Print Email Facebook Twitter Effect of droplet shrinking on surface acoustic wave response in microfluidic applications Title Effect of droplet shrinking on surface acoustic wave response in microfluidic applications Author Bui, T.H. (TU Delft Electronic Components, Technology and Materials) Nguyen, V.C. (Tohoku University) Vollebregt, S. (TU Delft Electronic Components, Technology and Materials) Morana, B. (TU Delft EKL-Users) van Zeijl, H.W. (TU Delft Electronic Components, Technology and Materials) Chu Duc, Trinh (Hanoi University of Engineering and Technology) Sarro, Pasqualina M (TU Delft Electronic Components, Technology and Materials) Date 2017 Abstract The effect of the contact angle and radius of a microsize droplet on the surface acoustic wave (SAW) response for microfluidic applications is reported. It is studied through the dynamic change of the droplet shape during the evaporation process. An aluminium nitride SAW device, operating at 125.7 MHz, is utilized to investigate the deformation of the droplet shape (contact angle and contact radius) caused by shrinking. The large cavity placed on the propagation path distorts the in-band SAW response one time at the centre frequency. The fractional coefficient of the SAW insertion loss, before and after dropping the liquid on the propagation path, is continuously recorded. The change in the fractional coefficient shows that the radiated acoustic kinetic energy depends on the contact area between the sessile micro-size droplet and the SAW device more than the contact angle of the droplet. Three droplet volumes have been considered, namely 0.05, 0.1 and 0.13 μl, and the electrical results show a better agreement with the theoretical data than the optical image data. The average duration of the fractional coefficient change for these cases is 420, 573 and 760 s, respectively. The effect of the hydrophobicity versus hydrophilicity of the contact surface on the duration of the fractional coefficient change is studied by coating the SAW with a silicon oxide or hexamethyldisilazane (HMDS) thin layer. For the same 0.05 μl sessile droplet on the hydrophobic surface, this duration is on average 110 s longer than that on the hydrophilic surface. Subject AcousticsMicrofluidicsPiezoelectricSAW devices To reference this document use: http://resolver.tudelft.nl/uuid:62010838-cb95-4ba2-b706-c75965ea7b1e DOI https://doi.org/10.1016/j.apsusc.2017.07.140 Embargo date 2019-07-29 ISSN 0169-4332 Source Applied Surface Science, 426, 253-261 Bibliographical note Accepted author manuscript Part of collection Institutional Repository Document type journal article Rights © 2017 T.H. Bui, V.C. Nguyen, S. Vollebregt, B. Morana, H.W. van Zeijl, Trinh Chu Duc, Pasqualina M Sarro Files PDF SAW_energy_emission_into_ ... ium_R2.pdf 1.35 MB Close viewer /islandora/object/uuid:62010838-cb95-4ba2-b706-c75965ea7b1e/datastream/OBJ/view