## 4 Conclusions  
A set polythiophene-derived composite material was prepared either by depositing CPs solutions or by performing in-situ polymerization onto three different sources of cellulose membranes using different processing methods. Two different processing approaches were evaluated to prepare in-situ composites materials: Casting and spray-coating methodologies. Spray coating presents multiple advantages respect casting, for instance, the processing time is quite short reducing the interaction solvent-substrate, which has been demonstrated that affects dramatically on mechanical properties,flexibility, and surface morphologies of the composite material. Another advantage is the low amount of polymer needed to coat efficiently the cellulose fibers obtaining continuous, homogeneous, and reproducible coatings. Another important factor is the use of methanol as preparation and processing solvent discarding the use of more toxic and harmful to the environment solvents. Moreover, 3D optical profilometry was demonstrated as an excellent tool to characterize the surface of these successfully prepared composite materials regardless of the substrate's roughness, on the one hand, to observe the quality of the CP coatings and quantify the heterogeneity of the surface roughness (Sa factor), on the other, to correlate Sa with the electrical conductivity of composite materials. Modulating the roughness of composite materials (from 0.2 to 20 \(\upmu\)m) by changing the source of cellulose, polymer, and/or processing conditions plays a crucial role in the resulting conductive properties of these materials. This relationship shows that the composite material prepared with PEDOT:Triflate through in-situ polymerization via spray coating results in new and versatile composite materials with promising characteristics, due to a balance between easy and fast processing, flexibility, homogeneous coatings (Sa = 6-9 \(\upmu\)m), high conductivity \(\sigma_{\text{s}}\) (\(\approx\)0.5-0.8 S-cm\({}^{-1}\)), and low polymer content (lower than 25 wt.%). These properties make it a scalable alternative for the preparation of flexible electrodes for energy storage applications.  
The following are available online at [[http://www.mdpi.com/2076-3417/9/16/3371/s1](http://www.mdpi.com/2076-3417/9/16/3371/s1)]([http://www.mdpi.com/2076-3417/9/16/3371/s1](http://www.mdpi.com/2076-3417/9/16/3371/s1)). Figure S1: 1\({}^{\text{1}}\)H-NMR spectra of PDBProDOT, Figure S2: GPC traces of PDBProDOT, Figure S3: TGA curves of PEDOT:Triflate composite materials onto W substrates, Figure S4: TGA curves of polythiophene-derived composite materials, Figure S5: FTIR-ATR spectra of polythiophene-derivatives composite materials, Figure S6: FTIR-ATR spectra of PDBProDOT/cellulose microfibers composite material, Figure S7: Bulk conductivity dependence with frequency for selected cellulose composite materials obtained by in-situ polymerization, Figure S8: Bulk conductivity dependence with frequency for selected cellulose composite materials obtained by CPs solutions, Figure S9: \(\sigma\)s and \(\sigma\) trends on Sa roughness, Figure S10: Sa values of raw substrates and selected composite materials, Table S1: T50, T5 and % residue for cellulose substrates and composite materials, Table S2: \(\sigma\), \(\sigma\)s and Sa of composite materials.  
[PERSON] and [PERSON] performed the data curation and formal analysis, [PERSON] conceived the investigation, [PERSON] and [PERSON] designed the methodology, [PERSON] and [PERSON] realized the supervision, [PERSON] and [PERSON] write the original draft, [PERSON] writing-review & editing, [PERSON] funding acquisition.  
This research was supported by CDTI research project IDI- 20180087. We also thanks the Consejo Nacional de Ciencia y Tecnologia for CVU 559770/Registro 297710 and S2013/MAE-2800.  
The authors declare no conflict of interest.