Diamagnetically levitating resonant weighing scale

[Display omitted] •A mass sensor is realized utilizing elastodynamics of diamagnetically levitating graphite plates.•The levitating sensor offers a low cost, easy to use platform for sensing nanolitre volume of droplets with high accuracy.•The millimeter levitating sensor achieves mass resolutions down to a few nanograms relevant to biological and chemical sensing concepts. Diamagnetic levitation offers stable confinement of an object from its environment at zero power, and thus is a promising technique for developing next generation unclamped resonant sensors. In this work, we realize a resonant weighing scale using a graphite plate that is diamagnetically levitating over a checkerboard arrangement of permanent magnets. We characterize the bending vibrations of the levitating object using laser Doppler vibrometry and use microgram glass beads to calibrate the responsivity of the sensor's resonance frequency to mass changes. The sensor is used for real-time measurement of the evaporation rate of nano-litre droplets with high-accuracy. By analyzing the resonator's frequency stability, we show that the millimeter graphite sensor can reach mass resolutions down to 4.0 ng, relevant to biological and chemical sensing concepts.