# Towards Environmentally Friendly Accelerometers Based on Bacterial Cellulose
## 4 Results and Discussion
### Structural, Thermal, and Mechanical Characterization  
The membrane characterization was carried out by TGA, ATR FTIR, SEM, and DMA analyses. The BC and BC/EMIMBF4 FTIR ATR spectra comparison (see Figure 4) shows that both have the 3000-3600 cm\({}^{-1}\) broad band (due to the O-H stretching of the hydroxyl group), the 2920-2880 cm\({}^{-1}\) band (due to the aliphatic C-H stretching), the 1640 cm\({}^{-1}\) band (bending of absorbed H-O-H), the 1424 cm\({}^{-1}\) band (due to in plane bending of H-C-H groups), and the 1110-874 cm\({}^{-1}\) bands (deriving from to the stretching of C-OH groups and from the asymmetric stretching of the C-O-C bonds). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Value** & **Unit** \\ \hline \(m\) & 0.000035 & kg \\ \hline \(k\) & 0.6 & N/m \\ \hline \(d\) & 0.00044 & N/ms\({}^{-1}\) \\ \hline \(G\) & 0.07 & V/m \\ \hline \(I_{n}\) & \(9.56\times 10^{-16}\) & m\({}^{4}\) \\ \hline \(E_{max}\) & \(3.4\times 10^{9}\) & N/m\({}^{2}\) \\ \hline \(l\) & 0.0400 & m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters. The IL absorption produces some disruption of the cellulose crystalline domains as suggested by the significant decrease in the intensity of two bands characteristic of the presence of cellulose crystalline structures (the one centered at 1424 cm\({}^{-1}\) and the one centered at 874 cm\({}^{-1}\)) [39]. The ATR-FTIR spectrum of the BC/EMIMBF4/PEDOT membrane (Figure 4) shows characteristic peaks of both cellulose and PEDOT. The signals due to cellulose are the ones centered at 1645 cm\({}^{-1}\), 1421 cm\({}^{-1}\), and 1041 cm\({}^{-1}\), while the ones due to the PEDOT electrode are centered at 1576 cm\({}^{-1}\) (C=C), 1254 cm\({}^{-1}\) (C-C), and 948 cm\({}^{-1}\) (S-O), characteristic of the thiophene ring. As a confirmation of the decrease of BC crystallinity, TGA showed that the presence of EMIM-BF4 promotes cellulose degradation (see Figure 5a,b). The maximum weight loss rate occurred at 336 \({}^{\circ}\)C for BC, while the BC/EMIMBF4 sample showed a marked decrease of such a temperature (302 \({}^{\circ}\)C). In the case of BC/EMIMBF4/PEDOT, the maximum weight loss rate occurred at 312 \({}^{\circ}\)C, presumably because the PEDOT-PSS layer offers an obstacle to degradation product loss, as confirmed by the shift toward higher temperatures of the last maximum weight loss rate centered at 446 \({}^{\circ}\)C in the case of BC and at about 531 \({}^{\circ}\)C for the BC/EMIMBF4/PEDOT sample. The SEM micrograph of BC (Figure 6a) showed a cellulose morphology consisting of regions rich in spherical agglomerates between which filamentous and rod-like structures can be seen. The sample BC/EMIMBF4 SEM images showed that after the IL treatment, only a few almost spherical agglomerates survive. These features probably suggest that BC interaction with IL produces swelling/degradation of the crystalline domain (Figure 6b), resulting in a fiber-like feature predominance. SEM images of BC/PEDOT sample showed that PEDOT deposition on the surface of BC determines the filling of the empty spaces among BC agglomerates, producing a regular surface where the shape of the underlying agglomerations can still be detected (Figure 6c). The SEM micrograph of the whole composite (BC/EMIM/PEDOT) showed that on the smooth and homogeneous conducting layer surface, it was possible to observe island features (Figure 6d), presumably rich in IL, as revealed by EDX. The results of the DMA investigation carried out on BC, BC/EMIM BF4, BC/PEDOT, and BC/EMIMBF4/PEDOT samples are shown in Figure 7. The investigation was performed as a function of the working temperature. The storage modulus of BC shows a negligible decrease (from 5.5 \(\times\) 10\({}^{3}\) MPa at 30 \({}^{\circ}\)C to 5.3 \(\times\) 10\({}^{3}\) MPa at 170 \({}^{\circ}\)C) as the temperature increases.