On the Pressure Sensing of Biological Fluids Using Microwaves

In vivo biological fluid pressures have been linked to many diseases. Elevated blood pressure is a major risk factor for heart disease that affects millions of people across the world. Non-invasive blood pressure monitoring techniques have been limited to extremities of the body, like limbs, and are unable to measure dynamic internal pressures observed in deeper internal anatomical spaces like cardiac chambers, principal veins, cranial cavity, etc. Novel methods to investigate the internal biological pressures non-invasively can unlock new therapies to treat a wide range of diseases. Microwave-based sensing for biomedical applications is an active research area with the potential to expand in sensing vital physiological indicators like pressure. This study is an experimental investigation into the role of pressure on the dielectric properties of water to broaden the biomedical applications of microwave-based sensing. An experimental setup consisting of a pressure chamber with water and a co-axial probe was built to measure the dielectric properties at pressures ranging from 0 to 240 mm of Hg over a frequency range of 0.5-20 GHz. A comparison of the measurements shows a small and significant change in dielectric properties with varying pressures revealing the challenges and a direction for future scientific research.