There are common problems with adsorption of analytes on the surfaces of microfluidic systems with physiological samples such as blood serum, plasma, and urine. The authors' investigation involves the interaction of serum components with fused-silica surfaces under various flow regimes in microcapillaries. Their focus will include the individual components of serum as well as fresh whole serum. The authors studied the whole serum components in our microfluidic system to uncover the responses of proteins in capillary and microchannel surfaces when influenced by the highly variable serum constituents. They have observed the whole serum with a total protein assay by using the bicinchoninic acid assay in combination with a characterization method, such as SDS polyacrylamide gel electrophoresis, and repeated observations for any change of flow rate in fused-silica capillaries (50 mu m inside diameter) under continuous flow. The authors' preliminary results contradict anecdotal evidence that proteins and other components of serum clog or prevent flow at steady low flow rates. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3475531]