Bifunctional ultraviolet/ultrasound responsive composite TiO2/polyelectrolyte microcapsules

Designing and fabricating multifunctional microcapsules are of considerable interest in both academic and industrial research aspects. This work reports an innovative approach to fabricate composite capsules with high UV and ultrasound responsive functionalities that can be used as external triggers for controlled release, yet with enhanced mechanical strength that can make them survive in a harsh environment. Needle-like TiO2 nanoparticles (NPs) were produced in situ into layer-by-layer (LbL) polyelectrolyte (PE) shells through the hydrolysis of titanium butoxide (TIBO). These rigid TiO2 NPs yielded the formed capsules with excellent mechanical strength, showing a free standing structure. A possible mechanism is proposed for the special morphology formation of the TiO2 NPs and their reinforcing effects. Synergistically, their response to UV and ultrasound was visualized via SEM, with the results showing an irreversible shell rapture upon exposure to either UV or ultrasound irradiation. As expected, the release studies revealed that the dextran release from the TiO2/PE capsules was both UV-dependent and ultrasound-dependent. Besides, the biocompatibility of the capsules with the incorporation of amorphous TiO2 NPs was confirmed by an MTT assay experiment. All these pieces of evidence suggested a considerable potential medicinal application of TiO2/PE capsules for controlled drug delivery

Thermo-hydraulic evaluation of oscillating-flow shell-and-tube-like regenerators for (elasto)caloric cooling

The development of novel regenerators for caloric cooling applications requires a detailed evaluation of their thermo-hydraulic properties. Structures similar to shell-and-tube heat exchangers are one of the most promising geometries for elastocaloric technology since they exhibit high thermal performance and can be applied under compressive loading to overcome the limited fatigue life of elastocaloric materials normally experienced in tension. However, thermo-hydraulic properties of shell-and-tube-like structures at the conditions relevant for caloric cooling applications (oscillating counter-flow regime at low Reynolds numbers