(A-9) Fabrication of Electrospun Nanofilament Staple Yarns for Biomedical Applications.

Introduction:: Textiles fabricated using biocompatible and biodegradable polymers such as Polycaprolactone (PCL), Polylactic acid (PLA) and, many more, can be employed in various biomedical applications. Electrospinning is a widely used nanofiber fabrication technique that can produce nanofibers with desirable properties. One of the applications of electrospinning is nanoyarns, which are yarns made from nanofibers filaments. Nanoyarns have already been employed in biomedical fields, which include but not are limited to scaffolds and implants for tissue engineering, and surgical sutures [1]. Currently, most nanoyarns manufacturing setups fabricate yarns directly from the electrospinning jet [2]. However, this approach limits the tuning of filament parameters. More important, current approaches do not allow for fibers to be post drawn before they are turned into a yarn. An alternative approach to yarn fabrication is the use of discrete filaments called staples, which are then twisted into yarns. This allows for the tuning of filament parameters as fiber spinning and yarn spinning do not occur simultaneously. This study aims to fabricate and evaluate mechanical properties of biocompatible polymers such as Polylactic acid (PLA), and Polycaprolactone (PCL) with the goal of employing them in the biomedical field.


Materials and Methods:: Electrospinning and fiber collection is done using the system demonstrated in figure 1a. A potential difference is applied between the tip of the polymer pumping needle and the collection tracks (spinning and solution parameters are summarized in table 1). Fibers produced were then continuously collected on a roving track in order to produce discrete filaments or staples. Filaments are then moved to a spinning device that is capable of turning said filaments into staple yarns. Mechanical Testing and characterization were performed in accordance with ASTM D2256.


Table 1: Summary of electrospinning parameters and solvent ratios for PCL and PLA solutions. DCM: dichloromethane. DMF: dimethylformamide.

Polymer	Solution mixture	Potential difference (kV)	Humidity
PCL	(17% v/v in 3:1 DCM:DMF)	10	50-60%
PLA	(17% v/v in 3:1 DCM:DMF)	10	30-40%

Results, Conclusions, and Discussions:: At the time of submission, testing and analysis was only performed on PCL yarns. Yarn parameters and mechanical parameters are summarized in table 2.

Table 2: Summary of mechanical characteristics of PCL yarn

Sample	Linear Density (g/m)	Specific Strength (Nm/kg)
PCL yarn (100 cm n =1)	0.034	0.45E+5
PCL yarn (15 cm n =5)	0.025±0.0046	0.74E+5±0.13E+5
PCL filament	0.0031	1.96E+5

Figure 2 shows a representative load vs displacement curve for PCL yarn segments with a gauge length of 15 cm. PCL yarn were able to achieve 37% of the specific strength of loose fiber filaments which is to be expected as yarns only retain a certain fraction of the strength of their individual filaments [3]. The mechanics of these yarns are comparable to contemporary textile industrial standards [4]. Future work will aim to incorporate and improve the tunability of filament and yarn parameters, such as draw ratio, linear density, twist per inch, and filament segment length.


Acknowledgements (Optional): : The project is funded by the National science foundation NSF 1653329


References (Optional): : References

[1] Shaohua Wu, Appl. Mater. Today. 2022; 27:101473-101473

[2] Divya Kamiredd, Polym Eng Sci. 2022;63:677-690

[3] Ning Pan, Textile Res. J. 2001;71:960-964

[4] Preston E Sasser, Textile Res. J. 1991;61:681-690