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A hallmark of subclinical atherosclerosis is the accumulation of vascular smooth muscle cell (SMC)-like cells leading to intimal thickening and lesion formation. While medial SMCs contribute to vascular lesions, the involvement of resident vascular stem cells (vSCs) remains unclear. We evaluated single cell photonics as a discriminator of cell phenotype in vitro before the presence of vSC within vascular lesions was assessed ex vivo using supervised machine learning and further validated using lineage tracing analysis. Using a novel lab-on-a-Disk(Load) platform, label-free single cell photonic emissions from normal and injured vessels ex vivo were interrogated and compared to freshly isolated aortic SMCs, cultured Movas SMCs, macrophages, B-cells, S100β+ mVSc, bone marrow derived mesenchymal stem cells (MSC) and their respective myogenic progeny across five broadband light wavelengths (λ465 - λ670 ± 20 nm). We found that profiles were of sufficient coverage, specificity, and quality to clearly distinguish medial SMCs from different vascular beds (carotid vs aorta), discriminate normal carotid medial SMCs from lesional SMC-like cells ex vivo following flow restriction, and identify SMC differentiation of a series of multipotent stem cells following treatment with transforming growth factor beta 1 (TGF- β1), the Notch ligand Jagged1, and Sonic Hedgehog using multivariate analysis, in part, due to photonic emissions from enhanced collagen III and elastin expression. Supervised machine learning supported genetic lineage tracing analysis of S100β+ vSCs and identified the presence of S100β+vSC-derived myogenic progeny within vascular lesions. We conclude disease-relevant photonic signatures may have predictive value for vascular disease. Graphical abstract

1. Abstract Optofluidics, understood as the synergistic combination between microfluidics and photonics, has been at the forefront of the scientific research due to its outmatching properties: on the one hand, microfluidics allows the handling of minute amounts of liquid samples at the microscale. On the other hand, photonics has proved to outmatch other detection methods (e.g. electrochemistry) in terms of sensitivity and selectivity. From the initial single analyte or spiked samples, currently the technology is mature enough for selective detection of a variety of analytes in raw, complex liquid samples. This will pave the way for the applicability of optofluidic devices for applications in the field or at the point of care. Here, we will revisit the current state of the art of optofluidic and photonic lab-on-a-chip systems for the analysis of real and biologically relevant samples: body fluids and water.

CE has been a continuously evolving analytical methodology since its first introduction in the 1980s of the last century. The development of new CE separation procedures, the coupling of these systems to more sensitive and versatile detection systems, and the advances in miniaturization technology have allowed the application of CE to the resolution of new and complex analytical problems, overcoming the traditional disadvantages associated with this method. In the present work, different recent trends in CE and their application to the determination of high complexity samples (as biological fluids, individual cells, etc.) will be reviewed: capillary modification by different types of coatings, microfluidic CE, and online microextraction CE. The main advantages and disadvantages of the different proposed approaches will be discussed with examples of most recent applications.

A fast double-flow microfluidic based liquid phase microextraction (DF-µLPME) combined with a HPLC-UV procedure using diode array detection has been developed for the determination of the four most widely used parabens: Ethyl 4-hydroxybenzoate (EtP), Propyl 4-hydroxybenzoate (PrP), Butyl 4-hydroxybenzoate (BuP) and IsoButyl 4-hydroxybenzoate (iBuP) in water samples. Parabens have successfully been determined in environmental (lake and river water) samples with excellent clean up, high extraction efficiency and good enrichment factor using double-flow conditions. The microfluidic device consists of two micro-channels, which contain the acceptor and sample solution separated by a flat membrane (support liquid membrane). The sample (0.32mM HCl) and acceptor phase (5.6mM NaOH) are delivered to the µLPME at 10µLmin-1 and 1µLmin-1 flow rate, respectively. The extraction efficiencies are over 84% for all compounds in water samples with enrichment factors within the range of 9-11 and recoveries over 80%. The procedure provides very low detection limits between 1.6 and 3.5µgL-1. The extraction time and the volume required for the extraction are 5min and 50µL, respectively; which are greatly lower compared to any previous extraction procedure for parabens analysis. In addition, this miniaturized DF- µLPME procedure significantly reduces costs compared to not only the existing methods for paraben detection, but also to the existing analytical techniques for sample preparation.

