Efficient modulated acoustic nebulisation for aerosol delivery and detection of plasma-activated water for surface disinfection and decontamination

Abstract

Chipscale surface and bulk acoustic nebulisers offer an efficient means for in situ production of plasma-activated aerosols for portable surface disinfection, although their adoption in practice is hampered by the low nebulisation rates that impose limits on the throughput and scalability of the platform. We demonstrate in this work the possibility of increasing the nebulisation rate of three different high frequency acoustic nebulisation platforms driven by surface, bulk (thickness mode) and hybrid (surface and bulk) acoustic waves through a unique hybrid modulation excitation scheme involving a combination of amplitude and pulse-width modulation. In particular, we show that such a hybrid modulation scheme provides stable nebulisation while maintaining the aerosol characteristics of these platforms, while substantially increasing the maximum peak surface acceleration on the piezoelectric substrate to yield efficiency gains in the nebulisation rate by up to 243%, albeit only over short intervals across a complete frequency cycle so as to limit increases in temperature that can be damaging to the device. While the hybrid modulation scheme works best with the SAW nebulisation platform, we also show the possibility of exploiting the bulk (Lamb) acoustic waves for detection of the electrical conductivity (>95% prediction accuracy via the neutral network) and hence ionic conductivity of the plasma-activated water, thereby facilitating the potential for concurrent detection during dispensing of the plasma-activated aerosols for disinfection in a low-cost portable integrated device that employs a common piezoelectric substrate material.