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Optical fibre bundles usually comprise a few thousand to tens of thousands of individually clad glass optical fibres. The ordered arrangement of the fibres enables coherent transmission of an image through the bundle and therefore enables analysis and viewing in remote locations. In fused bundles, this architecture has also been used to fabricate arrays of various micro to nano-scale surface structures (micro/nanowells, nanotips, triangles, etc.) over relatively large areas. These surface structures have been used to obtain new optical and analytical capabilities. Indeed, the imaging bundle can be thought of as a "starting material" that can be sculpted by a combination of fibre drawing and selective wet-chemical etching processes. A large variety of bioanalytical applications have thus been developed, ranging from nano-optics to DNA nanoarrays. For instance, nanostructured optical surfaces with intrinsic light-guiding properties have been exploited as surface-enhanced Raman scattering (SERS) platforms and as near-field probe arrays. They have also been productively associated with electrochemistry to fabricate arrays of transparent nanoelectrodes with electrochemiluminescent imaging properties. The confined geometry of the wells has been loaded with biosensing materials and used as femtolitre-sized vessels to detect single molecules. This review describes the fabrication of high-density nanostructured optical fibre arrays and summarizes the large range of optical and bioanalytical applications that have been developed, reflecting the versatility of this ordered light-guiding platform.

Optical fibre surface-enhanced Raman scattering (SERS) sensors offer a potential solution for monitoring low chemical concentrations in remote or in situ sensing scenarios. The SERS effect relies on the interaction of analyte molecules with nanostructured metal surfaces. We demonstrate a nanoscale biotemplating approach to fabricating these sensors, using nanoimprint lithography to replicate cicada wing antireflective nanostructures onto the end faces of standard silica optical fibres. These SERS-compatible nanoarrays are coated with silver to make them SERS active, and thiophenol and rhodamine 6G are used as test analytes, from which strong SERS spectra are collected using both direct endface illumination and through-fibre interrogation. This combination of biological templates with nanoscale replication and optical fibres demonstrates a high-resolution, low-cost approach to fabricating high-performance optical fibre SERS sensors.

The adhesion of bacteria to surfaces is an important biological process, but one that has resisted simple categorization due to the number and complexity of parameters involved. The roughness of the substrate is known to play a significant role in the attachment process, particularly when the surface irregularities are comparable to the size of the bacteria and can provide shelter from unfavorable environmental factors. According to this scenario, roughness on a scale much smaller than the bacteria would not be expected to influence the initial attachment. To test this hypothesis, the impact of nanometer-scale roughness on bacterial attachment has been investigated using as-received and chemically etched glass surfaces. The surface modification by etching resulted in a 70% reduction in the nanoscale roughness of the glass surface with no significant alteration of its chemical composition or charge. Nevertheless, the number of bacteria adhering to the etched surface was observed to increase by a factor of three. The increase in attachment was also associated with an alteration in cellular metabolic activity as demonstrated by changes in characteristic cell morphologies and increased production of extracellular polymeric substances. The results indicate that bacteria may be more sensitive to nanoscale surface roughness than was previously believed.