Endowing scaffold with antibacterial activity is an effective countermeasure to prevent bacterial infection in bone repair. Silver nanoparticles (Ag NPs) possess broad-spectrum antibacterial efficiency, whereas the agglomeration and burst releasing of Ag NPs hindered their clinic application in bone repair. In this work, Ag NPs were in situ grown on graphene oxide (GO) to construct Ag@GO nanohybrids and then were introduced into polymer scaffold. GO could efficiently load Ag NPs thereby improving their agglomeration in a scaffold, owing to their abundant active groups and large surface areas. Furthermore, GO could realize the sustained release of Ag ions from the scaffold. The results demonstrated the antibacterial scaffold exhibited robust antibacterial performance with an antibacterial rate of 95% against Staphylococcus aureus. On one hand, GO with honeycomb nanostructure and sharp edge could capture and pierce bacteria membrane, which results in physical damage of bacteria. On the other hand, the released Ag NPs from Ag@GO nanohybrids could promote the generation of reactive oxygen species, which causes the inactivation of bacteria. Encouragingly, the antibacterial scaffold also exhibited good cytocompatibility. This work developed an efficient antibacterial material for the scaffold in bone repair.

Resistivity is considered a significant parameter for printing a conductive pattern and nano-ink. Nevertheless, the resistivity of a sintered printing pattern varies with the performance of the pattern and nano-ink. The cross section or non-uniformity of the printing pattern is not taken into consideration, and the changes in resistivity are not measured during the whole sintering process. In this work, the cross section uniformity of the pattern is improved, which is attributable to the standard sample template fabricated by laser engraving. First, the ink containing 50 wt. % silver nanoparticles (AgNPs) with sizes ranging from 30 to 100 nm was prepared. Second, the prepared ink and commercial ink containing 50 wt. % AgNPs with an average size of 5 nm were separately injected into two standard sample templates. Finally, a four-probe platform was employed to carry out the sintering process at different temperatures. We studied the effects of sintering temperature on pattern resistivity and the subsequent performance of the prepared ink. Furthermore, the thermal conductivities of inks were calculated through the optimized Wiedemann–Franz law for different temperatures. The results showed that electrical resistivity of two inks changed after sintering, presenting the same trend of an initial linear increase, then a linear decrease, followed by a period of stability, and finally a linear increase as the sintering temperature increased. In addition, when the ink was sintered completely, the porosity observed using an optical microscope with 1000× magnification and resistivity and thermal conductivity of the prepared ink were 80.13%, 69.48%, and 66% smaller than those of commercial ink, respectively. The methods proposed in this paper lay the foundation for further research on nano-ink.

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Microstructure plays an important role in improving the performance of flexible sensors. Changing the shape of the dielectric layer microstructure is an effective countermeasure to promote the sensitivity of capacitive sensors. Nevertheless, traditional microstructure fabrication methods have high manufacturing costs, cumbersome manufacturing processes, and single structure manufacturing, which restrict the development of flexible sensors. In this work, electro-hydro-dynamic (EHD) printing method and aerosol jet (AJ) printing method were applied to fabricate 3D microstructures, in a manner of printing the same pattern in multiple layers. The height and morphology of 3D microstructures, under different printing parameters, were compared by changing the number of printing layers and printing speed. Additionally, the printing effects of the two printing methods were compared. The results demonstrated that various shapes and highly controllable 3D microstructures could be fabricated by both methods. The EHD printing method had higher manufacturing precision, whereas the AJ printing method had higher stacking efficiency. The height and morphology of 3D microstructures could be effectively controlled by changing the number of printed layers and the printing speed of the microstructures. It is indicated that the EHD printing method and the AJ printing method both have great potential in the fabrication of 3D microstructures and that both methods had their own advantages.

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