Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2018, Tutora: Aurora Hernandez MachadoIn this work we will propose a theoretical approach for a microfluidic device which can be used as a micro and portable rheometer. We will propose a theoretical model based on the dynamics of the fluid interface in the microchannel in a regime of constant pressure. In this experimental device we use a pump module of polydimethylsiloxane (PDMS) that absorbs the air in the micro fluidic system. Furthermore, we will be able to predict velocities and viscosities of the different Newtonian fluids by means of the properties of the fluid and the geometrical parameters of the experimental set-up. We will also study the diffusion process of the modular pump in order to understand the pressure generated for driving fluid. Finally, we demonstrated the utility of this model by comparing our predictions with the experimental data.