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
Using low-frequency sound to create non-contact sensations on and In the body
(Association for Computing Machinery, 2024-05-11) Hassan, Waseem; Marzo Pérez, Asier; Hornbæk, Kasper; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
This paper proposes a method for generating non-contact sensations using low-frequency sound waves without requiring user instrumentation. This method leverages the fundamental acoustic response of a confined space to produce predictable pressure spatial distributions at low frequencies, called modes. These modes can be used to produce sensations either throughout the body, in localized areas of the body, or within the body. We first validate the location and strength of the modes simulated by acoustic modeling. Next, a perceptual study is conducted to show how different frequencies produce qualitatively different sensations across and within the participants' bodies. The low-frequency sound offers a new way of delivering non-contact sensations throughout the body. The results indicate a high accuracy for predicting sensations at specific body locations.
Open Access
Comparing a mid-air two-hand pinching point-and-click technique with mouse, keyboard and touchfree
(Association for Computing Machinery, 2024-01-18) Lafuente Duque, Melchor; Elizondo Martínez, Sonia; Fernández Ortega, Unai Javier; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Some of our daily activities are performed by interacting with public touchscreens, such as food kiosks, bank tellers and newsstands. Nonetheless, the physical contact with these screens that are used by different people may be considered unhygienic. To avoid contact, some screens already integrate one-hand contactless interaction technologies, i.e. Leap Motion Controller, though they may lead to arm fatigue and slow performance. We present LeapPointer, a mid-Air two-hand pinching point-And-click technique. Specifically, this technique relies on a Leap Motion device to track both hands, and proposes a new software tool that allows bimanual selection through pointing and pinching gestures. A user study was performed to compare LeapPointer with two other techniques: The common mouse/keyboard and the current UltraLeap's TouchFree technique. Task completion time and accuracy as well as subjective data were gathered. The analysis of these data suggested that LeapPointer is significantly faster than the other touchless technique although less accurate. Self-reported fatigue was less with LeapPointer than with TouchFree.
Open Access
Full-space metasurface at millimeter-wave frequencies
(IEEE, 2023) Ruiz Fernández de Arcaya, María; Marzo Pérez, Asier; Beruete Díaz, Miguel; Institute of Smart Cities - ISC
Conventional metasurfaces provide control over the electromagnetic waves in a single working frequency operating either in transmission or reflection. Full-Space Metasurfaces (FSM) are an extension that allows operation at two different frequencies with independent functionalities in transmission and reflection. This paper presents a gradient index FSM device based on a 3-layered unit cell where the phase modulation is implemented following the Pancharatman-Berry (PB) principle. The device is designed to operate at millimeter waves, with the lowest frequency operating in reflection and the highest one in transmission. To check the structure performance, a metasurface was designed to provide beam steering in reflection at 49.4 GHz and an amplitude image hologram in transmission at 104 GHz.
Open Access
Mental workload of guiding devices: directional pulling forces, vibrotactile stimuli and audio cues
(Association for Computing Machinery, 2024-06-19) Donkov Bogdanov, Stefan; Elizondo Martínez, Sonia; Ezcurdia Aguirre, Íñigo Fermín; Sarasate Azcona, Iosune; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Asymmetric vibrations are known to produce a pulling sensation when stimulating the human hand. This effect has been exploited as a means of guidance. We conducted a user study to compare asymmetric vibrations, simple vibration, and sound cues for guidance in terms of task completion time and mental workload. Mental workload was evaluated (N=22) using the dual-task paradigm with a Stroop test and arithmetic operations test as secondary tasks. Audio cues improved significantly the task completion time for baseline and stroop tasks compared to the other methods. No significant differences were found for the reaction time for the guiding task. The use of audio cues was evaluated as the less mentally demanding guiding method on the NASA-TLX questionnaire.
