Aprisionamento de micropartículas em feixes acústicos superfocalizados

Abstract

Non-contact acoustic trapping and particle manipulation, provided by the phenomena of acoustic radiation force, has aroused great interest in the scientific environment, mainly due to its applications in various branches of biotechnology. Acoustic tweezers are techniques for trapping particles through acoustic beams, being one of the first applications of radiation force studies. Thus, in this work, we use the finite element method to analyze the microparticle entrapment criteria, by means of the acoustic radiation force generated by the immersion of these particles in a medium disturbed by a superfocalized acoustic beam. Through the numerical model used, we studied the behavior of the acoustic radiation force in particles positioned in the axial direction of the beam. By comparing the results obtained with the analytical method of partial wave expansion, we were able to analyze the components, conservative, scattering, and absorption of the acoustic radiation force in the particles, which allowed us to propose some explanations regarding the behavior of the particles in the beam. On the other hand, the numerical method gave us the freedom to increase the size of the analyzed particles, exceeding the limit at which the analytical model used is valid, in this case, the limit of particles much smaller than the wavelength, also known as the Rayleigh. Thus, in addition to identifying a pattern among the particles that were trapped, we also propose an explanation for the variability in the maximum particle size that can be trapped in the beam.