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1. An experimental study of the effect of motile bacteria on the fluid displacement in porous media

   https://doi.org/10.1051/e3sconf/202020508008  

   Jeong, Boyoung ; Zhao, Yumeng ; Kang, Dong-Hun ; Dai, Sheng ( January 2020 , E3S Web of Conferences)

   McCartney, J.S. ; Tomac, I. (Ed.)

   Multiphase flow patterns in porous media largely depend on the properties of the fluids and interfaces such as viscosity, surface tension, and contact angle. Microorganisms in soils change the fluid and interfacial properties, and thus can alter multiphase fluid flow in porous media. This study investigates the impact of motile bacterium Escherichia coli ( E. coli ) on fluid displacement patterns in a microfluidic chip. The fluid displacement is observed during the saturation and the desaturation processes of the microfluidic chip with and without E.coli suspension. Time-lapse photography results show that the presence of E.coli alters the displacement patterns during the wetting and drying process and changes the residual saturation of the chip. Although studies of the impacts of motility on interfacial properties remain elusive, these results bring the expectation to the manipulation of multiphase transport in porous media and the adaptive control of industrial and environmental flow processes using active particles. 

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2. Growth of microorganisms in an interfacially driven space bioreactor analog

   https://doi.org/10.1038/s41526-020-0101-4  

   Adam, Joe A. ; Gulati, Shreyash ; Hirsa, Amir H. ; Bonocora, Richard P. ( December 2020 , npj Microgravity)

   null (Ed.)

   Abstract Fluid bioreactors in microgravity environments may utilize alternative methods of containment and mixing. The ring-sheared drop (RSD) is a containerless mixing device which functions in microgravity using surface tension for containment and mixes through interfacially-driven flow. To assess the feasibility of using interfacially driven flow devices, such as the RSD, as bioreactors, Escherichia coli growth and recombinant protein expression were analyzed in a ground-based analog of the RSD called the knife edge surface viscometer (KEV). Results demonstrated that the KEV can facilitate the growth of E. coli and that growth rate increases logarithmically with increasing knife edge rotation rate, similar to the standard growth method on Earth (orbital shaker). Furthermore, the KEV was shown to be viable for supporting recombinant protein expression in E. coli at levels comparable to those achieved using standard growth methods. 

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3. No ordinary proteins: Adsorption and molecular orientation of monoclonal antibodies

   https://doi.org/10.1126/sciadv.abg2873  

   Kanthe, Ankit ; Ilott, Andrew ; Krause, Mary ; Zheng, Songyan ; Li, Jinjiang ; Bu, Wei ; Bera, Mrinal K. ; Lin, Binhua ; Maldarelli, Charles ; Tu, Raymond S. ( August 2021 , Science Advances)

   The interaction of monoclonal antibodies (mAbs) with air/water interfaces plays a crucial role in their overall stability in solution. We aim to understand this behavior using pendant bubble measurements to track the dynamic tension reduction and x-ray reflectivity to obtain the electron density profiles (EDPs) at the surface. Native immunoglobulin G mAb is a rigid molecule with a flat, “Y” shape, and simulated EDPs are obtained by rotating a homology construct at the surface. Comparing simulations with experimental EDPs, we obtain surface orientation probability maps showing mAbs transition from flat-on Y-shape configurations to side-on or end-on configurations with increasing concentration. The modeling also shows the presence of β sheets at the surface. Overall, the experiments and the homology modeling elucidate the orientational phase space during different stages of adsorption of mAbs at the air/water interface. These finding will help define new strategies for the manufacture and storage of antibody-based therapeutics. 

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4. Layer-by-layer fabrication of 3D hydrogel structures using open microfluidics

   https://doi.org/10.1039/c9lc00621d  

   Lee, Ulri N. ; Day, John H. ; Haack, Amanda J. ; Bretherton, Ross C. ; Lu, Wenbo ; DeForest, Cole A. ; Theberge, Ashleigh B. ; Berthier, Erwin ( February 2020 , Lab on a Chip)

   Patterned deposition and 3D fabrication techniques have enabled the use of hydrogels for a number of applications including microfluidics, sensors, separations, and tissue engineering in which form fits function. Devices such as reconfigurable microvalves or implantable tissues have been created using lithography or casting techniques. Here, we present a novel open-microfluidic patterning method that utilizes surface tension forces to form hydrogel layers on top of each other, into a patterned 3D structure. We use a patterning device to form a temporary open microfluidic channel on an existing gel layer, allowing the controlled flow of unpolymerized gel in device-regions. After layer gelation and device removal, the process can be repeated iteratively to create multi-layered 3D structures. The use of open-microfluidic and surface tension-based methods to define the shape of each individual layer enables patterning to be performed with a simple pipette and with minimal dead-volume. Our method is compatible with unmodified (native) biological hydrogels, and other non-biological materials with precursor fluid properties compatible with capillary flow. With our open-microfluidic layer-by-layer fabrication method, we demonstrate the capability to build agarose, type I collagen, and polymer–peptide 3D structures featuring asymmetric designs, multiple components, overhanging features, and cell-laden regions. 

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5. Machine learning (ML)-assisted surface tension and oscillation-induced elastic modulus studies of oxide-coated liquid metal (LM) alloys

   https://doi.org/10.1088/2515-7639/acf78c  

   Hossain, Kazi Zihan ; Kamran, Sharif Amit ; Tavakkoli, Alireza ; Khan, M. Rashed ( September 2023 , Journal of Physics: Materials)

   Pendant drops of oxide-coated high-surface tension fluids frequently produce perturbed shapes that impede interfacial studies. Eutectic gallium indium or Galinstan are high-surface tension fluids coated with a ∼5 nm gallium oxide (Ga₂O₃) film and falls under this fluid classification, also known as liquid metals (LMs). The recent emergence of LM-based applications often cannot proceed without analyzing interfacial energetics in different environments. While numerous techniques are available in the literature for interfacial studies- pendant droplet-based analyses are the simplest. However, the perturbed shape of the pendant drops due to the presence of surface oxide has been ignored frequently as a source of error. Also, exploratory investigations of surface oxide leveraging oscillatory pendant droplets have remained untapped. We address both challenges and present two contributing novelties- (a) by utilizing the machine learning (ML) technique, we predict the approximate surface tension value of perturbed pendant droplets, (ii) by leveraging the oscillation-induced bubble tensiometry method, we study the dynamic elastic modulus of the oxide-coated LM droplets. We have created our dataset from LM’s pendant drop shape parameters and trained different models for comparison. We have achieved >99% accuracy with all models and added versatility to work with other fluids. The best-performing model was leveraged further to predict the approximate values of the nonaxisymmetric LM droplets. Then, we analyzed LM’s elastic and viscous moduli in air, harnessing oscillation-induced pendant droplets, which provides complementary opportunities for interfacial studies alternative to expensive rheometers. We believe it will enable more fundamental studies of the oxide layer on LM, leveraging both symmetric and perturbed droplets. Our study broadens the materials science horizon, where researchers from ML and artificial intelligence domains can work synergistically to solve more complex problems related to surface science, interfacial studies, and other studies relevant to LM-based systems.

    

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