Strategies for Giant Mass Sensitivity Using Super-High-Frequency Acoustic Waves

Surface acoustic wave (SAW) devices are powerful platforms for mass sensing, chemical vapor or gas detection, and biomolecular identification. Great efforts have been made to achieve high sensitivities by using super-highfrequency SAW devices. Conventional SAW sensing is based on mass-loading effects at the acoustic wave propagation (or delay line) region between two interdigitated transducers (IDTs). However, formany super-high-frequencySAWdevices with their small sizes, there is a huge challenge that the sensitivity is difficult to be further increased, simply because there are very limited areas between the IDTs to deposit a sensing layer. Herein, we proposed a novel strategy based on giant mass-sensitivity effects generated on the global area of acoustic wave device (defined as areas of both delay line region and IDTs), which significantlyenhancessensitivity and reduces the detection limit of theSAWdevice. Both theoretical analysis and experimental results proved this new strategy and mechanism, which are mainly attributed to the efficient energy confinement at the IDTs' region for the super-highfrequency SAWdevices. The achievedmass sensitivity using this new strategy is as high as 2590 MHz center dot mm(2) center dot mu g(-1), which is about 500 times higher than that obtained from only using the acoustic wave propagation region with a SAW frequency of 4.43 GHz. Hypersensitive humidity detection has been demonstrated using this newly proposed sensing platform, achieving an extremely high sensitivity of 278 kHz/%RH and the fast response and recovery times of similar to 37 and similar to 35 s, respectively.

Automated summary

Surface acoustic wave (SAW) devices are powerful platforms for mass sensing, chemical vapor or gas detection, and biomolecular identification. A novel strategy based on giant mass-sensitivity effects on the global area of the SAW device is proposed to enhance sensitivity and reduce detection limit. The achieved mass sensitivity using this strategy is significantly higher than traditional methods.