Detection of anti-IgG using cantilever-type resonant microstructures vibrating in in-plane flexural modes

This work presents a cantilever-based mass-sensitive microsensor platform for the detection of biomolecules in the liquid phase. The resonant microstructures feature integrated thermal excitation and piezoresistive detection elements to excite and sense the structure´s fundamental in-plane flexural mode. A gold film on the cantilevers allows for the local immobilization of biomolecules using gold-thiol chemistry. Using the in-plane flexural mode, quality factors of the order of 30-50 are obtained in water at resonance frequencies around 500 kHz. The reduced liquid damping enables closed-loop operation of the resonators with frequency stabilities in the ppm-range. Using a microfabricated flow cell, anti-IgG is detected in PBS with limits of detection on the order of 50 ng/ml.