Paper TF-TuA9
Effect of Atomic Layer Deposition on the Mechanical Properties of Synthetic Nonwoven and Electrospun Polymer Fibers

Tuesday, November 1, 2011, 4:40 pm, Room 107

Nonwoven fiber mats and electrospun nanofiber films have been widely researched for their use in filtration, sensing, scaffolding for biological applications, and in many other areas. Nano- and microscale fibers can be functionalized using thin coatings deposited using ALD to impart mechanical strength, catalytic character, and increase conductivity while maintaining the fiber structure. We are interested in the mechanical properties of ALD coated micro and nano-sized fibers. Increasing the mechanical strength of these fibers allows for their use in more robust applications; however it is desirable for the fibers to maintain their flexibility. For this study, nylon nanofibers formed by electrospinning were coated with either TiO₂ or ZnO at temperatures between 60 and 75°C, and the mechanical tear resistance was characterized by optical microscopy under the application of lateral strain. For the TiO₂ coated samples, the tear resistance remained the same when coated with smaller cycle numbers. As the films become thicker the mechanical properties are more dependent on the character of the coating. Specifically, after oxide coating, the fibers show a more brittle response to bending, resulting in visible cracking under optical microscopy after bending by less than 5° for thicker coatings. Similar trends are observed when nylon nanofibers are coated with ZnO or Al₂O₃, however, using our technique, the measureable change in mechanical response was observed at lower cycle numbers for ZnO and even lower for Al₂O₃ , consistent with very different reactions between the nylon and the various ALD precursors. The difference in the tear resistance between these materials may be a result of the reactivity of the ALD precursors. Choosing a more robust and less brittle material to deposit on the fiber mats should improve their mechanical properties will maintaining the fiber structure and flexibility.