Questo lavoro è stato sponsorizzato dal fondo di ricerca accademica (AcRF) livello 1 (RG171/15), Ministero dell'istruzione, Singapore.

1. preparazione del canale microfluidico
<ol><li>Mescolare poli-dimetilsiloxano (PDMS) con un elastomero di base in un rapporto di 10:1.</li>
	<li>Degassare la miscela in un forno sottovuoto e versarlo su un wafer di silicio con un modello di photoresist tono negativo sulla parte superiore.</li>
	<li>Degassare il wafer di silicio a motivi nuovamente e scaldarlo a 70 ° C per 3 h in un'incubatrice per solidificazione.</li>
</ol>2. montaggio dei trasduttori Interdigital
<ol><li>Deposito 20 nm di Cr e 400 nm di su un wafer di3 LiNbO; modello 20 strisce con una larghezza di 150 µm e un'apertura di 2 cm su una maschera di plastica per fotolitografia depositando il photoresist positivo sul substrato.</li>
	<li>Rimuovere lo strato di Cr-sulla zona non esposte con acetone.</li>
	<li>Trattare la superficie del loro con plasma ad ossigeno (con un rapporto di azoto e ossigeno di 2:1) la potenza di 30 W per 60 s.</li>
	<li>Allineare il microchannel PDMS e legame al substrato3 LiNbO premendo con il pollice per pochi secondi.</li>
	<li>Posizionare il dispositivo integrato nella camera di riscaldamento a 60 ° C per 3 h.</li>
</ol>3. dual-frequenza eccitazione
<ol><li>Applicare contemporaneamente due componenti di frequenza (f1 e f3, la frequenza fondamentale e la terza armonica del fabbricato IDT, rispettivamente) con la differenza di fase φ tra di loro per la coppia di IDTs, affinché la sega prodotta può essere espressa come segue. <img alt="Equation 1" src="/files/ftp_upload/58085/58085eq1.jpg"> Qui, <img alt="Equation 2" src="/files/ftp_upload/58085/58085eq2.jpg">e <img alt="Equation 3" src="/files/ftp_upload/58085/58085eq3.jpg"> = le pressioni acustiche.</li>
	<li>Sintetizzare la forma d'onda doppia frequenza utilizzando l' Equation Editor del software applicativo di ArbExpress alla frequenza di campionamento di 100 MS/s e poi memorizzarlo per il generatore di funzioni come ingresso arbitrario per l'eccitazione di sega nell'esperimento via un cavo USB.</li>
	<li>Variare la potenza della frequenza fondamentale per la totale potenza emessa <img alt="Equation 4" src="/files/ftp_upload/58085/58085eq4.jpg"> da 100% (eccitazione alla frequenza puramente fondamentale) a 0% (eccitazione a puramente terza armonica); per un buon confronto, cambiare ma mantenere la potenza totale lo stesso.</li>
	<li>Variare la differenza di fase di eccitazione doppia frequenza da 0° a 360°.</li>
</ol>4. simulazione
<ol><li>Descrivere il moto del flusso incomprimibile laminare con basso Reynolds (cioè, Re = 0,55) e Mach i seguenti numeri35. <img alt="Equation 5" src="/files/ftp_upload/58085/58085eq5.jpg"> <img alt="Equation 6" src="/files/ftp_upload/58085/58085eq6.jpg"> Qui, <img alt="Equation 7" src="/files/ftp_upload/58085/58085eq7.jpg">= la velocità del fluido, <img alt="Equation 8" src="/files/ftp_upload/58085/58085eq8.jpg">= viscosità dinamica, <img alt="Equation 9" src="/files/ftp_upload/58085/58085eq9.jpg">= la densità del fluido, <img alt="Equation 10" src="/files/ftp_upload/58085/58085eq10.jpg">= la pressione del fluido, <img alt="Equation 11" src="/files/ftp_upload/58085/58085eq11.jpg">= la matrice di identità, e <img alt="Equation 12" src="/files/ftp_upload/58085/58085eq12.jpg">= una forza esterna.</li>
