Bubble dynamics under negative pressures: A missing link?

When liquid is subjected to a pressure below absolute zero, the phase change is favorable; however, phase change might be prevented or substantially hindered by the attractive interactions between the liquid molecules. Liquids subjected to negative pressure are abundant and could be utilized in several industrial and medical applications. While some promising industrial innovations harness this phenomenon, others seek to control and direct the nucleation occurring as the liquid relaxes back to a stable state. Numerous experimental apparatuses have been developed to generate negative pressure in liquids. However, there is a large discrepancy, which may exceed 100 MPa, between the maximal values of negative pressure a liquid may sustain before the onset of nucleation, as reported in different experiments. This gap raises fundamental questions regarding the nature of liquids under this extreme thermodynamic state while limiting our ability to employ this phenomenon reliably. We present a detailed survey of the theoretical background behind the phenomenon: thermodynamic stability and classical nucleation theory, followed by a review of recent theoretical and experimental studies regarding the nature of liquids under negative pressures. Key open questions are highlighted, and an outline for possible future research pathways may lead to a better understating of the elusive and fascinating nature of liquids under negative pressure. In light of the review presented here, we claim that a thorough understanding of bubble dynamics in stretched liquids is essential for fully describing nucleation induced by intense acoustic ultrasonic waves and generally understanding the apparent ambiguity of the present empirical results. I.e., studying the growth of bubbles nucleated within liquids under negative pressures could be a possible “missing link” that may allow answering the questions still open.