Tailoring Beam Mechanics Towards Enhancing Detection of Hazardous Biological Species S. Morshed & B.C. Prorok Received: 27 June 2006 / Accepted: 13 October 2006 / Published online: 26 January 2007 # Society for Experimental Mechanics 2007 Abstract Microcantilever based sensors have been widely employed for measuring or detecting various hazardous chemical agents and biological agents. Although they have been successful in detecting agents of interest, researchers desire to improve their performance by enhancing their mass sensitivity towards developing “detect to warn” detection capabilities. Moreover, there has been little work aimed at tailoring beam mechanics as a means to enhance mass sensitivity. In this paper, a numerical study is per- formed to assess the influence of microcantilever geometry on mass sensitivity in order to improve these devices for better detection of hazardous biological agents in liquid environments. Modal analysis was performed on micro- cantilevers of different geometries and shapes using ANSYS software and compared to the basic rectangular shaped microcantilever structures employed by most researchers. These structures all possessed a 50 μm length, 0.5 μm thickness and 25 μm width where the cantilever is clamped to the substrate, and were analyzed for their basic resonance frequency as well as the frequency shift for the attachment of a 0.285 pg of mass attached on their surfaces. These numerical results indicated that two parameters dominate their behavior, (1) the effective mass of the cantilever at the free end and (2) the clamping width at the fixed end. The ideal geometry was a triangular shape, which minimized effective mass and maximized clamping width, resulting in an order of magnitude increase in mass sensitivity (1,775 Hz/pg) over rectangular shaped cantilevers (172 Hz/pg) of identical length and clamping width. The most practical geometry was triangular shaped cantilever with a square pad at the free end for capturing the agent of interest. This geometry resulted in a mass sensitivity of 628 Hz/pg or nearly a 4-fold increase in performance over their rectangular counterparts. Keywords Microcantilever . Biosensor Introduction Recent developments in the detection of harmful biological species with microelectromechanical systems (MEMS) technology has enabled the possibility of sensors that are both effective and inexpensive [1–5]. These microscale sensors utilize a receptor, specific to a single biochemical or biological target, to immobilize the species of interest and then employ a wide variety of physical and chemical mechanisms for detection and transduction of its presence into quantifiable responses, for example frequency shift by mass addition of microcantilevers. These devices are fabricated using standard microfabrication techniques bor- rowed from the microelectronics industry, whereby, through batch processing numerous devices can be produced in a compact and cost effective manner. Microcantilever based sensors, in particular, are being employed and investigated for their high sensitivity and wide range of applicability [6–15]. In particular, research- ers have demonstrated their applicability as different chemical [16–23] and biological [24–33] sensors by functionalizing their surfaces to capture the specific target of interest. In fact, researchers at Cornell university have demonstrated that tiny cantilevers can possess attogram (1× 10 -18 g) sensitivity [24]. This celebrated achievement, Experimental Mechanics (2007) 47:405–415 DOI 10.1007/s11340-006-9015-7 S. Morshed : B.C. Prorok (*, SEM member) Department of Mechanical Engineering, Auburn University, Auburn, AL 36849-5341, USA e-mail: prorok@auburn.edu