Bicomponent fibres for controlled release of volatile mosquito repellents

Core-sheath structured fibres were developed for application as part of an alternative malaria vector control intervention aimed at reducing outdoor malaria transmission. The fibres were prepared by melt spinning of high density polyethylene (HDPE) as sheath and with a concentrate containing volatile N,N-Diethyl-m-toluamide (DEET) in poly(ethylene-co-vinyl acetate) (EVA) as core. The concentrate was prepared by a simple absorption processes to a content up to 40 wt% DEET. Scanning electron microscope imaging confirmed the formation of a bicomponent core-sheath fibre structure. Confocal Raman spectroscopy revealed the development of a concentration gradient of DEET in the sheath layer, suggesting a diffusion controlled release process. Excellent processability was demonstrated on an extrusion system melt spinning with take up speeds reaching 3000 m min^-1. Sample textiles knitted from such filaments showed high residual repellence activity even after 20 cold washes or after eight months ageing under laboratory conditions. These findings indicate that this technology offers an alternative way to prevent outdoor mosquito bites in an effective and affordable manner.