Interfacial Triboelectricity Lights Up Phosphor-Polymer Elastic Composites: Unraveling the Mechanism of Mechanoluminescence in Zinc Sulfide Microparticle-Embedded Polydimethylsiloxane Films.

Composites comprising copper-doped zinc sulfide phosphor microparticles embedded in polydimethylsiloxane (ZnS:Cu-PDMS) have received significant attention over the past decade because of their bright and durable mechanoluminescence (ML); however, the underlying mechanism of this unique ML remains unclear. This study reports empirical and theoretical findings that confirm this ML is an electroluminescence (EL) of the ZnS:Cu phosphor induced by the triboelectricity generated at the ZnS:Cu microparticle-PDMS matrix interface. ZnS:Cu microparticles that exhibit bright ML are coated with alumina, an oxide with strong positive triboelectric properties; the contact separation between this oxide coating and PDMS, a polymer with strong negative triboelectric properties, produces sufficient interfacial triboelectricity to induce EL in ZnS:Cu microparticles. The ML of ZnS:Cu-PDMS composites varies on changing the coating material, exhibiting an intensity that is proportional to the amount of interfacial triboelectricity generated in the system. Finally, based on these findings, a mechanism that explains the ML of phosphor-polymer elastic composites (interfacial triboelectric field-driven alternating-current EL model) is proposed in this study. It is believed that understanding this mechanism will enable the development of new materials (beyond ZnS:Cu-PDMS systems) with bright and durable ML.

Control of the Biodegradability of Piezoelectric Peptide Nanotubes Integrated with Hydrophobic Porphyrin.

Diphenylalanine (FF) is a piezoelectric material that is widely known for its high piezoelectric constant, self-assembly characteristics, and ease of manufacture. Because of its biocompatible nature, it is useful for implantable applications. However, its use in real applications is challenging because it degrades too easily in the body due to its solubility in water (0.76 g/mL). Upon incorporation of hydrophobic and biocompatible porphyrins into the FF, the degradability of the piezoelectric FF and their piezoelectric nanogenerators (PENGs) is controlled. Porphyrin-incorporated FFs are also formed as piezoelectric nanostructures well aligned on the substrate through self-assembly, and their piezoelectric properties are comparable to those of FF. The FF-based PENG degrades in only 5 min, whereas the FF-porphyrin-based PENG produces a stable output for >15 min in phosphate-buffered saline. This strategy for realizing biodegradable functional materials and devices with tunable degradation rates in the body can be applied to many implantable electronics.

Plasticized PVC-Gel Single Layer-Based Stretchable Triboelectric Nanogenerator for Harvesting Mechanical Energy and Tactile Sensing.

Triboelectric nanogenerators have garnered significant attention as alternative power sources for wearable electronics owing to their simple structure, easy fabrication, low cost, and superior power output. In this study, a transparent, stretchable, and attachable triboelectric nanogenerator (TENG) is built with an advanced power output using plasticized polyvinyl chloride (PVC)-gel. The PVC-gel exhibit very high negative triboelectric properties and electrically insulating PVC became an electrically active material. It is found that a single layer of PVC-gel can act as a dielectric and as a conducting layer. The PVC-gel based single layer of triboelectric nanogenerator (S-TENG) creates output signals of 24.7 V and 0.83 µA, i.e., a 20-fold enhancement in the output power compared to pristine PVC-based TENGs. In addition, the S-TENG can stably generate output voltage and current under stretching condition (80%). The S-TENG can be implemented as a tactile sensor that can sense position and pressure without combining multiple elements or electrode grid patterns. This study provides new applications of power sources and tactile sensors in wearable electronics.

Influence of Nasogastric Tubes on Swallowing in Stroke Patients: Measuring Hyoid Bone Movement With Ultrasonography.

OBJECTIVE: To investigate the influence of a nasogastric tube (NGT) on swallowing simulated saliva in stroke patients. METHODS: Three groups of participants were enrolled into the study: group A (20 stroke patients with a NGT), a control group B (25 stroke patients without a NGT), and group C (25 healthy adults with no brain lesions or dysphagia). Participants swallowed 1 mL of water to simulate saliva. Patients in group A were tested twice: once with a NGT (group A1) and once after the NGT was removed (group A2). The distance of hyoid bone movement was measured by subtracting the shortest distance between the mandible and hyoid bone (S) from the distance at resting state (R) measured with ultrasonography. The degree of the movement was calculated by (R-S)/R. The trajectory area of hyoid bone movement (Area) and the interval between the beginning of hyoid bone movement and the moment of the shortest hyoid-mandible approximation (Interval) was calculated by a computer program. RESULTS: From group A: R-S and (R-S)/R of group A2 at 1.14±0.36 cm and 0.30±0.09 cm and were significantly greater than those of group A1 at 0.81±0.36 cm and 0.22±0.08 cm (p=0.009 and p=0.005). After removing the NGT as seen in group A2, R-S and (R-S)/R were improved to the level of those of group B at 1.20±0.32 cm and 0.30±0.09 cm (p=0.909 and p=0.997). The Area of group A2 was larger and the Interval of group A2 was shorter than those of group A1 though a comparison of these factors between A2 and A1 did not show a statistically significant difference. CONCLUSION: A NGT interferes with the movement of the hyoid bone when swallowing 1 mL of water in stroke patients though the movement is restored to normal after removing the NGT.