Microfluidic channel depth determination with Tywman-Green interferometer

Link to publisher's homepage at http://link.springer.com/A microfluidic channel is fabricated on a silica wafer using reactive ion etching (RIE). The depth of the microfluidic channel has been measured using a surface profilometer and a Twyman-Green interferometer (TGI) setup. The TGI setup which mainly consists of a 660-nm wavelength He-Ne laser source, glass cube beam splitter and two prisms produced interference fringes based on the optical path difference between two interfering beams when the microfluidic channel is inserted into one of the beams. The TGI setup that was developed has shown high repeatability when measuring microfluidic channel depth and also eliminates back injection into the laser source and alignment criticality. The TGI setup applied a single photodiode to detect the shifting of the bright and dark fringe produced from the interference of the TGI. The depth of microfluidic channel obtained from the TGI is 1.79 ± 0.31 μm using fringe shifting and intensity measurements, while according to the surface profilometer the depth of microfluidic channel obtained is 1.67 ± 0.07 μm. The resolution of the TGI is 0.25 μm and can still go well below that depending on the wavelength of the laser source. This research describes the capability of the TGI to perform depth measurements on a microfluidic channel of a silica substrate which can also be improvised for other microscale devices and applications

Microchannel miter bend effects on pressure equalization and vortex formation

Link to publisher's homepage at http://www.springerlink.com/Simulations have been carried out for water flow in a square microchannel with a miter bend. The simulation considered a pressure-driven flow in a channel-hydraulic diameter of 5 μm for series of Reynolds number (Re) range from 0.056 to 560, in order to investigate water flow at bends. The result shows formation of two vortices after the miter bend, which are more discernible above Re 5.6. The critical inlet velocity for the generation of vortex in this particular geometry occurs at 1 m/s. A simple energy mechanism is postulated to explain the vortex formation as well as core skew direction. The high pressure region at the outer wall before and after the bend is a major factor for vortex formation since the liquid needs to reduce the additional energy effected by the high pressure region. Navier-Stokes equation is utilized with a no slip boundary condition for a total microchannel centerline length of 795 μm which is sufficient to produce a laminar flow pattern at the outlet

Shear Ram Height Investigation for Gold Wire Bond Shear Test

This paper presents the simulation of gold wire bond shear test. The stress and strain response of the gold ball bond during wire bond shear was examined. The simulation was done using a A 3D non-linear finite element model. The effects of the shear ram height on the stress and strain response of the gold ball bond were investigated. The results of the simulation confirms that shear ram height has a significant effect on the von mises stress and equivalent strain response of the gold ball bond during wire bond shear test.</jats:p