Virtual Filter Membranes in a Microfluidic System for Sorting and Separating Size-Based Micro Polystyrene Beads by Illumination Intensity Design in Optically Induced Dielectrophoresis (ODEP)

Abstract

In biomedical diagnosis, the efficient separation and purification of specific targets from clinical samples is the desired first step. Herein, the concept of virtual filter membranes based on optically-induced dielectrophoresis (ODEP) manipulation in a microfluidic channel is proposed as a light screening membrane for the separation of polystyrene (PS) microparticles with three different diameters of 15.8, 10.8 and 5.8 µm. The ODEP manipulation velocity of three types of PS microparticles reacted with the color brightness setting was investigated to determine the light intensity to induce an ODEP force higher than the drag force of fluid speed. The color brightness of the light bar in three areas of the light screening membrane was selected as 60%, 70% and 100% to isolate PS microparticles with diameters of 15.8, 10.8 and 5.8 µm, respectively. With a double light bar and a flow rate of 3 µL/min, the recovery rate and isolation purity was improved by 95.1~100% and 94.4~98.6% from the mixture of three types of PS microparticles within 2 min, respectively. This proposed light screening membrane could be a candidate for the separation of small-volume and rare biomedical samples, including circulating tumor cells (CTCs) and bacteria in the blood.

The Utilization of Optically Induced Dielectrophoresis (ODEP)-Based Cell Manipulation in a Microfluidic System for the Purification and Sorting of Circulating Tumor Cells (CTCs) with Different Sizes

“…Therefore, one can use ODEP-based cell manipulation to sort and separate the cells with different sizes based on their different ODEP manipulation force [36,41]. Apart from the factors described in Equation ( 1), the ODEP force generated on a microparticle is also increased with the intensity increase in the illuminated light, which was reported to be proportional to its color brightness ratio according to our previous study [38,39].…”

“…According to Stokes' law, thus, the ODEP manipulation force acting on the cell investigated can be experimentally assessed through measurements of the maximum velocity of a moving light image that can manipulate the cell [36,41]. Moreover, as described earlier, the ODEP force generated on a cell is influenced by the intensity (or color brightness ratio) of illuminated light, according to our previous study [38,39]. The previous evaluation of the ODEP manipulation force of the manipulated magnetic microbeads-bound Jurkat, OECM1, and HA22T cells was based on the use of the light image with 100% color brightness.…”

“…Briefly, the microfluidic chip consisted of a top processed polydimethylsiloxane (PDMS) substrate (Layer A), an indium-tin-oxide (ITO) glass (Layer B), a processed double-sided adhesive tape (thickness: 50 µm) with a hollow microchannel (Layer C), and a bottom ITO glass coated with a layer of photoconductive material (Layer D). The fabrication and experimental setup have been well described previously [36,38]. Briefly, the PDMS tube connector (Layer A; Figure 1b) was made by the CNC (EGX-400, Roland Inc., Hamamatsu, Japan) machining for positive polymethylmethacrylate (PMMA) mold fabrication and the subsequent PDMS (Sylgard ® 184, Dow Corning, Midland, MI, USA) replica molding for the tube connector making.…”

“…For Layer C (Figure 1b), the hollow structure of the microchannel was fabricated in the double-sided adhesive tape (L298, Sun-yieh, TYN, Taiwan) simply via a manual punching process using a custom-made metal mold. For Layer The fabrication and experimental setup have been well described previously [36,38]. Briefly, the PDMS tube connector (Layer A; Figure 1b) was made by the CNC (EGX-400, Roland Inc., Hamamatsu, Japan) machining for positive polymethylmethacrylate (PMMA) mold fabrication and the subsequent PDMS (Sylgard ® 184, Dow Corning, Midland, MI, USA) replica molding for the tube connector making.…”

“…First, the ODEP force acting on the cells with varied sizes is different [37]. Second, previous studies have demonstrated that the ODEP force generated on a cell is influenced by the intensity (or color brightness ratio) of illuminated light [38][39][40]. Based on these facts, two dynamic light image arrays were designed in the microchannel (i.e., the defined zone for cell separation) to first gather all cells to one side of the microchannel and then to sort and separate the magnetic microbeadsbound blood cells and the cancer cells with different sizes, respectively.…”