Session: 03-20-02: Manufacturing: General

Paper Number: 143196

143196 - Absolute Magnitude of the Acoustic Radiation Force in a Multi-Wavelength Patterning Device Before and After Pattern Formation 

Acoustophoretic assembly has shown promise for applications in advanced manufacturing, such as embedding electrical circuity in additive manufacturing. This technique uses an acoustic standing wave to exert acoustic radiation forces on dispersed small particles to move the particles into pre-defined patterns. The final locations of the small particles can be accurately predicted from the pressure nodes and antinodes of the acoustic wave while the magnitude of the acoustic radiation force influences how quickly the particles move, and thus, how quickly the pattern can be created. However, the absolute magnitudes of the acoustic radiation force are challenging to measure due to the small size of most acoustophoretic assembly applications. Inserting probes into the devices can also disrupt the acoustic wave and change the acoustic radiation forces. 

 

In addition to the challenges of measuring the acoustic radiation force during pattern formation, it is also unclear how the particle patterns, once they are formed, affect the acoustic wave and the acoustic radiation forces. When designing acoustophoretic assembly processes, the effect of the particles on the acoustic wave is usually ignored because the size of the particles is much smaller than the acoustic wavelength. During pattern formation, the particles move into agglomerations that can be a similar size or bigger than the wavelength, which may interact with the acoustic wave and thus change the acoustic radiation force on the particles. Understanding the impact of the formed particle pattern is important when multiple acoustic waves are applied in sequence to achieve more complex pattern geometries.

 

This work presents two methods to experimentally measure the magnitude of the acoustic radiation force. The first method uses particle tracking to create a 2D map of the acoustic radiation force during pattern formation while particles are dispersed. The second method rotates the device so that the acoustic radiation force can be determined through balance with gravity after the particle pattern has formed. By comparing the acoustic radiation force before and after the pattern formation, we can determine the impact of the particle agglomerations on the acoustic wave.

 

We apply these two measurement methods to characterize the acoustic radiation force on polystyrene microspheres inside a multi-wavelength planar standing wave device. The device was filled with a glycerol-water mixture and polystyrene microspheres. The movement of the microspheres are captured using video for particle tracking analysis. Our results show that packing the dilute dispersed polystyrene microspheres into dense bands does not significantly alter the acoustic radiation force on the microspheres. Additionally, the 2D force map showed spatial variations in the acoustic radiation force that were not visually apparent in the final polystyrene microsphere bands pattern but may have implications in part quality if acoustophoretic assembly is used in manufacturing.

Presenting Author: Y. Jenny Wang Massachusetts Institute of Technology

Presenting Author Biography: Yi Jenny Wang is a researcher at the Massachusetts Institute of Technology. She earned her PhD in Mechanical Engineering from MIT in 2022, and her thesis focused on quantifying the acoustophoretic assembly formation process so it can be more easily adopted into advanced manufacturing methods. In addition to moving things with sound, she also has experience on a variety of research topics ranging from lithium-ion batteries to molecular modeling. More recently, she has been working on connecting the physical and digital worlds using virtual reality, data, and custom hardware.

Authors:

Y. Jenny Wang Massachusetts Institute of Technology
Brian Anthony Massachusetts Institute of Technology