Systematic variation of polymer jacketed fibres and the effects on tip etching dynamics.

Using a chemically etched fibre probe through a plastic jacket provides a simple way to smooth a tip's surface. Convection flow in the plastic tube and lateral diffusion with fixed meniscus height has been proposed to explain such improvement. Fibres with additive thin polymer layers and bare fibres with thick untapered/tapered plastic layers have been prepared to verify the dominant mechanism. The additive layers greatly change the tip's geometry and bare-fibres with untapered plastics cannot form tips. This confirmed that lateral diffusion dominates the etching process. Based on our investigation, we propose a new non-meniscus end-etching method by using tapered plastics. Unlike etching methods with meniscus, the end-etching method can regularly form very smooth tips. It is insensitive to vibrations and temperature drifts and also suitable for most fibres.