Browsing by Subject "microfluidics"

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Open Access
Injection molding of polymeric microfluidic devices
(2013) Koska, Arif Koray
Mass-production of microfluidic devices is important for fields in which disposable devices are widely used such as clinical diagnostic and biotechnology. Injection molding is a well-known, promising process for the production of devices on a mass-scale at low-cost. The major objective of this study is to develop a technique for repeatable, productive and accurate fabrication of integrated microfluidic devices on a mass production scale. To achieve this, injection molding process is adapted for the fabrication of a microfluidic device with a single microchannel. During the design procedure, numerical experimentation was performed using Moldflow® simulation tool. To increase the product quality, high-precision mechanical machining is utilized for the manufacturing of the mold of the microfluidic device. A conventional injection molding machine is implemented for the injection molding process of the microfluidic device. Injection molding is performed at different mold temperatures. The warpage of the injected pieces is characterized by measuring the part deformation. The effect of the mold temperature on the quality of the final device is assessed in terms of part deformation and the bonding quality. From the experimental results, one-to-one correspondence between the warpage and the bonding quality of the molded pieces is observed. As the warpage of the pieces decresases, the bonding quality increases. A maximum point for the breaking pressure of the bonding and the minimum point for the warpage was found at the same mold temperature. This mold temperature was named as the optimum temperature for designed microfluidic device. The experimental results are also used to discuss the assessment of the simulation results. It was observed that although Moldflow® can predict many aspects of the process, all the physics of the injection molding process cannot be covered.
Open Access
Subwavelength surface plasmon interferometer for high-throughput sensing
(2012) Yavaş, Özlem
Small detection volume, increased analysis speed and reduced cost are the main driving forces for miniaturized lab-on-a-chip systems. Subwavelength holes on opaque metal films provide a unique configuration for miniaturized sensors. Transmitted light through these tiny holes is governed by the electronic resonance on the surface of the metal film. Excitation of surface plasmon-polaritons (SPPs) on the metal-dielectric interface characterizes the resonance condition. The sensitive dependence of the plasmon resonance condition on the dielectric constant of the medium is used for label free sensing applications. In this thesis, we demonstrate a refractive index sensor based on a subwavelength plasmon interferometer using monochromatic light. Very high contrast fringe pattern is generated by the plasmon interferometer that consists of a sub-wavelength slitgroove pair with a small angle between them. The small angle between the groove and the slit provides spatially varying slit-groove distance which generates a highcontrast interference pattern. By interrogating the relative position of interference fringes, one can determine the refractive index of the dielectric medium on the metal surface. The presented plasmon interferometer provides a practical yet sensitive refractive index measurement scheme with very small detection volume.