Octadecane was chosen as the active phase change material (PCM) to prepare the capsules owing to the melting point of 27 °C, suitable for maintaining cell temperature between the targeted 20-30 °C range. Additionally, octadecane has been previously suggested as a suitable PCM for BTMS. To characterise the phase change material capsules, Raman spectroscopy was used to confirm the formation of the composite shell material prior to encapsulation, (Figure ). An intensification of the band at ~2700 cm -1 , assigned to the 2D stretching mode of the carbon nanotubes, was observed in the composite material when compared with graphene oxide; the intensification of the 2D band in the composite material indicates the presence of carbon nanotubes, supported by the large band in the Raman spectrum of pure carbon naotubes. Carbon nanotube fibres can also be observed in the SEM image of the composite shell material, (Figure ).