Micromachined electrochemical T-switches for cell sorting applications

Abstract

MEMS micro-T-switches actuated via electrochemical bubbles for cell sorting applications in a monolithic chip level are proposed and successfully demonstrated. The electrolysis-bubble actuator, which has the features of low operation temperature and high surface-tension force, is developed to actuate the micro-T-switch sorting structure in our device. The double T-structure design, the T-shape microchannel with the movable micro-T-switch structure located at the junction of the T-shape microchannel, with the electrolysis-bubble actuator makes an active-binary switch function available for cell sorting applications. The room temperature operation and the low voltage required for electrolysis actuation minimize the possibility of cell-damage that happens in the conventional high electric separation instruments, such as flow cytometry. The function of our micro-T-switch chip with a low required actuation voltage of 3.0 approximately 3.5 V is demonstrated by using human hepatoma cells in this paper. The pH-value measurements characterize the pH-value variation and distribution in the actuating chambers and the mainstream microchannels to trace the possible liver-cell injury due to the pH-value variation during electrolysis-actuation operation. The 84.1% cell viability in the sorted human hepatoma cells through our micro-T-switch sorter is observed via the fluorescence assay technique. Furthermore, 70.2% of total injected cells recover in culture after sorting and grow into colonies after micro-T-switch sorting operation. In this paper, we describe the design, microfabrication, and characterization of our micro-T-switch cell-sorting chip. We also report the cell-sorting demonstration and the cell viability results for the mammalian liver cells through our micro-T-switch cell-sorting chip.

A trap-and-release integrated microfluidic system for dynamic microarray applications

“…For example, in the case of disposable diagnostic chips, where retrieval of beads is not necessary, an array made up of -Fluidic traps alone will be sufficient for observation purposes. As for the optical-based microbubbles technique developed here, we believe it has many other potential uses beyond microarrays applications; it can be used as actuators, valves, and pumps to replace conventional bubbles formed by resistive heating (22,23) or electrochemical means (24).…”

“…The microbubble technique is ideal for our application compared with electrokinetic (17)(18)(19), optical (20), and other techniques (21) because the force exerted by an expanding bubble is enough to counter the flow. However, conventional microbubblebased devices (22)(23)(24) suffer the drawback of complicated circuits and connections. In this device, the microbubbles are formed by using a new optical technique that does away with the need of complicated on-chip integrated circuits and connection to external control electronics, greatly simplifying fabrication and operation.…”

Recent advances in miniaturized microfluidic flow cytometry for clinical use

“…Since the first disposable microfabricated fluorescence-activated cell sorter was introduced in 1999 [41], many different microchip sorter systems have been described in the literature, which utilize electrokinetic flow control [42], switched valves [43], electrostatic force [35], dielectrophoresis [44], dielectrophoretic field-flow-fractionation [45], "T-switches" actuated via electrochemically generated bubbles [46], thermoreversible polymer [47], and optical manipulation [48]. Laminar flow streams were also elaborately combined with electrophoretic switches for the valveless sorting of microparticles [49].…”

Optical Manipulation of Microparticles in an SU-8/PDMS Hybrid Microfluidic Chip Incorporating a Monolithically Integrated On-Chip Lens Set

“…For this displacement, we believe it is sufficient to separate the target particles. In such a case, the proposed SU-8/PDMS microfluidic chip with a monolithically integrated compound on-chip lens structure is expected to be applied for applications in optofluidic sorting and switching [34], with the particle manipulation capability demonstratedinFig.12.…”