Maintaining transparency of a heated MEMs membrane for enabling long-term optical measurements on soot-containing exhaust gas
Journal article, 2020

Ensuring optical transparency over a wide spectral range of a window with a view into the tailpipe of the combustion engine, while it is exposed to the harsh environment of sootcontaining exhaust gas, is an essential pre-requisite for introducing optical techniques for long-term monitoring of automotive emissions. Therefore, a regenerable window composed of an optically transparent polysilicon-carbide membrane with a diameter ranging from 100 µm up to 2000 µm has been fabricated in microelectromechanical systems (MEMS) technology. In the first operating mode, window transparency is periodically restored by pulsed heating of the membrane using an integrated resistor for heating to temperatures that result in oxidation of deposited soot (600–700 °C). In the second mode, the membrane is kept transparent by repelling soot particles using thermophoresis. The same integrated resistor is used to yield a temperature gradient by continuous moderate-temperature heating. Realized devices have been subjected to laboratory soot exposure experiments. Membrane temperatures exceeding 500 °C have been achieved without damage to the membrane. Moreover, heating of membranes to ΔT = 40 °C above gas temperature provides sufficient thermophoretic repulsion to prevent particle deposition and maintain transparency at high soot exposure, while non-heated identical membranes on the same die and at the same exposure are heavily contaminated.

Thermophoretic repulsion of soot

Optical automotive instrumentation

On-board diagnostics

Suspended membranes

Optical MEMS

Heated silicon carbide window

Surface regeneration from soot deposits


Luke M. Middelburg

Delft University of Technology

Mohammadamir Ghaderi

Chalmers, Microtechnology and Nanoscience (MC2), Electronics Material and Systems Laboratory

David Bilby

Ford Motor Company

Jaco H. Visser

Ford Motor Company

Guo Qi Zhang

Delft University of Technology

Per Lundgren

Chalmers, Microtechnology and Nanoscience (MC2), Electronics Material and Systems Laboratory

Peter Enoksson

Chalmers, Microtechnology and Nanoscience (MC2), Electronics Material and Systems Laboratory

Reinoud F. Wolffenbuttel

Delft University of Technology


1424-8220 (ISSN) 1424-3210 (eISSN)

Vol. 20 1 3

Subject Categories

Energy Engineering

Atom and Molecular Physics and Optics

Other Chemical Engineering





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