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Weiche Materie Poster: Do., 13:00–15:30 D-P360
Investigation of micro mechanical cantilever sensors with micro-focus
GISAXS
Markus Wolkenhauer 1 , Gina-Gabriela Bumbu 1 , Yajun Cheng 1 , Stephan V.
Roth 2 , Jochen S. Gutmann 1,3
1 Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
– 2 Deutsches Elektronen Synchrotron (HASYLAB), Notkestr. 85, D-22603
Hamburg – 3 Institute for Physical Chemistry, Johannes Gutenberg University, Jakob-
Welder-Weg 10, D-55099 Mainz
Micro mechanical cantilevers covered with polymer brushes are of great interest for
fundamental research and practical applications [1]. Used in fundamental research
they allow an insight into the swelling behaviour of polymer brushes. Furthermore they
can be used for a wide variety of sensor applications. In priciple a micro mechanical
cantilever sensor consist of two main parts: the micromechanical cantilever that acts as
a transducer element and a coating which can be highly specific for different molecules
and produces specific response patterns for various analytes.
As transducers OCTOSENSIS silicon microarrays (Micromotive, Germany) were used
in order to investigate the swelling of polymer brushes. Each chip consists of eight
rectangular cantilevers, with a length of 750 µm, width of 90 µm and thickness of 1 µm
arranged at a pitch of 250 µm. Utilizing an atom transfer polymerisation (ATRP)
“grafting from” technique polymer brushes were grown on the silanated array surface
[2].
The quality of the coating, grafting density of the polymer brushes, layer thickness,
uniformity of the layer are very important for the response of the sensor on an external
stimulus. In our experiments we investigated the quality of the cantilever coatings,
especially the quality of the gold layer and proofing the existence sharp boundaries between
the polymer coated cantilevers and the ones gold coated. The experiments were
carried out at the BW4 beamline using a micro-focus-GISAXS setup using a detector
sample distance of 1.9 m and a 32x17 µm 2 micro-focus beam [3]. The small beam parameters
allowed to selectively analyze a single microcantilever with respect to coating
uniformity, composition and thickness in a µ-GISAXS experiment. Our findings clearly
correlate defects in the cantilever coatings to irregular behavior of the sensing element.
[1] H.P Lang, M. Hegner, Ch. Gerber, Materials Today, 8 (2005) 30.
[2] Bumbu GG, Kircher G, Wolkenhauer M, Berger R, Gutmann JS, Macromol. Chem.
Phys. 205 (2004) 1713.
[3] M. Wolkenhauer, G. G. Bumbu, Y. Cheng, S. V. Roth, J. S. Gutmann, APL,
submitted