## Appendix A  
In the work by [PERSON] et al. [34] polarised Raman spectroscopy was used to quantify the degree of alignment within slow-filtered SWCNT films. By varying the polarisation of the incident laser and the detection polarisation between horizontal and vertical, the intensity of the characteristic SWCNT peaks would vary wildly depending on whether the laser was polarised perpendicular or parallel to the CNT alignment direction. This technique was attempted with one of the slow-filtered SWCNT films. However, the Raman setup used lacked the capability to switch between horizontal and vertical polarisations. Thus, the incident laser polarisation was kept horizontally polarised and the sample rotated to observe any alignment effects. Three spectra were taken by recording non-polarised, horizontally polarised, and vertically polarised Raman scattering. It was observed that the intensity of the spectra changed significantly when repeated scans at the same location were performed. To account for this, 25 spectra were produced and averaged over a \(5\times 5\) grid with each spectrum produced from two separate scans. An averaged spectrum was produced for the slow-filtered film and the fast-filtered film.  
Figure 11 shows the Raman spectra of a slow filtered film recorded with the sample at two different angles 45 degrees apart (a 90 degree rotation of the sample may accidently lead to the same angular difference between laser polarisation and sample alignment, thus 45 degree separation was chosen) with different detection polarisations. As well as the characteristic D, G, and G' peaks, smaller peaks are visible at around 1000 cm\({}^{-1}\), 2400 cm\({}^{-1}\), and 2900 cm\({}^{-1}\). The 2400 cm\({}^{-1}\) peak may be due to highly oriented pyrolytic graphene, which displays a small peak at 2400 cm\({}^{-1}\)[45], whilst the 2900 cm\({}^{-1}\) peak may be due to a G + D peak [46]. The presence of these peaks indicates that there are graphene-like structures in the SWCNT film. Glass microscope slides display a peak at a little over 1000 cm\({}^{-1}\) when a 532 nm laser is used [47] (as was used here) thus this peak is likely caused by the glass substrates. Glass can also show a small peak at 2400 cm\({}^{-1}\) which may also be the cause of the 2400 cm\({}^{-1}\) peak in Figure 11. Peak intensities and the ratios between peak heights for the non-polarised spectra and the polarised spectra of the slow-filtered SWCNT film are tabulated in Table 11. The peak intensities do not change appreciably with rotation of the sample, indicating there is no preferred alignment direction of the carbon nanotubes in the film.  
Figure 14 shows that there is a significant difference between both the film thickness (from lowest height to average height) and film roughness (as determined from the full width half maximum measurements) for the fast-filtered films and the slow-filtered films. The roughness data backs up that shown in Table 1 further confirming that slow-filtered CNT films are much smoother than fast-filtered films. The film thickness data shows that the fast-filtered films are roughly three times as thick as the slow-filtered films. It was expected that the fast-filtered films would be thicker than the slow-filtered films as the samples were cut from homogeneous films, whereas the slow-filtered film samples were cut from the thinner areas of the inhomogeneous slow-filtered films (Figure 2c).