Characterization of fluid with suspended nanoparticles in microchannels has been studied as a part of a microfluidic based acute myocardial infarction (AMI) detection device. The AMI detection process uses heat stabilized human serum albumin (HSA) magnetic microspheres and specific antibodies to create a magnetic immunoassay used in the detection of AMI. Microanalysis systems have several advantages over conventional analysis systems due to their sensitivity, reliability and the amount of anlaytes needed for the test. The microchannels used in this work were fabricated at Sandia National Laboratories (SNL) using a SwIFT™ microfabrication surface micromaching process. Micro channels made of Poly(dimethylsiloxane)-glass (PDMS-glass) designed and fabricated at the Department of Chemistry at the Florida State University were also used in this work. The SwIFT™ microchannels had dimensions of 6µm in height, 20µm in width and 200µm in length where as the PDMS-glass microchannels had dimensions of 40µm in height, 200µm wide and 13mm in length.
Characterization of the microchannels was accomplished using a variety of techniques. The first method used to characterize the microchannels was to used a head pressure-flow set up to determine the pressure and flow characteristics of the SwIFT™ microchannels with the different fluids that the biodiagnostic process calls for, with average mass flow rate being 1.9x10-2 µg/s and Reynolds number of 1.45 at a pressure of 23kPa for a typical channel, these values approach the upper limit of the work accomplished. Since the HSA microspheres, 1µm in diameter and less, play a critical role in the detection protocol their compatibility to the SwIFT™ microchannels was investigated. Results showed the HSA microspheres agglomerated and adsorbed to the walls of the channels. Fluorescence correlation spectroscopy (FCS) was attempted on the SwIFT™ microchannels with 200nm and 40nm beads and the same conclusion of agglomeration and adsorption was reached which made these channels not suitable for
adaptation in the microanaylsis system considered for AMI detection. PDMS-glass microchannels head pressure-flow rates were also investigated showing an average mass flow rate of 1.76x10-1µg/s and a Reynolds number of 1.03 at a pressure of 4.5kPa. FCS was preformed on these channels successfully without any signs of agglomeration, though some adsorption of the beads to the walls of the channel was evident. FCS measured max velocity was equal to approximately 6.6 cm/s. Thus it is concluded that microchannels of similar sizes of the PDMS-glass will be needed in the microanalysis system that is being developed to detect for AMI markers.
