Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session F14: Biological Fluid Mechanics of Transport, Growth and ActuationFocus
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Sponsoring Units: DSOFT Chair: Joel Marthelot, Aix-Marseille Univ Room: Room 206 |
Tuesday, March 7, 2023 8:00AM - 8:36AM |
F14.00001: Secrets of insect excretion: how and why sharpshooters use droplet superpropulsion Invited Speaker: Saad Bhamla Food consumption and waste elimination are vital functions for living systems. Although how feeding impacts animal form and function has been studied for more than a century, how its obligate partner, excretion, controls, and constraints animal behavior remains largely unexplored. In this talk, I will describe how millimeter-scale sharpshooter insects eliminate their high-volume excreta by exploiting droplet superpropulsion, a phenomenon in which they can achieve higher velocities than the underlying actuator through temporal tuning. I will discuss why they have evolved to take advantage of this droplet ejection mechanism through energetic and scaling arguments. |
Tuesday, March 7, 2023 8:36AM - 8:48AM |
F14.00002: Mechanical description of Drosphila wing expansion Simon Hadjaje, Ignacio Andrade-Silva, Raphael Clement, Marie-Julie Dalbe, Joel Marthelot During its final transformation into its adult form, just after hatching from its pupal shell, an insect unfolds its wings within minutes. The wings expand rapidly from a compact, pleated structure to a plane that then solidifies to generate rigidity. We study wing expansion in Drosophila melanogaster. Expansion is regulated by increasing internal pressure and injecting a non-Newtonian viscous fluid (hemolymph) into a folded deployable structure under hormonal control (Bursicon). We first characterize the unfolding kinematics through macroscopic observations. Using optical microscopy imaging, we describe the shape of the initial origami-like folded wing and its relationship to the final network of veins. We then image fly wing sections using transmitted electron microscopy (TEM) to study the morphological evolution of the wing cross section at different stages of expansion. We use micro-tomography (micro-CT) to gain insight into the 3D structure of the folded wings as well as their internal structure. Next, we quantify the pressure and fluid flow in vivo in the insect during wing expansion. We inject fluorescent particles to follow the hemolymph flow and study the global and local characteristics of the flow in the wings. Mechanical traction tests of the wing allow us to determine its elastic properties. Finally, we combine scaling analysis, numerical simulations and experiments to build a fundamental understanding of the wing expansion dynamic. |
Tuesday, March 7, 2023 8:48AM - 9:00AM |
F14.00003: Pulsatile Driving Stabilizes Loops in Elastic Flow Networks Purba Chatterjee, Sean Fancher, Eleni Katifori Existing models of adaptation in biological flow networks consider their constituent vessels (e.g. veins and arteries) to be rigid, thus predicting a non physiological response when the drive (e.g the heart) is dynamic. Here we show that incorporating pulsatile driving and properties such as fluid inertia and vessel compliance into a general adaptation framework fundamentally changes the expected structure at steady state of a minimal one-loop network. In particular, pulsatility is observed to give rise to resonances which can stabilize loops for a much broader class of metabolic cost functions than predicted by existing theories. Our work points to the need for a more realistic treatment of adaptation in biological flow networks, especially those driven by a pulsatile source, and provides insights into pathologies that emerge when such pulsatility is disrupted in human beings. |
Tuesday, March 7, 2023 9:00AM - 9:12AM |
F14.00004: Fluid transport in artificial vascular networks inspired by the lymphatic system Martin Brandenbourger, Zohreh Kiani, Juan Huaroto, Pierre Lambert Liquid flows in vascular networks are among the most effective ways to transport matter and information for life. One striking example of swift and versatile transport is the lymphatic system in which lymph is transported across the whole body of mammals against intricate changes of pressures. In the collecting lymphatics, this transport is carried out by vessels contractions combined with valve leaflets that ensure unidirectional transport. The nature of the active contractions, the multi-scale and multi-physics of the system make it challenging to model. Numerical simulations have brought many answers to these limitations. Yet, questions on the propagation of the vessels contractions along the lymphatic network remain difficult to answer. |
Tuesday, March 7, 2023 9:12AM - 9:24AM |
F14.00005: Synchronization of flagella in cellular carpets derived from Volvox carteri Jane Y Chui, Raymond E Goldstein From unicellular ciliates to respiratory epithelium, the existence of cilia carpets on these cell surfaces enable important functions, such as travelling through the earth’s oceans or debris clearing via fluid flow generation respectively. These cilia are not centrally controlled, but rather work collectively by synchronizing their beating cycles and generating metachronal waveforms. Both theoretical and experimental studies of the mechanisms leading to the emergence of these metachronal waves have been done largely independent of boundary conditions, and so in this study we seek to investigate the validity of this assumption as well as observe the effects of different boundary conditions. Colonial alga Volvox carteri are an ideal model organism for this study due to their size and penchant for metachronal waves. We break these spherical colonies into pieces using a homogenizer, and use imaging techniques to observe how changes in the number of cells, shape, and boundary conditions change how the cilia interact and synchronize with each other. The characteristic shape and size of these broken-off pieces will also inform us on residual stresses in the extracellular matrix (ECM) of a volvox colony as it expands over its lifecycle, and contribute to important questions regarding structural integrity and aging as it relates to ECM in general. |
