Sub-micrometre fibre optic chemical sensor

The near-field interaction between an optical aperture of sub-micrometre diameter and a sample surface can be exploited to spectroscopically probe a biological medium with a resolution unattainable with traditional far-field techniques. A simple, low-cost technique is described for producing a chemical sensor which is based on the principles of near-field optics, and preliminary results obtained using this device to measure pH within individual mammalian cells is reported