Energy harvesting model of moving water inside a tubular system and its application of a stick-type compact triboelectric nanogenerator

As the first invention to efficiently harvest electricity from ambient mechanical energy by using contact electrification, the triboelectric nanogenerator has elicited worldwide attention because of its cost-effectiveness and sustainability. This study exploits a superhydrophobic nanostructured aluminum tube to estimate electrical output for solid-water contact electrification inside a tubular system. The linearly proportional relationship of short-circuit current and open-circuit voltage to the detaching speed of water was determined by using a theoretical energy harvesting model and experimentation. A pioneering stick-type solid-water interacting triboelectric nanogenerator, called a SWING stick, was developed to harvest mechanical energy through solid-water contact electrification generated when the device is shaken by hand. The electrical output generated by various kinds of water from the environment was also measured to demonstrate the concept of the SWING stick as a compact triboelectric nanogenerator. Several SWING sticks were connected to show the feasibility of the device as a portable and compact source of direct power. The developed energy harvesting model and the SWING stick can provide a guideline for the design parameters to attain a desired electrical output; therefore, this study can significantly increase the applicability of a water-driven triboelectric nanogenerator.

Mechanical properties of graphene oxide?silk fibroin bionanofilms via nanoindentation experiments and finite element analysis

Understanding the mechanical properties of bionanofilms is important in terms of identifying their durability.The primary focus of this study is to examine the effect of water vapor annealed silk fibroin on the indentation modulus and hardness of graphene oxide-silk fibroin(GO-SF)bionanofilms through nanoindentation experiments and finite element analysis(FEA).The GO-SF bionanofilms were fabricated using the layer-by-layer technique.The water vapor annealing process was employed to enhance the interfacial properties between the GO and SF layers,and the mechanical properties of the GO-SF bionanofilms were found to be affected by this process.By employing water vapor annealing,the indentation modulus and hardness of the GO-SF bionanofilms can be improved.Furthermore,the FEA models of the GO-SF bionanofilms were developed to simulate the details of the mechanical behaviors of the GO-SF bionanofilms.The difference in the stress and strain distribution inside the GO-SF bionanofilms before and after annealing was analyzed.In addition,the load-displacement curves that were obtained by the developed FEA model conformed well with the results from the nanoindentation tests.In summary,this study presents the mechanism of improving the indentation modulus and hardness of the GO-SF bionanofilms through the water vapor annealing process,which is established with the FEA simulation models.