Flow by Surface Acoustic Waves

Diamondlike Carbon and Hard Carbon-Based Sensors Sensors that are based upon diamond technology include thermistors, pressure and flow sensors, radiation detectors, and surface acoustic wave devices [103]. The relative ease of depositing prepattemed, dielectrically isolated insulating and. semiconducting (boron-doped p type) diamond films has made polycrystalline diamond-based sensors low-cost alternatives to those based on conventional semiconductors. Diamondlike carbon and diamond films synthesized by chemical... 

The combination of chemical and biological sensors with flow injection has been demonstrated. Both more-traditional-type sensors such as pH electrodes and newer sensors such as fiber optics and surface acoustic wave detectors have been incorporated into FIA systems with success. An advantage that FIA brings to the sensor field is the possibility of turning a moderately selective sensor into a selective sensor by incorporating into the FIA system some type of selectivity enhancement technique such as gas diffusion, dialysis, and reactors. Finally the FIA systems permit renewable systems since sensor surfaces and reaction cells can be washed, surface regenerated, and reagents replenished on demand. 

The droplet-based microfluidic platforms for Lab-on-a-Chip applications can be fundamentally divided into two basic setups, the channel-based and the planar surface approach [2]. The channel-based systems are mostly pressure driven with droplet generation and manipulation relying on actuation via liquid flows within closed microchaimels. For the planar surface-based platforms, droplets can be arbitrarily moved in two dimensions representing planar programmable Lab-on-Chips. They are actuated by electrowetting (EWOD) or surface acoustic waves (SAW). 

Surface acoustic wave (SAW) devices are widely used for frequency filtering in mobile communications [1]. Recently published works [2-10] have demonstrated the use of SAWs to manipulate liquid flow in microfluidic devices. A SAW is excited by the application of a radiofrequency (rf) signal to an interdigital transducer (IDT) on a piezoelectric substrate such as quartz or LiNbOs. The... 

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

By means of method of visualization with the help of acoustic waves [1,2] we could get the microstructure images of steel samples on different depths from the surface. The analysis of acoustic images gave the possibility to calculate the dimensions of grains, to observe their transformation in the period of time or under external influences. In accordance with the theory of Hall - Peach there were defined the strength characteristics, for example flow limit ( Go,2) of the materials under study. The significance obtained o0 2 is in proper correspondence with values that are table one for the type of steel under consideration. 

The objective of this investigation was to determine the effects of vibration on heat 1 transfer and scaling mechanisms related to saline water conversion processes. During the initial phases of this study the effect of both vibration of the heat transfer surface and resonant acoustic vibrations in water on forced convection heat transfer was explored. Forced convection heat transfer was considerably more influenced by a vibrating heat transfer surface than by a standing acoustic wave in the flow medium. The major portion of this study was therefore concentrated on forced convection heat transfer from a vibrating heat transfer surface. 

We have developed a proprietary acoustic wave device which permits the detection of a specific analyte in a flowing system. By coupling specific chemistry (Protein A) to the surface of the device, the mass loading of the device by the target analyte (Human IgG) was detected as a shift in phase which was measured in real time. Using conditions which mimic a bioprocess separation for IgG, we were able to separate and detect Human IgG at 1 mg/ml and 100 ug/ml in the absence and presence of 10% Fetal Bovine Serum. Such a detector has the potential to increase productivity in process chromatography in biopharmaceutical applications. 

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