Tuesday, March 7, 2023 9:24AM - 9:36AM |
F14.00006: The fluid-structure interaction of bristled wings Yuexia Lin, Matteo Pezzulla, Pedro Reis Slender structures covered with hairs, bristles, or branches are commonly observed in nature, from plants to marine animals and insects, to crustaceans and other arthropods. The functions of these porous, "hairy" structures are diverse and essential, ranging over feeding, sensing, and locomotion. A particularly intriguing example is the bristled wings of miniature insects, the smallest of which is comparable to a paramecium, a single-cell organism. Compared to the more familiar membrane wings, bristled wings reduce the amount of material in the wing, lowering the load the insects carry in flight. With bristled wings, miniature insects achieve flight via drag-based flght mechanisms. Operating at a low bristle Reynolds number, the seemingly leaky bristled wings act as paddles due to the viscous boundary layers plugging the flow between bristles. Due to their stunning size and geometry, bristled wings have garnered considerable interest in recent years. We tackle several yet-unsolved questions, such as: What is the optimal number of bristles on the wing? What is the most lightweight configuration that can withstand its own drag forces and avoid reconfiguration? To investigate the trade-off among weight, stiffness, and aerodynamic force generation of the bristled wings, we combine experiments and simulations to characterize the drag coefficients of idealized models of bristled wings. Particular emphasis is given to the role of elastic deformation of the bristles in modifying the generated drag. |
Tuesday, March 7, 2023 9:36AM - 9:48AM |
F14.00007: Eulerian simulation of fluid–structure interaction in bioinspired complex suspensions and locomotion Yue Sun, Christopher H Rycroft We present a computational method to simulate fluid–structure interaction (FSI) based on the lattice Boltzmann reference map technique (LBRMT). The LBRMT uses the reference map technique (RMT) to model large deformations of finite-strain solids on one fixed grid in an Eulerian framework, and couple fluids onto the same computational grid with the lattice Boltzmann (LB) method. In addition to the tractable features of Eulerian simulation and parallelizable fluid update of the LB method, the LBRMT is apt at simulating multi-body contact of complex geometries since it uses one global velocity field for both phases. Another integral part of our method is a new and simple implementation to model moving deformable boundary conditions for FSI problems in the LB method. Through diverse LBRMT simulations, we highlight its biological applications in sedimentation and flotation, flexible rotors, actuated microswimmer, and its potential to understand the spatiotemporal dynamics of collective motion. |
Tuesday, March 7, 2023 9:48AM - 10:00AM |
F14.00008: Dynamic Flow Response of Fluid-immersed Hair Beds Jonas Smucker, José R Alvarado Fluid immersed hair beds are a common occurrence in organisms. Bronchial cilia, the endothelial glycocalyx layer, and intestinal microvilli (among others) serve critical regulatory functions. To better understand these functions, and the role of passive hairs on fluid dynamics in biological settings, we investigate the transient characteristics of hair beds immersed in a low Reynolds number environment. Large amplitude oscillatory shear rheology experiments are conducted with the hair-beds and their response is characterized with the mechanical impedance, a quantity describing the system's effective viscosity. While the fluid and solid both have linear constitutive properties, we show that interactions between hair-bed deformations and fluid flows induce a nonlinear relationship between the forcing parameters and the system's impedance, contrasting the rigid limit. The nonlinearity of the system, and the ability of the hairs to respond with many degrees of freedom to shear makes them an interesting candidate to stir fluids. |
Tuesday, March 7, 2023 10:00AM - 10:12AM |
F14.00009: Changes in bacterial adherence in different flow conditions Kelsey M Hallinen, Zemer Gitai Fluid flows are dominant features of the environments of many bacterial species, yet the interactions between flow, surface association, and colonization factors remain largely underexplored. In dynamic bacterial populations, there are multiple interactions that occur between different length scales, from gene expression in single cells to collective behaviors or spatial effects in biofilm communities. With the addition of flow environments, we can further understand these emergent behaviors. One specific example is infective endocarditis, in which bacterial pathogens have long been known to preferentially colonize the heart valves with the greatest flow rates. The mechanisms underlying this important yet paradoxical behavior are unknown. To begin to address these questions I have developed a system for studying the effects of flow on colonization of several endocarditis-inducing pathogens including Staphylococcus aureus MRSA, Enterococcus faecalis and Streptococcus pneumoniae. In microfluidic devices I observed the bacteria growing from single cells to microcolonies and found a counter-intuitive result in which bacteria under high flow conditions colonized the surface better than those same species in low flow conditions. Under low flow, robust colonies form and disperse over the experimental run, whereas little dispersal is seen in the high dispersal case. My current focus is to determine both the biophysical and molecular mechanisms of this surprising bacterial adherence behavior. |
