Effect of photoresist coating on the reusable resonant cantilever sensors for assessing exposure to airborne nanoparticles
Silicon cantilever resonators were designed and fabricated in various shapes and dimensions to be used in an airborne nanoparticle (NP) sensing application. For a repeatedly usable sensor, the cantilever surface was covered by a sacrificial layer of photoresist prior to the airborne NP sampling. Using the electrostatic precipitation method, airborne NPs were sampled on the cantilever. Within a lift-off process of wet cleaning, the photoresist layer was removed together with the trapped NPs. The resonant frequency and the quality factor (Q-factor) of the fundamental and higher order flexural modes of the silicon cantilevers were characterized for different thickness given by viscosity of the photoresist layer. It was found that the proposed recycling technique was most effective when a thin photoresist film was used. By using higher order resonant modes, Q-factors of more than 1000 in air were maintained even after the photoresist coating.