I. Introduction
Piezoresistive affinity cantilevers have great potential in microsystems used for sensing biomolecules, such as in point-of-care systems. Such prototype systems using piezoresistive cantilevers in Wheatstone bridge configurations with integrated microfludics have been demonstrated [1]–[3]. These cantilevers have a multilayer structure in which the strain-sensitive layer is sandwiched between a structural layer and an encapsulation layer. Selective immobilization of biomolecules on either top or bottom surface of the cantilever generates differential surface stresses on the opposite faces of the cantilever which leads to a bending of the cantilever, thereby inducing a change in resistance of the strain-sensitive layer incorporated within it. For maximum sensitivity of cantilever biosensors, the selective immobilization of biomolecules is a prerequisite, since immobilization on both faces is expected to elicit a weaker response [4]. Studies have concentrated on the mechanical and electrical design of multilayer piezoresistive cantilevers, such as those for atomic force microscope cantilevers [5] as well as affinity cantilevers [6], [7]. For those affinity cantilevers, the electrical sensitivity, i.e., change in resistance due to applied surface stress is less than one part per million (–) which can get suppressed by electrical noise. Also, previous work does not comprehensively discuss engineering figures of merit such as signal-to-noise ratio (SNR), power dissipation, and mechanical stability in liquid media, thus posing practical limitations in the realization of cantilever sensors.