## 1 Introduction
### Basic Steps of CDP Synthesis Process  
The CDP preparation process can be summarized as follows: Initially, in a custom iCVD reactor, a fluorinated thin-film base layer was prepared on silicon (Si) wafers (Pure Wafer) using PFDA as the monomer. The silicon wafer was placed in the reactor chamber, which was maintained at a pressure of 400 mTorr, and a temperature-controlled stage kept at 35 \({}^{\circ}\)C. Subsequently, PFDA monomer vapor was delivered into the reactor chamber through a needle valve at a flow rate of 0.15 sccm, and argon carrier gas, as well as tert-butyl peroxide (TBPO), were introduced into the chamber through mass flow controllers at rates of 2.00 sccm and 0.60 sccm, respectively. A filament array was positioned approximately 3 cm above the substrate stage and heated to 300 \({}^{\circ}\)C to thermally decompose TBPO into tert-butoxyl and methyl radicals. These radicals initiated the thin-film polymerization upon contact with PFDA molecules adsorbed to the silicon wafer. The subsequent step in CDP, which serves as the final phase, involves the rapid polymerization of liquid monomer droplets to solidify them into robust polymer nanodomes. To achieve this, TBPO was supplied to the reactor chamber at a rate of 1.8 sccm. Inside the chamber, the heated filament array at 300 \({}^{\circ}\)C decomposed TBPO into tert-butoxyl (TBO) and methyl radicals. These TBO and methyl radicals reacted with the nanoscale condensed droplets, initiating a free radical polymerization process that solidified the droplets into polymer nanodomes within a mere 45 s. Following this, the reactor chamber was evacuated and any unreacted materials were removed, resulting in high-purity PNDs, as shown in Figure 1.  
In summary, the essence of the CDP method lies in controlling the formation of nanoscale, hemispherical condensed droplets and subsequently rapidly solidifying them into robust polymer nanodomes. This process is not dependent on the base layer material and can also be directly applied to the synthesis of PNDs on silicon substrates. In Figure 1C, small blue circles represent precursors in the vapor phase. Precursor monomer flow is delivered to the deposition chamber. In Step 1 of CDP, nanoscale condensation is accomplished only by the introduction of monomers into the gas phase, whereas volatile initiators, such as tert-butyl peroxide, are not introduced. Monomers physiosorb onto the substrate to be coated, and the filament above the reaction chamber is not enabled. The temperature of the substrate is kept at around 20-40 \({}^{\circ}\)C to promote monomer physisorption. Condensation of Monomer Vapor into CDP: The Essential Requirement of Pressure above Saturation Vapor Pressure  
Under conditions where the substrate temperature is lower than the ambient temperature and the surface energy is low, the condensation of water droplets can occur. Inspired by this phenomenon, [PERSON] [30] first observed intriguing occurrences during the iCVD synthesis process when the pressure exceeded the monomer's saturation vapor pressure. In such cases, the monomer vapor not only deposits on the substrate as a film but also undergoes gas-phase condensation to form droplets, which subsequently polymerize into non-spherical particles. However, achieving a pressure that surpasses the saturation vapor pressure is vital for the synthesis of PNPs (polymer nanoparticles). In Figure 2, depositions were conducted on Teflon FEP-coated surfaces. In Figure 2d, the size of the polymer nanoparticles is around 5 \(\upmu\)m, and the size of the PNPs increases with time. However, the shape of the polymer particles does not exhibit a uniform spherical crown morphology. On the other hand, from the image, it can be observed that during the nucleation stage, droplet coalescence occurs in the monomer condensation deposition process. Regarding the condensation of the monomer, it will be discussed later.