Open Access
Optimization of acoustic fields: advances towards its use for matter manipulation and contactless fabrication
(2023) Ezcurdia Aguirre, Íñigo Fermín; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Los campos de presión acústica son capaces de modelar y levitar partículas de una amplia gama de materiales y tamaños a través del aire, el agua o el tejido biológico. Esto tiene aplicaciones en cristalografía, manipulación celular, escenarios lab-on-a-chip, farmacología, transporte sin contacto e incluso levitación de seres vivos. En general, la investigación de campos de presión acústica ha experimentado avances significativos en los últimos años. Su flexibilidad y sus posibles aplicaciones han aumentado considerablemente con el desarrollo de técnicas holográficas y el uso de optimizadores. Sin embargo, aún hay margen de mejora, ya que las limitaciones dificultan la aplicación de los campos acústicos en diversos escenarios de investigación. Por ejemplo, no existe una plataforma de hardware unificada que motive de forma flexible la investigación exploratoria en aplicaciones de holografía acústica. La mayoría de los dispositivos comerciales o de caseros carecen de la resolución o la potencia que necesitan las personas investigadoras, por lo que tienen que fabricar dispositivos más complejos y caros. Además, investigaciones anteriores se han centrado en la levitación y manipulación de pequeñas partículas y gotas; sin embargo, aún no se ha desarrollado un prototipo completo para la fabricación sin contacto; no existen artículos científicos que estudien el atrapamiento de objetos alargados tanto en posición como en orientación. Además, la microfluídica está limitada en cuanto a la manipulación tridimensional (3D), el tamaño de las gotas y la contaminación cruzada. Esta tesis ofrece una introducción exhaustiva a la optimización de los campos acústicos, repasando su importancia en aplicaciones de múltiples ámbitos de la investigación y la industria. Esta tesis también examina las limitaciones y deficiencias previamente expuestas y presentes en el actual diseño y aplicación de campos acústicos. Se proponen algoritmos novedosos para generar los campos deseados y mejorar significativamente su resolución y potencia mediante multiplexación espacial y temporal. Se presenta una plataforma de hardware abierta y asequible para facilitar la adaptación a los requisitos experimentales de los investigadores que exploran nuevas aplicaciones de los hologramas ultrasónicos. Se diseñan y evalúan trampas acústicas óptimas para manipular elementos alargados controlando su posición y orientación. Se demuestra la fabricación sin contacto utilizando trampas acústicas de piezas alargadas mediante fabricación aditiva basada en partículas levitadas, varillas y resina UV; también se ilustra la adición sobre otros objetos y la construcción dentro de contenedores. Por último, se propone un sistema, destinado a microfluídica 3D, basado en ultrasonidos focalizados a través de una malla hidrófoba. Es sistema es capaz de manejar un gran número de gotas (> 40µL), y capaz de fusionarlas/dividirlas o propulsarlas verticalmente, este sistema mejora significativamente los sistemas EWOD ya existentes generando una menor contaminación superficial. Esta tesis presenta estos logros y sus trabajos relacionados, modelos, metodologías, procedimientos y conclusiones. Espero que estos trabajos supongan un avance significativo en la investigación de los campos acústicos y puedan inspirar y facilitar futuras aplicaciones novedosas de los hologramas acústicos por parte de las personas investigadoras en diversos ámbitos del mundo académico y de la industria.
Open Access
LeviPrint: contactless additive manufacturing using acoustic levitation with position and orientation control of elongated parts
(2021) Ezcurdia Aguirre, Íñigo Fermín; Morales González, Rafael; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
LeviPrint assembles small objects in a contactless way using ultrasonic phased-arrays and optimization algorithms. We explore a set of methods that enables 6 Degrees-of-Freedom (DoF) control of elongated bodies. We then evaluate different ultrasonic arrangements to optimize the manipulation of these bodies. The combination of arrangements and optimization algorithms allow us to levitate, orientate and assemble complex objects. These techniques and arrangements can be leveraged for the microfabrication of electromechanical components and in-vivo additive manufacturing. We highlight the reduction of cross-contamination and the capability to manufacture inside closed containers from the outside.
