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Biochemical analysis: capillarity, fluorescence and optical microscopy in small liquid volume measurement
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posted on 27.02.2017by Cheong, Brandon Huey-Ping
Biochemical Analysis deals with a number of techniques used to analyse substances within living cells and the chemical processes that are associated with it. Technologies that stem from biochemical analysis include the engineering of microfluidic devices and other instrumentation that enable scientists to obtain information from assays in a laboratory environment. These methods however, involve the use of complex and precise machinery in their manufacturing, and are not always available in a resource-limited laboratory. This thesis comprises an extensive study in small liquid volume measurement specifically in the context of capillarity, fluorescence and optical microscopy. Robust novel designs, methods and concepts have been researched and are presented here for their viable use. Dynamic flow was investigated through coverslip fluidics under a controlled environment and through the generation of a squeeze flow. A microfluidic channel was constructed to be used in conjunction with an optical microscope for the viewing of flagellate algal cells, and a squeeze flow generation between a microscope slide and circular coverslip was found to be effective for collection of various preconcentrated samples. Additionally, a simple method to measure the contact angle in a capillary tube was developed by lighting up its corresponding meniscus with an LED.
Fluorescent liquid sensing and detecting was done through the use of the capillary wells microplate and optical fibre light guide approaches. Standard wells of a microplate were substituted for capillary tubes enabling meniscus and bubble formation errors to be eliminated, and the use of light guide optical fibres placed in very close proximity to a fluorescent droplet, enhanced measurement sensitivity.
Microplate technology was also studied and a transparency based microplate was developed. This design resulted in higher fluorescent intensity readings to a standard microplate and was due to liquids contained in incised wells adopting a convex meniscus form. Mixing was also accomplished in a microplate well by inserting a superhydrophobic rod at the centre of a droplet.
Finally, a liquid between two glass rods microplate was established with the added benefits of mixing, fluorescent measuring and integration on to lab-on-a-chip (LOC) devices. Two glass rods were placed in parallel with one another and a fluorescent liquid was dispensed between them and held in place by capillary forces. By inserting an optical fibre (attached to an LED) into one of the capillary tubes, fluorescent readings were obtained with an optical microscope and through mechanical actuation, complete homogeneous mixing was achieved through the coalescence of droplets. Additionally, an open analyte system and prospects of a dynamic system suggested potential for integration on to LOC devices.