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Micromotors have gained increasing attention in last two decades, due to their controllable self-propulsion maneuverability at micro scales. However, the effect of particle size on micromotors is still vague and interwoven due to the micromotors’ size, polydisperse distribution, and structural variations. Microfluidic technology is used to clarify the phenomenon, due to its precise micro scale fabrication. Herein, we fabricated a H₂O₂-driven self-electrophoretic Janus micromotor and systematically explored the effects of particle size on their dynamics, the sputtering distribution, and the rectifying voltages. Their speeds were found to be inversely proportional to their sizes. When the particle size was fixed, their speeds increased as coating thickness increased until its hemisphere was fully coated, and this critical coating thickness was also proportional to the sizes of the micromotors. As further investigation goes on, we noticed that electrical voltage to rectify micromotor was proportional to its size too. To summarize, our results showed that larger micromotors moved more slowly, required a thicker metal coating to reach full speeds, and needed higher voltages to be rectified. Through all of these investigations, we believed that microfluidic technology is a valuable tool, which can systematically probe micromotors dynamics and clarify our understanding of micromotors behaviors.

The fluids with well-defined inner structure and intrinsic responsibility are demanding to the maintenance and regulation of normal functions in living systems. Inspired by this, responsive Janus droplets are constructed by small molecules of magneto-surfactants, and the traditional vortex mixing is applied to guarantee large-scale fabrication. Silicone oil (SO) and Vegetable oil (VO) as two immiscible oils are introduced as inner phases of the Janus emulsions. The topology and subsequently the magnetic responsive performance of Janus emulsion is controlled by adjusting the oil composition with various viscosity, the surfactant concentration and the mass ratio of two oils. Moreover, the remote control of the emulsion stability is realized by the external magnetic field, of which the demulsification mechanism is investigated. The anisotropic and responsive droplets with advantages of deformability, encapsulation capability, and biocompatibility would expand the application of emulsions in targeted therapy, drug delivery and magnetic materials science.

The design of biocompatible multiple emulsions is an important challenge in the field of controlled delivery systems for protecting and delivering compounds encapsulated and protected in the innermost phase. In this paper, we use biocompatible water – Miglyol®812 water-in-oil-in-water (W/O/W) emulsions stabilized by a stimuli-responsive diblock copolymer consisting of poly(dimethylsiloxane) (PDMS) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) to design an easy-to-process new delivery W/O/W system. Such emulsions are formed in a single emulsification step. They present a high encapsulation yield and are shown to be stable over months. As such, the encapsulation of a hydrophilic dye (Alexa fluor) in the innermost water phase is successfully demonstrated over months. These emulsions are stimulable either by a shift in pH level or in ionic strength. The former destabilizes the multiple emulsion and leads to a simple one while the latter partly maintains the multiple character. Eventually both stimulations are effective in the dye release and molecular mechanisms are proposed for explaining the observed two-stage kinetics of release.

Understanding the relationship between colloidal building block shape and self-assembled material structure is important for the development of novel materials by self-assembly. In this regard, colloidal superballs are unique building blocks because their shape can smoothly transition between spherical and cubic. Assembly of colloidal superballs under spherical confinement results in macroscopic clusters with ordered internal structure. By utilizing Small Angle X-Ray Scattering (SAXS), we probe the internal structure of colloidal superball dispersion droplets during confinement. We observe and identify four distinct drying regimes that arise during compression via evaporating droplets, and we track the development of the assembled macrostructure. As the superballs assemble, we found that they arrange into the predicted paracrystalline, rhombohedral C₁-lattice that varies by the constituent superballs’ shape. This provides insights in the behavior between confinement and particle shape that can be applied in the development of new functional materials.

A facile one-step method of roughened copper foils of 0.0076 ​mm thickness heated on the open flame for 15 ​s produced superhydrophilic surfaces that exhibited superwetting at average radial growths of 10.8 ​mm/s following drop dispensation. Superhydrophilicity was found to deteriorate over time and XRD analysis ruled out compositional change as the cause of this behaviour. Instead, SEM imaging revealed wrinkled 20–30 ​nm-thick nanoflakes that were predominantly stretched out initially to engender superwetting properties via Wenzel wetting. These extended microstructures folded up with time due to relaxation of the residual stresses from the thermal oxidation process, resulting in temporal reduction in superhydrophilicity, which can be restored by reapplying thermal oxidation. The impingement of air with 80 psi pressure on the substrate also caused similar deterioration. The superwetting characteristic also endowed these substrates with anti-bacterial properties where a 56% reduction in bacteria count with Staphylococcus epidermidis was found.

A majority of carbonate reservoirs are preferably oil-wet or intermediate wet. Spontaneous imbibition represents an important mechanism to enhance oil production. Targeting an oil-wet carbonate reservoir with high temperature and high salinity, several surfactant formulations were investigated to improve oil production by imbibition, focusing on the capacity in interfacial tension (IFT) reduction and surfactant partitioning in water and oil phases in addition to dominant wettability alteration effect. Oil production potentials using different surfactants were evaluated by spontaneous imbibition in Amott cells at 95 ​°C. A base case imbibition test was conducted using a high salinity water with IFT value of 15.2 ​mN/m and an oil-wet carbonate core, and the oil production was 6.4% of oil originally saturated in core. Reducing the oil-water IFT to 10° ​mN/m magnitude achieved 4% incremental oil production beyond base case. When the IFT was further reduced to 10⁻¹ ​mN/m magnitude, the incremental oil production reached 10%. For the case of water-wet core and at the same IFT range, the incremental oil production was 13%. When the IFT was reduced to 10⁻² ​mN/m, the incremental oil production was up to 17% for the tests using oil-wet cores, and up to 23% for the water-wet counterpart. When further reducing the IFT to ultra-low magnitude of 10⁻³ ​mN/m, the oil production was close to that using the imbibition agents with IFT of 10⁻² ​mN/m magnitude. For surfactants with no obvious wettability alteration capacity, those surfactants with higher molecular fraction in oil phase and higher adsorption on rock surfaces could remove more oil from the pore wall, and yielded higher imbibition efficiency. This work systematically investigated the major effects of surfactant on oil mobilization during imbibition process, which can help for better understanding of chemical imbibition in carbonates. The findings will shed light on the selection of high performance imbibition agents for carbonate reservoirs.