Open Access
Smarterial – Smart matter optomagnetic
(2021) Irisarri Erviti, Josu; Marzo Pérez, Asier; Galarreta Rodríguez, Itziar; Estatistika, Informatika eta Matematika; Ingeniaritza; Zientziak; Institute of Smart Cities - ISC; Institute for Advanced Materials and Mathematics - INAMAT2; Estadística, Informática y Matemáticas; Ingeniería; Ciencias
Smart materials, also known as programmable materials, are a combination of different components that have the capability to change shape, move around and adapt to numerous situations by applying an external controllable field. Previous works have used optically guided matter or magnetically actuated materials, but similarly to soft robots, they are limited in spatial resolution or strength. Here we propose combining a low temperature thermoplastic polymer Polycaprolactone (PCL) with ferromagnetic powder particles (Fe). Focused light can heat this compound at specific locations and make it malleable. These heated spots can be actuated by external magnetic fields. Once the material cools down, this process can be repeated, or reversed. The compound can be actuated contact-less in the form of 3D slabs, 2D sheets, and 1D filaments. We show applications for reversible tactile displays and manipulation of objects. The laboratory team has characterised the density, weight, magnetic attraction, magnetic force, phase change, thermal and electrical conductivity and heat difusión (spread point test) for smart ferromagnetic compounds of different mixture proportions. The main advantages of this smart matter optomagnetic are the high spatial resolution of light and the strong force of magnetic attraction whilst mechanical properties of polymers are practically conserved. Due to the low temperature required and the possibility to use infrared or electromagnetic induction to heat the compound, the smart material can be used in air, water, or inside biological tissue. Eventually, Smart materials will enrich collaborative movements, such as grab and hold, and more complex ones, as reshaping and reassembling.
Open Access
TipTrap: a co-located direct manipulation technique for acoustically levitated content
(Association for Computing Machinery, 2022) Jankauskis, Eimontas; Elizondo Martínez, Sonia; Montano Murillo, Roberto; Marzo Pérez, Asier; Martinez Plasencia, Diego; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
Acoustic levitation has emerged as a promising approach for mid-air displays, by using multiple levitated particles as 3D voxels, cloth and thread props, or high-speed tracer particles, under the promise of creating 3D displays that users can see, hear and feel with their bare eyes, ears and hands. However, interaction with this mid-air content always occurred at a distance, since external objects in the display volume (e.g. user’s hands) can disturb the acoustic fields and make the particles fall. This paper proposes TipTrap, a co-located direct manipulation technique for acoustically levitated particles. TipTrap leverages the reflection of ultrasound on the users’ skin and employs a closed-loop system to create functional acoustic traps 2.1 mm below the fingertips, and addresses its 3 basic stages: selection, manipulation and deselection. We use Finite-Differences Time Domain (FDTD) simulations to explain the principles enabling TipTrap, and explore how finger reflections and user strategies influence the quality of the traps (e.g. approaching direction, orientation and tracking errors), and use these results to design our technique. We then implement the technique, characterizing its performance with a robotic hand setup and finish with an exploration of the ability of TipTrap to manipulate different types of levitated content.
Open Access
Comparison of experiment and simulation of ultrasonic mid-air haptic forces
(IEEE, 2022) Morales González, Rafael; Georgiou, Orestis; Marzo Pérez, Asier; Frier, William; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
Ultrasound mid-air haptics is an emerging technology with many applications in human-computer interactions. Despite great advances in related hardware and software, physics models that predict the resulting forces on a surface (e.g., someone's hand) are either too simple (inaccurate) or too complex (computationally expensive). In this paper, we show that simple models are not sufficient when predicting the force on an experimental setup involving two prototype devices and a precision scale. Specifically, we demonstrate that our experimental measurements cannot be accurately predicted using a linear acoustic model.
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.
Open Access
Holographic acoustic tweezers
(National Academy of Sciences, 2019) Marzo Pérez, Asier; Drinkwater, Bruce W.; Ingeniería; Ingeniaritza
Acoustic tweezers use sound radiation forces to manipulate matter without contact. They provide unique characteristics compared with the more established optical tweezers, such as higher trapping forces per unit input power and the ability to manipulate objects from the micrometer to the centimeter scale. They also enable the trapping of a wide range of sample materials in various media. A dramatic advancement in optical tweezers was the development of holographic optical tweezers (HOT) which enabled the independent manipulation of multiple particles leading to applications such as the assembly of 3D microstructures and the probing of soft matter. Now, 20 years after the development of HOT, we present the realization of holographic acoustic tweezers (HAT). We experimentally demonstrate a 40-kHz airborne HAT system implemented using two 256-emitter phased arrays and manipulate individually up to 25 millimetric particles simultaneously. We show that the maximum trapping forces are achieved once the emitting array satisfies Nyquist sampling and an emission phase discretization below π/8 radians. When considered on the scale of a wavelength, HAT provides similar manipulation capabilities as HOT while retaining its unique characteristics. The examples shown here suggest the future use of HAT for novel forms of displays in which the objects are made of physical levitating voxels, assembly processes in the micrometer and millimetric scale, as well as positioning and orientation of multiple objects which could lead to biomedical applications.