We present a novel chemical sensor based on a microfabricated array
of silicon cantilevers. Individual cantilevers are sensitized for the detection
of analytes using metal coatings, self-assembled monolayers or polymers.
Analyte molecules chemisorbing or physisorbing on the cantilever coating
and chemical reactions produce a change in interfacial stress between adsorbed
analyte molecule layer and cantilever surface. This leads to a nanomechanical
response of the cantilever, i.e. bending
Combining various sensors within an array creates a device which can
be employed as a Nanomechanical Olfactory Sensor (NOSE). Cantilever bending
is detected using a time-multiplexed optical beam-deflection technique.
From magnitude and temporal evolution of the bending, quantitative information
on analyte species and concentration is derived. Using an automatized gas
handling system, we demonstrate detection of ethene with such a nanomechanical
nose.
Other analytes, such as water and various primary alcohols can be investigated
by conducting the carrier gas through a vessel filled with a few ul of
liquid analyte by means of the gas handling system. Employing polymer coatings
as cantilever sensor layers we can observe diffusion of analyte-saturated
carrier gas into the polymer layer by tracking the bending of cantilevers.
Applying principal component analysis (PCA) chemical analytes can be
distinguished by different temporal evolution of sensor responses.