Open Access
Holographic acoustic elements for manipulating levitating particles. Applications in human-computer interaction
(2016) Marzo Pérez, Asier; Ardaiz Villanueva, Óscar; Ingeniería Matemática e Informática; Matematika eta Informatika Ingeniaritza
En esta tesis doctoral demostramos simultáneamente atrapamiento 3D, traslación y rotación de las partículas utilizando dispositivos de una sola cara. Esto se logra mediante el ajuste de manera óptima los retardos de fase usados para alimentar los transductores; de esta manera se generan estructuras acústicas sin precedentes y sin recurrir a lentes físicas, transductores hechos a medida o accionamiento mecánico. Nuestro método genera trampas óptimas en las posiciones deseadas con cualquier disposición espacial de los transductores; además, mejora significativamente los manipuladores anteriores. Presentamos tres trampas acústicas óptimas: trampas pinza, un nuevo fenómeno acústico que también puede rotar objetos; trampas tornado, cuyas capacidades de levitación se mostraron teóricamente y recientemente se observaron experimentalmente usando una lente acústica fija; y trampas en botella, que nunca han sido ni probadas ni sugeridas para levitar objetos. También introducimos el concepto de elementos holográficos acústicos basado en la interpretación de los retardos de fase como una placa holográfica que combina la codificación de elementos acústicos. Esta teoría permite el análisis y la generación eficiente de trampas acústicas, así como comparaciones con trampas ópticas. Este trabajo lleva las ventajas de la levitación óptica (es decir, un solo haz, rotación, control holográfico y múltiples partículas) a la eficiencia y versatilidad de la levitación acústica. Como resultado, esperamos el desarrollo de potentes rayos tractores, pantallas físicas 3D o control de micro-máquinas que están dentro de nuestro cuerpo. Nuevas aplicaciones en interacción hombre-máquina (IHM) se pueden derivar de la posibilidad de posicionar en medio del aire objetos a distancia e incluso a través de obstáculos. En la configuración más básica, movemos partículas sobre una superficie para pintar sobre la arena o líquidos a distancia y sin contacto. Un sistema más avanzado puede posicionar un par de objetos en 3D, esto nos permite representar funciones y posiciones de objetos tales como aviones o asteroides. El objetivo final sería crear un display compuesto de cientos de partículas que levitan de forma independiente para formar diferentes formas.
Open Access
Holographic acoustic elements for manipulation of levitated objects
(Nature Publishing Group, 2015) Marzo Pérez, Asier; Seah, Sue Ann; Drinkwater, Bruce W.; Sahoo, Deepak Ranjan; Long, Benjamin; Subramanian, Sriram; Ingeniería Matemática e Informática; Matematika eta Informatika Ingeniaritza
Sound can levitate objects of different sizes and materials through air, water and tissue. This allows us to manipulate cells, liquids, compounds or living things without touching or contaminating them. However, acoustic levitation has required the targets to be enclosed with acoustic elements or had limited manoeuvrability. Here we optimize the phases used to drive an ultrasonic phased array and show that acoustic levitation can be employed to translate, rotate and manipulate particles using even a single-sided emitter. Furthermore, we introduce the holographic acoustic elements framework that permits the rapid generation of traps and provides a bridge between optical and acoustical trapping. Acoustic structures shaped as tweezers, twisters or bottles emerge as the optimum mechanisms for tractor beams or containerless transportation. Single-beam levitation could manipulate particles inside our body for applications in targeted drug delivery or acoustically controlled micro-machines that do not interfere with magnetic resonance imaging.
