Researchers at the Max Planck Institute for the Science of Light (MPL) in Erlangen, Germany, have pioneered a groundbreaking method to measure negative pressure in liquids, shedding light on an elusive and fascinating state of matter. Their innovative approach combines optical and acoustic waves, enabling precise measurements with detailed spatial resolution.
Pressure is a fundamental physical quantity encountered in a myriad of scientific fields, including meteorology, medicine, and everyday applications such as pressure cookers and vacuum-sealed foods. It is typically defined as the force per unit area acting perpendicular to the surface of a solid, liquid, or gas. In most contexts, the numerical value of pressure is always positive.
However, liquids possess a peculiar characteristic. They can exist in a unique metastable state characterized by negative pressure values. In this state, even the slightest external influence can trigger a transition to a different phase, akin to a delicate balance perched at the top of a roller coaster. Any perturbation can send it hurtling down one side or the other.
The MPL research team, in collaboration with the Leibniz Institute of Photonic Technologies in Jena (IPHT), sought to explore this metastable state of liquids with negative pressure. To achieve this, they employed a two-fold approach. First, they encapsulated minuscule amounts of liquid, measured in nanoliters, within a fully sealed optical fiber.
This setup allowed them to subject the liquid to both highly positive and negative pressures. Subsequently, they harnessed the specific interaction of optical and acoustic waves within the liquid to sensitively measure the effects of pressure and temperature in various liquid states.
The interaction between optical and acoustic waves effectively acts as sensors for scrutinizing negative pressure values, thereby offering researchers a unique and precise means to explore this exotic state of matter. In this context, negative pressure causes the liquid to behave like a stretched rubber band, a consequence of adhesive forces retaining the liquid within the glass fiber capillary. This effect leads to the “stretching” of the liquid, a phenomenon crucial to understanding negative pressure.
Traditionally, the measurement of negative pressure involved complex and potentially hazardous setups, often necessitating significant laboratory space and posing risks when dealing with toxic liquids. However, the MPL researchers have devised a compact, streamlined method that leverages light and sound waves. The optical fiber used in this approach is as thin as a human hair, enabling precise pressure measurements.
Dr. Birgit Stiller, head of the Quantum Optoacoustics research group at MPL, expressed her excitement about the possibilities of this research, stating, “Some phenomena which are difficult to explore with ordinary and established methods can become unexpectedly accessible when new measurement methods are combined with novel platforms. I find that exciting.”
The combination of optoacoustic measurements with tightly sealed capillary fibers opens up new avenues for investigating chemical reactions in toxic liquids and exploring thermodynamic states within challenging materials and microreactors. This innovative method facilitates the study of negative pressure and nonlinear optical phenomena, potentially leading to the discovery of novel properties in unique thermodynamic states.
The collaboration between the research groups at MPL in Erlangen and IPHT in Jena, each with their respective expertise, has paved the way for groundbreaking insights into thermodynamic processes and regimes. This research offers a compact and user-friendly optical platform for studying high pressures and other thermodynamic conditions, promising further discoveries in the realm of materials science.
In summary, the scientists at MPL have developed a pioneering method to measure negative pressure in liquids, providing a deeper understanding of this unique state of matter and its implications in various scientific disciplines.
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Reference: https://www.sciencedaily.com/releases/2023/09/230925153812.htm