Tuesday, March 7, 2023 10:12AM - 10:24AM |
F14.00010: Modeling human red blood cell damage using experiments and machine learning Oliver McRae, Aldair Gongora, Alice E White Circulating human red blood cells (erythrocytes) are exposed to fluid stressors. If the stressors are large enough, these erythrocytes can be damaged, and even destroyed (hemolysis). In particular, hemolysis can cause organ injury, negatively affecting a person’s health. While prior studies have shown an increase in hemolysis with the fluid shear rate, they contain large uncertainties in the experimental results, too large to offer insight on a per-person basis. Here, we predict hemolysis of human erythrocytes using a combination of experimental measurements and machine learning (ML). We conduct microfluidic experiments to directly measure the degree of hemolysis after the erythrocytes are exposed to a known stressor. We then combine experimental measurements, patient demographics, and ML-modeling. Additionally, we demonstrate the use of active learning to guide experiment selection. We anticipate these results to offer insights on how to combine human biology-focused experiments and ML. Specifically, these results may drive the development of new devices and procedures designed to reduce hemolysis on a per-patient basis. |
Tuesday, March 7, 2023 10:24AM - 10:36AM |
F14.00011: The dynamics of microjet spitting in termite soldiers Elio J Challita, PANKAJ ROHILLA, Prateek Sehgal, Jacob Harrison, Saad Bhamla Tropical cone-head termite soldiers (Nasutitermites sp.) spit a sticky, noxious liquid jet through their nozzle-shaped heads to defend their nests from invaders. While previous work qualitatively described these insects' spitting behavior, how their jets' fluid dynamics aid them in 'fortress defense' is still unknown. In this talk, we uncover the fluid dynamics and physical properties of these minute jets (V ~10 nL, D ~ 10 μm) taken in the Peruvian Amazon rainforest with high-speed imaging and micro-rheological experiments. We mathematically and experimentally show that these termites exploit head oscillations to transition from generating liquid rope coils to producing large lasso-like viscous threads (x 2-3 body length) to ward off larger predators. Combining micro-CT scans with computational fluid dynamic simulation, we model the pressure-driven flow across their pointed head (nasus) and show how its geometry influences the jet dynamics. Understanding the biomechanics of these termites and the fluid mechanics of the microjets ejected by them will not only advance the knowledge of the biophysical limits of these termites' defensive behavior but might also guide the design of jet extrusion nozzles at the microscale. |
Tuesday, March 7, 2023 10:36AM - 10:48AM |
F14.00012: Snowflake yeast overcome diffusion limited nutrient acquisition by the generation of spontaneous flows Nishant Narayanasamy, Emma Bingham, Ozan Bozdag, William C Ratcliff, Peter Yunker, Shashi Thutupalli Snowflake yeast is a laboratory evolved multicellular organism, whose macroscopic size puts demands on its nutrient requirement, which cannot be met via diffusion alone, necessitating mixing of the local fluid environment. Typically, such mixing is achieved via appendages that mechanically stir the external fluid. While this requires the emergence of novelty and its subsequent fixation in early multicellular organisms, purely physical mechanisms such as emergent nutrient density gradients can also mix the local environment. Our work shows how fluid density driven instabilities, generated spontaneously via the organismal metabolic activity, can mitigate diffusion limitation in the nascent multicellular organism snowflake yeast allowing it to reach macroscopic sizes. Furthermore, we show how these flows help the organism achieve exponential growth up to macroscopic (millimetric) sizes. |
Tuesday, March 7, 2023 10:48AM - 11:00AM |
F14.00013: High-Throughput Microfluidic Platform for Phototransfection Julia Radzio, Paulo E Arratia, James H Eberwine, Quentin Brosseau High throughput transient transfection of mammalian cells is crucial for intracellular gene delivery. Optoporation in a microfluidic device offers advantages over conventional physical methods for transient membrane-disruption-mediated transfection such as dosage control and scalability. Here, we describe an iterative microfluidic phototransfection platform for high throughput delivery of COVID-19 Spike Protein mRNA and CD80 mRNAs into 3T3 cells. Laminar flow focusing is used to selectively expose cells to user-defined concentrations of mRNA (dictated by scRNA seq) during which laser light is focused on individual cells to accomplish the transfection. These same cells can be repeatedly phototransfected with the same or different RNAs which is not possible with conventional approaches. This device is capable of successful phototransfection of specified numbers of RNAs into tens of thousands of cells during an experiment facilitating cell-based therapies. |
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