A spider uses up to seven different types of silk, all having specific functions, to build its web. For scientists, native silk - directly extracted from spiders - is a tough, biodegradable and biocompatible thread used mainly for tissue engineering and textile applications. Blessed with outstanding optical properties, this protein strand can also be used as an optical fibre and is, moreover, intrinsically sensitive to chemical compounds. In this communication, a pioneering proof-of-concept experiment using spider silk, in its pristine condition, as a new type of fibre-optic relative humidity sensor will be demonstrated and its potential for future applications discussed.
A frequency-domain method is proposed to measure the inertial response of forward stimulated Brillouin scattering, so that the acoustic impedance of a liquid medium outside an uncoated 30 m standard single-mode fibre can be sensed. The proposed technique overcomes the linewidth distortion present in the time-domain approach due to Kerr effect and reduce time and complexity for data post-processing. Experimental results demonstrate that acoustic impedances of water and ethanol agree well with the expected values.
Whilst being thoroughly used in the textile industry and biomedical sector, silk has not yet been exploited for fibre optics-based sensing although silk fibres directly obtained from spiders can guide light and have shown early promises to being sensitive to some solvents. In this communication, a pioneering optical fibre sensor based on spider silk is reported, demonstrating for the first time the use of spider silk as an optical fibre sensor to detect polar solvents such as water, ammonia and acetic acid.