	<li>Descrivere la forza di trascinamento di Stoke prodotta sull'oggetto come segue36. <img alt="Equation 13" src="/files/ftp_upload/58085/58085eq13.jpg"> Qui, <img alt="Equation 14" src="/files/ftp_upload/58085/58085eq14.jpg">= il raggio della microparticella, <img alt="Equation 15" src="/files/ftp_upload/58085/58085eq15.jpg">= velocità del fluido, e <img alt="Equation 16" src="/files/ftp_upload/58085/58085eq16.jpg">= la velocità delle microparticelle.</li>
	<li>Derivare la forza di radiazione acustica applicata alla microparticella in microchannel lungo la x-asse (su tutta la larghezza di microchannel) presso una singola frequenza come segue16 . <img alt="Equation 17" src="/files/ftp_upload/58085/58085eq17.jpg"> Qui, <img alt="Equation 18" src="/files/ftp_upload/58085/58085eq18.jpg">= volume della microparticella, <img alt="Equation 19" src="/files/ftp_upload/58085/58085eq19.jpg">= la densità della microparticella, <img alt="Equation 20" src="/files/ftp_upload/58085/58085eq20.jpg">= la densità del mezzo, <img alt="Equation 21" src="/files/ftp_upload/58085/58085eq21.jpg">= la compressibilità della microparticella, e <img alt="Equation 22" src="/files/ftp_upload/58085/58085eq22.jpg">= la comprimibilità del mezzo.</li>
	<li>Derivare la forza risultante radiazione acustica dell'eccitazione doppia frequenza come segue. <img alt="Equation 23" src="/files/ftp_upload/58085/58085eq23.jpg">
</li>
	<li>Esprimere il movimento trasversa su tutta la larghezza del canale (lungo il y-axis) sotto la forza di radiazione acustica sia il Stokes trascinare forza disciplinato dalla seconda legge di Newton come segue. <img alt="Equation 24" src="/files/ftp_upload/58085/58085eq24.jpg">
</li>
	<li>Risolvere le equazioni differenziali ordinarie (ODEs) sopra utilizzando il metodo di Runge-Kutta di quarto ordine su un personal computer. Impostare il passo temporale e la durata totale come 1 µs e 20 s, rispettivamente.</li>
</ol>5. osservazione sperimentale
<ol><li>Girare la soluzione nella concentrazione di 5,9 x 107 con 4 µm verde fluorescente perle di polistirolo / 1 mL Vortex per circa 2-3 min e poi immergerlo in un sonicatore ultrasuoni per 10 minuti per distruggere qualsiasi agglomerazione prima di ogni test.</li>
	<li>Versare la miscela in una siringa da 3 mL e quindi guidare con una pompa a siringa ad una portata di 3-5 µ l/min.</li>
	<li>Guidare la IDT con il segnale di doppia frequenza da un generatore di funzione seguito da un amplificatore di potenza.</li>
	<li>Osservare le microparticelle stabilizzate nel microchannel a valle sotto un microscopio chiaro a un ingrandimento 40x e registrare l'immagine con una fotocamera digitale.</li>
	<li>Misurare la posizione delle microparticelle accumulate nelle immagini digitali acquisite utilizzando ImageJ e la scala stabilita e quindi determinare quantitativamente la concentrazione della microparticella accumulato con la luminosità di fluorescenza normalizzata a ogni nodo di pressione.</li>
</ol>

