The objective of this project is to develop novel multifunctional fibers for the controlled delivery of environmentally friendly, low toxicity insect repellents encapsulated in the core of nylon fibers via coaxial electrospinning and demonstrate feasibility for transition. Building upon the success of a FY19 Limited Scope effort (WP19-1187), individual fibers will be engineered by electrospinning, as well as scalable extrusion methods, to exhibit one or more functionalities providing multiple approaches for the production of yarn and/or fabric composites for environmentally sustainable multifunctional textiles.

A dynamic Department of Defense team will use electrospinning as a rapid prototyping method to develop insect repellent fibers containing active additives and demonstrate transition to conventional textile fibers to improve durability and maintain physical performance of traditional fabric. As demonstrated during the initial Limited Scope effort, coaxial electrospinning affords the ability to create hierarchically-structured functional micro- to nano-scale fibers by controlling the composition of specific areas of the fiber (core vs. surface). This is critical for the insect repellent application in which the release should occur slowly throughout the lifetime of the garments. First, nylon electrospun fibers containing dual insect repellents (picaridin and DEET) will be fabricated and evaluated for complementary release profiles and synergistic enhancement of repellency (Task 1). Second, electrospun fibers will be physically spun into yarns and threads to demonstrate capability for direct scale-up of design concepts (Task 2). Once the core-shell fiber approach has been demonstrated using the low material requirements and flexible processing controls afforded by electrospinning, the technology will then be applied to conventional fiber drawing techniques (e.g. melt extrusion) for demonstration of scale-up potential (Task 3). Finally, coaxial fiber designs will be employed to show proof of concept for incorporation of additional functionalities, including fire retardant and antimicrobial additives, into the insect repellent fibers (Task 4). Overall, the approach will provide the development of insect repellent nylon fibers with controlled release of multiple insect repellents, demonstrate their capability to scale-up through current manufacturing processes, and prototype next generation multifunctional fiber proof of concepts (insect repellent and fire retardant/antimicrobial) for improved performance for multifunctional uniform applications.

The encapsulation of insect repellent (i.e. picaridin, DEET) into textile fibers via a bottom-up approach affords the potential to create fabrics and garments that offer long-term protection to the warfighter from insect-borne diseases. Incorporation of the active materials into the core of the fibers will greatly enhance the durability of these functionalities to laundering, especially when compared with surface treatments, strongly reducing the current health hazards present for surface treated fibers and increasing their environmental sustainability. The insect repellent fibers that will result from this project have the potential to greatly reduce environmental and health risks during their lifecycle by 1) increasing the longevity of functionalities after laundering, 2) reducing direct skin contact of active additives by encapsulation within the core of a benign material, and 3) generating novel fibers from which textiles and garments could be intelligently designed with functionalities localized and limited only to the areas in which they are needed.