Design Analysis of Silicon Cantilever for Label-less Sensing using Finite Element Method

Silicon cantilevers are principal sensing components in measuring physical parameters, chemical and biochemical sensing, and monitoring DNA changes. In this paper, silicon cantilever that can sense micro/nano objects without the aid of any label for sensing has been designed and analyzed. In order to do so, deformation of cantilever itself will act as sensing unit. Finite element method was employed for design implementation. Design target is to achieve high sensitivity in bending without the use of fluorescence or radioactive label. Design parameters under consideration were length and thickness of the cantilever. Finite element model was developed as a thin cantilever of uniform rectangular cross-section discretized with 8-node quadrilateral brick elements. The micro-scaled mechanical properties of silicon were taken from published reports. For the purpose of having objects to be sensed, differential surface stress and additional weight in sub-micron scale were created as disturbance to the cantilever. Linear static stress analyses were performed to extract the amount of bending and the stress induced by different loadings. Finite element modeling and design analysis were implemented in general-purpose FE code. The results show that the feasible size of silicon cantilever that can sense any object at micron or sub-micron scale is 1000 times 100 times 0.4 mum provided that it does not impose the fabrication problem.