No abstract

High-performance stretchable strain sensors, particularly those with high sensitivity and broad sensing range, are highly important for wearable devices. Herein, a novel auxetic bilayer conductive mesh strain sensor (ABSS), composed of multihardness silicones, is proposed and fabricated by the direct ink writing 3D printing and ink spraying technique. The bilayer conductive mesh comprises a thin layer of high-conductive and crack-prone single-walled carbon nanotubes (SWCNTs) coated on a stretchable carbon-black-doped Ecoflex silicone rubber (CB/ Ecoflex) mesh. The former serves as the dominant sensing material by generating SWCNT cracks in the full strain range, while the latter mainly plays the roles of both generating the resistance change and maintaining the conductive paths under high strain conditions. The presence of high-hardness auxetic frame contributes to the formation of longitudinal SWCNT cracks on transverse meshes, enhancing the sensitivity of the sensors. It is shown that the synergistic effect of the bilayer conductive mesh, strain concentration, and auxetic deformation strategy endow ABSS with a high gauge factor (∼ 13.4) that is 6.6 times larger than that of the common sensor. Additionally, this study demonstrates the superior sensing performance of the ABSS for wearable applications including swallowing recognition, respiration monitoring, and joint movement detection.

An antibacterial coating with stable antibacterial properties and favorable biocompatibility is recognized as an effective method to prevent bacterial adhesion and biofilm formation on biomedical implant surfaces. In this study, a convenient and low-cost printing-spray-transfer process was proposed that enables reliably attaching antibacterial and biocompatible coatings to patient-specific silicone implant surfaces. A desktop three-dimensional printer was used to print the mold of silicone implant molds according to the characteristics of the diseased areas. Multiwalled carbon nanotubes (MWCNTs) uniformly decorated with silver nanoparticles (AgNPs/CNTs) were synthesized as the antibacterial materials for the spray process. The well-distributed AgNPs/CNT coating was anchored to the silicone surface through an in-mold transfer printing process. Stable adhesion of the coatings was assessed via tape testing and UV–vis spectra. Hardly any AgNPs/CNTs peeled off the substrate, and the adhesion was rated at 4B. Antibacterial activity, Ag release, cell viability and morphology were further assessed, revealing high antibacterial activity and great biocompatibility. The process proposed herein has potential applications for fabricating stable antibacterial coatings on silicone implant surfaces, especially for patient-specific silicone implants such as silicone tracheal stents.