This paper reports on a miniaturized and highly integrated lab-on-a-chip (LoC) combining both optical and electrochemical transduction modes for self-validating determination of biological analytes that undergo enzyme-catalyzed-reactions. This LoC monolithically integrates a biofunctionalized microfluidic mixer, also working as bioreactor, together with a measurement chamber, both fabricated in polydimethylsiloxane (PDMS) and applied for enzyme-mediated detection of glucose in continuous flow regime. The measurement chamber combines a multiple internal reflection (MIR) photonic cuvette and a tailor-made electrochemical cell, where gold electrode areas are defined by a silicon oxide passivation layer. Having separated mixing/reaction and measurement chambers greatly facilitates the functionalization process during the microsystem fabrication and the further calibration/rinsing steps carried out during the microsystem performance. A cascade bi-enzymatic reaction involving glucose oxidase (GOx) and horseradish peroxidase (HRP) together with azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) mediator is applied to carry out the glucose dual detection. The optical and electrochemical properties of the ABTS enable simultaneous absorbance and amperometric measurements, without cross-talk. The system requires low sample volumes below 15 μL and presents tunable analytical properties that can be adjusted by varying the flow rate. Linear ranges extending up to 1.6 mM and 2 mM glucose and limits of detection of 0.23 ± 0.02 mM and 0.064 ± 0.001 mM are achieved with the optical and electrochemical detection approaches, respectively, when operating simultaneously at 10 μL/min flow rate. The high degree of integration results in a minimization of dead volumes, reagent consumption and response time, providing with a high performance self-validating structure ideal for biomedical applications.

In this work, the traditional liquid phase microextraction (LPME) has been miniaturized into a microfluidic device (μLPME) where liquid phase microextraction is combined with an HPLC procedure. This integration enables extraction and determination of acid drugs by μLPME and HPLC, respectively. The analytes selected for the test are five widely used non-steroidal anti-inflammatory drugs (NSAIDs): salicylic acid (SAC), ketoprofen (KTP), naproxen (NAX), diclofenac (DIC) and ibuprofen (IBU). They have successfully been detected in biological (urine and saliva) and environmental (lake and river water) samples with excellent clean up, high extraction efficiency and good enrichment factor under stopped-flow conditions. The μLPME consists of two small channels (acceptor and donor channel) separated by a support liquid membrane and has been implemented to allow a simple membrane replacement an arbitrary number of times. The sample (pH 12) and acceptor phase (pH 1.5) are delivered to the μLPME at 1 μL min-1 flow rate and the extraction is completed after 6 min. Under these conditions, the recoveries obtained in urine samples are over 87% for all compounds. For environmental water analysis, different types of water samples have been analyzed obtaining recoveries over 75% for all compounds. The sample consumption is dramatically decreased (

In multiplexed analysis, lab on a chip (LoC) devices are advantageous due to the low sample and reagent volumes required. Although optical detection is preferred for providing high sensitivity in a contactless configuration, multiplexed optical LoCs are limited by the technological complexity for integrating multiple light sources and detectors in a single device. To address this issue, we present a microfluidic-controlled optical router that enables measurement in four individual optical channels using a single light source and detector, and without movable parts. The optofluidic device is entirely fabricated in polydimethylsiloxane (PDMS) by soft-lithography, compatible with standard microfabrication technologies, enabling monolithic integration in LoCs. In the device, in-coupled light from an optical fiber is collimated by a polymeric micro-lens and guided through a set of four sequentially connected micro-chambers. When a micro-chamber is filled with water, light is transmitted to the next one. If it is empty of liquid, however, total internal reflection (TIR) occurs at the PDMS-air interface, re-directing the light to the output optical fiber. The router presents high performance, with low cross-talk (, The research leading to these results has received funding from the European Research Council under the European Community's ERC grant agreement no 209243 and the Horizon 2020 (H2020) project ND4ID (grant agreement no 675412). Dr. X. M.-B. was supported by the “Ramón y Cajal” program from the Spanish Government. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).

A photonic lab-on-a-chip (PhLoC) was developed for rapid determination of interleukin-2 (IL-2) levels secreted by lymphocytes using measurement of optical absorbance. Optical and microfluidic components, including lenses, mirrors, and flow channels, were monolithically created using poly(dimethylsiloxane) (PDMS). Sample and reagent solutions were processed in the form of liquid columns separated by air. A flow channel structure with an air bypass was used to release air between solution columns and to exchange solutions in the measuring chamber, avoiding the intrusion of air into the measuring chamber and the denaturation of the capture antibodies. The concentration of IL-2 was measured by enzyme-linked immunosorbent assay (ELISA) in the PhLoC. The total time required for the ELISA was less than 30 min. Clear concentration dependence was confirmed for IL-2 concentrations ranging from 50 to 1000 pg/mL. Thus, the concentration of IL-2 secreted by lymphocytes following activation by concanavalin A (Con A) co...

