Kenny Hey Tow

Spider silk : a novel optical fibre for biochemical sensing

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.

Exploring the Use of Native Spider Silk as an Optical Fiber for Chemical Sensing

A spider uses up to seven different types of silk, all having specific functions, as building material, weapon, and sensory organ to detect the presence of preys on its web. Recently, scientists have put under the limelight the extraordinary properties of this ancient material. Indeed, 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 a bioresorbable optical fiber and is, moreover, intrinsically sensitive to chemical compounds. In this communication, the waveguiding properties of native dragline silk are assessed and a pioneering proof-of-concept experiment using pristine spider silk as an optical fiber to measure humidity content is demonstrated. The feasibility of using silk-based optical fiber chemical sensors is also discussed.

Mapping the Uniformity of Optical Microwires Using Phase-Correlation Brillouin Distributed Measurements

The distributed Brillouin gain profile of an ultrathin optical microwire made of chalcogenide-glass is characterized using a phase-modulated correlation-domain measurement technique. Method resolves variations of uniformity below 5% along a 13 cm-long microwire.

Distributed photothermal measurements of gas presence along holey optical fibers

Chirped-pulse phase-sensitive optical time domain reflectometry has shown a remarkable performance when applied to dynamic measurements of strain and temperature, recently reaching ranges of several kilometers while interrogating the fiber at acoustic frequencies. In this work, its sensitivity, fast response, and high spatial resolution are exploited to implement a proof-of-concept of a selective distributed chemical sensor based on the photothermal effect. The presented scheme is able to perform distributed spectroscopic measurements of acetylene presence along a 10 m-long holey fiber. This potentially gives rise to a new kind of distributed chemical sensors capable of tracking the concentration of chemical species over kilometres.

Towards a new generation of fibre-optic chemical sensors based on spider silk threads

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.

All-fiber molecular frequency reference at 2 μm based on a versatile laser modulation sideband locking and a hollow-core fiber gas cell

Sensing of atmospheric trace gases is crucial for climate monitoring and to predict global climate changes. The required global coverage and spatial resolution have driven the studies of space-borne differential absorption lidar (DIAL) instruments to remotely monitor atmospheric gases from a satellite to ground. The performance of such instruments is notably determined by the frequency stability and accuracy of a low-power continuous-wave laser that seeds the pulsed laser transmitter. For a CO2 DIAL, this reference laser needs to be stabilized with an adjustable frequency-detuning from the center of the probed molecular transition and the 2.05-μm spectral range is of high interest from a spectroscopic point-of-view [1].

FIRST INVESTIGATION OF AN ALL-FIBER VERSATILE LASER FREQUENCY REFERENCE AT 2 MICRON FOR CO2 LIDAR APPLICATIONS

Nowadays, space-borne differential absorption lidar (DIAL) instruments are under investigation by space agencies to monitor the integrated column density or the atmospheric density profile of gaseous species from space to ground.

Distributed photothermal spectroscopy in microstructured optical fibers: towards high-resolution mapping of gas presence over long distances

Chemical sensing using optical fibers is often challenging, as it is generally difficult to achieve strong interaction between the guided light and the analyte at the wavelength of interest for performing the detection. Despite this difficulty, many schemes exist (and can be found in the literature) for point chemical fiber sensors. However, the challenge increases even further when it comes to performing fully distributed chemical sensing. In this case, the optical signal which interacts with the analyte is typically also the signal that has to travel to and from the interrogator: for a good sensitivity, the light should interact strongly with the analyte, leading inevitably to an increased loss and a reduced range. Few works in the literature actually provide demonstrations of truly distributed chemical sensing and, although there have been several attempts to realize these sensors (e.g. based on special fiber coatings), the vast majority of these attempts has failed to reach widespread use due to several reasons, among them: lack of sensitivity or selectivity, lack of range or resolution, cross sensitivity to temperature or strain, or need to work at specific wavelengths where fiber instrumentation becomes extremely expensive or unavailable. In this work we provide a preliminary demonstration of the possibility of achieving distributed detection of gas presence with spectroscopic selectivity, high spatial resolution, potential for long range measurements and feasibility of having most of the interrogator system working at conventional telecom wavelengths. For a full exploitation of this concept, new fibers (or more likely, fiber bundles) should be developed capable of guiding specific wavelengths in the IR (corresponding to gas absorption wavelengths) with good overlap with the analyte while also having a solid core with good transmission behavior at 1.55 μm, and good thermal coupling between the two guiding structures.

Weaving our way towards a new generation of fibre-optic chemical sensors based on spider silk

From the spiders perspective, silk is not only a building material but also a safety net, a weapon and a sensory organ to detect the presence of preys on its web. Indeed, this primeval material has been shaped over hundreds of millions of years by spiders to create a myriad of silk fibre types with different level of toughness, elasticity, stickiness depending on its attributed function in the web. From a human perspective, scientists are currently working on harnessing all the extraordinary properties of this material for applications spiders would never thought of, from biocompatible tissue engineering (enhancement of skin regeneration and nerve guides) to biodegradable electronics and development of specialised textile and composites. However, the potential of using spider silk fibre for chemical sensing has been overlooked. In this communication, we will explore the potential of using spider silk as a new type of fibre optic chemical sensor in a fully bio-inspired approach.

Spider silk thread as a fiber optic chemical sensor

Monitoring the properties of light transmitted through a thread of spider silk enables detection of trace amounts of chemical compounds.