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Fast and controllable surface acoustic wave (SAW) driven digital microfluidic temperature changes are demonstrated. Within typical operating conditions, the direct acoustic heating effect is shown to lead to a maximum temperature increase of about 10 °C in microliter water droplets. The importance of decoupling droplets from other on-chip heating sources is demonstrated. Acoustic-heating-driven temperature changes reach a highly stable steady-state value in ?3 s, which is an order of magnitude faster than previously published. This rise time can even be reduced to ?150 ms by suitably tailoring the applied SAW-power excitation profile. Moreover, this fast heating mechanism can lead to significantly higher temperature changes (over 40 °C) with higher viscosity fluids and can be of much interest for on-chip control of biological and/or chemical reactions. Fast and controllable surface acoustic wave (SAW) driven digital microfluidic temperature changes are demonstrated. Small temperature changes in typical SAW microfluidic conditions and the possibility for rapid and controllable high temperature changes, for use with lab-on-a-chip devices, are shown.

The relevant length scales in sub-nanometer amplitude surface acoustic wave-driven acoustic streaming are demonstrated. We demonstrate the absence of any physical limitations preventing the downscaling of SAW-driven internal streaming to nanoliter microreactors and beyond by extending SAW microfluidics up to operating frequencies in the GHz range. This method is applied to nanoliter scale fluid mixing. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface chemical and biochemical functionalization is a fundamental process that is widely applied in many fields to add new functions, features, or capabilities to a material’s surface. Here, we demonstrate that surface acoustic waves (SAWs) can enhance the chemical functionalization of gold films. This is shown by using an integrated biochip composed by a microfluidic channel coupled to a surface plasmon resonance (SPR) readout system and by monitoring the adhesion of biotin-thiol on the gold SPR areas in different conditions. In the case of SAW-induced streaming, the functionalization efficiency is improved ≈ 5 times with respect to the case without SAWs. The technology here proposed can be easily applied to a wide variety of biological systems (e.g., proteins, nucleic acids) and devices (e.g., sensors, devices for cell cultures).

A miniaturized centrifugal microfl uidic platform for lab-on-a-chip applications is presented. Unlike its macroscopic Lab-on-a-CD counterpart, the miniature Lab-on-aDisc (miniLOAD) device does not require moving parts to drive rotation of the disc, is inexpensive, disposable, and signifi cantly smaller, comprising a 10-mm-diameter SU-8 disc fabricated through two-step photolithography. The disc is driven to rotate using surface acoustic wave irradiation incident upon a fl uid coupling layer from a pair of offset, opposing single-phase unidirectional transducers patterned on a lithium niobate substrate. The irradiation causes azimuthally oriented acoustic streaming with suffi cient intensity to rotate the disc at several thousand revolutions per minute. In this fi rst proof-of-concept, the capability of the miniLOAD platform to drive capillary-based valving and mixing in microfl uidic structures on a disc similar to much larger Lab-on-a-CD devices is shown. In addition, the ability to concentrate aqueous particle suspensions at radial positions in a channel in the disc dependent on the particles’ size is demonstrated. To the best of our knowledge, the miniLOAD concept is the fi rst centrifugal microfl uidic platform small enough to be self-contained in a handheld device.

On-chip functional blocks for sample preprocessing are necessary elements for the implementation of fully portable micrototal analysis systems (mu TAS). We demonstrate and characterize the microparticle and whole-blood manipulation capabilities of surface acoustic wave (SAW) driven counterflow micropumps. The motion of suspended cells in this system is governed by the two dominant acoustic forces associated with the scattered SAW (of wavelength ?f): acoustic-radiation force and acoustic-streaming Stokesian drag force. We show that by reducing the microchannel height (h) beyond a threshold value the balance of these forces is shifted toward the acoustic-radiation force and that this yields control of two different regimes of microparticle dynamics. In the regime dominated by the acoustic radiation force (h less than or similar to f), microparticles are collected in the seminodes of the partial standing sound-wave arising from reflections off microchannel walls. This enables the complete separation of plasma and corpuscular components of whole blood in periodical predetermined positions without any prior sample dilution. Conversely, in the regime dominated by acoustic streaming (h less than or similar to f), the microbeads follow vortical streamlines in a pattern characterized by three different phases during microchannel filling. This makes it possible to generate a cell-concentration gradient within whole-blood samples, a behavior not previously reported in any acoustic-streaming device. By careful device design, a new class of SAW pumping devices is presented that allows the manipulation and pretreatment of whole-blood samples for portable and integrable biological chips and is compatible with hand-held battery-operated devices.

