Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session ZC10: Drops: General III |
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Chair: Nicolo Scapin, Princeton University Room: Ballroom J |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC10.00001: Programming spatially-selective droplet motion using metamaterials Mohammad Charara, Zakari Kujala, Sungyon Lee, Stefano Gonella Motion control of droplets has generated much attention for its application to microfluidics, where precisely controlling small fluid volumes facilitates a variety of chemical and biological micro-processes. Mechanical vibrations have been used to induce controllable depinning, and the activation of a variety of drop-motion regimes. However, existing vibration-based strategies generate a homogeneous landscape of vibrations -- drops behave the same regardless of their location on a substrate – and therefore lack any tunability or spatial-selectivity. On the other hand, elastic metamaterials provide a framework for spatially and spectrally selective drop motion due to their ability to generate bandgaps – frequency intervals where vibrations are greatly attenuated. In this work, we experimentally demonstrate a variety of droplet motion capabilities on the surface of a vibrating metaplate endowed with resonant stubs. Furthermore, the LEGO® component-based framework used allows us to demonstrate on-demand tuning of the spectral and spatial selectivity of the metaplate. This work begins to explore the broader application of elastic metamaterials in a context where their signature wave- control capabilities are not the end goal, but rather a tool used to enable complex multi-physical effects. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC10.00002: Magnetically reconfigurable rectifiers for versatile 3D liquid manipulation Jiaqi Miao, Alan C. H. Tsang Manipulating small-volume liquids is crucial in nature and industry. However, current liquid manipulation technologies often need complex energy inputs or fixed surfaces, limiting their real-world applications. Here, we introduce a simple and adjustable three-dimensional (3D) liquid manipulation paradigm that controls liquid behaviors by coupling interfacial energy with programmable static magnetic fields. This paradigm centers around a hierarchical rectifier with magnetized microratchets, enabling multimodal directional control of small-volume liquids. Under pre-programmed magnetic fields, the rectifier can reconfigure its morphology and harness interfacial energy to support rich liquid behaviors without dynamic real-time control. Switchable reconfigurations show improved rectification performance, offer flexible transport direction control, and promote spatiotemporally controllable inchworm-like 3D liquid manipulation, which may promote versatile engineering and biochemistry applications. |
Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC10.00003: ABSTRACT WITHDRAWN
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Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC10.00004: Liquid droplet oscillations on a vibrating substrate King Lun Ng, Michał Klamka, Luis Henrique Carnevale, Piotr Deuar, Tomasz Bobinski, Panagiotis E Theodorakis We study the oscillations of liquid droplets on substrates in macroscopic scale using Many-body Dissipative Particle Dynamics (MDPD). In this study, we focus on the harmonic droplet oscillations which are induced by sinusoidal forcing from horizonal substrate vibrations in one-dimension. Our investigation examines the topological changes of the droplet in various sizes and oscillation modes, considering different vibration frequencies and amplitudes. We also explore the role of the droplet's natural oscillation mode. Additionally, we demonstrate the effect of surface wettability on droplet oscillations, ranging from hydrophilic to superhydrophobic surfaces, by parametrically tuning the equilibrium contact angles. Our MDPD simulations are compared with experimental literature results. This approach aims to optimize systems involving droplet movement driven by vibrating substrates. |
Tuesday, November 26, 2024 1:42PM - 1:55PM |
