Extending the lifetime of resonant atmospheric particulate mass sensors with solvent rinses

The cleaning of a collection-based sensor extends its lifetime and reduces its effective cost. Existing cleaning regimes for silicon-based devices typically require access to large laboratory equipment. A simple cleaning method based on solvent rinses is presented here for the application of microresonator atmospheric particulate mass sensors. The suggested approach is intended for scenarios with limited access to laboratory equipment. Two piezoelectric resonator topologies (in-plane bulk mode and out-of-plane flexural) collected particles via impaction for an hour before rinsing. The solvent rinses reset the resonant frequency and quality factor of each resonator to within 0.4% and 10% of their original values, respectively. Subsequent mass collections were largely repeatable despite fluctuations in particle concentration and deposition location. The presented method provides a straightforward but effective cleaning method for soluble particulate removal. A physical cleaning method is required after substantial insoluble particle adsorption

Reducing dissipation in piezoelectric flexural microplate resonators in liquid environments

© 2017 Elsevier B.V. While piezoelectric microplates are emerging as a promising MEMS liquid-based sensing platform, often acoustic radiation losses limit device performance. This paper presents a new analysis of microplate acoustic radiation losses through the use of traditional analytical models for the fundamental mode and a new finite element model that is used to analyze trends affecting Q for both the fundamental and higher order flexural modes. Results from these models are compared with experimental measurements of frequency and Q measured using both electrical characterization and the laser Doppler vibrometer for multiple modes of the microplate in water as compared to air and vacuum. Finally, a microplate mode with a high initial Q of around 150 in air and that demonstrates an increase in Q going from air to water is presented as a strong candidate for use in droplet based sensing applications

Solid-state nanopore sensors

Nanopore-based sensors have established themselves as a prominent tool for solution-based, single-molecule analysis of the key building blocks of life, including nucleic acids, proteins, glycans and a large pool of biomolecules that have an essential role in life and healthcare. The predominant molecular readout method is based on measuring the temporal fluctuations in the ionic current through the pore. Recent advances in materials science and surface chemistries have not only enabled more robust and sensitive devices but also facilitated alternative detection modalities based on field-effect transistors, quantum tunnelling and optical methods such as fluorescence and plasmonic sensing. In this Review, we discuss recent advances in nanopore fabrication and sensing strategies that endow nanopores not only with sensitivity but also with selectivity and high throughput, and highlight some of the challenges that still need to be addressed