The rapid development of various scanning probe methods like SFM or AFM involving microcantilever based sensor
technology has slowly enabled mechanical motion to regain its place in the field of science and engineering by
miniaturization of mechanical systems down to sub-micron dimensions. Such scaling down of dimensions of
microstructures exhibit very high sensitivity to mechanical deformations due to various induced loads. The most widely
used Optical beam deflection method (OBDM) for measuring such deflections in microcantilever based sensors is
limited by diffraction effects due to dimensional constraints of the structures involved. The use of polymer materials like
poly HDDA having very low elastic modulus has the potential to achieve high mechanical deformation sensitivity for
even moderately scaled down structures. Poly-HDDA based microcantilever sensors are being fabricated in an in house
realized Microstereolithographic system. The objective is to fabricate a double micro-cantilever structure of length
600 μm, width 60 μm and thickness 40 μm each with a gap of 100 μm between the two along the thickness dimension.
The relative deflection profile of one of the fabricated cantilevers due to induced surface stress by the self-assembly of
Alkanethiol on Gold is proposed to be measured by an optical diffraction based method. Proposed surface stress
resolution achieved in such a typical microcantilever based sensor is of the order of 1 mN/m for a deflection of 0.5 nm at
free end of one of the micro-structures subjected to self-assembly mechanism. The high thermal stability and very low
elastic modulus of Poly-HDDA enables its application as a low noise, very high sensitive sensor material for detection of
mechanical deforming agents in microcantilever based sensor technology.
A new method based on analysis of a single diffraction pattern is proposed to measure deflections in micro-cantilever
(MC) based sensor probes, achieving typical deflection resolutions of 1nm and surface stress changes of 50μN/m. The
proposed method employs a double MC structure where the deflection of one of the micro-cantilevers relative to the
other due to surface stress changes results in a linear shift of intensity maxima of the Fraunhofer diffraction pattern of the
transilluminated MC. Measurement of such shifts in the intensity maxima of a particular order along the length of the
structure can be done to an accuracy of 0.01mm leading to the proposed sensitivity of deflection measurement in a
typical microcantilever. This method can overcome the fundamental measurement sensitivity limit set by diffraction and
pointing stability of laser beam in the widely used Optical Beam Deflection method (OBDM).
A method to reliably extract object profiles even with height discontinuities (that leads to 2nπ phase jumps) is
proposed. This method uses Fourier transform profilometry to extract wrapped phase, and an additional image formed by
illuminating the object of interest by a novel gray coded pattern for phase unwrapping. Simulation results suggest that
the proposed approach not only retains the advantages of the original method, but also contributes significantly in the
enhancement of its performance. Fundamental advantage of this method stems from the fact that both extraction of
wrapped phase and unwrapping the same were done by gray scale images. Hence, unlike the methods that use colors,
proposed method doesn't demand a color CCD camera and is ideal for profiling objects with multiple colors.
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