The objective of this study is to reveal the potential of micro scale hydrodynamic bubbly cavitation for the use of kidney stone treatment. Hydrodynamically generated cavitating bubbles were targeted to the surfaces of 18 kidney stone samples made of calcium oxalate, and their destructive effects were exploited in order to remove kidney stones in in vitro experiments. Phosphate buffered saline (PBS) solution was used as the working fluid under bubbly cavitating conditions in a 0.75 cm long micro probe of 147 μm inner diameter at 9790 kPa pressure. The surface of calcium oxalate type kidney stones were exposed to bubbly cavitation at room temperature for 5 to 30 min. The eroded kidney stones were visually analyzed with a high speed CCD camera and using SEM (scanning electron microscopy) techniques. The experiments showed that at a cavitation number of 0.017, hydrodynamic bubbly cavitation device could successfully erode stones with an erosion rate of 0.31 mg/min. It was also observed that the targeted application of the erosion with micro scale hydrodynamic cavitation may even cause the fracture of the kidney stones within a short time of 30 min. The proposed treatment method has proven to be an efficient instrument for destroying kidney stones.

Hydrodynamic cavitation is a physical phenomenon characterized by vaporization and bubble formation in liquids under low local pressures, and their implosion following their release to a higher pressure environment. Collapse of the bubbles releases high energy and may cause damage to exposed surfaces. We recently designed a set-up to exploit the destructive nature of hydrodynamic cavitation for biomedical purposes. We have previously shown that hydrodynamic cavitation could kill leukemia cells and erode kidney stones. In this study, we analyzed the effects of cavitation on prostate cells and benign prostatic hyperplasia (BPH) tissue. We showed that hydrodynamic cavitation could kill prostate cells in a pressure- and time-dependent manner. Cavitation did not lead to programmed cell death, i.e. classical apoptosis or autophagy activation. Following the application of cavitation, we observed no prominent DNA damage and cells did not arrest in the cell cycle. Hence, we concluded that cavitation forces directly damaged the cells, leading to their pulverization. Upon application to BPH tissues from patients, cavitation could lead to a significant level of tissue destruction. Therefore similar to ultrasonic cavitation, we propose that hydrodynamic cavitation has the potential to be exploited and developed as an approach for the ablation of aberrant pathological tissues, including BPH.

The aim of this study is to focus on the effect of probe-to-specimen distance in kidney stone treatment with hydrodynamic bubbly cavitation. Cavitating bubbles were generated by running phosphate buffered saline (PBS) through stainless steel tubing of inner diameter of 1.56 mm at an inlet pressure of ∼10,000 kPa, which was connected to a 0.75 mm long probe with an inner diameter of 147 μm at the exit providing a sudden contraction and thus low local pressures. The bubbles were targeted on the surface of nine calcium oxalate kidney stones (submerged in a water pool at room temperature and atmospheric pressure) from three different distances, namely, 0.5 mm, 2.75 mm, and 7.75 mm. The experiments were repeated for three different time durations (5 min, 10 min, and 20 min). The experimental data show that amongst the three distances considered, the distance of 2.75 mm results in the highest erosion amount and highest erosion rate (up to 0.94 mg/min), which suggests that a closer distance does not necessarily lead to a higher erosion rate and that the probe-to-specimen distance is a factor of great importance, which needs to be optimized. In order to be able to explain the experimental results, a visualization study was also conducted with a high speed CMOS camera. A new correlation was developed to predict the erosion rates on kidney stones exposed to hydrodynamic cavitation as a function of material properties, time, and distance.

An experimental setup is designed to simulate the heat dissipated by electronic devices and to test the effects of nanostructured plates in enhancing the heat removal performance of jet impingement systems in such cooling applications under boiling conditions. Prior experiments conducted in single phase have shown that such different surface morphologies are effective in enhancing the heat transfer performance of jet impingement cooling applications. In this paper, results of the most recent experiments conducted using multiphase jet impingement cooling system will be presented. Distilled water is propelled into four microtubes of diameter 500 μm that provide the impinging jets to the surface. Simulation of the heat generated by miniature electronic devices is simulated through four aluminum cartridge heaters of 6.25 mm in diameter and 31.75 mm in length placed inside an aluminum base. Nanostructured plates of size 35mm×30mm and different surface morphologies are placed on the surface of the base and two thermocouples are placed to the surface of the heating base and the base is submerged into deionized water. Water jets generated using microtubes as nozzles are targeted to the surface of the nanostructured plate from a nozzle to surface distance of 1.5 mm and heat removal characteristics of the system is studied for a range of flow rates and heat flux, varying between 107.5–181.5 ml/min and 1–400000 W/m2, respectively. The results obtained using nanostructured plates are compared to the ones obtained using a plain surface copper plate as control sample and reported in this paper.