Multimode PDMS waveguides fabricated using a hot-embossing technique

A novel method for fabricating multimode PDMS waveguides is presented. This process is based on a hot-embossing technique and generates high quality optical waveguides without a substantial residual layer after embossing. Furthermore, the process allows for low-cost fabrication since it relies on a replication technique and additionally only commercially available materials are used. The measured propagation loss is smaller than 0.24dB/cm and can be further reduced by improving the master mould quality

Embedded flexible optical shear sensor

Monitoring shear stresses is increasingly important in the medical sector, where the sensors need to be unobtrusive, compact and flexible. A very thin and flexible sensor foil is presented based on the shear stress dependent coupling change of optical power between a laser and photodiode chip that were separated by a deformable sensing layer. These opto-electronic components were embedded in a very thin foil of only 40 mu m thick. The sensitivity and measurement range can be modified by selecting the material properties of the sensing layer. The sensor response showed to be reproducible and the influence of normal pressure on the sensor was very limited

Packaging technology enabling flexible optical interconnections

This paper reports on the latest trends and results on the integration of optical and opto-electronic devices and interconnections inside flexible carrier materials. Electrical circuits on flexible substrates are a very fast growing segment in electronics, but opto-electronics and optics should be able to follow these upcoming trends. This paper presents the back-thinning and packaging of single opto-electronic devices resulting in highly flexible and reliable packages. Optical waveguides and optical out-of-plane coupling structures are integrated inside the same layer stack, resulting in complete VCSEL-to-PD links with low total optical losses and high resistance to heat cycling and moisture exposure

Determination of five folate monoglutamates in rodent diets

A method for the quantitative determination of folates in rodent diets is very important for correct interpretation of folate intake during feeding trials, given the possible discrepancy between the actual folate concentration in the diet and that mentioned on the product sheet. Liquid chromatography tandem-mass spectrometry is the method of choice to differentiate and quantify the individual folate species present. This discrepancy may be accounted for by, e.g., inaccurate folic acid supplementation and/or the presence of endogenous reduced and substituted folates. We developed a method, validated based on FDA guidelines, that allows the measurement of added and endogenous folates by quantitative determination of 5 folate monoglutamates with linear ranges from 8 mu g to 2 mg/kg feed. This information, combined with feed intake data, allows insight into the actual folate intake in animal feeding studies. The relevance of this method was illustrated by the analysis of several feed samples of varying composition, by the investigation of the effect of casein incorporation, and by evaluating the variability of the folate content between pellets and production batches

Optical fiber sensors embedded in flexible polymer foils

In traditional electrical sensing applications, multiplexing and interconnecting the different sensing elements is a major challenge. Recently, many optical alternatives have been investigated including optical fiber sensors of which the sensing elements consist of fiber Bragg gratings. Different sensing points can be integrated in one optical fiber solving the interconnection problem and avoiding any electromagnetical interference (EMI). Many new sensing applications also require flexible or stretchable sensing foils which can be attached to or wrapped around irregularly shaped objects such as robot fingers and car bumpers or which can even be applied in biomedical applications where a sensor is fixed on a human body. The use of these optical sensors however always implies the use of a light-source, detectors and electronic circuitry to be coupled and integrated with these sensors. The coupling of these fibers with these light sources and detectors is a critical packaging problem and as it is well-known the costs for packaging, especially with optoelectronic components and fiber alignment issues are huge. The end goal of this embedded sensor is to create a flexible optical sensor integrated with (opto)electronic modules and control circuitry. To obtain this flexibility, one can embed the optical sensors and the driving optoelectronics in a stretchable polymer host material. In this article different embedding techniques for optical fiber sensors are described and characterized. Initial tests based on standard manufacturing processes such as molding and laser structuring are reported as well as a more advanced embedding technique based on soft lithography processing

Low-cost fully integrated fiber Bragg grating interrogation system

Fiber Bragg gratings can be used for monitoring different parameters in a wide variety of materials and constructions. The interrogation of fiber Bragg gratings traditionally consists of an expensive and spacious peak tracking or spectrum analyzing unit which needs to be deployed outside the monitored structure. We present a dynamic low-cost interrogation system for fiber Bragg gratings which can be integrated with the fiber itself, limiting the fragile optical in- and outcoupling interfaces and providing a compact, unobtrusive driving and read-out unit. The reported system is based on an embedded Vertical Cavity Surface Emitting Laser (VCSEL) which is tuned dynamically at 1 kHz and an embedded photodiode. Fiber coupling is provided through a dedicated 45° micromirror yielding a 90° in-the-plane coupling and limiting the total thickness of the fiber coupled optoelectronic package to 550 µm. The red-shift of the VCSEL wavelength is providing a full reconstruction of the spectrum with a range of 2.5 nm. A few-mode fiber with fiber Bragg gratings at 850 nm is used to prove the feasibility of this low-cost and ultra-compact interrogation approach

Hydroxychloroquine decreases human MSC-derived osteoblast differentiation and mineralization in vitro

We recently showed that patients with primary Sjögren Syndrome (pSS) have significantly higher bone mineral density (BMD) compared to healthy controls. The majority of those patients (69%) was using hydroxychloroquine (HCQ), which may have favourable effects on BMD. To study the direct effects of HCQ on human MSC-derived osteoblast activity. Osteoblasts were cultured from human mesenchymal stromal cells (hMSCs). Cultures were treated with different HCQ doses (control, 1 and 5 µg/ml). Alkaline phosphatase activity and calcium measurements were performed to evaluate osteoblast differentiation and activity, respectively. Detailed microarray analysis was performed in 5 µg/ml HCQ-treated cells and controls followed by qPCR validation. Additional cultures were performed using the cholesterol synthesis inhibitor simvastatin (SIM) to evaluate a potential mechanism of action. We showed that HCQ inhibits both MSC-derived osteoblast differentiation and mineralization in vitro. Microarray analysis and additional PCR validation reveale