Lotus flowers, rose petals, some plant leaves and insects have a naturally super-hydrophobic surface. In fact, the surface of a Lotus leaf is covered by micro and nano structures mixed with wax, which makes its surface superhydrophobic. In microfluidics, superhydrophobicity is an important factor in the rheometers on a chip. It is also sought in other complex fluids applications like the self-cleaning and the antibacterial materials. The wettability of the surface of solid support can be modified by altering its chemical composition. This means functionalizing the interface molecules to different chemical properties, and/or forming a thin film on the surface. We can also influence its texturing by changing its roughness. Despite considerable efforts during the last decade, superhydrophobic surfaces usually involve, among others, microfabrication processes, such as photolithography technique. In this study, we propose an original and simple method to create superhydrophobic surfaces by controlling elastic instability of poly-dimethylsiloxane (PDMS) films. Indeed, we demonstrate that the self-organization of wrinkles on top of non-wettable polymer surfaces leads to surperhydrophobic surfaces with contact angles exceeding 150°. We studied the transition Wenzel-Cassie, which indicated that the passage of morphology drops “impaled” to a type of morphology “fakir” were the strongest topographies.

In this Letter, a low-cost interrogation technique for multiple fiber Bragg gratings (FBGs) is demonstrated. The design utilizes the major advantage of the distributed feedback lasers, which is tuning their emitted wavelength by current modulation and temperature variation. The sensitivity of this method and the influence of optical losses on the measurement have been carefully studied, and an accuracy of 5 pm is achieved.

In this paper a new low-cost fiber Bragg grating (FBG) interrogation technique for static applications is demonstrated. The idea is based on the multiplication between the FBG reflectivity profile and the emission of a sawtooth modulated distributed feedback (DFB) laser source. The variation of the FBG wavelength generates a modification in the shape, in time domain, of the reflected light signal. The concept has been proven, using simulation, to cover FBG wavelength shift up to 1.7 nm. Experimental validation was performed for FBG temperature ranging from 6 °C to 50 °C (equivalently 440 pm) with a modulation frequency of 1 kHz. Sensitivity higher than 3.5 mV/pm is achieved in all circumstances with an estimated resolution of 8 pm.

In this paper, we propose a Fiber Bragg Grating (FBG) interrogation system based on the modulation of the laser wavelength. Key component of the interrogation scheme is in a Digital Supermode -Distributed Bragg Reflector (DS-DBR) Laser. The DS-DBR features a large spectral range and a fast modulation capability in a low cost device. When the laser spans over the FBG spectral range, the power of the reflected signal changes over time according the FBG spectral shape. The information on the Bragg wavelength can be extracted from the modulated signal reflected by the FBG in the time domain. We implemented the proposed interrogation scheme by discrete components demonstrating its capability to retrieve the Bragg wavelength of one or more FBGs. The interrogation system features an intrinsic tradeoff between spectral resolution and interrogation speed. A Bragg wavelength resolution of 1.5 pm has been obtained using 1 kHz modulating frequency. The proposed interrogation system is particular suited in applications in which an adaptive interrogation strategy can be conveniently adopted.