Method for forming a volume holographic sensor in a porous medium

A method for preparing a sensor, wherein the sensor comprises a holographic element comprising a medium and a reflection hologram disposed throughout the volume of the medium, wherein an optical characteristic of the reflection hologram changes as a result of a variation of a physical property occurring throughout the volume of the medium, the method comprising:

• forming the medium by polymerization of monomers or comonomers in the presence of water and methanol, whereby removal of the water forms pores in the polymer;
• removing the water so that it is not present in the sensor, to produce a porous medium, and
• forming a reflection hologram in the porous medium;
• wherein pores of the porous medium are sized to accommodate a large biological molecule, and
• wherein the pores of the porous medium allow diffusion of the large biological molecule into and throughout the porous medium.