PVDF piezoelectric flow sensor for velocity measurements aiming malaria diagnostics: a preliminary approach

Malaria is a parasitic disease widely spread in the tropical and subtropical regions of the globe, commonly associated with underdeveloped countries with poor healthcare conditions. Appropriate diagnosis and treatment are essential for reducing malaria mortality. The measurement of the blood velocity in capillary vessels can be used as a principle for malaria diagnostics. Therefore, this work focuses on developing the actuation, acquisition and readout electronics systems of a piezoelectric acoustic transducer for measuring the velocity of a liquid, aiming malaria diagnostics. The measurement is based on the phase differences between the emitted and the received acoustic signals that interact with the fluid, driven by a voltage-controlled oscillator that generates an 8.5 MHz acoustic wave. The material of the piezoelectric transducer is based on the polyvinylidene fluoride (PVDF) polymer placed in a water chamber. The system was tested in water with different flow conditions, from rest up to 30 ml/min. It was compared the effect of two different thin-film PVDF transducers, with 28 and 110 µm thickness, and it was observed that both allowed to detected flows above 5 ml/min, with 84% and 77% linearity, respectively. Therefore, the developed prototype system of the acoustic transducer for measuring the velocity of a liquid sample may be reliable, since it detects velocity variations within the typical range of blood flow velocities in capillary vessels. Future work is essential to improve the sensor overall characteristics to make it a reliable tool for malaria diagnostics.