A review of single-mode fiber optofluidics

We review the field we describe as “single-mode fiber optofluidics” which combines the technologies of microfluidics with single-mode fiber optics for delivering new implementations of well-known single-mode optical fiber devices. The ability of a fluid to be easily shaped to different geometries plus the ability to have its optical properties easily changed via concentration changes or an applied electrical or magnetic field offers potential benefits such as no mechanical moving parts, miniaturization, increased sensitivity and lower costs. However, device fabrication and operation can be more complex than in established single-mode fiber optic devices

Modeling and characterization of an electrowetting based single mode fiber variable optical attenuator

We report an optofluidics-based variable optical attenuator (VOA) employing a tapered side-polished single-mode optical fiber attached to an electrowetting-on-dielectric (EWOD) platform. The side polishing of the fiber cladding gives access to the evanescent field of the guided mode, while the EWOD platform electrically controls the stepwise translation of a liquid droplet along the variable thickness polished cladding of the fiber. The penetration of the evanescent field into the droplet leads to tunneling of optical power from the fiber core to the droplet, from where it is radiatively lost. As a result of the variable cladding thickness, the position of the droplet along the length of the polished fiber determines the degree of penetration of the evanescent field into the droplet. The droplet position can be electrically changed; thus, controlling the optical power loss from the fiber. This approach has been used to demonstrate an optofluidic continuous-fiber VOA typically providing up to 26 dB of broadband attenuation in the 1550-nm transmission window, with a wavelength dependent loss less than 1.1 dB. In this paper, we present the theoretical modeling and experimental characterization of the system, discussing the influence of the design parameters on the performance of this VOA

In-line single-mode fiber variable optical attenuator based on electrically addressable microdroplets

We report an in-line, fiber optic, broadband variable optical attenuator employing a side-polished, single-mode optical fiber integrated on a digital microfluidics platform. The system is designed to electrically translate a liquid droplet along the polished surface of an optical fiber using electrowetting forces. This fiber optic device has the advantage of no moving mechanical parts and lends itself to miniaturization. A maximum attenuation of 25 dB has been obtained in the wavelength range between 1520 nm and 1560 nm

Panoramic optical and near-infrared SETI instrument: prototype design and testing

The Pulsed All-sky Near-infrared Optical Search for ExtraTerrestrial Intelligence (PANOSETI) is an instrument program that aims to search for fast transient signals (nano-second to seconds) of artificial or astrophysical origin. The PANOSETI instrument objective is to sample the entire observable sky during all observable time at optical and near-infrared wavelengths over 300 - 1650 nm$^1$. The PANOSETI instrument is designed with a number of modular telescope units using Fresnel lenses ($\sim$0.5m) arranged on two geodesic domes in order to maximize sky coverage$^2$. We present the prototype design and tests of these modular Fresnel telescope units. This consists of the design of mechanical components such as the lens mounting and module frame. One of the most important goals of the modules is to maintain the characteristics of the Fresnel lens under a variety of operating conditions. We discuss how we account for a range of operating temperatures, humidity, and module orientations in our design in order to minimize undesirable changes to our focal length or angular resolution.Comment: 12 pages, 8 figures, 1 tabl

Housing influence on multi-band directional MEMS microphones inspired by Ormia ochracea

A new bio-inspired multi-band directional MEMS microphone based on the hearing properties of the fly Ormia ochracea is presented, together with the behavioral influence of 3D-printed housings. The multi-user foundry fabricated microphone operates on four frequency bands, all below 10 kHz and acts as a pressure gradient directional microphone with figure of eight polar pattern, or as an omni-directional microphone depending on the housing. The influence of an open or closed backside housing on the frequency response and directionality is shown, leading to the loss of directionality with no acoustic access to the backside of the fly-ear inspired microphone membrane

Characterization of custom-made thin film AlN MEMS ultrasound transducers

Photoacoustic (PA) imaging and sensing has attracted a lot of attention in biomedical applications. This is due to its potential in improved specificity and resolution when compared to using ultrasound as imaging source [1]. In the presented work we focus on the miniaturization of custom MEMS ultrasound receivers for applications in PA detection. These devices are of interest as they can lead to broad bandwidth transducers and have the potential for mass production with a reduction in cost [2]. The array of MEMS ultrasound receivers are fabricated using a cost-efficient multi-user process (PiezoMUMPs) and consist of a 500 nm thick film of aluminium nitride as piezo-active layer on a 10 µm thick silicon-on-insulator wafer. A multi-element single bandwidth and a multi-bandwidth MEMS chip have been designed with a centre frequency of 1.3 MHz and centre frequencies of 1.15 MHz, 0.75 MHz, 0.45 MHz, 0.3 MHz (smallest to largest diameter), respectively (see Fig. 1). The designs were immersed in an oil bath and characterized using the pitch-catch technique and PA excitation. The PA excitation was generated using a 10 ns Nd:YAG laser (Brilliant B, Quantel) at 532 nm and a pulse repetition frequency of 10 Hz with pulse energies of 2.6 mJ, focussed with a 30 mm lens onto a highly absorbing gelatine phantom. The devices’ performance in ultrasound and PA wave detection will be shown and their advantages discussed

