Manipulation of submicron particles in fluid using microbubbles in microporous arrays as seeds

Abstract

Existing bubble-acoustic microstreaming is merely capable of handling micron-sized particles. In this study, microbubbles confined in microporous arrays were used as seeds to manipulate submicron particles in fluid. To understand the working principle, a theory of governing equations of particle motion in bubble-acoustic microfluidics was built. A three-dimensional finite element model was developed to study the formation mechanism of submicron particles (r = 400 nm) in an acoustic streaming field. As follows, an experimental study is performed to verify the theory. In the experiments, bulk acoustic waves with a frequency of 830KHz is used to excite microbubble oscillations in microporous arrays. Microbubbles, oscillating in large aperture microporous arrays (30um and 40um) as seeds, have an unstable effect on capturing and pumping submicron particles(r = 400 nm). When the diameter of micropores is reduced to 15um, the microbubbles can capture a large number of submicron particles efficiently. Furthermore, the efficiency of trapping submicron particles is nearly ten times higher than that of using solid particles as seeds. The wavelength of acoustic waves is four orders of magnitude larger than the size of the submicron particles. The results showed that low-frequency bubble-acoustic microfluidic devices could provide a simple and cost-effective solution for effective and uniform manipulation of submicron biological particles.