Acoustic effects on micro-channel flow of Newtonian and non-Newtonian fluids

The present paper provides a comprehensive numerical investigation into the use of surface acoustic waves (SAWs) as a means for enhancing the efficiency in a micro-channel flow of Newtonian (water) and non-Newtonian (blood) fluids. A three-dimensional computational model simulates the flow within a rectangular cavity made of polydimethylsiloxane bonded to a lithium niobate (LiNbO3) substrate. Gold interdigital transducers are designed on the substrate to generate SAWs, influencing the flow characteristics of water and blood. The effects of different acoustic frequencies ranging from 10 to 50 MHz on velocity and pressure are analyzed and compared. The study reveals that acoustic pressure and velocity vary between 40 and 80 Pa and 3 × 10−5 to 2 × 10−5 m/s, respectively, for both fluids across most frequencies, except at 20 MHz. Notably, a sharp spike in acoustic velocity is observed for blood at 20 MHz, while no such spike occurs for water. The average flow velocity of blood at 20 MHz in the microchannel reaches 6.6 × 10−5 m/s, significantly higher than the 2.6 × 10−5 m/s observed for water, indicating a 153% increase. This enhancement in blood flow is attributed to intensified acoustic streaming due to its higher acoustic absorption coefficient compared to water. This phenomenon is further supported by the greater peak displacement recorded for blood flow at 20 MHz. Additionally, an empirical seventh-order polynomial expression is developed to model the relationship between acoustic pressure, velocity, and frequency for the blood flow. The results demonstrate that SAWs, particularly at resonant frequencies, enhance acoustic streaming, improving mixing efficiency and flow performance in microchannels, providing valuable insights for lab-on-chip and biomedical microfluidic applications.