Acoustophoretic contactless transport and handling of matter in air

Abstract

Levitation and controlled motion of matter in air have a wealth of potential applications ranging from materials processing to biochemistry and pharmaceuticals. We present a unique acoustophoretic concept for the contactless transport and handling of matter in air. Spatiotemporal modulation of the levitation acoustic field allows continuous planar transport and processing of multiple objects, from near-spherical (volume of 0.1-10 μL) to wire-like, without being limited by the acoustic wavelength. The independence of the handling principle from special material properties (magnetic, optical, or electrical) is illustrated with a wide palette of application experiments, such as contactless droplet coalescence and mixing, solid-liquid encapsulation, absorption, dissolution, and DNA transfection. More than a century after the pioneering work of Lord Rayleigh on acoustic radiation pressure, a path-breaking concept is proposed to harvest the significant benefits of acoustic levitation in air.acoustics | fluid | ultrasounds | manipulation | microfluidics

Optimisation of an acoustic resonator for particle manipulation in air

“…Acoustic levitation and transport of particles in air have been reported in the literature [17,[28][29][30], as has the ability to trap liquid droplets [31,32].…”

“…Manipulation of particles as small as 500 µm in an acoustic resonator has been demonstrated [17]. However, most work with small particles has been performed in water within microfluidic resonators [20,33,34].…”

“…A third method, to be investigated here, uses forces generated by an ultrasonic field [14,15]. This technique, also known as acoustophoresis, can be integrated into small-scale devices to manipulate particles and droplets in both liquids and gases [16,17].…”

Vibroacoustic handling and levitation of microparticles in air

“…By switching the driving conditions of the divided electrodes in the direction of the circle, the vibration plate nodal lines can be rotated, and trapped particles can be manipulated with a circular trajectory in air. In [2] an acoustophoretic concept for material contactless transport and handling in air is presented. Spatiotemporal modulation of the levitation acoustic field allows continuous processing and transport of several objects from close to spherical to wire type, but not limited to acoustic wavelength.…”

Inverted Leidenfrost-like Effect during Condensation

“…Droplet manipulation can be obtained using passive techniques such as wettability gradients or "designed" surface textures, 1−4 as well as using active techniques where droplets may respond to external stimuli such as vibrations, 5−7 light, 8,9 electric fields, 10 acoustics, 11 magnetic fields, 12,13 or cyclical mechanical deformation of the substrate. 14 In addition to the abovementioned methods, droplet manipulation in many heat transfer applications can also be obtained passively using in situ phase change processes as exemplified by the Leidenfrost effect 15,16 (Figure 1a), self-propelled motion during evaporation, 17,18 and water droplet motion during condensation on phase change materials (PCMs).…”