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Il movimento della microparticella in microchannel di un SSAW presso la doppia frequenza di eccitazione è stato studiato estesamente in questo studio, e una tecnica di campitura efficacemente sintonizzabile variando i segnali di due frequenze di eccitazione è stata sviluppata e testata. La produzione di tali una forma d'onda è facilmente realizzata dalla maggior parte dei generatori di funzione, e l'approccio di regolazione è molto conveniente. S12- sia S11-risposte in frequenza del fabbricato I...

LOC la tecnologia integra una o diverse funzioni su un microchip per biologia, chimica, biofisica e processi biomedici. LOC permette un setup del laboratorio su scala più piccola di Sub-millimetri, velocità di reazione veloce, un tempo di risposta breve, un controllo di processo ad alta, un consumo basso volume (meno costo reagenti dei rifiuti, più basso e meno volume di campione richiesto), un throughput elevato dovuto parallelizzazione, a basso costo in futuro la produzione di massa e conveniente monouso, un'elevata sicurezza per gli studi chimici, radioattivi o biologici e i vantaggi di un dispositivo compatto e portatile1,2. Manipolazione cellulare preciso (cioè, accumulo e separazione) è fondamentale in un basato su LOC analisi e diagnosi3,4. Tuttavia, l'accuratezza e la riproducibilità della microparticella manipolazione hanno una varietà di sfide. Molte tecniche, come elettro-osmosi5, dielettroforesi (DEP)6, magnetophoresis7, submicronica8,9, un approccio ottico10, un optoelettronici approccio11 , un approccio idrodinamico12e acoustophoresis13,14,15, sono stati sviluppati. In confronto, approcci acustici sono appropriati per un'applicazione di LOC perché, teoricamente, molti tipi di cellule e di microparticelle possono essere manipolati in modo efficace e non invadente con un sufficientemente elevato contrasto (densità e compressibilità) rispetto con il fluido circostante. Pertanto, rispetto ai loro omologhi, approcci acustici sono intrinsecamente idonei per la maggior parte delle microparticelle e oggetti biologici, non importa di loro proprietà ottiche, elettriche e magnetiche16.
Onde acustiche superficiali (Seghe) dal IDTs propagano per lo più sulla superficie di un substrato piezoelettrico allo spessore di diverse lunghezze d'onda e quindi perdita l'angolazione di Rayleigh nel fluido nel microchannel, secondo legge17, di Snell 18,19,20,21,22. Hanno i vantaggi tecnici di un'elevata efficienza energetica lungo la superficie a causa della loro localizzazione dell'energia, una grande flessibilità progettuale ad alta frequenza, un'integrazione di buon sistema con il canale di microfluidica e miniaturizzazione utilizzando tecnologia del sistema di micro-elettronici-meccanici (MEMS) e un elevato potenziale di produzione di massa23. In questo protocollo, seghe vengono generati da una coppia di identico IDTs e propagati in direzione opposta per generare un'onda stazionaria o SSAW, in microchannel, dove le microparticelle sospese sono spinti ai nodi di pressione, per lo più da acustica applicata forza di radiazione24. L'ampiezza di tale forza risultante è determinata dalla frequenza di eccitazione, microparticella dimensioni e relativo contrasto acustico fattore22,25.
Tale acoustophoresis ha la limitazione dei motivi di manipolazione predeterminati che non sono facilmente regolabili. La frequenza di eccitazione del IDTs è determinata dalla loro distanza periodica, quindi la larghezza di banda è piuttosto limitata. Diverse strategie sono state sviluppate per migliorare la funzionalità di accordabilità e manipolazione. La prima e la seconda modalità di onde stazionarie acustiche applicate in diverse parti del microchannel potrebbe separare microparticelle in modo più efficace in funzione delle velocità differenti di movimento verso le linee nodali26. Queste due modalità potrebbe essere applicata anche alla parte intera del microchannel e commutato in alternativa27,28,29. Tuttavia, per questo, un gran numero di attrezzature (cioè, tre generatori di funzione, due unità di adattamento di impedenza e un relè elettromagnetico) è richiesto, con la maggiore complessità di costo e controllo della disposizione sperimentale a causa del diverso impedenze elettriche presso la frequenza fondamentale e la terza armonica del piezoceramico piastra30. Inoltre, potrebbero essere applicati dito inclinato interdigital trasduttori (SFITs) per regolare le cellule e microparticelle patterning eccitando un periodo delle dita inclinate per una certa risonanza20,31. Tuttavia, allora, la larghezza di banda è inversamente proporzionale al numero di dita inclinate. Più linee nodali di pressione hanno una maggiore efficienza di separazione e la sensibilità rispetto alla singola linea nodale nel separatore convenzionale basato su SSAW microparticella. In alternativa, la posizione dei nodi pressione potrebbe anche essere cambiata semplicemente regolando la differenza di fase applicata alle due IDTs in progettazione32,33.
La frequenza fondamentale e la terza armonica del IDTs avere simili risposte in frequenza, in modo che essi possono essere eccitati simultaneamente, che fornisce ulteriori accordabilità per la manipolazione di microparticelle34. In confronto l'eccitazione di IDT convenzionale a una singola frequenza, regolazione pressioni acustiche di eccitazione doppia frequenza e la fase tra di loro fornisce tecniche unicità, come fino a ~ 2 volte ridotto tempo di movimento alla pressione nodale linea o il centro della microchannel, il vario numero e posizione delle linee nodali di pressione e le concentrazioni di microparticelle.

