Microfluidic separation of multisized particles using acoustic standing waves for stem cell sorting
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The sorting and isolation of target cells and suspended particles from a medium is of great importance to cell biology, drug delivery, and related fields in biomedicine. Furthermore, the ability to separate and sort stem cells is of profound interest to the biomedical community to obviate current clinical limitations. Stem cells are considered as a repair system for the body and adipose tissue (fat) is a rich source of stem cells. The regenerative medicine discipline is attempting to harness the innate ability of stem cells to form tissues de novo, and innovative strategies are required to repair the tissue defects. The focus of this work is to develop an acoustically driven, microfluidic cell sorter that will separate particles according to size-based differential migration with high throughput and accuracy, tunable spatial-temporal resolution, and low power consumption. We fabricated three types of cell sorters based on polydimethylsiloxane (PDMS), SU-8 and silicon channels with rectangular cross-section through soft lithography, surface micromachining and bulk micromachining technologies. Acoustic standing wave is launched into the microfluidic channels through an array of integrated piezoelectric plate transducers. Acoustic radiation pressure is simulated and experimentally verified. The acoustic sorting technique provides unique features and complements previous sorting methods. The device design is simple, and it is easy to fabricate. While sorting occurs, there is no direct physical contact which prevents cells or particles from being severely defected. The acoustic sorting can potentially be applied to handle many cell types or particles.