Micromodels with a simplified porous network that represents geological porous media have been used as experimental test beds for multiphase flow studies in the petroleum industry. We present a new method to fabricate reservoir micromodels with heterogeneous wetting properties. Photopatterned, copolymerized microstructures were fabricated in a bottom-up manner. The use of rationally designed copolymers allowed us to tailor the wetting behavior (oleophilic/phobic) of the structures without requiring additional surface modifications. Using this approach, two separate techniques of constructing microstructures and tailoring their wetting behavior are combined in a simple, single-step ultraviolet lithography process. This microstructuring method is fast, economical, and versatile compared with previous fabrication methods used for multi-phase micromodel experiments. The wetting behaviors of the copolymerized microstructures were quantified and demonstrative oil/water immiscible displacement experiments were conducted.
Micromodels with simplifi ed porous microfl uidic systems are widely used to mimic the underground oil-reservoir environment for multiphase fl ow studies, enhanced oil recovery, and reservoir network mapping. However, previous micromodels cannot replicate the length scales and geochemistry of carbonate because of their material limitations. Here a simple method is introduced to create calcium carbonate (CaCO 3 ) micromodels composed of in situ grown CaCO 3 . CaCO 3 nanoparticles/polymer composite microstructures are built in microfl uidic channels by photopatterning, and CaCO 3 nanoparticles are selectively grown in situ from these microstructures by supplying Ca 2+ , CO 3 2− ions rich, supersaturated solutions. This approach enables us to fabricate synthetic CaCO 3 reservoir micromodels having dynamically tunable geometries with submicrometer pore-length scales and controlled wettability. Using this new method, acid fracturing and an immiscible fl uid displacement process are demonstrated used in real oil fi eld applications to visualize pore-scale fl uid-carbonate interactions in real time.
converting an API to a salt, but many APIs are not compatible with this type of chemical transformation. [13] Therefore, formulation nanotechnologies are a more general and powerful approach to improve the solubility and absorption, distribution, meta bolism, and excretion properties of hydrophobic APIs toward improving clinical performance. In contrast, current nanomedicines have primarily focused on targeted delivery (e.g., cellular uptake) of oncology drugs, [14] albeit with slow and expensive development. [15] Solubility enhancement requires a sensitive balance of API solid state stability and the solubility in aqueous solution. Approaches such as lipid-based systems (such as self-emulsifying drug delivery systems), [16,17] cyclodextrin complexation, [18] and nanovehicles (micelles, liposomes, or dendrimers) [19] improve solubility by introducing a more hydrophobic interface onto which the API partitions in equilibrium with the aqueous solution. However, these co-solutes can hinder API-target binding if partitioning is too effective and also yield low API loading and toxicity concerns due to significant excipient content. [20] Methods such as nanocrystal formation, [4,[21][22][23] amorphous polymer nanoparticles, [24] and porous nanoparticles [5,25] improve the solubility and dissolution rate by stabilizing the API in a state with high surface energy (that depends on API particle size, crystallinity, and polymorph). [26,27] Of the available formulation nanotechnologies, nanocrystal formation has been the most successful for hydrophobic APIs and is used in several food and drug administrationapproved products. [4,21,22] By retaining the crystalline structure, nanocrystals are more stable than amorphous API and are relatively stable to polymorph transformations. [28] Nanocrystals can be synthesized with sizes as small as 100 nm with minimal stabilizer material to limit toxicity and increase drug loading. [4,22,[29][30][31] The large curvature and surface area of nanocrystals provide a driving force for higher solubility (Ostwald-Freundlich equation) and correspondingly faster dissolution (Noyes-Whitney equation) relative to particles on the micrometer scale or larger. [32] In the case of orally delivered nanocrystals, absorption and thus bioavailability are directly correlated with solubility and dissolution rate. [4] An improved dissolution rate also contributes Formulation technologies are critical for increasing the efficacy of drug products containing poorly soluble hydrophobic drugs, which compose roughly 70% of small molecules in commercial pipelines. Nanomedicines, such as nanocrystal formulations and amorphous solid suspensions, are effective approaches to increasing solubility. However, existing techniques require additional processing into a final dosage form, which strongly influences drug delivery and clinical performance. To enhance hydrophobic drug product efficacy and clinical throughput, a hydrogel material is developed as a sacrificial template to simultaneously form and encapsulate nanocrystal...
Liquid entrapment over patterned surfaces has applications in diagnostics, oil recovery, and printing processes. Here we study the process of oil displacement upon sequential injection of water over a photopatterned structure in a confined geometry. By varying the amplitude and frequency of triangular and sinusoidal patterns, we are able to completely remove oil or trap oil in varying amounts. We present a theoretical model based on geometrical arguments that successfully predicts the criterion for liquid entrapment and provides insights into the parameters that govern the physical process.
We propose a method to trap liquid (both oil and water) in a microchannel by sequentially injecting oil and water (or vice versa) over photopatterned obstacles with controlled wetting properties. We present a simple geometrical model to understand the liquid-entrapment process and predict the evolution of the water/oil interface over an obstacle. Our analysis provides an analytic solution that can successfully predict useful properties such as angular position of pinch-off and the amount of captured liquid. We show that we are able to obtain a liquid bridge over two circular obstacles, and we are also able to predict the condition for the formation of a bridge. We further demonstrate the effect of the obstacle shape and how a sudden change in gradient results in larger liquid entrapment. We also demonstrate the ability to entrap isolated liquid chambers for parallel experimentation.
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