An overview is given of research activities in the field of fluid components or systems built with microfabrication technologies. This review focuses on the fluidic behaviour of the various devices, such as valves, pumps and flow sensors as well as the possibilities and pitfalls related to the modelling of these devices using simple flow theory. Finally, a number of microfluidic systems are described and comments on future trends are given.

https://iopscience.iop.org/article/10.1088/0960-1317/3/4/002/pdf

Microfluidics-a review

Thermal sensors based on the seebeck effect

This paper discusses the design and application of silicon thermal flow sensors. It is shown how the transduction path in the complete measurement system, going from flow variable to electrical signal, results in three fundamental problems, which can be associated with, respectively, the mechanical, thermal and electrical signal domains. These aspects are further discussed in relation to the silicon flow-sensor research performed at the Electronic Instrumentation Laboratory.

Silicon thermal flow sensors

A multielement monolithic mass flow sensor which developed for possible use in automotive and industrial process control applications is reported. The chip illustrates the use of a common microstructure (a thin dielectric window/diaphragm) for the simultaneous measurement of flow velocity (rate), flow direction, gas type, and pressure. These transducers are merged with on-chip interface electronics to amplify and multiplex the transducer signals, control on-chip actuators, perform self-test, reduce the number of external leads required, and demonstrate process compatibility with a p-well CMOS process. The on-chip circuitry also implements a bandgap sensor for the measurement of ambient temperature. Thus, the chip simultaneously monitors all parameters needed for the computation of true mass flow, requires only ten external leads, and delivers high-level buffered output signals. >

An integrated mass flow sensor with on-chip CMOS interface circuitry

A highly sensitive silicon chip microtransducer for air flow and differential pressure sensing applications

A manolithic integrated direction-sensitive flow sensor for measuring the velocity of gas or liquid flow is described. Its operation is based on the transfer of heat from a heated chip to a flowing fluid. Temperature differences on the chip are a measure for the flow velocity and flow direction in a plane parallel with the chip's surface. The sensor can be embedded in a wall, for example, in a wall of a tube conducting a fluid flow, and can be shielded from a direct contact with the fluid. Measurements are stated for velocities in a range below 3 m/s for air at room temperature.

W. Verhoef

Papers

Monolithic integrated direction-sensitive flow sensor