Hypothesis

Biophysical property and water evaporation retardation through a lipid nanofilm can be altered by model tear protein and topical ophthalmic formulation.

Experiment

Evaporation rate and dynamic surface pressure were measured using a sessile drop technique. Water evaporations from 5 individual protein solutions, their mixture, and 6 ophthalmic formulations were quantified. Biophysical property and evaporation through model lipid nanofilms spread on model electrolyte solutions, tear protein solutions, and ophthalmic formulations were assessed.

Findings

Model lipid nanofilms spread on electrolyte solution reduced evaporative fluxes by 43–60%. Evaporative fluxes from individual protein solutions without lipids were 3–19% lower than from electrolytes solution. Evaporative fluxes through lipid nanofilms were decreased by the presence of albumin or lactoferrin in solutions but increased by lysozyme and mucin.

Evaporative fluxes from ophthalmic formulations were 10–43% lower than from electrolyte solution. Evaporations through lipid nanofilms spread on formulations were higher than through lipids on electrolyte solution. Model lipid nanofilms spread on Diquas appeared more rigid than on electrolyte solution but showed softening when spread on Refresh Mega-3.

Some proteins and ophthalmic formulations altered model lipid nanofilms evaporative barriers. Ophthalmic formulation induced changes in biophysical property of model lipid nanofilms in vitro may suggest possible tear film destabilization in vivo.

Investigation into the use of thermally reversible Diels-Alder chemistry coupled with magnetic iron oxide nanoparticles has grown over the last decade. This technology has been used for a variety of applications such as thermoresponsive materials, catalytic chemistry, and drug delivery systems. In this study, we evaluate two distinct thermally labile Diels-Alder linkers for the release of payloads from the surface of magnetic iron oxide nanoparticles. Density functional theory (DFT) computational predictions of the Gibbs free energy and enthalpy reaction barriers were performed and revealed a dramatic difference in reverse energy barriers between the two linkers. These thiophene-based cycloadducts were then synthesized, conjugated to the surface of iron oxide nanoparticles, and characterized by NMR and ESI-MS. The results of the modeling were confirmed when the functionalized nanoparticles were subjected to immersion heating and the payload release rates observed were in agreement with the DFT calculations. Similarly, AMF-RF hysteretic heating of the functionalized nanoparticles revealed payload release rates that correlated with the DFT calculations and the data from the heat immersion studies. Together, these results indicate that these distinct thermally labile Diels-Alder linkers can be used to fine-tune the kinetics of payload release from nanoparticles.

There is an increasing demand for emulsions with low viscosity, a large fraction of dispersed phase, high transparency, or long shelf life. Emulsions consisting of nanosized dispersed droplets meet these criteria, but conventional nanoemulsions require large quantities of surfactants, some of which are unwanted due to health and environmental concerns. Surfactants can then be replaced by solid particles, forming the so-called Pickering emulsions. Combining nanosized droplets and particle-stabilized emulsions leads to Pickering nanoemulsions. Since their first appearance in 2012, they have received increasing attention, but several points remain challenging; the choice of particles according to their origin, shape, sizes, and wetting properties and the process to produce drop sizes in the nano range. This review describes the recent advances in terms of manufacturing processes and destabilization mechanisms of Pickering nanoemulsions. It reports the particles used to stabilize the oil-water interface and strategies to improve their wetting properties, as well as examples of applications for the design of formulations in the pharmaceutics, food packaging, and enhanced oil recovery sectors.

Defect engineering has been proved to be an effective strategy to adjust the electronic structures and photocatalytic activities of semiconductor oxides. However, due to lack of convenient approach to construct defect, the effect of oxygen vacancy defect on photocatalytic hydrogen evolution has always been controversial. Herein, we proposed a facile molten-salt defect engineering (MSDE) strategy to introduce oxygen vacancies (Vos) defects in TiO₂(B) nanobelt (TNB). By tuning the addition amount of NaBH₄ during molten-salt calcination process, the concentration of surface oxygen vacancies can be effectively adjusted. As a result, the appropriate oxygen vacancies on TNB not only suppressed the recombination of photogenerated electrons and holes, but also raised the conduction band position of TNB, thereby increasing the reduction potential of photogenerated electrons. The as-prepared photocatalyst TNB-NaBH₄-2 with optimal Vos concentration exhibited highly efficient photocatalytic hydrogen evolution performance at a rate of 3.2 ​mmol ​g⁻¹h⁻¹ under simulate solar light, nearly 1.85 times than that of pristine TNB. This work proposes a simple method for constructing moderate oxygen vacancies on metal oxides for enhancing photocatalytic hydrogen evolution.