Density sensor: Faster transfer from prototype to product
What is the mineral content of water? When does biogas contain enough methane in order to be fed into the gas network?
For the company TrueDyne, we transformed an MEMS chip prototype into a product in no time at all. The sensor measures the smallest changes in the thickness of liquids and gases. We mass-produce them in our clean room in Villlingen-Schwenningen.
The chip's core part is a self-supporting silicon conduit with a cross section measuring 160x200 µm (only four times thicker than a human hair) that is situated on a glass substrate. The fluid flows into the conduit through holes in the glass base, which is converted into resonance vibration via plate capacitors. This resonance vibration is also measured via plate capacitors. The conduit's resonance frequency and performance change according to the fluid's thickness and viscosity.
In order to decouple the high-precision measurement from environmental factors, the conduit is situated beneath a silicon cover that includes a vacuum. In order to manufacture such a sophisticated chip, 4 wafers and more than 100 process steps are necessary in total.