disease due to RBC-rich clots such as non-cardioembolic stroke. The findings will advance mechanistic understanding of cavitation-induced clot degradation and support HC's clinical potential for thrombosis treatment.

Aim: To investigate the impact of different tourniquet pressures and application durations on venous diameter and compliance in children, in order to optimise conditions for peripheral intravenous catheter insertion. Methods: This non-randomised clinical study included 21 healthy children aged 6–10 years. Vein diameter was measured using ultrasound. The force required to fully compress the vein was measured with a pressure-sensing device. Tourniquet pressures of 20–100 mmHg were applied for 60 s, with measurements every 10 s. Data were analyzed using non-parametric methods to assess changes over time and correlations between variables. Results: Vein diameter changed significantly over time at all applied pressures. All tourniquet pressures showed a significant reduction in venous compliance. Substantial interindividual variation was observed in the pressure and timing that yielded optimal changes in vein diameter and compliance. Vein diameters ranged from 1 to 5 mm, with no consistent correlation with age or body weight. Conclusion: Paediatric tourniquet application markedly increases venous diameter and reduces venous compliance. The substantial interindividual variation in these responses motivates individualised rather than universal approaches. Future research should aim to develop practical techniques to assess and optimise venous conditions, thereby improving the success rate of paediatric intravenous catheter insertion.

This study introduces the first experimental analysis of shear cavitation in a microscale backward-facing step (BFS) configuration. It explores shear layer cavitation under various flow conditions in a microfluidic device with a depth of 60 μm and a step height of 400 μm. The BFS configuration, with its unique characteristics of upstream turbulence and post-reattachment pressure recovery, provides a controlled environment for studying shear-induced cavitation without the complexities of other microfluidic geometries. Experiments were conducted across four flow patterns: inception, developing, shedding, and intense shedding, by varying upstream pressure and the Reynolds number. The study highlights key differences between microscale and macroscale shear cavitation, such as the dominant role of surface forces on nuclei distribution, vapor formation, and distinct timescales for phenomena like shedding and shockwave propagation. It is hypothesized that vortex strength in the shear layer plays a significant role in cavity shedding during upstream shockwave propagation. Results indicate that increased pressure notably elevates the mean thickness, length, and intensity within the shear layer. Instantaneous data analysis identified two vortex modes (shedding and wake modes) at the reattachment zone, which significantly affect cavitation shedding frequency and downstream penetration. The wake mode, characterized by stronger and lower-frequency vortices, transports cavities deeper into the channel compared to the shedding mode. Additionally, vortex strength, proportional to the Reynolds number, affects condensation caused by shockwaves. The study confirms that nuclei concentration peaks in the latter half of the shear layer during cavitation inception, aligning with the peak void fraction region.

The elimination of micropollutants such as highly fluorinated substances, including per- and polyfluoroalkyl substances (PFAS), in wastewater treatment plants has been receiving growing attention due to the urgent need to minimize their adverse effects on natural water and associated ecosystems. Conventional treatment methods often fall short in effectively removing PFAS. In this study, the Hydrodynamic Cavitation on a Chip concept (HCOC) was utilized to degrade 11 common PFAS variants (PFAS11) for the first time in three different hydrodynamic cavitation reactor set-ups, each enhanced with surface modifications involving roughness elements. Stockholm municipal wastewater treated by a Membrane BioReactor (MBR) process was subjected to fully developed cavitating flow treatment using the three distinct microscale hydrodynamic cavitation (HC) reactors. The obtained results indicate that the chemical-free HCOC technique employed in this study has a significant potential in the degradation of nearly all investigated PFAS11 compounds at a notable rate of 36.1 % while the combination with MBR process can prevent blockage within the fluidic channels, enabling continuous operation with high throughput processing rates. Our proposed methodology demonstrated promising results in eliminating PFAS and could contribute to advancements in the use of microscale HC to treat micropollutants in wastewater. These findings could be a major leap in water treatment technologies addressing the global burden of resource-efficient micropollutant water treatment.

Contrast agents are widely used in ultrasound imaging. Many imaging techniques have been developed to improve the contrast between tissue and the agents, based on the nonlinear response of microbubbles. In this study, heterodyne excitation was introduced and was compared with traditional sinusoidal signal and chirp excitation for visualizing polymer-shelled microbubbles and degassed water in a tissue-mimicking phantom. Pulse inversion technique was implemented under plane wave (PW) and focused imaging mode. Image enhancement was evaluated by contrast-to-tissue ratio (CTR) at different transmitting peak negative pressures (PNPs). Experimental results showed that heterodyne excitation had a better suppression effect on tissue signals in PW imaging. The CTR reached an approximation of 17 dB at a low peak negative pressure, which was much higher compared to other excitations. In focused wave imaging, a saturation threshold of CTR was observed for the sinusoidal wave burst and chirp excitation at high PNPs. Heterodyne excitation showed considerable contrast-to-noise ratio under both imaging modes. The response of a polymer-shelled microbubble under heterodyne excitation was simulated. Simulations suggest that in future work, specific filters are required to extract the nonlinear components, such as at the two-peak frequencies around fundamental frequency, to achieve a better image enhancement effect.

The cellulose nanofiber(CNF)-shelled perfluoropentane (PFP) droplets were the subject of the evaluation in this work. CNF-shelled PFP droplets  Mechanical and acoustic properties were studied previously and reported elsewhere [1-4], however more insights into the biological effects of these droplets are needed to translate previous in vitro tests into in vivo applications as drug carriers in ultrasound-mediated drug delivery. 