Distributed optical fibre sensing in synthetic fibre ropes and cables

Distributed strain measurements on synthetic fibre ropes as used in marine applications are reported. The ropes incorporate single mode fibre-optic sensors for strain measurement. A Brillouin-amplification-based distributed strain measuring system has been utilised to interrogate the fibre sensors incorporated into a parallel yarn aramid rope. Initial results are presented to conclusively demonstrate the technical feasibility of the approach

DIFFERENTIATION BETWEEN Nocardia spp. AND Mycobacterium spp.: CRITICAL ASPECTS FOR BACTERIOLOGICAL DIAGNOSIS

New methodologies were developed for the identification of Nocardia but the initial diagnosis still requires a fast and accurate method, mainly due to the similarity to Mycobacterium, both clinical and bacteriologically. Growth on Löwenstein-Jensen (LJ) medium, presence of acid-fast bacilli through Ziehl-Neelsen staining, and colony morphology can be confusing aspects between Nocardia and Mycobacterium. This study describes the occurrence of Nocardia spp. in a mycobacterial-reference laboratory, observing the main difficulties in differentiating Nocardia spp. from Mycobacterium spp., and correlating isolates with nocardiosis cases. Laboratory records for the period between 2008 and 2012 were analyzed, and the isolates identified as Nocardia sp. or as non-acid-fast filamentous bacilli were selected. Epidemiological and bacteriological data were analyzed as well. Thirty-three isolates identified as Nocardia sp. and 22 as non-acid-fast bacilli were selected for this study, and represented 0.12% of isolates during the study period. The presumptive identification was based on macroscopic and microscopic morphology, resistance to lysozyme and restriction profiles using the PRA-hsp65 method. Nocardia spp. can grow on media for mycobacteria isolation (LJ and BBL MGIT™) and microscopy and colony morphology are very similar to some mycobacteria species. Seventeen patients (54.8%) were reported and treated for tuberculosis, but presented signs and symptoms of nocardiosis. It was concluded that the occurrence of Nocardia sp. during the study period was 0.12%. Isolates with characteristics of filamentous bacilli, forming aerial hyphae, with colonies that may be pigmented, rough and without the BstEII digestion pattern in PRA-hsp65 method are suggestive of Nocardia spp. For a mycobacterial routine laboratory, a flow for the presumptive identification of Nocardia is essential, allowing the use of more accurate techniques for the correct identification, proper treatment and better quality of life for patients

Phenotypic Overlap between MMP-13 and the Plasminogen Activation System during Wound Healing in Mice

BACKGROUND: Proteolytic degradation of extracellular matrix is a crucial step in the healing of incisional skin wounds. Thus, healing of skin wounds is delayed by either plasminogen-deficiency or by treatment with the broad-spectrum metalloproteinase (MP) inhibitor Galardin alone, while the two perturbations combined completely prevent wound healing. Both urokinase-type plasminogen activator and several matrix metallo proteinases (MMPs), such as MMP-3, -9 and -13, are expressed in the leading-edge keratinocytes of skin wounds, which may account for this phenotypic overlap between these classes of proteases. METHODOLOGY: To further test that hypothesis we generated Mmp13;Plau and Mmp13;Plg double-deficient mice in a cross between Mmp13- and Plau-deficient mice as well as Mmp13- and Plg-deficient mice. These mice were examined for normal physiology in a large cohort study and in a well-characterized skin wound healing model, in which we made incisional 20 mm-long full-thickness skin wounds. PRINCIPAL FINDINGS: While mice that are deficient in Mmp13 have a mean healing time indistinguishable to wild-type mice, wound healing in both Plau- and Plg-deficient mice is significantly delayed. Histological analysis of healed wounds revealed a significant increase in keratin 10/14 immunoreactive layers of kerationcytes in the skin surface in Mmp13;Plau double-deficient mice. Furthermore, we observe, by immunohistological analysis, an aberrant angiogenic pattern during wound healing induced by Plau-deficiency, which has not previously been described. CONCLUSIONS: We demonstrate a phenotypic overlap, defined as an additional delay in wound healing in the double-deficient mice compared to the individual single-deficient mice, between MMP-13 and the plasminogen activation system in the process of wound healing, but not during gestation and in postnatal development. Thus, a dual targeting of uPA and MMP-13 might be a possible future strategy in designing therapies aimed at tissue repair or other pathological processes, such as cancer invasion, where proteolytic degradation is a hallmark