2.9. Prototype Bite-Resistant Fabrics Tested for Garment Construction

Three knitted fabrics (H, B, S; Table 1 and Figure S3B–D) were developed as component textiles for garment construction. They were selected from a dataset of candidate bite resistant fabrics that were predicted safe by our bite-resistance model. These textiles were assayed using arm-in-cage bioassays since the goal later was to test them in garments on human subjects in walk-in-cage studies.

Case 1 H. The Case 1 fabric H (the high-density fabric, H; Figure S3B) was an ultra-fine synthetic knit of 80 percent polyamide of 20 denier count and 20 percent elastane of 20 denier count and had a weight of 96 g/m². Its pattern is a jersey plated knit structure of 84 wales and 112 courses per inch and with a pore size between 20 µm and 28 µm, allowing air passage but preventing mosquito biting. It had a high elasticity of 400% stretch in the course direction and 160% stretch in the wale direction (Figure S7C). The H fabric has a more elastane content and smaller pore size compared with T1, which came from the same knitting technology. It was made into a base layer in the following section “construction of protective garments”. Although the H fabric was not a 100% bite-resistant material due to an irregular pore distribution in the knit pattern, when combined as a base layer with military issued garments, a 100% bite resistance was possible in whole-garment testing.

Case 1 B. Fabric B (a bonded fabric; Figure S3C) is the combination of two layers of H fabric that was made by applying a small dot pattern of dry low-melt adhesive (CG-1698 polyurethane adhesive, Chemix Guru Ltd., Taichung, Taiwan) to one surface and then feeding the two fabrics back-to-back together applying pressure using heated drums (temperature 120 °C, duration 20 s). The two fabrics are fused together at regular intervals, and then the adhesive dots subjected to cool circulating air for 24 h to eliminate volatiles that might affect mosquito biting. The paste dot application procedure is particularly gentle to the substrate, and the wide range of options for formulating the paste provides the user flexibility in the application procedure. The relative nature, drape, porosity, and flexibility of the fabric is maintained, and this method only adds approximately 5% to the total weight. The B fabric is highly stretchable and demonstrated high mosquito bite resistance, which makes it suitable to being used as an outer protective garment.

Case 2 S. The S fabric (3D spacer fabric; Figure S3D) was a commercially available 3D warp knit spacer fabric (Production ID: 34836, Springs Creative Products Group, LLC, Rock Hill, SC, USA) that was predicted safe for bite protection using our Case 2 model. The surface (top and bottom) yarns are PA filament tows, and the pile yarns used in the middle layer were PA monofilaments. The surface patterns are shown in Figure S3D. The S fabric had a stable structure with large openings outside that allowed air flow into and under the garment, thereby transporting of heat and sweat out.

Case 3. Case 3 fabrics were translucent due to their large pores and not practical when used alone for typical garments where human body parts need to be covered and not seen by others. Therefore, we did not use the Case 3 fabrics to assemble a garment. This is not to say this fabric does not have uses for mosquito protection in parts of the body where it is ok to show the skin or as a cover at the beach or in the tropics where there are mosquitoes and also high thermal challenges to the body. The materials could also have uses for garment ventilation in specific areas of a garment.

Base on the color requirement for military garments, the H fabric was dyed to a light brown color before assembly into the base layer. B and S were dyed to a camo color before assembly into the military-style shirt (NCSU shirt).