<table><tbody><tr><td>poly-dimethylsiloxane</td><td>Dow Corning</td><td>Sylgard 184</td><td></td></tr><tr><td>poly-dimethylsiloxane elastomer base</td><td>Dow Corning</td><td>Sylgard 184</td><td></td></tr><tr><td>silicon wafer</td><td>Bonda Technology</td><td>SI8PSPD</td><td></td></tr><tr><td>negative tone photoresist</td><td>Microchem</td><td>SU-8</td><td></td></tr><tr><td>double-side polished LiNbO&lt;sub&gt;3&lt;/sub&gt; wafer</td><td>University Wafer</td><td>Y-128&amp;deg;</td><td></td></tr><tr><td>positive photoresist</td><td>Nicolaus-Otto-Stra&amp;szlig;e</td><td>AZ 9260</td><td></td></tr><tr><td>oxygen plasma</td><td>Harrick Plasma</td><td></td><td></td></tr><tr><td>plastic mask</td><td>Infinite Graphics</td><td></td><td></td></tr></tbody></table>

microparticle manipulation by standing surface acoustic waves with dual-frequency excitations

Dimostriamo un metodo per aumentare la capacità aggiuntiva di un'onda acustica di superficie in piedi (SSAW) per la manipolazione delle microparticelle in un sistema di lab-on-a-chip (LOC). L'eccitazione simultanea della frequenza fondamentale e la terza armonica, che è definito come doppia frequenza di eccitazione, a una coppia di trasduttori interdigital (IDTs) potrebbe generare un nuovo tipo di permanente onde acustiche in un canale di microfluidica. Variando la potenza e la fase di eccitazione doppia frequenza segnali risultati in un campo riconfigurabile della forza di radiazione acustica applicata a microparticelle attraverso il microchannel (ad esempio, il numero e la posizione dei nodi pressione e la concentrazioni di microparticelle ai corrispondenti nodi di pressione). Questo articolo viene illustrato che può essere ridotto il tempo di movimento della microparticella nodo sola pressione ~ 2 volte presso il rapporto di potenza della frequenza fondamentale maggiore di ~ 90%. Al contrario, ci sono tre nodi di pressione nel microchannel se inferiore a questa soglia. Inoltre, regolando la fase iniziale tra la frequenza fondamentale e risultati del terzo armonici nei tassi di moto diversi i tre nodi di pressione SSAW, nonché della percentuale di microparticelle in ciascun nodo di pressione nel microchannel. C'è un buon accordo tra l'osservazione sperimentale e le previsioni numeriche. Questo metodo di eccitazione romanzo può in modo non invasivo e facilmente integrare nel sistema LOC, con un ampia sostenibilità e solo poche modifiche alla disposizione sperimentale.

Le distribuzioni di pressione acustica e la forza di radiazione acustica di un SSAW presso la doppia frequenza di eccitazione (6,2 e 18,6 MHz) sono mostrati nella Figura 1. Qui, la doppia frequenza di eccitazione si verifica su microparticelle polistirolo (4 µm di diametro) in un microchannel con una larghezza di 300 µm ad una potenza acustica di 146 mW. La pressione acustica risultante è sempre in fase quando P1 > 90%, così che una s...

Watch this Scientific Journal Video about Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations at JoVE.com

Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations

Un protocollo per manipolare le microparticelle in un canale di microfluidica con una doppia frequenza di eccitazione è presentato.

Manipolazione di microparticelle levandosi in piedi le onde acustiche superficiali con doppia frequenza eccitazioni

We demonstrate a method for increasing the tuning ability of a standing surface acoustic wave (SSAW) for microparticles manipulation in a lab-on-a-chip ...

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Universidad de Cartagena UDEC

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Unit 1

Application of Newton's Laws of Motion

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6.9K Views.  Nanyang Technological University. Un protocollo per manipolare le microparticelle in un canale di microfluidica con una doppia frequenza di eccitazione è presentato.

