Intrusive temperature measurement of the cavitation bubbles using cold wire

Abstract

Cavitation is a phenomenon of rupturing a liquid when the liquid is subjected to a decrease in pressure at roughly constant temperature. Cavitation is the fundamental reason for the material erosion when the bubbles are collapsing closer to the surface. These bubbles also produce a very high temperature (thousands of degrees Celsius) for a very short time (in the order of nano or microseconds). Cavitation is also being used in the non-invasive cancer tumor ablation treatment using high intensity focused ultrasound (HIFU) called histotripsy. So, our research in measuring the temperature of the bubble collapse will help the histotripsy treatment to understand its thermal behavior. We have designed a cold wire sensor of the thickness of ∼10 to 50 micrometers. And, the sensing region is 2 millimeter. These cold wires are made with kevlar or nylon fibers, titanium, nickel, silver, and silicon dioxide. The single bubble or histotripsy cloud, is allowed to collapse on the sensor, and we measure the temperature based on its change in resistance. These changes in resistance are corresponded to the temperature using the mathematical function which is calibrated prior to the experiment. We measure it in three different experimental settings like Tube Arrest Method (TAM), LASER induced bubbles, and HIFU induced bubbles. The preliminary results have shown that the temperature of the single spherical bubble collapse (TAM) can rise to thousands of degrees celsius as mentioned in the literature based on the theoretical analysis.