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Blood coagulation tests are a critical part in diagnosis of patients with bleeding disorders and cardiovascular diseases. However, most conventional blood coagulation tests require large and expensive instruments and skilled personnel. Here, we present a simple and low-cost approach to evaluate blood coagulation using Lamb wave-based device. To assess coagulation, we monitored the acoustic streaming of 5 μm fluorescent particles suspended in citrated plasma. Using a Lamb wave, citrated blood plasma and coagulation reagents can be mixed in a few seconds and the viscosity of the droplet increases due to blood coagulation. Then, the acoustic streaming of particles eventually stops, at which the “coagulation time” is defined. As a preliminary test, coagulation time was reduced with increasing calcium concentration from 0 to 25 mM. Prothrombin time results from the Lamb wave-based device were validated by comparing with those of commercial instruments with the correlation coefficient (R 2 ) as 0.9432. Using the Lamb wave for blood coagulation test, the temperature can be controlled as 37 °C simultaneously by modulating experimental conditions. Our device enables lithography-free, simple and low-cost measurement of blood coagulation, which can be applied to clinical settings and developing countries. [ABSTRACT FROM AUTHOR]

Sensors based on thin film electroacoustic (TEA) devices have emerged as a promising alternative to quartz crystal microbalance and surface acoustic wave devices, in view of sensibility, miniaturization and easy integration. TEA devices include quasi-shear film bulk acoustic resonators (QS-FBAR) and S 0 mode Lamb wave resonators (S 0 -LWR) based on AlN films. Despite the work done on the application of TEA devices as in-liquid biological and chemical sensors, a theoretical framework for S 0 -LWRs properly describing their sensing mechanisms is still needed. Here we validate a finite element analysis model on QS-FBARs and study the sensing mechanisms of S 0 -LWRs in liquid media. We show that S 0 -LWRs can sense changes in the dielectric permittivity of the liquid and demonstrate different sensitivities to viscosity and density. A complementary assessment of the S 0 -LWRs losses, dependent in a non-specific manner on the square root of the density viscosity product, provides the ability to discriminate density from viscosity changes on the entire device surface. Finally, with an S 0 -LWR optimization study we show that resolution improves with the decrease of the membrane thickness; however, a trade-off between sensitivity, quality factor and membrane fragility has to be considered. [ABSTRACT FROM AUTHOR]

Abstract: A new type of hydrogen sensor using Lamb waves is proposed and fabricated. The sensor consists of an aluminum thin plate-based hydrogen sensing medium that can be easily replaced, a medium grip component, and a piezoelectric sensor. In addition to structural uniqueness, the proposed hydrogen sensor provides two wave parameters, peak amplitude and phase shift, to detect changes in hydrogen concentration. The proposed sensor can provide reliable sensitivity, decreased fabrication and operational costs, and significantly increased lifetime because its hydrogen sensing medium can be replaced when it shows low sensitivity. [Copyright &y& Elsevier]