Spark‐generated microbubble cell sorter for microfluidic flow cytometry

Abstract

High-speed and accurate cell sorting is of great significance for cell analysis regarding both bioresearch and clinical application. Different from the jet-in-air sorting of commercial flow cytometers, sorting in fully enclosed and disposal microfluidic chips can avoid aerosols and crosscontamination, thus contributing to the improvement of biosafety and test accuracy. However, current microfluidic sorters usually require complicated structures, or otherwise cannot attain high throughput. In this article, a sorting mechanism for microfluidics is proposed for the first time based on the jet flow induced by the spark-generated cavitation microbubble that can be easily realized by a pair of electrodes. The sorter was integrated into a microfluidic chip based on three-dimensional (3D) hydrodynamic focusing and a binary optical element (BOE) for laser illumination. Besides, several aspects of the sorting mechanism were studied to optimize the device. It achieved a switching time of 250 μs at the sample flow velocity of 5 m/s and performed the continuous operation at 200 Hz. Both the stability of fluorescence signals and the viability of cells were basically maintained. To conclude, this work explores a new on-chip sorting mechanism which possesses the merits of simple structure, easy control, and fast switching. © 2018 International Society for Advancement of Cytometry.

New advances in microfluidic flow cytometry

“… and Zhao et al. both reported the electrically actuated vapor bubble jet flow sorter. They utilized the resistive metal heater and the high‐voltage electric spark discharge to generate the bubbles instead of the pulse laser, respectively.…”

“…This sorter could reach a throughput of 23 000 cells/s with 90% purity. In addition, based on the same principles, De Wijs et al [92] and Zhao et al [93] both reported the electrically actuated vapor bubble jet flow sorter. They utilized the resistive metal heater and the high-voltage electric spark discharge to generate the bubbles instead of the pulse laser, respectively.…”

Microfluidic FACS becoming real

“…Among several microfluidic FACS (mFACS) technologies, Miltenyi employed a MEMS valve to momentarily divert the entire cell flow, while more reports generate a side "jet flow" perpendicular to the constant cell-feeding flow to deflect the total cell trajectory. Several different physical transducers were demonstrated for the jet flow generation such as by piezoelectric disc or thermal bubble creation, such as Zhao's report in the recent issue of Cytometry A (5).…”

“…The motivations behind seem to be sound and clear. The recent report by Zhao et al proposed a novel method of generic bubble-based microfluidic cell sorting (5). The aerosol induced during sorting also triggers biosafety concerns (1).…”

“…Today a variety of miniaturized sorting techniques are available: some stay with cell-marker-based sorting just like FACS (2,3) but some sort cells by their specific physical properties (4). The recent report by Zhao et al proposed a novel method of generic bubble-based microfluidic cell sorting (5). After all, whether FACS should be miniaturized, in which style, is largely dependent on why and where cells sorting is needed, and on the pros and cons of the novel technologies.…”