Poly-HDDA microstructure fabrication using microstereolithography for microcantilever-based sensor technology

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.