Continuous acoustic separation in a thermoplastic microchannel

Abstract

Acoustic manipulation of particles and cells has been widely used for trapping and separation in microfluidic devices. Previously, the resonant components of these devices have been fabricated from silicon, glass, metals, or other materials having high acoustic impedance. Here, we present experimental results showing continuous acoustic focusing and separation of blood cells in a microchannel fabricated entirely from polystyrene. The efficiency and flow rates approach those reported in silicon and glass systems. We find that the optimum operating frequencies differ from those predicted by conventional approximations which have been developed for more rigid materials. Additionally, we introduce a method for fabrication of the devices, using an adaptation of thermofusion bonding that preserves critical channel dimensions. To control channel cross section during bonding, we introduced a collapsible fiberboard material in the bonding press. This structure provided a self-limiting force and mitigated deformation of the polystyrene. Together, these advances may enable new applications for acoustic focusing and separation in medical devices.

Optimizing Polymer Lab-on-Chip Platforms for Ultrasonic Manipulation: Influence of the Substrate

“…They are the focus of a growing community of researchers from academia and industry. In particular, polymeric micro-resonators actuated by ultrasounds offer a real alternative to glass and silicon chips for prototyping micro-separators, as demonstrated by the authors of this work for particle separation [45] and tumour cell extraction from peripheral blood samples [46] and other authors also tested in later experiments [47,48]. These microfluidic devices admit structural changes into their designs for their performance optimization.…”

Microfluidic bio-particle manipulation for biotechnology

“…The material of choice for acoustofluidic devices, which is excited with surface acoustic waves, is polymers with low acoustic impedance and with good shear wave carrying capacity such as PDMS [87][88][89]. For the silicon-based devices, fabrication through standard photolithography and wet or dry etching are common approaches [61,94,69,95,47,96]. In the case of polymers and particularly PDMS devices, standard soft lithography methods [87,89,93] and rapid prototyping are commonly employed [97].…”

“…ACT methods have been implemented for bio-particle wash [95,47,96,84,125,92], trapping [125,92,[126][127][128][129][130][131][132][133][134] and separation [69,108,85,91,9,81,135,94,136,137]. Bio-particle washing relies on focusing the particles to the center of the channel, and out flowing the bio-particles collected at the center into another suspension medium.…”

“…Bio-particle washing relies on focusing the particles to the center of the channel, and out flowing the bio-particles collected at the center into another suspension medium. Utilizing this concept, the bio-particles such as RBCs [95,47,96] and yeast [84] have been washed with a microfluidic device. The idea of acoustics based bio-particle trapping can be used in the applications of bio-particle enrichment (concentration) [125] as well as clarification of these bio-particles from the suspension [92] through entrapment at certain locations within the microchannels or trapping them in droplets [126].…”

Safety of acoustic separation in plastic devices for extracorporeal blood processing

“…As acoustic apheresis technology progresses toward clinical development, establishing the safety of using acoustic energy on blood is paramount. We previously developed disposable, rectangular, polystyrene microchannels for acoustophoresis, measured separation of red blood cells (RBCs) from plasma, and estimated applied acoustic energy density . Subsequently, with further tuning of operating parameters, we attained 94% recovery of RBCs and 91% recovery of leukocytes; and, under different conditions, we attained 92% platelet recovery .…”