The integration of micro-optical elements with microfluidics leads to the highly promising photonic lab-on-a-chip analytical systems (PhLoCs). In this work, we re-examine the main principles which are underneath the on-chip spectrophotometric detection, approaching the PhLoC concept to a nonexpert audience.

Photonic nanofences consisting of high aspect ratio polymeric optical subwavelength waveguides have been developed for their application into photonic sensing devices. They are up to millimeter long arrays of 250 nm wide and 6 μm high ridges produced by an advanced lithography process on a silicon substrate enabling their straightforward integration into complex photonic circuits. Both simulations and experimental results show that the overlap of the evanescent fields propagating from each photonic nanofence allows for the formation of an effective waveguide that confines the overall evanescent field within its limits. This permits a high interaction with the surrounding medium which can be larger than 90% of the total guided light intensity (approximately 20000 times larger than the evanescent field of a standard waveguide with equivalent dimensions). In this work, we not only investigate the photonic properties of these structures but also demonstrate their successful integration into a photonic sensor. An absorbance-based sensor for the determination of lead in water samples is therefore achieved by the combination of the photonic nanofences with an ion-sensitive optical membrane. The experimental results for lead detection in water show a sensitivity of 0.102 AU/decade, and a linear range between 10(-6) M and 10(-2) M Pb(II). A detection limit as low as 7.3 nM has been calculated according to IUPAC for a signal-to-noise ratio of 3.

The accumulation of vascular smooth muscle (SMC)-like cells within the intima contributes significantly to intimal medial thickening (IMT) and vascular remodeling typical of arteriosclerotic disease. Light has emerged as a powerful tool to interrogate cells label-free and facilitates discriminant observations both in vitro and in vivo . The auto-fluorescence (AF) profile of individual cells isolated from arteriosclerotic vessels, captured on V-cup array and interrogated across five wavelengths using a novel Lab-on-a-Disc platform, was significantly increased at the 565 ± 20nm wavelength concomitant with a reduction in Myh11 expression, when compared to differentiated vascular smooth muscle (SMC) cells from control vessels. In vitro, TGF-β1 promoted myogenic differentiation of murine bone-marrow derived Sca1 + /CD44 + mesenchymal stem cells (MSC) and murine Sca1 + C3H 10T1/2 cells concomitant with enrichment of the specific SMC epigenetic histone mark, H3K4me2 at the Myh11 promoter, Myh11 promoter transactivation and increased SMC differentiation marker mRNA and protein expression. Myogenic differentiation resulted in a significant increase in the AF intensity across 565 ± 20nm wavelength, an effect not observed for TGF-β1 treated RAMOS human B lymphocytes but mimicked by Notch activation of resident Sca1 + multipotent vascular stem cells (MVSCs) with Jagged1 and inhibited following elastin and collagen III depletion, respectively. Moreover, the temporal increase in the AF intensity at 565 ± 20nm wavelength during myogenic differentiation was similar to the AF profile of dissociated cells from arteriosclerotic vessels at this same wavelength. These data suggest that an AF photonic fingerprint of stem cell-derived myogenic progeny in vitro mimics that of vascular cells ex vivo following injury.

The accumulation of vascular smooth muscle (SM)-like cells within the intima contributes significantly to intimal medial thickening (IMT) and vascular remodelling typical of arteriosclerotic disease. The source of these cells remains controversial. Light has emerged as a powerful tool to interrogate cells label-free and facilitates discriminant observations both in vitro and in vivo. The auto-fluorescence (AF) profile of individual cells isolated from arteriosclerotic vessels, captured on V-cup array and interrogated across five wavelengths using a novel Lab-on-a-Disc platform, was significantly increased at the 565±20 nm wavelength concomitant with a reduction in Myh11 expression, when compared to differentiated vascular smooth muscle cells (SMC) from control vessels. In vitro, TGF-β1 promoted myogenic differentiation of murine bone-marrow derived Sca1+/CD44+mesenchymal stem cells (MSC) and murine Sca1+ C3H 10 T1/2 cells concomitant with enrichment of the specific SMC epigenetic histone mark, H3K4me2 at the Myh11 promoter, Myh11 promoter transactivation and increased SMC differentiation marker mRNA and protein expression. Myogenic differentiation resulted in a significant increase in the AF intensity across 565±20 nm wavelength, an effect not observed for TGF-β1 treated RAMOS human B lymphocytes but mimicked by Notch activation of resident Sca1+multipotent vascular stem cells (MVSCs) with Jagged1 and inhibited following elastin and collagen III depletion, respectively. Moreover, the temporal increase in the AF intensity at 565±20 nm wavelength during myogenic differentiation was similar to the AF profile of dissociated cells from arteriosclerotic vessels at this same wavelength. These data suggest that an AF photonic fingerprint of stem cell-derived myogenic progeny in vitro mimics that of vascular cells ex vivo. following IMT.