Open Access
Numerical and experimental investigation of the stability of a drop in a single-axis acoustic levitator
(American Institute of Physics, 2019) Brizzotti Andrade, Marco Aurélio; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Acoustic levitation can be employed to hold liquid drops in midair, enabling novel applications in X-ray scattering of proteins, amorphous crystallization of solutions, or contactless mixing. Multiple studies have characterized the physical behavior of a levitated drop inside an acoustic field. Here, we present a numerical and experimental study on the acoustic levitation of water drops in a single-Axis acoustic levitator consisting of an ultrasonic transducer and an opposing reflector. Instead of modeling an abstract incident acoustic field, our model considers the shape of the drop as well as the real geometry of the levitator. We also use a high-speed camera to observe the disintegration and the undesired oscillations of the drops. Our results show that the insertion of a drop in the levitator provokes a shift in its resonant frequency that depends on the shape of the drop. Second, the levitation behavior depends on whether the levitator operates slightly below or above the resonance. Third, if the levitator is driven above the resonant frequency, it is possible to levitate with more strength and avoid disintegration of the drop. This research provides an insight on how to achieve more stable experiments that avoid the bursting and undesired oscillations of the levitated sample. We hope that it will facilitate numerous experiments involving acoustically levitated liquid drops.
Open Access
Acoustic virtual vortices with tunable orbital angular momentum for trapping of Mie particles
(American Physical Society, 2018) Marzo Pérez, Asier; Caleap, Mihai; Drinkwater, Bruce W.; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Acoustic vortices can transfer angular momentum and trap particles. Here, we show that particles trapped in airborne acoustic vortices orbit at high speeds, leading to dynamic instability and ejection. We demonstrate stable trapping inside acoustic vortices by generating sequences of short-pulsed vortices of equal helicity but opposite chirality. This produces a “virtual vortex” with an orbital angular momentum that can be tuned independently of the trapping force. We use this method to adjust the rotational speed of particles inside a vortex beam and, for the first time, create three-dimensional acoustics traps for particles of wavelength order (i.e., Mie particles).
Open Access
Avatarians: playing with your friends' data
(ACM, 2012) Marzo Pérez, Asier; Ardaiz Villanueva, Óscar; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Gobierno de Navarra / Nafarroako Gobernua
This article describes a new game mechanic called Game Entity Social Mapping (GESM) based on using social networking data fetched from a remote site about the player and his contacts to create characters, items or scenarios. A preliminary evaluation consisting of applying this mechanic to three different games was conducted. A small number of users tested those games to measure the enjoyment and learning about their contacts information.
Open Access
Nonlinear trapping stiffness of mid-air single-axis acoustic levitators
(American Institute of Physics, 2018) Fushimi, Tatsuki; Hill, Thomas L.; Marzo Pérez, Asier; Drinkwater, Bruce W.; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
We describe and experimentally explore a nonlinear stiffness model of the trapping of a solid particle in a single-axis acoustic levitator. In contrast to the commonly employed linear stiffness assumption, our nonlinear model accurately predicts the response of the system. Our nonlinear model approximates the acoustic field in the vicinity of the trap as a one-dimensional sinusoid and solves the resulting dynamics using numerical continuation. In particular, we predict a softening of stiffness with amplitude as well as period-doubling bifurcations, even for small excitation amplitudes of 2% of the wavelength. These nonlinear dynamic features are observed experimentally in a single-axis levitator operating at 40 kHz and trapping millimetre-scale expanded polystyrene spheres. Excellent agreement between the observed and predicted behaviour is obtained suggesting that this relatively simple model captures the relevant physical phenomena. This new model enables the dynamic instabilities of trapped particles to be accurately predicted, thereby benefiting contactless transportation and manipulation applications
Open Access
Automatic contactless injection, transportation, merging, and ejection of droplets with a multifocal point acoustic levitator
(AIP Publishing, 2018) Brizzotti Andrade, Marco Aurélio; Camargo, Thales S. A.; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
We present an acoustic levitation system that automatically injects, transports, merges and ejects liquid droplets in mid-air. The system consists of a phased array operating at 40 kHz on top of a plane reflector. The phase array generates multiple focal points at independent positions that form standing waves between the array and the reflector. In the reflector there is an inlet for a piezoelectric droplet injector which automatically inserts liquid droplets at the lower pressure nodes of the standing waves, and a hole that serves as an outlet for ejecting the processed droplets out of the system. Simulations of the acoustic radiation potential acting on the levitating droplets are in good agreement with the experiments. High-speed footage captured the functioning of the system in four fluidic operations: injection, transport, merging and ejection of liquid droplets. Having these operations integrated reliably into a single automatic system paves the way for the adoption of mid-air acoustophoretic processing in biological, chemical and pharmaceutical applications.