The aim of this work is to investigate the effect of CNF-shelled PFP droplets on cell viability of 4T1 cells, a murine breast cancer cell line. Cells were exposed to different concentrations of droplets with or without the addition of paclitaxel, i.e. a hydrophobic cancer drug.

[1].  Ghorbani M, Olofsson K, Benjamins J-W, Loskutova K, Paulraj T, Wiklund M, Grishenkov D, Svagan A J, Unravelling the Acoustic and Thermal Responses of Perfluorocarbon Liquid Droplets Stabilized with Cellulose Nanofibers, Langmuir 35(40): 13090-13099, 2019.

[2].  Song X, Loskutova K, Chen H, Shen G, Grishenkov D, Deriving acoustic properties for perfluoropentane droplets with viscoelastic cellulose nanofiber shell via numerical simulations, The Journal of the Acoustical Society of America 150(3): 1750-1761, 2021.

[3].  Loskutova K, Nimander D, Gouwy I, Chen H, Ghorbani M, Svagan A J, Grishenkov D, A Study on the Acoustic Response of Pickering Perfluoropentane Droplets in Different Media, ACS Omega 6(8): 5670-5678, 2019.

[4].  Loskutova K, Olofsson K, Hammarström B, Wiklund M, Svagan A J, Grishenkov D, Measuring the Compressibility of Cellulose Nanofiber-Stabilized Microdroplets Using Acoustophoresis, Micromachines 12(12): 1465, 2021.

The concept of "hydrodynamic cavitation on a chip" offers facile generation of cavitating flows in microdomains, which can be easily scaled up by arranging short microchannels (micro-orifices) in cascade formations. In this regard, microscale cavitation in an energy-efficient test rig has the potential of increasing utilization possibilities of cavitation in a wide range of applications such as liquid-phase exfoliation. In this study, a new experimental test rig was constructed to generate microscale hydrodynamic cavitation. This setup enables cavitation bubble generation at low upstream pressures through the control of the downstream pressure of the device. Particular attention was directed to the classification of flow patterns, scale effects, and cavitating flow evolutions with an in-depth categorization of underlying mechanisms such as Kelvin-Helmholtz instability. Cavitation inception appeared in the form of a single bubble. The appearance of different attached cavitating flow patterns within the microfluidic device was accompanied by new physics, which revealed that cavitation generation and development are affected by the existence of various fluid flow phenomena, particularly the jet flow. The outcome of this study makes hydrodynamic cavitation on a chip attractive for applications, where the cavitation effects are sought in the presence of multiphase fluid flows.

Purpose: To study the effect of cellulose nanofiber (CNF)-shelled perfluoropentane (PFP) droplets on the cell viability of 4T1 breast cancer cells with or without the addition of non-encapsulated paclitaxel.

Methods: The CNF-shelled PFP droplets were produced by mixing a CNF suspension and PFP using a homogenizer. The volume size distribution and concentration of CNF-shelled PFP droplets were estimated from images taken with an optical microscope and analyzed using Fiji software and an in-house Matlab script. The thermal stability was qualitatively assessed by comparing the size distribution and concentration of CNF-shelled PFP droplets at room temperature (~22°) and 37°C. The cell viability of 4T1 cells was measured using a 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Additionally, a hemolysis assay was performed to assess blood compatibility of CNF-shelled PFP droplets.

Results: The droplet diameter and concentration of CNF-shelled PFP droplets decreased after 48 hours at both room temperature and 37°C. In addition, the decrease in concentration was more significant at 37°C, from 3.50 ± 0.64× 10^6 droplets/mL to 1.94 ± 0.10× 10^6 droplets/mL, than at room temperature, from 3.65 ± 0.29× 10^6 droplets/mL to 2.56 ± 0.22× 10^6 droplets/mL. The 4T1 cell viability decreased with increased exposure time and concentration of paclitaxel, but it was not affected by the presence of CNF-shelled PFP droplets. No hemolysis was observed at any concentration of CNF-shelled PFP droplets.

Conclusion: CNF-shelled PFP droplets have the potential to be applied as drug carriers in ultrasound-mediated therapy.

Amongst the advanced oxidation processes (AOPs), hydrodynamic cavitation (HC) has emerged as one of the most cost-efficient, simple and ecologically friendly approaches in the recent decade. This type of the cavitation, in contrast to its counterpart (acoustic cavitation), has a huge potential to upscale to the industrial levels. In the recent years, the micro-scale HC (HC on a chip concept) has exhibited favorable efficacy in terms of nucleation type, surface effects and flow pattern dominancy. In this study, the chemical effects of the HC on a chip concept are shown for the first time by considering the effects of the cavitating flow patterns. So, this is the first attempt to understand the effects of the inception and developed cavitating flow patterns on the chemical reactions during the bubble collapse in the micro-scale. In addition, a particular attention is paid to the chemical reaction effects before the cavitation bubble observation in this investigation. Our results indicated that the triiodide releasing amount was interestingly maximum before the inception occurred, especially at the first cycle. The released amount decreased at the inception and increased for the case of the developed twin cavities. We also showed that, comparing to our previous studies, the cavitation arrived at a relatively lower upstream pressure in the open loop cavitation test rig. Therefore, the outcome of this approach reveals the significance of the in-depth investigations of the complex and very transient nature of the cavitation at different flow patterns. Furthermore, this study implied that reactors benefitting HC on a chip concept will be environmentally friendly tools for producing products from the wastes and worthless materials in the near future.