## 3 Impact of Cold Plasma on Packaging Properties
### Surface Roughness
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c} \hline \hline \multicolumn{13}{c}{**Types of**} & \multicolumn{13}{c}{**Finite Properties**} & \multicolumn{13}{c}{**R**} \\
**Biopolymers** & **Device Diagram** & **Conditions** & **TS** & **EAB** & **CA** & **SR** & **WVP** & **OP** & **Tg** & **Tm** & **AM** & **Tdeg** & **B.D** & **R** \\ \hline \hline \multicolumn{13}{c}{**Finite \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline Types of & Device Diagram & Processing Conditions & \multicolumn{8}{c}{Flim Properties} & \multicolumn{8}{c}{R} \\ \cline{3-14}
**Biopplymers** & **Device Diagram** & **Conditions** & **TS** & **EAB** & **CA** & **SR** & **WVP** & **OP** & **Tg** & **Tm** & **AH** & **Tdeg** & **R.D** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Cont. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c} \hline \hline
**Type of** & **Type of** & **Device Diagram** & **Processing** & \multicolumn{8}{c}{**Filin Properties**} & \multicolumn{1}{c}{**R**} \\  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline
**Types of** & **Device Diagram** & **Processing** & \multicolumn{8}{c}{**Filin Properties**} & \multicolumn{8}{c}{**R**} \\ \cline{3-13}
**liopolymers** & **Device Diagram** & **Conditions** & **TS** & **LAB** & **CA** & **SR** & **WVP** & **OP** & **Tg** & **Tm** & **AH  
Figure 3: **(I)** AFM images of the surface of untreated and DBD plasma-treated zein films showing the impact of variation in voltage: (**a**) untreated, (**b**) 60 kV-5 min, (**c**) 70 kV-5 min, (**d**) 80 kV-5 min. Reprinted with permission from Ref. [75], Wiley Online Library, 2022; (**II**) AFM micrographs of untreated (UNT) and Dry air, Ar, He, and N\({}_{2}\) plasma-treated surface of the PEOT/PBT films; Bar chart shows the variation in root mean square roughness (R\({}_{\text{q}}\)). Reprinted from Ref. [76]. Figure 4 shows the etching effect influencing another physical property of the film i.e., diffusion. The increased surface roughness of the films shows an enhanced diffusion coefficient of the reactive ingredients present in the film matrix when encountered with an aqueous solution. For instance, the application of DBD plasma into chitosan/thymol antimicrobial films showed increased diffusion of thymol when in contact with water [77]. This is due to the increase in roughness as a result of the etching effect that decreased the thickness and thus increased the diffusion rate. Similarly, an increase in thymol diffusion coefficient was noticed in zein/thymol film upon application of DBD plasma [88]. In another study, [PERSON], [PERSON] [89] showed that cold plasma treatment modified the surface of low-density polyethylene films allowing the controlled absorption of nisin leading to the development of active packaging film [89]. Similar to the diffusion phenomena, plasma treatment also influences the adsorption characteristic of polymer surfaces and it varies based on type plasma treatment. [PERSON], [PERSON] [90] reported that exposure of LDPE to different plasma (N\({}_{2}\), and Ar/O\({}_{2}\)) influenced the nisin adsorption. The untreated and N\({}_{2}\) plasma treated films showed lower adsorption of nisin as compared to Ar/O\({}_{2}\) plasma treated films, which could be attributed to higher surface roughness of LDPE film caused by Ar/O\({}_{2}\) plasma then the N\({}_{2}\) plasma treated or untreated film [90]. Cold plasma treatment enhances adhesion between different surfaces and enables the production of multilayer films as shown in Figure 4. [PERSON], [PERSON] [43] reported that the application of atmospheric cold plasma improved the attachment of carboxymethyl cellulose with polypropylene films. Similarly, [PERSON], [PERSON] [57] found a significant enhancement of adhesion between air plasma-treated cellulose fiber and thermoplastic starch.