Preparation of pH-sensitive alginate-based hydrogel by microfluidic technology for intestinal targeting drug delivery.

Hydrogel microspheres stand out in drug delivery due to their small particle size, biocompatibility and good internal stability. In this paper, pH-sensitive hydrogels are prepared by microfluidic technology for targeted drug delivery in the small intestine. A coaxial dual-channel microfluidic chip is constructed. By analyzing the effects of flow rates and three fracture stages (Rayleigh-Plateau instability crushing stage, pressure difference crushing stage and shear force crushing stage) on the size of hydrogel microspheres, the optimal control stage of the microsphere size is determined (shear force crushing stage). Based on this, the accurate control model of the hydrogel microsphere size is proposed. In addition, based on the coaxial dual channel microfluidic chip, a monolayer hydrogel microcapsule loaded with Indometacin is prepared. The core-shell hydrogel microcapsules loaded with Indometacin are prepared by an improved coaxial three channel microfluidic chip. The swelling rates of both microcapsules in simulated intestinal fluid are significantly higher than those in simulated gastric fluid. The results of in vitro simulated release experiments show that the two hydrogel microcapsules basically do not release in simulated gastric juice. In simulated intestinal fluid, single-layer hydrogel microcapsules show rapid release, while core-shell hydrogel microcapsules showed slow release. In conclusion, the alginate-based hydrogel microcapsules have good stability and pH sensitivity, and are suitable for targeted drug delivery in the small intestine.

Magnetically actuated hydrogel-based capsule microrobots for intravascular targeted drug delivery.

Microrobots for targeted drug delivery in blood vessels have attracted increasing interest from researchers. In this work, hydrogel-based capsule microrobots are used to wrap drugs and deliver drugs in blood vessels. In order to prepare capsule microrobots of different sizes, a triaxial microfluidic chip is designed and built, and the formation mechanism of three flow phases including the plug flow phase, bullet flow phase and droplet phase during the preparation of capsule microrobots is studied. The analysis and simulation results show that the size of the capsule microrobots can be controlled by the flow rate ratio of two phases in the microfluidic chip, and when the flow rate of the outer phase is 20 times that of the inner phase in the microfluidic chip, irregular multicore capsule microrobots can be prepared. On this basis, a three degree of freedom magnetic drive system is developed to drive the capsule microrobots to reach the destination along the predetermined trajectory in the low Reynolds number environment, and the magnetic field performance of the magnetic drive system is simulated and analyzed. Finally, in order to verify the feasibility of targeted drug delivery of the capsule microrobots in the blood vessel, the motion process of the capsule microrobots in the vascular microchannel is simulated, and the relationship between the motion performance of the capsule microrobots and the magnetic field is studied. The experimental results show that the capsule microrobots can reach a speed of 800 µm s-1 at a low frequency of 0.4 Hz. At the same time, the capsule microrobots can reach a peak speed of 3077 µm s-1 and can continuously climb over a 1000 µm high obstacle under a rotating magnetic field of 2.4 Hz and 14.4 mT. Experiments show that the capsule microrobots have excellent drug delivery potential in similar vascular curved channels driven by this system.

Dramatically Improved Thermoelectric Properties by Defect Engineering in Cement-Based Composites.

In recent years, the problem of overheating in summer has been of great concern. Pavements are continuously exposed to solar radiation, and because of high temperatures, pavement temperatures reach 60 to 70 °C. This potential low-grade heat has been unused. Cement-based composites with thermoelectric properties can convert this low-grade heat to useful electrical energy. The importance of this green technology for generating renewable energy and sustainable development has been widely accepted and noticed. However, the power factor of current cement-based composites is too low, and harvesting low-grade heat on a large scale and at low cost requires improving the thermoelectric properties of cement-based composites. In this paper, we present a method to increase the electrical conductivity of ZnO and thus improve the thermoelectric properties of cement-based composites by defect engineering, obtaining a high power factor of 224 µWm-1 K-2 at 70 °C, a record value recently reported for thermoelectric cement-based composites. Zinc oxide powder was treated with a reducing atmosphere to increase the content of oxygen defects and thus improve the electrical conductivity. Pretreated ZnO powder of 5.0 and 10.0 wt % expanded graphite were added to the cement matrix. The ZnO/expanded graphite cement-based composites were made and tested for their thermoelectric properties using a dry pressing process, which exhibited excellent thermoelectric properties. The result showed high conductivity (12.78 S·cm-1), a high Seebeck coefficient (-419 µV/°C), a high power factor (224 µWm-1 K-2), and a high figure of merit value (8.7 × 10-3), which facilitate future large-scale applications. Using the cement-based composites to lay a road of 1 km in length and 10 m in width, 35.2 kW·h of electricity can be collected in 8 h. This study will inspire how to improve thermoelectric performance of cement-based composites.