Microfluidics involves manipulating small volumes of fluids within micron-scale channels. In recent years, microfluidics has evolved into a multidisciplinary field, finding widespread use across many areas of biology, chemistry and biotechnology. For this research, the suitability of microfluidics for applications in protein biochemistry is being investigated. A key property of fluid flow in micro-channels is that it is typically laminar, meaning that it occurs in smooth parallel streams, with no significant mixing between streams, other than by diffusion. This property can be exploited to measure diffusion coefficients of biomolecules such as proteins, and the inherent size-dependence of diffusion coefficients makes it possible to use a microfluidic device for the analysis of protein size and size-change inducing biochemical events. Thus, one aim of this research is to develop a new analytical tool to study protein-protein interactions. As a first step, measurements of the diffusion coefficients of several proteins of different sizes have been made in a custom microfluidic device. The ultimate goal here is to develop microfluidic platforms for the detection of biomolecules in complex solutions, which will form the basis of medically-relevant devices of commercial value.