A droplet-based piezoelectric concave diaphragm biosensor with self-enhancing functionality for label-free detection of protein–ligand interactions

This paper presents an innovative micromachined piezoelectric concave diaphragm transducer with self-enhancement capability for label-free real-time biosensing. The transducer, composed of lead zirconate titanate (PZT) piezoelectric material and functioning as a resonator, was successfully fabricated and tested. Experiments were conducted by pipetting analyte droplets into the cavity of the resonator. The biosensor exhibits good stability and sensitivity when operated at its resonant frequency of 100 MHz. This paper proposes novel self-enhancing detection mechanisms to increase the protein–ligand interactions and demonstrates them using external excitation signals with frequency sweep (50–200 kHz) and fixed-frequency (50 MHz) schemes. Results show that the enhancement with the 50 MHz external signal manipulation improves 41% in sensitivity compared to the unenhanced case.