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

We report on the design of two different surface acoustic wave (SAW) driven rotary motors. Both designs use 20-30 MHz transducers patterned onto Lithium Niobate (LN), geometrically tailored to generate Rayleigh waves that are incident on opposing sides of each rotor. The first design exploits the efficient coupling between SAWs and fluids by use of a fluid coupling layer between the rotor and substrate, leading to rotations of a 5 mm disc shaped rotor over 2,500 rpm with a start-up torque of 60 nN m. The second design exploits a dry friction contact between the surface and rotors for further miniaturisation. In the latter design 1 mm steel rotors are driven up to 6,000 rpm with no external preload required.

The association between physical activity, potential intermediate biomarkers and lung cancer risk was investigated in a study of 230 cases and 648 controls nested within the European Prospective Investigation of Cancer and Nutrition. Data on white blood cell aromatic-DNA adducts by 32P-post- labelling and glutathione (GSH) in red blood cells were available from a subset of cases and controls. Compared with the first quartile, the fourth quartile of recreational physical activity was associated with a lower lung cancer risk (odds ratio (OR) 0.56, 95% confidence interval (CI) 0.350.90), higher GSH levels (1.87 μmol GSH g-1 haemoglobin, p 0.04) but not with the presence of high levels of adducts (OR 1.05, 95% CI 0.382.86). Despite being associated with recreational physical activity, in these small-scale pilot analyses GSH levels were not associated with lung cancer risk (OR 0.95, 95% CI 0.841.07 per unit increase in GSH levels). Household and occupational activity was not associated with lung cancer risk or biomarker levels. © 2010 Informa UK Ltd.

The concentration and indeed mixing of particle suspensions are important procedures in microfluidic processes. Relying on diffusion for mixing leads to unreasonably long mixing times, and enhancing or avoiding it by promoting chaotic mixing typically relies on complex geometries. Concentric circular and elliptical single-phase unidirectional transducers (SPUDTs) were used to focus the SAW, with a straight SPUDT as a benchmark for comparison. Due to the increased wave intensity and asymmetry of the wave, we found both circular and elliptical SPUDTs concentrate particles in under one second, one order of magnitude faster than the straight SPUDT and several orders of magnitude faster than conventional microscale devices. The concentric circular SPUDT was found to be most effective at a given input power since it generated the largest azimuthal velocity gradient within the fluid to drive particle shear migration. On the other hand, the concentric elliptical SPUDT generated the highest micromixing intensity due to the more narrowly focused SAW radiation that substantially enhances acoustic streaming in the fluid.

The seaward migration of juvenile salmonids was monitored by the National Marine Fisheries Service (NMFS) at Bonneville and John Day Dams on the Columbia river in 1995. The NMFS Smolt Monitoring Project is part of a larger Smolt Monitoring Program (SMP) coordinated by the Fish Passage Center (FPC) for the Columbia Basin Fish and Wildlife Authority. This program focuses on protecting, mitigating, and enhancing fish populations affected by the development and operation of hydroelectric power plants on the Columbia River. The purpose of the SMP is to monitor the migration of the juvenile salmonid stocks in the Columbia basin and make flow and spill recommendations designed to facilitate fish passage. Data are also used for travel time, migration timing, and relative run size analysis. The purpose of the NMFS portion of the program is to provide FPC with species and project specific real time data from John Day and Bonneville Dams.