Despite the higher benefit of smart tattoos compared to a transdermal optic fibre, no in vivo smart tattoo has yet been demonstrated, whereas fibre-based systems have been shown to be potential sensors [REF].
For fibre-based biosensors to work, the protein must be immobilized to the fibre that can either entrapped in a hollow tube made of dialysis membrane[REF][REF][REF][REF][REF] or entrapped in a hydrogel [REF].