Inverted tapered pillars for mass sensing

Micro and nano resonators have been proposed as mass sensors with very high sensitivity. A special class of resonators, vertical micro-pillars, has been recently introduced with increasing mass detection capability, high sensor density and uniformity and reduced sensitivity to contamination and non-specific target absorption. Herein, we describe a newly conceived vertical micro-resonator with inverted tapered shape. With sensitivity of 33 Hz/fg and the reproducibility of 0.1 fg. The proposed geometry allowed the development of a new self-calibrating functionalization strategy which also makes our pillars very suitable for passing from liquid to dry environment. Selective adsorption of molecules is demonstrated and the application of the detector for a test target made of a self assembled monolayer of organic molecules is reported. The measured mass of the adsorbed molecules is 64 fg which corresponds to a density of 6.1 × 1014 mol/cm2.