Video: Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations

Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects.

Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

Attivazione molecole, ioni e particelle solide con Acoustic Cavitazione

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic ...

Ricerca

Chimica

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

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.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

Fabbricazione, il funzionamento e la visualizzazione del flusso in superficiali acustiche onda-driven Microfluidics Acoustic-controcorrente

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

Ingegneria

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

Acoustofluidic devices use ultrasonic waves within microfluidic channels to manipulate, concentrate and isolate suspended micro and nanoscopic entities. This protocol describes the fabrication and operation of such a device supporting bulk acoustic standing waves to focus particles in a central streamline without the aid of sheath fluids.

Realizzazione e di funzionamento dei dispositivi che supportano Acoustofluidic Bulk onde acustiche piedi per guaina di messa a fuoco di particelle

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must ...

A Microfluidic Platform for Precision Small-volume Sample Processing and Its Use to Size Separate Biological Particles with an Acoustic Microdevice

A major advantage of microfluidic devices is the ability to manipulate small sample volumes, thus reducing reagent waste and preserving precious sample. However, to achieve robust sample manipulation it is necessary to address device integration with the macroscale environment. To realize repeatable, sensitive particle separation with microfluidic devices, this protocol presents a complete automated and integrated microfluidic platform that enables precise processing of 0.15&#8211;1.5 ml samples using microfluidic devices. Important aspects of this system include modular device layout and robust fixtures resulting in reliable and flexible world to chip connections, and fully-automated fluid handling which accomplishes closed-loop sample collection, system cleaning and priming steps to ensure repeatable operation. Different microfluidic devices can be used interchangeably with this architecture. Here we incorporate an acoustofluidic device, detail its characterization, performance optimization, and demonstrate its use for size-separation of biological samples. By using real-time feedback during separation experiments, sample collection is optimized to conserve and concentrate sample. Although requiring the integration of multiple pieces of equipment, advantages of this architecture include the ability to process unknown samples with no additional system optimization, ease of device replacement, and precise, robust sample processing.

This protocol describes a system architecture for performing automated small volume (0.15&#8211;1.5 ml) particle separations using a microfluidic device, and discusses methods to optimize acoustofluidic device performance and operation.

Una piattaforma per l&#39;elaborazione di precisione Microfluidic piccola Volume del campione e il suo uso per Dimensione particelle biologiche separate con un Microdevice Acoustic

A major advantage of microfluidic devices is the ability to manipulate small sample volumes, thus reducing reagent waste and preserving precious sample. ...

Bioingegneria

Multiplexing Focused Ultrasound Stimulation with Fluorescence Microscopy

By focusing low-intensity ultrasound pulses that penetrate soft tissues, LIPUS represents a promising biomedical technology to remotely and safely manipulate neural firing, hormonal secretion and genetically-reprogrammed cells. However, the translation of this technology for medical applications is currently hampered by a lack of biophysical mechanisms by which targeted tissues sense and respond to LIPUS. A suitable approach to identify these mechanisms would be to use optical biosensors in combination with LIPUS to determine underlying signaling pathways. However, implementing LIPUS to a fluorescence microscope may introduce undesired mechanical artefacts due to the presence of physical interfaces that reflect, absorb and refract acoustic waves. This article presents a step-by-step procedure to incorporate LIPUS to commercially-available upright epi-fluorescence microscopes while minimizing the influence of physical interfaces along the acoustic path. A simple procedure is described to operate a single-element ultrasound transducer and to bring the focal zone of the transducer into the objective focal point. The use of LIPUS is illustrated with an example of LIPUS-induced calcium transients in cultured human glioblastoma cells measured using calcium imaging.

Low-Intensity Pulsed Ultrasound Stimulation (LIPUS) is a modality for non-invasive mechanical stimulation of endogenous or engineered cells with high spatial and temporal resolution. This article describes how to implement LIPUS to an epi-fluorescence microscope and how to minimize acoustic impedance mismatch along the ultrasound path to prevent unwanted mechanical artefacts.

