The depth, width, and length were measured optically within an accuracy of ±0.2%. The surface roughness of the channel was measured with a surface profilometer. During the experiments, the surface of the flow channel was so designed that the surface was kept hydrophilic in order to have the buffer solution flow through the microchannels with a definite surface resistance. Pressure gradients in the present curved channels generated modified (due to centrifugal force) parabolic flow,

such that shear flow occurred near the channel walls. GDC-0449 solubility dmso Furthermore, microfluidic semi-circular curved ducts created a periodic oscillating flow, in which flow pressure gradient alternated directions selleck products at a definite time and extended observations of DNA molecules. DNA visualization and

buffer solution preparation An experimental setup scheme combined with a laser light source (Ar-ion laser 488 nm/HeNe laser 532 nm) and scanning system used to implement μPIV measurement is shown in Figure 2. The flow cell was mounted onto an epifluorescent microscope (IX71/FV300, Olympus, Tokyo, Japan) equipped with a × 40 magnification and NA 0.85 air immersion objective lens, following the description in [2, 9]. The use of the μPIV technique is very attractive in microfluidics because it helps to determine the detailed flow phenomena of microsystems by utilizing flow-tracing particles to map the flow in the microchannels. Streak images and video microscopy assist in the investigation into the flow kinematics in the circular curved microchannels; μPIV is used to quantify the flow field in the vicinity of the curved channels. In this study,

the stained DNA molecules (JOJO-1, Invitrogen, Carlsbad, CA, USA) were used as seeding. The probe used to visualize the DNA was JOJO-1 at a dye with base pair ratio of 1:5. Incubation for the DNA and probe was initiated. GNE-0877 The dyed λDNA had a this website contour length (L e) of 21 μm and the longest relaxation time (τ) of 7.6 s. Figure 2 Schematic for the present measuring instruments. Shear flow system A custom-made flow system was developed to enable the simultaneous generation of controlled shear flows and visualization of the DNA molecular conformation dynamics. The present DNA solution was found to be highly shear thinning at high shear rates, with a shear viscosity μ (cP) defined as the power law (one of typical relations). Flows of water and diluted DNA solution (λDNA, 31.