Role of surface energy and nano-roughness in the removal efficiency of bacterial contamination by nonwoven wipes from frequently touched surfaces

Figures & data

Figure 1. Surface energy of the nonwoven fabrics vs. plasma exposure time, measured via the OWRK method [26]. Fit line and data points for C₂F₆ treated lyocell, unless specified otherwise. Data are the mean of five replicates. Error bars = standard deviation.

Figure 2. Negative ion ToF-SIMS spectra of untreated and C₂F₆ plasma treated lyocell nonwoven fabrics. Mass range m/z = 0–360.

Figure 3. AFM micrographs of untreated and plasma treated fibre surfaces. (A) Untreated lyocell fibre surface; (B) C₂F₆ plasma-treated lyocell fibre surface after 1 min exposure; (C) C₂F₆ plasma-treated lyocell fibre surface after 4 min exposure; (D) C₂F₆ plasma-treated lyocell fibre surface after 20  min exposure; (E) O₂ plasma-treated lyocell fibre surface after 20  min exposure; (F) untreated polypropylene fibre surface.

Table 1. Mean contact angles and wetting tensions of PMMA wiping surfaces according to organic load, as measured by goniometry.

Organic load	Water contact angle	Wetting tension
Unsoiled surface(alcohol sterilised)	29.2°	63.5 mJ m^−2
Low organic load (0.015 g m^−2 BSA)	62.3°	33.8 mJ m^−2
High organic load(0.15 g m^−2 BSA)	81.4°	10.9 mJ m^−2

Figure 4. Bacterial removal by wiping. (A) Mean E. coli removal by adpression method; (B) mean S. aureus removal by adpression method; (C) mean E. faecalis removal by adpression method; (D) mean E. coli removal by dynamic wiping; (E) mean S. aureus removal by dynamic wiping; (F) mean E. faecalis removal by dynamic wiping. Data presented are the average of nine replicates and error bars represent standard error of the mean.

Table 2. Comparison of static wiping vs. dynamic wiping via paired-sample t-test.

	Wipe sample	Significant difference	p-value
E. coli	Lyocell	+++	<0.001
	C2F6 lyocell (20 min)	+++	<0.001
	O2 lyocell (20 min)	+	0.002
	PP	+++	<0.001
S. aureus	Lyocell	+	0.008
	C2F6 lyocell (20 min)	++	0.005
	O2 lyocell (20 min)	+++	<0.001
	PP	+++	<0.001
E. faecalis	Lyocell	+	0.025
	C2F6 lyocell (20 min)	+	0.009
	O2 lyocell (20 min)	+++	<0.001
	PP	+	0.001

Lugscheider E, Bobzin K, Möller M. The effect of PVD layer constitution on surface free energy. Thin Solid Films. 1999;355-356:367–373.10.1016/S0040-6090(99)00543-X

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