Multiplexing focalizzato ad ultrasuoni stimolazione con microscopia di fluorescenza

By focusing low-intensity ultrasound pulses that penetrate soft tissues, LIPUS represents a promising biomedical technology to remotely and safely ...

Fabrication of Nanoheight Channels Incorporating Surface Acoustic Wave Actuation via Lithium Niobate for Acoustic Nanofluidics

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order surface acoustic wave (SAW) devices generate tremendous acceleration on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid manipulation at the microscale, although more recently SAW has been used to produce similar phenomena at the nanoscale through an entirely different set of mechanisms. Controllable nanoscale fluid manipulation offers a broad range of opportunities in ultrafast fluid pumping and biomacromolecule dynamics useful for physical and biological applications. Here, we demonstrate nanoscale-height channel fabrication via room-temperature lithium niobate (LN) bonding integrated with a SAW device. We describe the entire experimental process including nano-height channel fabrication via dry etching, plasma-activated bonding on lithium niobate, the appropriate optical setup for subsequent imaging, and SAW actuation. We show representative results for fluid capillary filling and fluid draining in a nanoscale channel induced by SAW. This procedure offers a practical protocol for nanoscale channel fabrication and integration with SAW devices useful to build upon for future nanofluidics applications.

We demonstrate fabrication of nanoheight channels with the integration of surface acoustic wave actuation devices upon lithium niobate for acoustic nanofluidics via liftoff photolithography, nano-depth reactive ion etching, and room-temperature plasma surface-activated multilayer bonding of single-crystal lithium niobate, a process similarly useful for bonding lithium niobate to oxides.

Fabbricazione di canali Nanoheight che incorporano l'atuazione delle onde acustiche superficiali tramite Litio Niobate per la Nanofluidica acustica

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order ...

Fabrication of Surface Acoustic Wave Devices on Lithium Niobate

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order surface acoustic wave (SAW) devices generate enormous accelerations on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid handling at the microscale&#8212;and even at the nanoscale. In this paper we explicitly demonstrate two major fabrication methods of SAW devices on lithium niobate: the details of lift-off and wet etching techniques are described step-by-step. Representative results for the electrode pattern deposited on the substrate as well as the performance of SAW generated on the surface are displayed in detail. Fabrication tricks and troubleshooting are covered as well. This procedure offers a practical protocol for high frequency SAW device fabrication and integration for future microfluidics applications.

Two fabrication techniques, lift-off and wet etching, are described in producing interdigital electrode transducers upon a piezoelectric substrate, lithium niobate, widely used to generate surface acoustic waves now finding broad utility in micro to nanoscale fluidics. The as-produced electrodes are shown to efficiently induce megahertz order Rayleigh surface acoustic waves.&#160;

Fabbricazione di dispositivi a onde acustiche superficiali su Liithium Niobate

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order ...

Fabrication and Characterization of Thickness Mode Piezoelectric Devices for Atomization and Acoustofluidics

We present a technique to fabricate simple thickness mode piezoelectric devices using lithium niobate (LN). Such devices have been shown to atomize liquid more efficiently, in terms of &#64258;ow rate per power input, than those that rely on Rayleigh waves and other modes of vibration in LN or lead zirconate titanate (PZT). The complete device is composed of a transducer, a transducer holder, and a &#64258;uid supply system. The fundamentals of acoustic liquid atomization are not well known, so techniques to characterize the devices and to study the phenomena are also described. Laser Doppler vibrometry (LDV) provides vibration information essential in comparing acoustic transducers and, in this case, indicates whether a device will perform well in thickness vibration. It can also be used to &#64257;nd the resonance frequency of the device, though this information is obtained more quickly via impedance analysis. Continuous &#64258;uid atomization, as an example application, requires careful &#64258;uid flow control, and we present such a method with high-speed imaging and droplet size distribution measurements via laser scattering.

Fabrication of piezoelectric thickness mode transducers via direct current sputtering of plate electrodes on lithium niobate is described. Additionally, reliable operation is achieved with a transducer holder and &#64258;uid supply system and characterization is demonstrated via impedance analysis, laser doppler vibrometry, high-speed imaging, and droplet size distribution using laser scattering.

