Droplet Streaming and Nebulization Induced by the Shear Horizontal Surface Acoustic Wave

Droplet streaming and nebulization on a shear horizontal surface acoustic wave device made of 36o Y-cut LiTaO3 have been reported. The streaming pattern inside the droplet is sensitive to the droplet shape, the position to the interdigital transducer, and the aperture size. Droplet nebulization was enhanced with the increased aperture size of the driven IDTs and mainly occurred in horizontal direction along two lateral sides of the droplet, which is perpendicular to the designed SAW propagation direction. The atomization duration increases with the droplet size and decreases with the driven power at a given droplet size. The maximum rate of the atomization is ~0.2 μL/s at an applied power of 6.7 W. This provides a simple and effective method of the integration of both bio-liquid sensing and fluid manipulation on a single substrate for lab-on-chip biosensing platform.

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Evaluation of Shear Horizontal Surface Acoustic Wave Biosensors Using “Layer Parameter” Obtained from Sensor Responses during Immunoreaction

Sensors ◽

10.3390/s21144924 ◽

2021 ◽

Vol 21 (14) ◽

pp. 4924

Author(s):

Koji Kano ◽

Hiromi Yatsuda ◽

Jun Kondoh

Keyword(s):

Acoustic Wave ◽

Surface Acoustic Wave ◽

Horizontal Surface ◽

Propagation Characteristics ◽

Viscosity Change ◽

Layer Parameter ◽

Antibody Reaction ◽

Antigen Antibody ◽

Shear Horizontal ◽

Molecular Dimensions

Shear horizontal surface acoustic wave (SH-SAW) biosensors measure the reaction of capture antibodies immobilized on the sensing surface to capture test molecules (antigens) by using the change in SH-SAW propagation characteristics. SH-SAW displacement exists not only on the SH-SAW propagating surface, but also partially penetrates the specimen liquid to a certain depth, which is determined by the liquid properties of the specimen and the operating frequency of the SH-SAW. This phenomenon is called viscosity penetration. In previous studies, the effect of viscosity penetration was not considered in the measurement of SH-SAW biosensors, and the mass or viscosity change caused by the specific binding of capture antibodies to the target antigen was mainly used for the measurement. However, by considering the effect of viscosity penetration, it was found that the antigen–antibody reaction could be measured and the detection characteristics of the biosensor could be improved. Therefore, this study aims to evaluate the detection properties of SH-SAW biosensors in the surface height direction by investigating the relationship between molecular dimensions and SH-SAW propagation characteristics, which are pseudo-changed by varying the diameter of gold nanoparticles. For the evaluation, we introduced a layer parameter defined by the ratio of the SH-SAW amplitude change to the SH-SAW velocity change caused by the antigen–antibody reaction. We found a correlation between the layer parameter and pseudo-varied molecular dimensions. The results suggest that SH-SAW does not only measure the mass and viscosity but can also measure the size of the molecule to be detected. This shows that SH-SAW biosensors can be used for advanced functionality.

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