Construction And Performance Of Full 3D-printing Polyvinylidene Fluoride Based Triboelectric Nanogenerator

In recent years,the development of the Internet of Things and artificial intelligence has placed stringent requirements on the power supply for lightweight and convenient micro-electronic devices.To meet this challenge,triboelectric nanogenerators（TENG）,as a novel energy conversion technology that converts mechanical energy from the surrounding environment into electrical energy.It has great advantages in material selection,structural design and functional applications to meet the needs of different sizes and application scenarios.Importantly,the choice of triboelectric material directly affects the performance of TENG.Polyvinylidene fluoride（PVDF）,as a flexible material,has excellent mechanical properties and chemical stability,and its polarβcrystal form shows excellent electroactivity and electron affinity.Therefore,PVDF can be used as an effective dielectric and high-quality triboelectric layer for TENG.In this paper,highβ-phase composites are prepared by the synergistic induction among barium titanate（BaTiO₃,BT）,ionic liquid（IL）and PVDF.Then emerging 3D printing technology is combined with TENG construction.Using the flexible structural design of fused deposition molding（FDM）,TENG is constructed with triboelectric layer,electrode,and support structure to realize the continuous one-shot molding of devices without post-processing.This provides a more convenient and effective molding method for the preparation of TENG,thus further broadening its applications.First,the highβ-phase BT/IL/PVDF composites were prepared by melt blending.Through the combination of the negatively charged F of PVDF and the positively charged oxygen vacancies on BT,and the ion-dipole interaction between the-CF₂ of PVDF and the imidazolium cation of IL,a large amount ofα-phase toβ-phase transition in the PVDF system was induced synergistically.As a result,the relativeβ-phase content can reach 84.01%.At the same time,BT acts as a nucleating agent to alleviate the decrease of crystallinity brought by IL,so that the totalβ-phase content can be increased to 36.88%,which is 2.77 times higher than that of pure PVDF.And the compound system significantly improves the dielectric properties of the composite,and the dielectric constant of the composite can reach 36.3 at 100 Hz,which is 4.5 times that of PVDF.In addition,the compound system also improves the thermal stability performance,melt flow performance,and thermal conductivity of the material.Secondly,the effects of nozzle temperature,platform temperature,printing speed and nozzle diameter on the crystallization behavior and product quality of BT/IL/PVDF products by FDM molding were investigated,and the influence law of printing parameters on the products was explored.The optimal FDM process parameters for BT/IL/PVDF composites are determined as follows:nozzle temperature of 200℃,platform temperature of 120℃,printing speed of 30 mm/s,and nozzle diameter of 0.4 mm.The totalβ-phase content of the products obtained under the optimal printing parameters is 37.97%,which is a small increase compared with the totalβ-phase content under melt blending,demonstrating that the FDM molding process helps to increase theβ-phase content in the BT/IL/PVDF composites.Finally,a single-electrode TENG was molded by dual-nozzle FDM under suitable FDM printing parameters,with a self-made highβ-phase BT/IL/PVDF composite and a conductive thermoplastic elastomer（TPE）as the material base.The effects of printing patterns,print area and number of printing layers on the output performance of the TENG were investigated.The output voltage of the device can reach 15.46 V.In addition,it is found that the sensitivity of the TENG to pressure is about 0.31 V/kPa at a pressure of 6～27.78 kPa,which can achieve force-to-electricity conversion.Meanwhile,in order to enable a more efficient and stable output of the TENG,a vertical separation-contact TENG with three-dimensional surface pattern modification was fabricated by fully 3D-printing.And the peak output voltage can reach 9.59 V,which is 109.85%higher than that of the device without pattern modification.When the external load is 100 MΩ,the maximum power density of the device is 2.3 m W/m².In this paper,an efficient and simple method for constructing TENG is developed,which does not require post-processing and complicated assembly process.By using the design flexibility of fully 3D-printing,TENG can meet the needs of different sizes and application scenarios,and can be applied to self-powered sensors and human motion monitoring.A highly efficient and continuous molding method of TENG is developed,which has the advantages of flexible structure and adjustable multi-parameters.It is expected to be applied in the fields of self-powered sensing and human motion monitoring.