## 1 Introduction
The deposited soot creates a rough hierarchical architecture on the substrate that imparts hydrophobic properties [18, 19, 20]. (v) Nanoimprint lithography involves a pre-etched stamp that is used to mold nanoscale features onto a polymer that has been heated (Figure 1e). Once the polymer is heated to its glass transition temperature the stamp is pressed into the polymer, deforming the polymer and creating micro- and nano-architectures [31]. The polymer/stamp are cooled, and once the polymer has solidified the stamp is removed, leaving the substrate and imprinted polymer bonded together. The mentioned methods are effective and have been shown to create hydrophobic and superhydrophobic surfaces; however, the flame method distinguishes itself as being exceedingly simple and rapid, with researchers using fuels as simple as a candle to create hydrophobic surfaces in minutes. Recently, the flame deposition of hydrophobic carbon deposits onto the surface of substrates has garnered interest by researchers for further development and exploration (Table 1). Researchers have recognized the potential of the flame method's simple, single step process that is inexpensive, rapid, and readily scalable. The following studies have shown that a variety of different flames and deposition parameters can produce hydrophobic and superhydrophobic surfaces on substrates. Figure 1: Schematics of available methods to create hydrophobic surfaces: (**a**) the plasma etching method; (**b**) the electrospinninging method; (**c**) the chemical vapor deposition method; (**d**) the flame deposition method; and (**e**) the nanoimprint lithography method. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Author** & **Flame Deposition Process** & **Study Findings** & **Fuel * \\ \hline [PERSON] et al. [26] & & & Ethylene \\ \hline [PERSON] et al. [21] & & Alcohol Lamp filled & 1.5m 1G7C & 2.5m 1G7C \\ [PERSON] et al. [20] & & & \\ \hline [PERSON] et al. [20] & & Glass beads & 1.5m 1G7C & 2.5m 1G7C \\ [PERSON] et al. [20] & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Schematic of various flame techniques used to create hydrophobic carbon layers. Work by [PERSON] et al. used an ethylene/air co-flow burner to form hydrophobic soot depositions on a silicon substrate [26]. It was found that different deposition areas of the flame produced layers with varying hydrophobic capabilities (Table 1). The morphology of hydrophobic areas was described as \"spongy nanobeads\" and were located near the center of the substrate. However, depositions at the substrate edge produced hydrophilic globule-like structures. The differences in hydrophobicity were attributed to oxidation of the deposits. Within the fuel cone (central depositions), the small amount of available oxygen promotes soot precursors and the formation of nanobeads that produce hydrophobic layers. [PERSON] et al. utilized an alcohol lamp filled with ethanol to synthesize hydrophobic materials on glass substrates; additionally, flame temperature was measured at deposition areas [21]. It was determined that hydrophobicity of the deposited soot was dependent on the flame temperature, with flame temperature increasing from 672 \({}^{\circ}\)C at the base of the flame to 813 \({}^{\circ}\)C near the tip of the flame (Table 1). At a given flame height the temperature decreased from the flame center outwards. At all flame heights tested the outer region of the deposited soot was hydrophilic. At flame heights less than 2 cm the entirety of the deposited soot layer was hydrophilic and at flame heights greater than 2 cm the central area of deposited soot was hydrophobic (Table 1). The pattern of central soot deposits displaying hydrophobic qualities while outer soot deposits were hydrophilic is similar to that observed by [PERSON]. However, unlike [PERSON], [PERSON] found that both hydrophobic and hydrophilic soot depositions had similar chainlike nano and microstructures when analyzed using SEM.