Flexible substrates and methods of attaching components as a roll-to-roll process have made it possible to implement fully flexible and conformable electronic devices. Wireless connectivity together with wireless charging of battery enable such structures e.g. to be overmolded with elastomers to provide hermetic seal. As an alternative to conventional flexible substrates such as polyimide, nanocellulose-polyurethane composite provides the possibility to tune the mechanical properties of the substrate by varying its composition, which is an important feature for wearable medical devices. As a promising alternative for conductor material, aluminium doped zinc oxide (AZO) can be used as a transparent conductor, e.g. to implement transparent antennas, but its thermoelectric properties are also potentially useful in energy harvesting or temperature sensing. In addition, the use of graphene has been studied to exploit its best properties in the field of flexible electronics.