Sensors and Actuators A 125 (2005) 69–75 Simulation and design of piezoelectric microcantilever chemical sensors Wei Zhou a , Abdul Khaliq a , Yanjun Tang a , Haifeng Ji a,c , Rastko R. Selmic a,b,∗ a Institute for Micromanufacturing, Louisiana Tech University, Ruston LA 71272, USA b Department of Electrical Engineering, Louisiana Tech University, Ruston LA 71272, USA c Department of Chemistry, Louisiana Tech University, Ruston LA 71272, USA Received 17 May 2004; accepted 21 July 2005 Available online 1 September 2005 Abstract This paper presents an analytical modeling of a piezoelectric multi-layer cantilever used as a micro-electro-mechanical-system (MEMS) chemical sensor. Selectively coated microcantilevers have been developed for highly sensitive chemical sensor applications. The proposed piezoelectric chemical sensor consists of an array of multi-layer piezoelectric cantilevers with voltage output in the millivolt range that replaces the conventional laser-based position-sensitive detection systems. The sensing principle is based upon changes in the deflection induced by environmental factors in the medium where a microcantilever is immersed. Bending of the cantilever induces the potential difference on opposite sides of the piezoelectric layer providing an information signal about the detected chemicals. To obtain an application specific optimum design parameters and predict the cantilever performance ahead of actual fabrication, finite element analysis (FEM) simulations using CoventorWare (a MEMS design and simulation program) were performed. Analytical models of multi-layer cantilevers as well as simulation concept are described. Both mechanical and piezoelectric simulation results are carried out. The cantilever structures are analyzed and fabrication process steps are proposed. © 2005 Elsevier B.V. All rights reserved. Keywords: Microcantilever; MEMS; Piezoelectric; Chemical sensor; Cantilever; MEMS simulation 1. Introduction There has been a growing interest in piezoelectric thin films applied in variety of MEMS devices. These piezoelec- tric MEMS devices may take a form of individual or dis- tributed mini-actuators or sensors. Highly sensitive MEMS chemical sensors with position-sensitive detector (PSD) have been developed, as shown in Fig. 1. In order to replace tradi- tional laser-based PSD devices and design sensors that can be used in the field, novel chemical sensors based on piezoelec- tric principle have been studied. The novel sensors offer many advantages including higher sensitivities, simplified sensing systems, lower costs, and do not require complex and bulky PSDs. ∗ Corresponding author. Tel.: +1 318 257 4641; fax: +1 318 257 4922. E-mail address: rselmic@latech.edu (R.R. Selmic). URL: http://www.latech.edu/∼rselmic/. Smits and Choi [1] presented electromechanical charac- teristics of a heterogeneous piezoelectric bender subjected to various electrical and mechanical boundary conditions: a mechanical moment at the end of the bender, a force applied perpendicular to the tip of the bender, and a uniform load applied over the entire length of the bender. Cheng et al. [2] developed a model of multilayer piezoelectric cantilever beam micro-mirror and micro-laser arrays and used them in the closed-loop control structure in order to improve the mirror effectiveness. Zhang and Sun [3] described the rela- tion between minimum detectable force gradients and level dimensions in non contact scanning force microscopy using piezoelectric microcantilever. Meng et al. generalized analyt- ical formulation of mechanical formation of the piezoelectric laminated micro actuators [4]. There is a need for highly accurate and efficient model- ing of the piezoelectric devices that can be used in a design stage [9–11,14]. Finite element analysis simulations using CoventorWare have been carried out in this study to pre- 0924-4247/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.sna.2005.07.009