Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session E15: Microfluidic Devices: Special TopicsMicro
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Chair: Prashanta Dutta, Washington State University Room: 601 |
Sunday, November 19, 2017 4:55PM - 5:08PM |
E15.00001: Biomimetic Unidirectional Capillary Action Eric Rupert, Patrick Moran, Jason Dahl In arid environments animals require specialized adaptations to collect adequate water. The Texas horned lizard (P. cornutum) has superhydrophylic skin which draws water out of moist soil or directly from water sources. The water then makes its way into the lizard's unidirectional capillary system, made of overlapping scales, which serves to channel water to its mouth. Testing different channel geometries, repeated “D” shaped chambers as in Commans et al (2015) and truncated isosceles triangle chambers, as found in P. cornutum, we show the ability to have passive, unidirectional, fluid transport. Tests were carried out with the capillaries in a horizontal configuration. While both capillary geometries produced the desired traits, the triangular chambers showed superior unidirectionality, with no observed back flow, while “D” chambers showed back flow under testing conditions. The chambers provided similar flow rates. These types of channel systems will find use in microfluidics, notably in medical, printing, and lab-on-chip applications. [Preview Abstract] |
Sunday, November 19, 2017 5:08PM - 5:21PM |
E15.00002: Fabrication of Artificial Leaf to Develop Fluid Pump Driven by Surface Tension and Evaporation Minki Lee, Hosub Lim, Jinkee Lee Plants transport water from roots to leaves via xylem through transpiration, which is an evaporation process that occurs at the leaves. During transpiration, negative pressure can be generated by the porous structure of mesophyll cells in the leaves. Here, an artificial leaf mimicking structure using hydrogel, which has a nanoporous structure is fabricated. The cryogel method is used to develop a hierarchy structure on the nano- and microscale in the hydrogel media that is similar to the mesophyll cells and veins of a leaf, respectively. The theoretical model is analyzed to calculate the flow resistance in the artificial leaf, and compare the model with the experimental results. The experiment involves connecting a glass capillary tube at the bottom of the artificial leaf to observe the fluid velocity in the glass capillary tube generated by the negative pressure. The use of silicone oil as fluid instead of water to increase the flow resistance enables the measurement of negative pressure. The negative pressure of the artificial leaf is affected by several variables (e.g., pore size, wettability of the structure). Finally, by decreasing the pore size and increasing the wettability, the maximum negative pressure of the artificial leaf, -7.9 kPa is obtained. [Preview Abstract] |
Sunday, November 19, 2017 5:21PM - 5:34PM |
E15.00003: Distinct and Unique transitions in flow through softwalled microchannels Sagar Srinivas The flow in a rectangular channel with walls made of polyacrylamide gel is experimentally studied to examine the effect of soft walls on transition and turbulence. The bottom wall is fixed to a substrate and the top wall is unrestrained. As the Reynolds number increases, two different flow regimes are observed. The first is the ‘soft-wall turbulence’ (Srinivas & Kumaran, J. Fluid Mech., vol. 780, 2015, pp. 649–686). There is a large increase in the magnitudes of the velocity fluctuations after transition and the fluid velocity fluctuations appear to be non-zero at the soft walls, although higher resolution measurements are required to establish the nature of the boundary dynamics. The fluid velocity fluctuations are symmetric about the centreline of the channel, and they show relatively little downstream variation. The wall displacement measurements indicate that there is no observable motion perpendicular to the surface to within the experimental resolution, but displacement fluctuations parallel to the surface are observed after transition. As the Reynolds number is further increased, there is a second ‘wall-flutter’ transition, which involves visible downstream travelling waves in the top (unrestrained) wall alone. [Preview Abstract] |
Sunday, November 19, 2017 5:34PM - 5:47PM |
E15.00004: Hypoxic Response of Tumor Tissues in a Microfluidic Environment Adnan Morshed, Prashanta Dutta Inside a tumor tissue, cells growing further away from the blood vessel often suffer from low oxygen levels known as hypoxia. Cancer cells have shown prolonged survival in hostile hypoxic conditions by sharply changing the cellular metabolism. In this work, different stages of growth of the tumor tissue and the oxygen transport across the tissue are investigated. The tissue was modeled as a contiguous block of cells inside a microfluidic environment with nutrient transport through advection and diffusion. While oxygen uptake inside the tissue is through diffusion, ascorbate transport from the extracellular medium is addressed by a concentration dependent uptake model. By varying the experimentally observed oxygen consumption rate, different types of cancer cells and their normoxic and hypoxic stages were studied. Even when the oxygen supply in the channel is maintained at normoxic levels, our results show the onset of hypoxia within minutes inside the cellblock. Interestingly, modeled cell blocks with and without a structured basal layer showed less than 5{\%} variation in hypoxic response in chronic hypoxia. Results also indicate that the balance of cell survival and growth are affected by the flow rate of nutrients and the oxygen consumption rate. [Preview Abstract] |
Sunday, November 19, 2017 5:47PM - 6:00PM |
E15.00005: ABSTRACT WITHDRAWN |
Sunday, November 19, 2017 6:00PM - 6:13PM |
E15.00006: Guiding original micrometric morphologies induced by optical and acoustical focused waves on liquid interfaces Hugo Chesneau, Julien Petit, Nicolas Bertin, Hamza Chraibi, Etienne Brasselet, R\'egis Wunenburger, Jean-Pierre Delville We present here a study about liquid waveguides which can adapt themselves continually to optical or acoustical wave properties. By exploiting the radiation pressure exerted by a wave, it is possible to deform a two-phase liquid interface and create a liquid waveguide which can also play the role of a microfluidic flow channel. The incident wave can induce two kinds of morphologies depending whether the phase velocity of the wave decreases or increases when crossing the interface; the latter will either adopt a step-like or a needle profile. The aim of this investigation is to study numerically the coupling between propagation of the wave and deformation of the interface. Two assumptions are put forward and compared to experimental and theoretical results: In the one hand, step-like interfaces behave as stacks of cylindrical waveguides and in the other hand needle interfaces are induced by a total internal reflection of the incident wave into the deformation. These results could serve as a basis to develop versatile and adaptable microfluidic waveguides and flow channels. [Preview Abstract] |
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