Open Access
Mental workload of guiding devices: directional pulling forces, vibrotactile stimuli and audio cues
(ACM, 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
LeviPrint: contactless fabrication using full acoustic trapping of elongated parts
(ACM, 2022) Ezcurdia Aguirre, Íñigo Fermín; Morales González, Rafael; Andrade, Marco A.B.; Marzo Pérez, Asier; Institute of Smart Cities - ISC
LeviPrint is a system for assembling objects in a contactless manner using acoustic levitation. We explore a set of optimum acoustic fields that enables full trapping in position and orientation of elongated objects such as sticks. We then evaluate the capabilities of different ultrasonic levitators to dynamically manipulate these elongated objects. The combination of novel optimization algorithms and levitators enable the manipulation of sticks, beads and droplets to fabricate complex objects. A system prototype composed of a robot arm and a levitator is tested for different fabrication processes. We highlight the reduction of cross-contamination and the capability of building on top of objects from different angles as well as inside closed spaces. We hope that this technique inspires novel fabrication techniques and that reaches fields such as microfabrication of electromechanical components or even in-vivo additive manufacturing.
Open Access
Mid-air contactless haptics to augment VR experiences
(Association for Computing Machinery, 2023) Ezcurdia Aguirre, Íñigo Fermín; Fernández Ortega, Unai Javier; Olaz Moratinos, Xabier; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
We present four technologies to deliver contactless haptic stimuli for enriching Virtual Reality (VR) experiences. The technologies are electrostatic piloerection, focused light-induced heat, electric plasma, and ultrasound; the user does not require to wear or touch any device. We describe the working principle behind each technology and how these technologies can provide new exciting sensations in VR experiences. Additionally, we showcase a VR demo experience gathering all four remote haptic stimuli along a circuit for the users to experiment with these new sensations.
Open Access
Generating airborne ultrasonic amplitude patterns using an open hardware phased array
(MDPI, 2021) Morales González, Rafael; Ezcurdia Aguirre, Íñigo Fermín; Irisarri Erviti, Josu; Andrade, Marco A.B.; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Gobierno de Navarra / Nafarroako Gobernua
Holographic methods from optics can be adapted to acoustics for enabling novel applications in particle manipulation or patterning by generating dynamic custom-tailored acoustic fields. Here, we present three contributions towards making the field of acoustic holography more widespread. Firstly, we introduce an iterative algorithm that accurately calculates the amplitudes and phases of an array of ultrasound emitters in order to create a target amplitude field in mid-air. Secondly, we use the algorithm to analyse the impact of spatial, amplitude and phase emission resolution on the resulting acoustic field, thus providing engineering insights towards array design. For example, we show an onset of diminishing returns for smaller than a quarter-wavelength sized emitters and a phase and amplitude resolution of eight and four divisions per period, respectively. Lastly, we present a hardware platform for the generation of acoustic holograms. The array is integrated in a single board composed of 256 emitters operating at 40 kHz. We hope that the results and procedures described within this paper enable researchers to build their own ultrasonic arrays and explore novel applications of ultrasonic holograms.
Open Access
PointerVol: a laser pointer for swept volumetric displays
(ACM, 2024-10-11) Fernández Ortega, Unai Javier; Sarasate Azcona, Iosune; Ezcurdia Aguirre, Íñigo Fermín; López-Amo Ocón, Manuel; Fernandez Fernandez, Ivan; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika
A laser pointer is a commonly used device that does not require communication with the display system or modifications on the applications, the presenter can just take a pointer and start using it. When a laser pointer is used on a volumetric display, a line rather than a point appears, making it not suitable for pointing at 3D locations. PointerVol is a modified laser pointer that allows users to point to 3D positions inside a swept volumetric display. We propose two PointerVol implementations based on timing and distance measurements, we evaluate the pointing performance using them. Finally, we present other features such as multi-user pointing, line patterns and a multi-finger wearable. PointerVol is a simple device that can help to popularize volumetric displays, or at least to make them more usable for presentations with true-3D content.
