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■Bio-mathematics, Statistics and Nano-Technologies: Mosquito Control Strategies

For COT/PET fabric, the sample treated with O2 only and the 30 nm a-C:H is 20 - 30

mm/s lower than the reference. The thicker coating shows a higher R of about 15 mm/s,

which is probably due to the fact that the cotton content is more susceptible to damage, as

shown previously. Here, all refinements increase R, except the fabric with 60 nm a-C:H,

where it is 20 mm/s less for IO add-on and even 15 mm/s more for the IO+WG combina-

tion. For the IO finished samples, there is a slightly increased R of about 10 mm/s, which

is significantly higher for the oxygen plasma-treated samples with around 60 mm/s. It

could be that the oxygen treatment activates or etches the surface more strongly, and sub-

sequent finishing results in a smoother surface that increases R.

Tensile tests (Figure 15.2, two lower rows) are used to check whether there are stabil-

ity changes caused by the applied surface treatments. Cotton fabrics tear most easily, the

maximum force (Fmax) is reached at about 700 N. The O2 treatment strengthens the ten-

sile resistance by about 500 N. For the combined IO+WG finishing it reverts to the initial

value. The 30 nm a-C:H deposition on cotton increases in stability only with an additional

IO treatment and even lowers with the IO+WG combination. While for the 60 nm, partially

incomplete a-C:H layer on cotton both add-ons are an improvement, there is none for the

carbon layer alone.

In the case of PET, there is no improvement due to plasma treatment and finishing de-

tectable. In addition, the fabrics can only withstand an Fmax of about 1000 N instead of

1600 N previously. A significant deterioration in stability compared with the initial condi-

tion, despite the more homogeneous coating.

The COT/PET withstands higher tensile strength due to its fabric structure, which is

only slightly changed by the plasma treatment. The O2 plasma reduces Fmax by about 200

N first and in turn increases it by about 100 N for the subsequent a-C:H coating. Finishing

with both add-ons improves it around 100 N for 30 nm and 200 N for 60 nm a-C:H,

compared to the pure one. A closer inspection of the stretched fabric samples revealed

that the cotton fibers have become more stretchable as a result of the oxygen treatment. In

contrast, the PET fibers seem to have become more brittle and thus more unstable. For the

COT/PET mix there is nothing observable, suggesting the two properties cancel each other

out due to the balanced fiber proportions.

15.4

CONCLUSION

The results demonstrate firstly, the plasma treatment does not change the breathabil-

ity nor does it reduce the tensile strength by stress generation, except for the PET fabric.

Second, for cotton fabrics, the current a-C:H thicknesses are not suitable yet to ensure

layer uniformity. The data indicates that the fabric structure is not significantly affected

by current plasma treatments. Thus, the current plasma processes are appropriate for sur-

face activation and the resulting surface modifications (O2 treatment and a-C:H coating)

serve as suitable platform with improved attraction for finishing agents, that can be used

against vector-borne diseases, for example. In further investigations, the possible effects