# Icing Mitigation by MEMS-Fabricated Surface Dielectric Barrier Discharge
## 2 SDBD Preparation
### Geometry and Sample Preparation  
The common strategy of investigation is to include a reference area on the sample in addition to the SDBD due to the stochastic nature of the icing process. For this reason, only the lower half of the sample (24.5 mm \(\times\) 66.5 mm) is equipped with the anti-icing SDBDs and the upper half serves as a reference area. A sketch of the electrode geometry G1 is depicted by Figure 3. The SDBD consists of 16 high-voltage electrodes and a single continuous ground electrode on the other side of the substrate.  
The high-voltage electrode was micro-structured by right-angled triangles with a base of 250 um as shown in the inset of geometry G1 in Figure 3. The same triangle structure was also used in the erosion studies of Figure 2. The micro-structure was intended to increase the electric field locally which can be an advantage at combining SDBDs with biomimetic structures [39]. In our case, the structure has a minor influence on the ignition voltage.  
The same geometry was realized with the PCB as well as with the MEMS-fabrication to compare the performance of differently manufactured discharge arrangements in the experiment. The PCB-samples were manufactured on the substrate FR-4 TG135 by IBR Leiterplatten GmbH & Co KG. In the PCB-based fabrication, glass fibers woven in epoxy resin (FR-4) are pressed together with thin copper foils which severely restricts the smallest possible thickness of the copper layer. The post-processing (etching, micro-milling) of these relatively thick (35 um) foils then leads to a rounding of the desired electrode geometry. The difference between PCB and MEMS electrodes is clearly depicted in the SEM images of Figure 4. Note that the size of the observed samples restricts the inclination angle to 55\({}^{\circ}\) for technical reasons that makes the width of the MEMS electrodes less noticeable.  
On the basis of our previous research [32; 34] a second electrode pattern G2 (right side of Figure 3) was implemented to investigate the impact of the ionic wind. The green arrows in Figure 3 indicate the generated ionic wind direction. The actuator area creates an ionic wind in downstream direction. At the SDBD area the ionic wind is generated in both directions neutralizing itself. A detailed description of the generation mechanism and the implications of the ionic wind can be found in [PERSON] et al. [15] and the references therein. For the sake of simplicity and fast prototyping, this geometry was realized only on PCB samples.  
Additional investigations were carried out to characterize the dielectric materials. For data concerning the substrate roughness, the surface wettability, the dielectric permittivity  
Figure 4: SEM images of the PCB-fabricated electrodes (**top**) compared to MEMS-realized electrodes (**bottom**). The pictures were taken with an inclination angle of \(\alpha=55^{\circ}\) (**left**) and from top view (**right**). The two insets show profilometer measurements of the electrode steps.  
Figure 3: Sketch of the SDBD geometry G1 (**left**) and a photograph of the SDBD manufactured with geometry G2 (**right**). The high-voltage (HV) electrodes are at the substrate top (red) and the ground electrode on the backside (blue) of the substrate. All dimensions are shown in millimeters. The green arrows on the photograph indicate the direction of the ionic wind generated by one electrode.  
and the dielectric dissipation factor, we refer to the substrate properties column of Table 1. See Supplementary S6 and S7 for more information.