7861wileyonlinelibrary.com and electrical double layer overlapping and its effect on charge permselectivity and electroosmosis must be taken into account. They are indeed essential for applications, for example, detection of individual DNA molecules, [11] DNA stretching analysis, [12] energy conversion/ storage, [13][14][15] water purification, [16,17] and the investigation of liquid properties, [18] all very difficult to achieve in a microfluidic platform. However, the large surface and viscous forces that resist fluid motion at very small scales are associated with a low Reynolds number in most micro-or nanofluidic systems. Such low Reynolds number hydrodynamics pose significant challenges, not the least of which are the low fluid transport speeds that undermine micropumping [19] and the difficulty in generating turbulent vortices and irregular fluid flow required for micromixing. [20,21] In addition, fluid in microchannels is often manipulated with hydrostatic pressure, achieving well-controlled fluid flow remains a challenge. [22][23][24] The scenario worsens when it comes to pressure-driven flow in nanochannels with the requirement of much higher pressure [25,26] to produce fluid flow due to the power-law relation between the pressure and the cross-sectional size of the channel. [27] Chip-based fluidic actuators using surface acoustic waves (SAW) have become popular among microfluidic practitioners who continue to explore new applications in acoustofluidic integration. [28,29] Planar devices employing lithium niobate in conjunction with deposited and patterned interdigital electrodes (IDTs) were first reported in the 1960s by White and Voltmer, [30] delivering Rayleigh SAW as a nanometer-order amplitude electromechanical wave propagating from the IDT. [28] One of the most attractive aspects of using SAW for microfluidic actuation and manipulation is their very efficient fluidstructural coupling: most of the energy in the substrate is adjacent the solid-fluid interface, within four to five wavelengths of SAW from the surface. When SAWs come into contact with a fluid in its wave path, energy is leaked from the SAW into the fluid to form sound propagating at the Rayleigh angle from the solid-fluid interface owing to the mismatch of sound velocities between the fluid and the SAW in the substrate. [28] Most importantly, through the combination of acoustic streaming and direct acoustic forces on objects in the fluid, the MHz-order Controlled nanoscale manipulation of fluids and colloids is made exceptionally difficult by the dominance of surface and viscous forces. Acoustic waves have recently been found to overcome similar problems in microfluidics, but their ability to do so at the nanoscale remains curiously unexplored. Here, it is shown that 20 MHz surface acoustic waves (SAW) can manipulate fluids, fluid droplets, and particles, and drive irregular and chaotic fluid flow within fully transparent, high-aspect ratio 50-250 nm tall nanoslits fabricated via a new direct, room temperature bonding method for lithiu...