Microforce sensor for microbiological applications based on a floating-magnetic principle

In this paper, we present the design of a new magnetic nano and microforce sensor for microbiological applications. The sensing part of the sensor presents a naturally stable six degrees of freedom equilibrium state using the combination of upthrust buoyancy and magnetic force. The sensor allows force measurement without deformation of the sensing element using a feedback control loop and is able to measure the components, in the horizontal plan, of the external force applied. The measurement range varies between around plusmn100 muN with a resolution of 20 nN and a linear output. The mechanical stiffness of the passive system is about 0.018 Nm^-1 (same order of magnitude than an AFM micro-cantilever). A complete static study and experimental validation of the used principle are presented in this paper.