Electrospun Hydrolyzed Collagen From Tanned Leather Shavings For Bio-triboelectric Nanogenerator

In recent years,with the miniaturization development of portable electronic equipment,energy utilization has been transferred from centralized to decentralized and from high quality to low quality.In 2012,based on coupling friction electrification and electrostatic induction,Wang’s group invented TENG that can efficiently convert mechanical energy into electricity,which brings a breakthrough in the technology of energy conversion and utilization.In tannery production,more than 80%of the solid waste is wastes of shaving and trimming,with collagen as the main component.As a kind of natural biomaterials,the collagen has unparalleled biocompatibility and degradability.It has a great potential to become the triboelectric positive material layers of bio-TENGs due to its rich electron-donating groups,which is significant to realize the high value-added utilization of tanning process resources.Electrospinning is a versatile,efficient and viable technique for generating continuous fibers.The electrospun nanofibers with rough surface and high porosity and specific surface area offers enriched sites for capturing and maintaining large amounts of surface charge.Therefore,designing the friction layer by electrospinning fabrication procedures is beneficial to induce a high surface charge density,which is an efficient way to prepare TENG.In this work,we presented a shaving collagen-based bio-TENG with an all-nanofiber structure.7wt%Na OH/12wt%urea solvent system was applied to hydrolyze the waste tanned leather shavings in 30℃to generate collagen molecule.The main electrospinning parameters were adjusted to optimize the microstructural morphologies of nanofibers and the spinning process.PVA was used as additive and the optimal concentration is 10 wt%～12 wt%.The main electrospinning parameters such as voltages,feeding rates had been carefully adjusted with the optimum ranges of 18-20 k V and 0.3-0.9 m L/h to achieve continuous and uniform spinning with the fiber diameter between 500nm-700nm.Based on the optimized collagen/PVA electrospinning conditions,collagen/PVA/Ag NWs composite nanofiber membranes were prepared and the mechanical properties,antibacterial properties and biocompatibility were evaluated.Furthermore,carbon nanotubes(CNTs)and graphene nanosheets(GNPs)were doped into the spinning solution to prepare collagen/PVA/CNTs and collagen/PVA/GNPs composite nanofiber film.A series of contact-separation-mode Bio-TENGs were fabricated using the prepared collagen-based composite fiber membranes as positive layers.The effects of different conductive powder adding amount,contact area,frequency and other factors on the open circuit voltage were explored.The of collagen/PVA/Ag NWs(8%)can deliver the maximum output voltage,current and instantaneous power up to 118V,3.8 n A and 21.06 m W/m~2 with contact area of 2 cm×2 cm that can serve as a reliable power source to drive small electronics like 30 LEDs and electronic calculators.This research provides a simple and economical strategy to utilize the waste biomaterial for the construction of bio-TENG,and proposes a promising idea in designing mechanical energy harvester to supply low-power devices.