One aspect of the present invention relates to a method of fabricating a chemically active fibre device (1) by thermal drawing. The method comprises the steps of providing a preform, the preform comprising a support element (3) at least partially made of a first polymeric material; and carrying out a thermal drawing process of the preform to produce a thermally drawn fibre. The preform comprises one or more chemically active agents and/or biological materials configured to react with a fluid sample when the one or more chemically active agents and/or biological materials are in contact with the fluid sample. In this manner miniaturised lab-in-fibre devices can be fabricated.