Open Access
Experimental investigation of the particle oscillation instability in a single-axis acoustic levitator
(AIP Publishing, 2019) Brizzotti Andrade, Marco Aurélio; Polychronopoulos, Spyros; Memoli, Gianluca; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Single-axis acoustic levitators are employed in biomedicine, chemistry and physics experiments due to their ability to trap in mid-air objects of a wide range of materials and sizes. Although this type of levitator has been studied for decades, there are effects that are not well understood. One of these effects is the particle oscillation instability, in which the levitating particle starts to oscillate with increasing amplitude until it is ejected out of the levitator. Most of the operations performed with acoustic levitation require high accuracy regarding the positioning of the particle, thus a lack of stability severely hinders the experiments. In this paper, we present an experimental setup that consists of a single-axis levitator, a mechanized stage to control the separation between the emitter and the reflector, a scale to measure the radiation force and a high-speed camera. We experimentally investigate the effect of the distance between the emitter and the reflector on the apparatus resonant frequency and on levitation stability. In accordance with previous theoretical studies, three types of levitation behavior were experimentally identified: stable levitation, oscillation of constant amplitude and unstable oscillation. We also show that the type of levitation behavior can be controlled by changing the distance between the emitter and the reflector.
Open Access
Acoustic lock: position and orientation trapping of non-spherical sub-wavelength particles in mid-air using a single-axis acoustic levitator
(American Institute of Physics, 2018) Cox, L; Croxford, A; Drinkwater, Bruce W.; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
We demonstrate acoustic trapping in both position and orientation of a non-spherical particle of sub-wavelength size in mid-air. To do so, we multiplex in time a pseudo-one-dimensional vertical standing wave and a twin-trap; the vertical standing wave provides converging forces that trap in position, whereas the twin-trap applies a stabilising torque that locks the orientation. The device operates at 40 kHz, and the employed multiplexing ratio of the 2 acoustic fields is 100:50 (standing:twin) periods. This ratio can be changed to provide tunability of the relative trapping strength and converging torque. The torsional spring stiffness of the trap is measured through simulations and experiments with good agreement. Cubes from k/5.56 (1.5 mm) to k/2.5 (3.4 mm) side length were stably locked. We also apply this technique to lock different non-spherical particles in midair: cubes, pyramids, cylinders, and insects such as flies and crickets. This technique adds significant functionality to mid-air acoustic levitation and will enable applications in micro-scale manufacturing as well as containment of specimens for examination and 3D-scanning.
Open Access
Acoustophoretic volumetric displays using a fast-moving levitated particle
(AIP Publishing, 2019) Fushimi, Tatsuki; Marzo Pérez, Asier; Drinkwater, Bruce W.; Hill, Thomas L.; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Displays have revolutionized the way we work and learn, and thus, the development of display technologies is of paramount importance. The possibility of a free-space display in which 3D graphics can be viewed from 360° without obstructions is an active area of research - holograms or lightfield displays can realize such a display, but they suffer from clipping and a limited field of view. Here, we use a phased array of ultrasonic emitters to realize a volumetric acoustophoretic display in which a millimetric particle is held in midair using acoustic radiation forces and moved rapidly along a 3D path. Synchronously, a light source illuminates the particle with the target color at each 3D position. We show that it is possible to render simple figures in real time (10 frames per second) as well as raster images at a lower frame rate. Additionally, we explore the dynamics of a fast-moving particle inside a phased-array levitator and identify potential sources of degradation in image quality. The dynamics are nonlinear and lead to distortion in the displayed images, and this distortion increases with drawing speed. The created acoustophoretic display shows promise as a future form of display technology.