Enhanced micro-droplet splitting, concentration, sensing and ejection by integrating ElectroWetting-On-Dielectrics and Surface Acoustic Wave technologies

This paper demonstrates several enhanced microfluidic functions achieved by integrating two different micro droplet actuation systems (Surface Acoustic Waves (SAW) and ElectroWetting-On-Dielectric (EWOD)). The paper reports how SAW can be employed to help EWOD create and split droplets by augmenting the EWOD force to complete the operation. It also demonstrates how EWOD can be used to guide and precisely position microdroplets for further efficient SAW actuated movement (pumping), concentration and ejection of droplets. The paper also highlights how this combination can also be employed to position droplets for shear wave SAW sensing

Integrated microfluidics system using surface acoustic wave and electrowetting on dielectrics technology

This paper presents integrated microfluidic lab-on-a-chip technology combining surface acoustic wave (SAW) and electro-wetting on dielectric (EWOD). This combination has been designed to provide enhanced microfluidic functionality and the integrated devices have been fabricated using a single mask lithographic process. The integrated technology uses EWOD to guide and precisely position microdroplets which can then be actuated by SAW devices for particle concentration, acoustic streaming, mixing and ejection, as well as for sensing using a shear-horizontal wave SAW device. A SAW induced force has also been employed to enhance the EWOD droplet splitting function

Streaming phenomena in microdroplets induced by Rayleigh surface acoustic wave

This paper reports the numerical simulation and experimental characterization of three-dimensional acoustic streaming behavior of a liquiddroplet subjected to a Rayleigh surface acoustic wave. The streaming behavior of the droplet was studied as a function of radio-frequency (RF) power, aperture of the interdigitated transducer, and size of the liquiddroplet. The hydrodynamic flow field within the droplet was determined by solving the laminar incompressible Navier–Stoke’s equations. The numerical and experimental results are shown to be in good agreement over the range of parameters examined. The ratios of the position of butterfly central line (axis of rotation) to radius of the droplet are demonstrated to be fairly constant for moderate droplet volumes and to vary by less than 12% at large droplet volumes. Besides that, an increase in the RF power and a decrease in the droplet size result in an increased surface acoustic wave(SAW) streaming velocity. The numerical results also suggest that a maximum streaming velocity is achieved when the SAW width is approximately half of the droplet radius

Shear horizontal surface acoustic wave induced microfluidic flow

In this letter, we demonstrate that surface acoustic waves(SAWs) excited on 36°Y-X LiTaO3 have both Rayleigh and shear horizontal components, which can result in different acoustic streaming patterns in micro-droplets. The shear horizontal surface acoustic wave streaming pattern exhibits a quasi-stable counterflow in the SAW propagation direction with velocities of up to 16 mm/s, with minimal damping observed within the droplets. A pumping function was realized at a threshold power of 30 dBm with a large rotation vector on hydrophobically treated devices

Studies on the Heterogeneous Organic Antibody Part I Studies on the Vital Reaction by the Sensitization of Heterogeneous Organ

The various vital reactions occured to the sensitized animal were serologically observed on the sensitization of animal (rabbit) by the heterogeneous organic (gallbladder and colon) antigen. And the results were as follows. 1. The antibody reacting to the heterogeneous organic antigen was rapidly produced for 1-2 weeks after the beginning of the sensitization, on the sensitization by the heterogeneous organic antigen, it's antibody titer became the most high titer 3-4 weeks of the continuous sensitization and it continued for the fixed period. 2. As the vital reactions occured to the sensitized animals with the production of heterogenous antibody, the loss of weight decline of hemoglobin value and decrease of erythrocyte count, leukocytosis in the leukocyte count, lymphocytosis in the classification of leukocyte, decrease of total serum protein value and increase of γ-globulin in the serum protein picture and the vicissitude of α-, β-globulin preceeding to γ-globulin were observed. 3. The vicissitude of complement titer on the sensitization by the hetrogeneous organic (gallbladder and large intestine) antigen scarecely showed the change and it slightly showed the decreasing tendency at 5-6 week after th sensitization. 4. The heterogeneous organic antibody considerably showed the organic peculiarity to it's organic antigen on the crossreaction with each organic antigen. And the common antigenicity was partly observed on each organic antigen

Scaling effects on flow hydrodynamics of confined microdroplets induced by Rayleigh surface acoustic wave

This paper reports an experimental and numerical investigation on the scaling effects in the flow hydrodynamics for confined microdroplets induced by a surface acoustic wave (SAW). The characteristic parameters of the flow hydrodynamics were studied as a function of the separation height, H, between the LiNbO3 substrate and a top glass plate, for various droplets volumes and radio-frequency powers. The ratio of the gap height to attenuation length of the SAW, H/l SAW, is shown to be an important parameter affecting the streaming flow induced in this confined regime. The reported numerical and experimental results are in good agreement over the range examined in this study and demonstrate that, at a lower gap heights of H ≤ 100 μm, a significant decrease in streaming velocity or Reynolds number is induced, with the velocity approaching zero when the gap height is decreased to ~50 μm. An increase in the gap height results in an increased streaming velocity; however, if the gap height exceeds 70 % of the SAW attenuation length, any further increase in the gap height induces a drop in the streaming velocity

Nonlinear hydrodynamic effects induced by Rayleigh surface acoustic wave in sessile droplets

We report an experimental and numerical characterization of three-dimensional acoustic streaming behavior in small droplets of volumes (1–30 μl) induced by surface acoustic wave (SAW). We provide a quantitative evidence of the existence of strong nonlinear nature of the flow inertia in this SAW-driven flow over a range of the newly defined acoustic parameter F NA =Fλ / (σ/Rd) ≥0.01, which is a measure of the strength of the acoustic force to surface tension, where F is the acoustic body force, λ is the SAW wavelength, σ is the surface tension, and Rd is the droplet radius. In contrast to the widely used Stokes model of acoustic streaming, which generally ignores such a nonlinearity, we identify that the full Navier-Stokes equation must be applied to avoid errors up to 93% between the computed streaming velocities and those from experiments as in the nonlinear case. We suggest that the Stokes model is valid only for very small acoustic power of ≤1 μW (F NA <0.002). Furthermore, we demonstrate that the increase of F NA above 0.45 induces not only internal streaming, but also the deformation of droplets