Fabbricazione e caratterizzazione dei dispositivi piezoelettrici della modalità Thickness per atomizzazione e acoustofluidica

We present a technique to fabricate simple thickness mode piezoelectric devices using lithium niobate (LN). Such devices have been shown to atomize liquid ...

Induction of Microstreaming by Nonspherical Bubble Oscillations in an Acoustic Levitation System

When located near biological barriers, oscillating microbubbles may increase cell membrane permeability, allowing for drug and gene internalization. Experimental observations suggest that the temporary permeabilization of these barriers may be due to shear stress that is exerted on cell tissues by cavitation microstreaming. Cavitation microstreaming is the generation of vortex flows which arise around oscillating ultrasound microbubbles. To produce such liquid flows, bubble oscillations must deviate from purely spherical oscillations and include either a translational instability or shape modes. Experimental studies of bubble-induced flows and shear stress on nearby surfaces are often restricted in their scope due to the difficulty of capturing shape deformations of microbubbles in a stable and controllable manner. We describe the design of an acoustic levitation chamber for the study of symmetry-controlled nonspherical oscillations. Such control is performed by using a coalescence technique between two approaching bubbles in a sufficiently intense ultrasound field. The control of nonspherical oscillations opens the way to a controlled cavitation microstreaming of a free surface-oscillating microbubble. High-frame rate cameras allow investigating quasi-simultaneously the nonspherical bubble dynamics at the acoustic timescale and the liquid flow at a lower timescale. It is shown that a large variety of fluid patterns may be obtained and that they are correlated to the modal content of the bubble interface. We demonstrate that even the high-order shape modes can create large-distance fluid patterns if the interface dynamics contain several modes, highlighting the potential of nonspherical oscillations for targeted and localized drug delivery.

A fast and reliable technique is proposed to control the shape oscillations of a single, trapped acoustic bubble that is based on coalescence technique between two bubbles. The steady-state, symmetry-controlled bubble shape oscillations allow analysis of the fluid flow generated in the vicinity of the bubble interface.

Induzione del microstreaming mediante oscillazioni di bolle non sferiche in un sistema di levitazione acustica

When located near biological barriers, oscillating microbubbles may increase cell membrane permeability, allowing for drug and gene internalization. ...

Assembly and Characterization of an External Driver for the Generation of Sub-Kilohertz Oscillatory Flow in Microchannels

Microfluidic technology has become a standard tool in chemical and biological laboratories for both analysis and synthesis. The injection of liquid samples, such as chemical reagents and cell cultures, is predominantly accomplished through steady flows that are typically driven by syringe pumps, gravity, or capillary forces. The use of complementary oscillatory flows is seldom considered in applications despite its numerous advantages as recently demonstrated in the literature. The significant technical barrier to the implementation of oscillatory flows in microchannels is likely responsible for the lack of its widespread adoption. Advanced commercial syringe pumps that can produce oscillatory flow, are often more expensive and only work for frequencies less than 1 Hz. Here, the assembly and operation of a low-cost, plug-and-play type speaker-based apparatus that generates oscillatory flow in microchannels is demonstrated. High-fidelity harmonic oscillatory flows with frequencies ranging from 10-1000 Hz can be achieved along with independent amplitude control. Amplitudes ranging from 10-600 &#181;m can be achieved throughout the entire range of operation, including amplitudes &#62; 1 mm at the resonant frequency, in a typical microchannel. Although the oscillation frequency is determined by the speaker, we illustrate that the oscillation amplitude is sensitive to fluid properties and channel geometry. Specifically, the oscillation amplitude decreases with increasing channel circuit length and liquid viscosity, and in contrast, the amplitude increases with increasing speaker tube thickness and length. Additionally, the apparatus requires no prior features to be designed on the microchannel and is easily detachable. It can be used simultaneously with a steady flow created by a syringe pump to generate pulsatile flows.

The protocol demonstrates a convenient method to produce harmonic oscillatory flow from 10-1000 Hz in microchannels. This is performed by interfacing a computer-controlled speaker diaphragm to the microchannel in a modular manner.

Assemblaggio e caratterizzazione di un driver esterno per la generazione di flussi oscillatori sub-kilohertz in microcanali

Microfluidic technology has become a standard tool in chemical and biological laboratories for both analysis and synthesis. The injection of liquid ...