A microfluidic chip for cross-linked enzyme crystals (McCLEC) is presented and demonstrated to be a stable, reusable and robust biocatalyst-based device with very promising biotechnological applications. The cost-effective microfluidic platform allows in situ crystallization, cross-linking and enzymatic reaction assays on a single device. A large number of enzymatic reuses of the McCLEC platform were achieved and a comparative analysis is shown illustrating the efficiency of the process and its storage stability for more than one year., This work has been partly funded by the MICINN (Spain) projects BIO2010-16800 (JAG) and BIO2012-34937 (SMR), the European Commission (Contract No. 317916) under the LiPhos project (AL and IRR), “Factoría Española de Cristalización” Consolider-Ingenio 2010 (JAG and MCM) and EDRF Funds (JAG and AL). MCM thanks the Consejo Superior de Investigaciones Científicas (CSIC, Spain) for a JAE predoc fellowship.

We propose a PDMS-based photonic system for the accurate measurement of protein concentration with minute amounts of the sample. As opposed to the state of the art approach, in the multiple path photonic lab on a chip (MPHIL), analyte concentration or molar absorptivity is obtained with a single injection step, by performing simultaneous parallel optical measurements varying the optical path length. Also, as opposed to the standard calibration protocol, the MPHIL approach does not require a series of measurements at different concentrations. MPHIL has three main advantages: firstly the possibility of dynamically selecting the path length, always working in the absorbance vs. concentration linear range for each target analyte. Secondly, a dramatic reduction of the total volume of the sample required to obtain statistically reliable results. Thirdly, since only one injection is required, the measurement time is minimized, reducing both contamination and signal drifts. These characteristics are clearly advantageous when compared to commercial micro-spectrophotometers. The MPHIL concept was validated by testing three commercial proteins, lysozyme (HEWL), glucose isomerase (d-xylose-ketol-isomerase, GI) and Aspergillus sp. lipase L (BLL), as well as two proteins expressed and purified for this study, B. cereus formamidase (FASE) and dihydropyrimidinase from S. meliloti CECT41 (DHP). The use of MPHIL is also proposed for any spectrophotometric measurement in the UV-VIS range, as well as for its integration as a concentration measurement platform in more advanced photonic lab on a chip systems.

International audience; A low cost fabrication process for photonic lab on a chip systems is here proposed. For the implementation of the masters suitable for cast molding fabrication, an inexpensive dry film photoresist, patternable using standard laboratory equipment, is benchmarked against standardized SU-8 masters obtained using UV lithography and systems manufacture in clean room facilities. Results show adequate system fabrication and a comparable performance of the photonic structures for absorbance/extinction measurements.

This paper reports and compares the implementation of magnetic variable optical attenuators (M-VOA) by two fabrication strategies. In the first case, a two-layer structure containing a non-doped polydimethylsiloxane (PDMS) layer on a magnetic PDMS (M-PDMS) layer is fabricated by soft lithography (SLT). M-PDMS is obtained by doping PDMS with different ferrofluid (FF) volumes. The second technology consists of selectively dispense FF microdroplets using the inkjet printing technique (UP) on a non-doped, non-cured PDMS structure, previously defined by SLT. In this second case, FF volumes are encapsulated inside the polymer matrix. The optical and mechanical properties of structures fabricated using both strategies and containing similar ferrofluid amounts are compared. (C) 2014 Elsevier B.V. All rights reserved.

