Fabrication of Polyvinylidene Fluoride-Co Hexafluoropropylene (PVDF-HFP) Staple Yarns Using Discrete Electrospun Nano filaments and Evaluation of Their Mechanical and Piezoelectric Properties

Textiles fabricated from biocompatible and biodegradable polymers, such as Polyvinylidene fluoride-co hexafluoropropylene (PVDF-HFP), hold immense promise for various biomedical applications, including scaffolds and implants. Electrospinning, a well-established nanofiber fabrication technique, allows for producing nanofibers with exceptional properties at high throughput. One intriguing application of electrospinning is the creation of nano yarns spun from nanofibers. However, the conventional approach employs continuous filaments, limiting the control over filament parameters. An alternative approach involves the fabrication of yarns using discrete filaments, termed "staples," enabling precise tuning of filament parameters as fiber spinning and yarn spinning occur separately. Building upon previous work, this study introduces a high-throughput yarn-spinning device capable of producing staple yarns with repeatable and consistent parameters. By decoupling the electrospinning and yarn-spinning processes, we harness the unique properties of nanofibers and gain control over their parameters, a feat unattainable with current yarn fabrication methods. This advancement will facilitate an in-depth investigation into the impact of tunable fiber parameters on yarn mechanics. PVDF-HFP staple yarns are crafted from electrospun nanofilaments with varying parameters, such as draw ratio, density, segment length, and more, and their effects on yarn mechanical properties are explored.<br/>Methods: Electrospinning and fiber collection are carried out using a Track electrospinning system. A potential difference is applied between the polymer tip (30% w/v PVDF-HFP in a 2:1 DMF: Acetone solution) pumping needle and the collection tracks. Continuous collection of fibers onto a roving track produces discrete filaments. These filaments are then transported to a spinning device that converts them into staple yarns. Mechanical testing and characterization adhere to ASTM D2256 standards.<br/>Textile products created from biocompatible polymers, such as Polyvinylidene fluoride-co hexafluoropropylene (PVDF-HFP), find applications in biomedical technology. Electrospinning, a widely employed nanofabrication technique, enables the production of nanofibers with superior properties at a rapid production rate. One intriguing application of electrospinning is the creation of nano yarns spun from nanofibers. Currently, nano yarns are produced using continuous filaments.<br/>PVDF-HFP exhibits remarkable properties, including excellent chemical resistance, high stability, low dielectric loss, a high dielectric constant, and biocompatibility. When electrospun, PVDF-HFP yields nanofibers with exceptional mechanical strength and an impressive surface area-to-volume ratio. Post-drawing of thin films enhances the β-phase content of these fibers. This copolymer boasts diverse applications, from developing susceptible sensors for measuring blood pressure and joint pressure to transforming mechanical energy from body movements into electrical energy. PVDF-HFP is also well-suited for energy harvesting systems in implantable medical devices. Furthermore, PVDF-HFP is being investigated for actuators and transducers capable of converting electrical energy into mechanical motion and finding applications in medical devices, such as microsurgical tools and drug delivery systems.<br/>The ongoing research aims to transform electrospun PVDF-HFP filaments into yarn using a specialized spinning device to assess the piezoelectric responses of the resulting yarns for various biomedical applications. This study presents a significant advancement in developing PVDF-HFP staple yarns, offering a more versatile and tunable approach for biomedical applications. Integrating electrospinning and yarn spinning at distinct stages enables precise control over yarn parameters, expanding the potential for harnessing the remarkable properties of PVDF-HFP in diverse medical devices and systems.