Editing Nanosensor (section)

==== Chemical etching ====
Two different types of chemical etching have been reported. In the [https://patents.google.com/patent/US4469554A/en#patentCitations Turner method], a fiber is etched to a point while placed in the meniscus between [[hydrofluoric acid]] and an organic [[overlayer]]. This technique has been shown to produce fibers with large taper angles (thus increasing the light reaching the tip of the fiber) and tip diameters comparable to the pulling method. The second method is tube etching, which involves etching an optical fiber with a single-component solution of [[hydrogen fluoride]]. A silica fiber, surrounded with an organic [[Cladding (fiber optics)|cladding]], is polished and one end is placed in a container of hydrofluoric acid. The acid then begins to etch away the tip of the fiber without destroying the cladding. As the silica fiber is etched away, the polymer cladding acts as a wall, creating microcurrents in the hydrofluoric acid that, coupled with [[capillary action]], cause the fiber to be etched into the shape of a cone with large, smooth tapers. This method shows much less susceptibility to environmental parameters than the Turner method.<ref name=":2" />