Low-cost polymeric microcantilever sensor with titanium as piezoresistive material

This paper presents the design and fabrication of a polymeric microcantilever sensor with a low cost and accessible fabrication method. Polymeric microcantilevers such as SU-8 have a very low Young's modulus, so SU-8-based microcantilever with metal encapsulated sensor is almost as sensitive to stress changes as Si-based microcantilevers. Conventionally, in polymeric microcantilever, metals have been used as a piezoresistive material and the low resistance of metals can reduce the Johnson and 1/f noise. Despite this promise, self-heating of the piezoresistors due to the applied voltage over the low resistance metals increases the microcantilevers heat-up and so influences biochemical measurements. To avoid self-heating of the microcantilevers, designers are enforced to some limitations concerning the minimum widths of metal piezoresistors of at least 2 pm. In this paper, titanium thin film has been chosen as a metallic piezoresistive material, which results in a resistivity of 1320 Omega nm that is approximately 3.2 times higher compared to that of bulk titanium. Therefore, the minimum size can be increased to 40 mu m and the lithography step does not require access to an ultra-clean room. In addition, to facilitate electrical interconnections, an isotropic conductive paste has been employed, which enables the microcantilever sensor to be utilized in air and liquid media. The proposed microcantilever deflection sensitivity reveals the gauge factor of approximately equal to 3.78. Hence, the results show that it can used as an optimal solution in order to perform as a non-complicated, accessible, high sensitivity and low-cost fabrication method without changing the sensor performance in comparison with other types of microcantilever sensor. (C) 2012 Elsevier B.V. All rights reserved.