ZC10.00005: Formation and control of liquid droplets on a rotating wafer Hyunji Lee, Heeyun Choi, Hyungmin Park We experimentally investigate the formation of liquid droplets generated from a thin liquid (DI water) film on a rotating wafer. The primary droplets propelled radially from ligaments subsequently collide with a chamber wall, leading to the formation of secondary droplets. Since the secondary droplets can cause defects in various semiconductor processes, it is important to have a way to control. Using a high-speed shadowgraphy, we capture and analyze the droplets generated at the wafer edge and their subsequent collisions with the wall. Through image processing, we examine the trajectory and size of the primary droplets formed at the wafer edge, as well as the mechanisms, size, and trajectories of the resulting secondary droplets. While varying the rotational speed of a wafer in the range of 200–500 rpm (fixed flow rate of 1 LPM), we conduct experiments on various walls with contact angles ranging from 20° to 160° (i.e., different wettability). The larger the contact angle with the wall, such as with a superhydrophobic surface, the larger the secondary droplets that are formed. Additionally, these droplets make smaller angles with the wall in their flight direction. Conversely, for surfaces like glass with a small contact angle, very small secondary droplets are formed and exhibit very sporadic bounces. |
Tuesday, November 26, 2024 1:55PM - 2:08PM |
ZC10.00006: ABSTRACT WITHDRAWN
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Tuesday, November 26, 2024 2:08PM - 2:21PM |
ZC10.00007: Anomalous interference drives oscillatory dynamics in wave-dressed active particles Austin Mitchell Blitstein, Rodolfo R Rosales, Pedro J Saenz A recent surge of discoveries has sparked significant interest in driven-dissipative systems where a particle self-propels due to a resonant interaction with its self-generated wave field. These wave-dressed active particles frequently undergo rapid changes in velocity due to a variety of factors, including boundaries altering their direction of motion, media inhomogeneities distorting their wave field, and direct interactions with their own wave field. We deduce the emergence of a nonlocal wave-mediated force caused by an anomalous type of wave interference in the vicinity of jerking points, places where the particle's velocity changes most rapidly. In contrast to the typical case of constructive interference at points of stationary phase, waves excited by the particle at jerking points avoid cancellation through rapid changes in frequency. Through an asymptotic analysis, we approximate the wave force at jerking points, allowing us to rationalize in-line speed oscillations, non-specular reflections off potential walls, and wave-like statistics in certain potential wells. The results we derive are generic, and thus applicable to a relatively large class of wave-dressed active particles. |
Tuesday, November 26, 2024 2:21PM - 2:34PM |
ZC10.00008: Simulating laser-induced droplet deformation Hugo L França, Mikheil Kharbedia, Dion Engels, Karl Schubert, Oscar Versolato, Maziyar Jalaal We investigate the dynamics of a tin droplet shot by a nanosecond laser pulse. We use numerical simulations and particularly study how the curvature of the droplet changes over time and as a function of the laser beam and droplet sizes. We show that particular attention is required for the initial conditions of the simulations to be able to recover the experimental observations. To this end, we find the correct form of the initial pressure and velocity fields and compare the late-time shapes of the droplets with our experimental data. The process simulated in this work finds applications in the EUV nanolithography industry, in which a laser pulse deforms a droplet into a sheet, which is subsequently ionized by a second laser pulse, creating an EUV-emitting plasma. |
Tuesday, November 26, 2024 2:34PM - 2:47PM |
ZC10.00009: High-precision optical measurements of microdroplet diameters using pixel intensity averaging and thresholding Bryan Oller, Armin Kalita, Claudiu Andrei Stan Droplet diameter measurements are often made in microfluidic applications using optical images, with an accuracy that is typically limited by the optical resolution. However, experiments in laser ablation, evaporation, and whispering gallery mode photonics may require droplet diameter measurements with nanoscale accuracy. Achieving such accuracy can also enable improvements in the precision and stability of drop generation and manipulation. We imaged optically single microdroplets in free flight using a high-resolution optical system with uniform illumination and high contrast. To achieve submicron precision, we calculated the average pixel intensity as a function of the distance from the center of the droplet, which provided a low-noise intensity profile from which we extracted the drop radius via thresholding. At the submicron scale, two systematic effects became the dominant source of diameter error: injection instabilities and illumination asymmetries. These effects can be measured and corrected for through non-linear intensity transformations, compensating for focus drifts, and by finding more accurate centers of the droplets. After corrections, we achieved a standard deviation of the diameter of less than 10 nm for droplets with diameters around 40 µm. |
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