Acoustic mixing in a dome-shaped chamber-based SAW (DC-SAW) device.

The use of an open droplet system for surface acoustic wave (SAW)-based applications has been limited by droplet instability at high input power. This study introduces a dome-shaped chamber-based SAW (DC-SAW) device for the first time, which can be fabricated simply using a single adhesive tape and a drop of ultraviolet-curable material without soft lithography processes. The dome-shaped chamber device with a contact angle of 68° enables the maximizing of the effect of SAW transmitted at a refraction angle of roughly 22°, negating the droplet instability. The DC-SAW device was applied to acoustic mixing to estimate its capability. Acoustic mixing of two different fluids (i.e., deionized water and fluorescent particle suspension) was demonstrated in the dome-shaped chamber device. Moreover, the effect of flow rate and applied voltage on mixing performance was estimated. With the decreasing flow rate and increasing applied voltage, mixing performance was enhanced. At an applied voltage of 20 V, mixing indices were higher than 0.9 at a total flow rate of 300 µl min-1.

Sheathless High-Throughput Circulating Tumor Cell Separation Using Viscoelastic non-Newtonian Fluid.

Circulating tumor cells (CTCs) have attracted increasing attention as important biomarkers for clinical and biological applications. Several microfluidic approaches have been demonstrated to separate CTCs using immunoaffinity or size difference from other blood cells. This study demonstrates a sheathless, high-throughput separation of CTCs from white blood cells (WBCs) using a viscoelastic fluid. To determine the fluid viscoelasticity and the flow rate for CTC separation, and to validate the device performance, flow characteristics of 6, 13, and 27 µm particles in viscoelastic fluids with various concentrations were estimated at different flow rates. Using 0.2% hyaluronic acid (HA) solution, MCF-7 (Michigan Cancer Foundation-7) cells mimicking CTCs in this study were successfully separated from WBCs at 500 µL/min with a separation efficiency of 94.8%. Small amounts of MCF-7 cells (~5.2%) were found at the center outlet due to the size overlap with WBCs.

Determination of red blood cell deformability using centrifugal force in a three-dimensional-printed mini-disk (3D-PMD).

Measuring red blood cell (RBC) deformability has become important for clinical disease diagnostics. Various methods for measuring RBC deformability have been developed; however, they require costly and large instruments, long measuring time, and skilled personnel. In this study, we present a three-dimensional-printed mini-disk (3D-PMD) for measuring RBC deformability to overcome the previous limitations. For a miniaturized and low-cost setup, the 3D-PMD was fabricated by a 3D printing technique, which had not yet been used for fabricating a lab-on-a-compact disk (LOCD). Using a 3D printing technique, a multi-layered fluidic channel on the mini CD could be fabricated easily. During rotation by a spinning motor, the difference of the length of compressed RBCs in the fluidic channel was measured and analysed as compressibility indices (CIs) of normal and glutaraldehyde-treated hardened RBCs. The rotation speed and time were decided as 3000 rpm and 30 min, respectively, at which the difference of CI values between normal and hardened RBCs was largest (CInormal-CIhardened = 0.195).

Miniaturized thermocycler based on thermoelectric heating for diagnosis of sexually transmitted disease by DNA amplification.

Sexually transmitted disease (STD) is among the most common infectious diseases; therefore, it is necessary to develop sensitive early diagnostic techniques. As the gold standard, polymerase chain reaction (PCR) has been most widely employed for STD diagnosis; however, PCR requires large and expensive instruments. In this study, miniaturized thermal cycler using Peltier modules was developed for the PCR analysis. In comparison with the conventional PCR instrument, the Peltier-based micro-PCR (P-mPCR) device developed in this study enables one to amplify and successfully distinguish between DNA of different sizes. Furthermore, by using the clinical vaginal sample collected with the vaginal swab and tampon, different kinds of STD bacteria could be detected with high accuracy (∼94.19%) and high sensitivity (∼95.6%). Therefore, the P-mPCR device will be applicable in STD diagnosis as well as the detection of other bacteria/viruses using DNA amplification in regions including those with limited resources.