Micro/nano acoustofluidics: materials, phenomena, design, devices, and applications

Abstract

Acoustic actuation of fluids at small scales may finally enable a comprehensive lab-on-a-chip revolution in microfluidics, overcoming long-standing difficulties in fluid and particle manipulation on-chip. In this comprehensive review, we examine the fundamentals of piezoelectricity, piezoelectric materials, and transducers; revisit the basics of acoustofluidics; and give the reader a detailed look at recent technological advances and current scientific discussions in the discipline. Recent achievements are placed in the context of classic reports for the actuation of fluid and particles via acoustic waves, both within sessile drops and closed channels. Other aspects of micro/nano acoustofluidics are examined: atomization, translation, mixing, jetting, and particle manipulation in the context of sessile drops and fluid mixing and pumping, particle manipulation, and formation of droplets in the context of closed channels, plus the most recent results at the nanoscale. These achievements will enable applications across the disciplines of chemistry, biology, medicine, energy, manufacturing, and we suspect a number of others yet unimagined. Basic design concepts and illustrative applications are highlighted in each section, with an emphasis on lab-on-a-chip applications.

Recent advances in direct current electrokinetic manipulation of particles for microfluidic applications

“…. A variety of force fields, ranging from the ubiquitous gravity to centrifugal , acoustic , electric , magnetic , optical , and flow fields, have thus far been demonstrated to manipulate particles for microfluidic applications. Each of these fields generates a particle motion, whose dependence on particle size and other physicochemical properties is significantly different from each other (Table ).…”

“…DC electric fields are involved in capillary (zone) electrophoresis [32], which drive both fluid electroosmosis and particle electrophoresis through straight uniform (both geometrically and physicochemically) microchannels [33,34]. A hydrodynamic pumping of the particulate solution, which is required in nearly all other field Gravity b) Sedimentation and centrifugation: Relative density of particles and fluids [11] a 2 Acoustic Acoustophoresis: Relative density and compressibility of particles and fluids [12] a 2…”

Enabling Rapid Charging Lithium Metal Batteries via Surface Acoustic Wave‐Driven Electrolyte Flow

“…By contrast, surface acoustic wave (SAW) devices offer extraordinary power density in a fingernail-sized device, and are useful in drop handling, biological sensors, cell manipulation, and particle collection in microfluidics. [14][15][16][17] Uniquely, they generate locally extreme accelerations of 10 8 -10 10 m s −2 , driving acoustic streaming-driven fluid flow at up to 1 m s −1 , and imparting acoustic forces upon objects present in the fluid, such as cells and micro to nanoscale particles. [18] SAW devices can be inexpensively produced through a standard ultraviolet photolithography and lift-off process to deposit interdigitated metallic electrodes onto a low-loss, single crystal piezoelectric Li niobate substrate, a commodity from decades of development and use in telecommunications.…”

“…However, the ultrasonicators in these past works have always been large, inefficient, electrochemically incompatible, and very heavy—unsuitable for integration into a practical LMB. By contrast, surface acoustic wave (SAW) devices offer extraordinary power density in a fingernail‐sized device, and are useful in drop handling, biological sensors, cell manipulation, and particle collection in microfluidics 14–17. Uniquely, they generate locally extreme accelerations of 10 8 –10 10 m s −2 , driving acoustic streaming‐driven fluid flow at up to 1 m s −1 , and imparting acoustic forces upon objects present in the fluid, such as cells and micro to nanoscale particles 18.…”

Leveraging collective effects in externally driven colloidal suspensions: experiments and simulations

“…Another way to drive colloidal particles is to use acoustic fields [96,97,98] 1 . Historically, acoustic waves have been used in microfluidics for particle sorting via acoustic levitation.…”