Microfluidic platform for Coriolis-based sensor and actuator systems

The ability to measure the amount of fluid that flows from one location to another is of use in a wide variety of applications and applications that require very small fluid flows become more and more important. It is often not only the flow of a fluid that needs to be monitored, but also the composition of the fluid. For this, multiple parameters of the fluid need to be measured, preferably using a very small sensing system with a very low volume. In the past, many different microfluidic devices have been introduced that can measure these parameters. However, to integrate these different devices, it is often necessary to use external fluidic interconnects which have a relatively large volume, resulting in slow response times and requiring large sample sizes. For this, the research presented in this thesis is divided into two parts. The first part of the research has been focused towards realization of a microfluidic platform that enables on-chip integration of many different microfluidic devices. This platform allows design of microfluidic channels, right underneath the surface of the device, of many different sizes and shapes integrated on the same chip, with functional structures in close proximity of the fluid. As a result, many different sensing principles can be applied to the fluid to measure its parameters. The second part of the research has been focused on realizing different sensor and actuator systems in this platform. Here the emphasis has been on research on a micromachined Coriolis mass flow sensor. For this, a numerical model has been made that models the mechanical behavior of the sensor under influence of a fluid flow. Using this model, designs have been optimized for specific goals. The optimized designs have been fabricated and characterized. For high sensitivity, a sensor has been made that can measure as low as 14ng/s while a sensor has been made, optimized for high flows, that can measure as high as 50g/h at only 1bar pressure drop. To be able to manipulated the measured flow to reach a preferred set point, two different proportional control valve have been realized in the same fabrication process to form a fully integrated Coriolis mass flow controller. Besides Coriolis mass flow sensors, other sensors have been designed, realized and characterized to be able to measure different fluid parameters. Capacitive pressure sensors have been realized to measure the pressure inside the channel, which also allows measurement of the viscosity of the fluid. Thermal flow sensors have been used together with the Coriolis flow sensors to increase the total dynamic flow range of the sensor or to find thermal properties of the fluid like the specific heat capacity or the thermal conductance. Resonating channels have been used to measure the density of the fluid inside them and in the case of proteins that adhere to the channel wall, the mass of these proteins. A sensor to measure the relative permittivity of the fluid has been realized and a design for improvements have been proposed.