Increased responsivity for resonant, mems mass sensor for in-liquid monitoring of picogram bioparticles

Abstract

MEMS cantilever mass sensors are renowned for their exceptionally high sensitivity, achieving detection limits in the zeptogram range under vacuum conditions [1]. However, in liquid environments, sensitivity is significantly reduced due to mass loading from the surrounding fluid and viscous damping, typically limiting detection to the nanogram range [2]. In this study, we introduce a novel resonant MEMS sensor design optimized for liquid-phase detection of bioparticles, leveraging a specific class of higher-order vibrational modes known as “roof-tileshaped” modes. Prior research demonstrated that these modes are less susceptible to viscous damping and fluidinduced mass loading [3]. Our work extends these findings by demonstrating that such modes also exhibit enhanced mass responsivity. This was experimentally verified by functionalizing the cantilever’s surface with streptavidin and subsequently binding biotinylated latex beads to it (compare Figure 1). During this procedure, the conductance spectrum of the resonant mode was measured, and shifts of the resonance frequency were recorded. This improvement enables the detection of minute biological particles such as proteins, viruses, or fungal spores in liquid media like water or blood. Combined with the scalability and cost-effectiveness of silicon micromachining, this approach presents a promising platform for affordable, real-time biosensing applications.