Design and Fabrication of Piezoelectric Trampoline Resonators for Nanomechanical Photothermal Sensing

Nanomechanical photothermal sensing is a promising alternative technology to super-resolution microscopy; it relies on nanoparticles to overcome the common limitation of biochemical probes, namely photochemical instability and cell impermeability. Nanomechanical photothermal sensing images the nanoparticles using a scanning laser, which heats up the particles as it irradiates them. This causes the structure also to heat up, generating perturbation that can be sensed to indicate the nanoparticle presence. However, the sensitivity of this technology is currently limited by its low heat isolation characteristics, mainly due to the choice of magnetostrictive actuation. This report addresses this issue by introducing piezoelectric transduction for both actuation and detection, which generates minimal heating. Here, a piezoelectric-based device was designed to have heat isolation performance more than 10 times better than the state-of-the-art while also maximizing its transduction efficiency. Furthermore, the device fabrication method and parameters are shown, consisting of three main steps: piezoelectric stack fabrication, resonator fabrication, and device release. Finally, the device actuation and detection operation were confirmed and characterized. It was found that the piezoelectric actuation worked in vacuum with a quality factor of 9000 and a minimum Allan deviation of 0.8×10−6 at 1.25𝐻𝑧, measured using a laser Doppler vibrometer setup, and 1×10−7 at 0.3𝐻𝑧 using the piezoelectric detection.