Researchers in Portugal have modified cotton fabric to emit a lemony citronella aroma on contact with sweat – opening up potential for new body-odour-fighting garments to deal with hot summer weather, stressful situations and intense workouts.

The team from the Centre of Biological Engineering at the University of Minho, looked at two ways to release the fragrance – β-citronellol, a lemongrass-derived scent used in some insect repellants – from fabrics.

In recent years, scientists have developed smart fabrics that react to stimuli such as light, temperature or mechanical stress and respond in certain ways, such as by changing colour or conducting an electrical signal. Researchers have also explored different methods to release fragrances from fabrics.

The first approach involved an odourant-binding protein (OBP) found in pigs' noses that binds to β-citronellol and other scent molecules. To the OBP, the researchers attached a protein domain, called a carbohydrate-binding module (CBM), that binds to cotton. 

In their second strategy, the researchers packaged the fragrance in liposomes that displayed CBMs, which anchored the lipid carriers and their cargo to the fabric. 

The team exposed the modified cotton fabrics to an acidic sweat solution, and the low pH of the simulated perspiration caused the OBP and liposomes to release β-citronellol. 

Comparing the two strategies revealed that the OBP released a quick burst of scent, while the liposomes showed a slower, controlled release. 

The liposomes could also hold more fragrance than the other approach. The two strategies could prove useful for different clothing applications, the researchers say.

The project, which is reported in the journal ACS Applied Materials & Interfaces, has received funding from the Portuguese Foundation for Science and Technology and the European Regional Development Fund.