Open Access
Content adaptation and depth perception in an affordable multi-view display
(MDPI, 2020) Ezcurdia Aguirre, Íñigo Fermín; Arregui Roldán, Adriana; Ardaiz Villanueva, Óscar; Ortiz, Amalia; Marzo Pérez, Asier; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Gobierno de Navarra / Nafarroako Gobernua, 0011-1365-2019-000086; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PJUPNA1923
We present SliceView, a simple and inexpensive multi-view display made with multiple parallel translucent sheets that sit on top of a regular monitor; each sheet reflects different 2D images that are perceived cumulatively. A technical study is performed on the reflected and transmitted light for sheets of different thicknesses. A user study compares SliceView with a commercial light-field display (LookingGlass) regarding the perception of information at multiple depths. More importantly, we present automatic adaptations of existing content to SliceView: 2D layered graphics such as retro-games or painting tools, movies and subtitles, and regular 3D scenes with multiple clipping z-planes. We show that it is possible to create an inexpensive multi-view display and automatically adapt content for it; moreover, the depth perception on some tasks is superior to the one obtained in a commercial light-field display. We hope that this work stimulates more research and applications with multi-view displays.
Open Access
Hand-as-a-prop: using the hand as a haptic proxy for manipulation in virtual reality
(Springer, 2023) Marichalar Baraibar, Sebastian Roberto; Ezcurdia Aguirre, Íñigo Fermín; Morales González, Rafael; Ortiz Nicolás, Amalia; Marzo Pérez, Asier; Ardaiz Villanueva, Óscar; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Haptic feedback can be almost as important as visual information in virtual reality environments. On the one hand, in Active Haptic Feedback, specialized devices such as vibrotactile gloves are employed; however, these solutions can be expensive, vendor-specific or cumbersome to setup. On the other hand, Passive Haptic Feedback approaches use inexpensive objects as proxies for the virtual entities; but mapping virtual objects to real props is not scalable nor flexible. We propose the Hand-as-a-Prop technique, which consists in using human hands as object props. We implemented two modalities: Self, where the user¿s non-dominant hand act as the virtual object while the dominant hand grabs, translates and releases it; and External, where the hand of another person is used. Hand-as-a-Prop can represent multiple shapes with a single prop and does not require extra hardware. We performed an evaluation comparing both Self and External Hand-as-a-Prop with traditional Object Props in terms of user experience (goodness, ease, realism, fatigue, and preference) and performance (task completion time and translation time). Results showed that Hand-as-a-Prop was rated as neutral tending to positive, and in some cases, the performance was similar to Object Props. Users preferred Self Hand-as-a-Prop over External Hand-as-a-Prop and also obtained better results.
Open Access
Microfluidic platform using focused ultrasound passing through hydrophobic meshes with jump availability
(Oxford University Press, 2023) Koroyasu, Yusuke; Nguyen, Thanh-Vinh; Sasaguri, Shun; Marzo Pérez, Asier; Ezcurdia Aguirre, Íñigo Fermín; Nagata, Yuuya; Yamamoto, Tatsuya; Nomura, Nobuhiko; Hoshi, Takayuki; Ochiai, Yoichi; Fushimi, Tatsuki; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Institute of Smart Cities - ISC
Applications in chemistry, biology, medicine, and engineering require the large-scale manipulation of a wide range of chemicals, samples, and specimens. To achieve maximum efficiency, parallel control of microlitre droplets using automated techniques is essential. Electrowetting-on-dielectric (EWOD), which manipulates droplets using the imbalance of wetting on a substrate, is the most widely employed method. However, EWOD is limited in its capability to make droplets detach from the substrate (jumping), which hinders throughput and device integration. Here, we propose a novel microfluidic system based on focused ultrasound passing through a hydrophobic mesh with droplets resting on top. A phased array dynamically creates foci to manipulate droplets of up to 300 mu L. This platform offers a jump height of up to 10 cm, a 27-fold improvement over conventional EWOD systems. In addition, droplets can be merged or split by pushing them against a hydrophobic knife. We demonstrate Suzuki-Miyaura cross-coupling using our platform, showing its potential for a wide range of chemical experiments. Biofouling in our system was lower than in conventional EWOD, demonstrating its high suitability for biological experiments. Focused ultrasound allows the manipulation of both solid and liquid targets. Our platform provides a foundation for the advancement of micro-robotics, additive manufacturing, and laboratory automation.