In this project, we will combine well-known thermal flow sensing principles with micromachined mechanical sensors that measure the flow through the bending or displacement of a mechanical structure. In this way, we expect that, in addition to mass flow, many relevant gas parameters can be measured, such as thermal conductivity, density, specific heat, and dynamic viscosity.
For the measurement of gas flows, (micromachined) thermal flow sensors are often used because of their high sensitivity, low pressure drop, and relatively straightforward operating principle. However, their response is dependent on the properties of the fluid, especially the thermal conductivity and heat capacity. Micromachined mechanical flow sensors, based on bending or moving microstructures, have been primarily used for specific applications, such as measuring turbulence, where small and fast sensor elements are required. However, their response is dependent on the viscosity and density of the gas. The combination of thermal and mechanical sensing elements in a single device will reveal valuable information on the gas properties and, therefore, on the composition of the gas.
Important drawbacks of mechanical sensors are the fragility of the sensitive mechanical structures and susceptibility to contamination like dust particles. These drawbacks are not present when operated inside flow channels with clean gases, which is the case for the applications addressed in this project. We will focus on two types of sensors:
- miniature probe sensors that can be placed inside larger flow channels, and
- sensors integrated inside microchannels fabricated in the so-called surface channel technology, which allows integration with thermal sensors and even micro Coriolis sensors on a single chip.
In the new project “Flow and fluid composition sensing using integrated drag force flow sensors”, new sensor designs as well as their cleanroom fabrication by silicon micromachining will be investigated. The main challenges are (1) the design and modelling of new sensor topologies, (2) development of the MEMS fabrication processes, (3) fabrication of the sensor chips in the MESA+ cleanroom and (4) evaluation of the resulting performance in flow and gas property sensing in our MEMS measurement lab. The project is part of the KIC FLOW++ programme “Break-through technologies in flow and fluid composition measurement”. It involves close cooperation with flow sensor companies and the TU Delft, where a post-doc will focus on the electronic interfacing of the sensors.
The PhD candidate will work at the Integrated Devices and Systems (IDS) group within the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) at the University of Twente in Enschede, the Netherlands. You will carry out the research at the University of Twente, with guidance from senior scientists and support from a senior engineer. Various teaching activities in your field of expertise may take up to 20% of your time.