This paper presents the applicability of a microtechnologically fabricated microbubble column as a screening tool for submerged aerobic cultivation. Bubbles in the range of a few hundred micrometers in diameter were generated at the bottom of an upright-positioned microdevice. The rising bubbles induced the circulation of the liquid and thus enhanced mixing by reducing the diffusion distances and preventing cells from sedimentation. Two differently sized nozzles (21 × 40 µm(2) and 53 × 40 µm(2) in cross-section) were tested. The gas flow rates were adjustable, and the resulting bubble sizes and gas holdups were investigated by image analysis. The microdevice features sensor elements for the real-time online monitoring of optical density and dissolved oxygen. The active aeration of the microdevice allowed for a flexible oxygen supply with mass transfer rates of up to 0.14 s(-1). Slightly higher oxygen mass transfer rates and a better degassing were found for the microbubble column equipped with the smaller nozzle. To validate the applicability of the microbubble column for aerobic submerged cultivation processes, batch cultivations of the model organism Saccharomyces cerevisiae were performed, and the specific growth rate, oxygen uptake rate, and yield coefficient were investigated.

The legislation of food industry is becoming increasingly strict with regard to the quality of food products. Therefore, the market is demanding for automatic systems of analysis that allow fast and accurate monitoring of the evolution of quality parameters in agrofood products or permit obtaining information to optimize production processes. In this context, sensors and more specifically microsensors play an important role since they allow fast and reproducible measurement of a large number of quality parameters with good reliability and can be implemented in portable systems. This paper presents a review of the results obtained with an electronic tongue based on different kinds of microsensors applied to wine analysis by the team of IMB-CNM. This multisensor system allows on one hand classifying the wine according to its features like grape variety, geographic origin, year, and organoleptic characteristics and on the other hand quantifying some parameters of interest in quality control, such as alcoholic degree, pH, ions, total acidity, glycerol, and color.

A multisensor system combined with multivariate analysis is applied for the characterization and classification of white grape juices. The proposed system, known as hybrid electronic tongue, consists of an array of electrochemical microsensors and a colorimetric optofluidic system. A total of 25 white grape juices representing the large variability of vines grown in the Northwest Iberian Peninsula were studied. The data obtained were treated with Principal Component Analysis (PCA) and Soft Independent Modeling Class Analogy (SIMCA). The first tool was used to train the system with the reference genotypes -Albariño, Muscat à Petit Grains Blanc and Palomino- and the second to study the feasibility of the hybrid electronic tongue to distinguish between different grape juice varieties. The results show that the three reference genotypes are well differentiated in the PCA model and this can be used to interpolate the rest of varieties and predict their basic characteristics. Besides, using the SIMCA, the system demonstrates high potential for classifying and discriminating grape varieties. © 2013 American Chemical Society.

We analyze the influence of the fabrication technique and the silicon excess on the power efficiency and evolution with time of the electroluminescence of silicon rich silicon oxide in metal-oxide-semiconductor like light emitting capacitors under direct current. The silicon rich silicon oxide layers have been fabricated using two different techniques, namely plasma enhanced chemical vapor deposition and silicon ion implantation. Six different silicon excesses have been studied, ranging from 6 at. % to 15 at. %. It is shown that both the power efficiency and external quantum efficiency increase with the silicon excess due to a decrease in the electroluminescence current threshold. The maximum value of the power efficiency has been found to be (2.6±0.3)×10-5 in the ion implanted sample with 15 at. % silicon excess. Significant differences in the evolution of the electroluminescence with time are found depending on the fabrication technique.

Fully combined metal-oxide-semiconductor compatible light-emitting devices based on nano bi-layer structures are fabricated. The active layers are composed of silicon nitride on top of a silicon-enriched silicon dioxide film with different Si concentrations. Electro and photo luminescence spectra of the devices and the active materials are analyzed and correlated to verify if the origin of the emission is the same. Differences found between electrically and optically stimulated photo-emission in the studied region of the spectra are concluded to be due to optical phenomena introduced by the gate and multilayer configuration, meaning that the same radiative centers are stimulated optically and electrically.

A poly(dimethylsiloxane) biophotonic lab-on-a-chip (bioPhLoC) containing two chambers, an incubation chamber and a monitoring chamber for cell retention/proliferation and pH monitoring, respectively, is presented. The bioPhLoC monolithically integrates a filter with 3 mu m high size-exclusion microchannels, capable of efficiently trapping cells in the incubation chamber, as well as optical elements for real-time interrogation of both chambers. The integrated optical elements made possible both absorption and dispersion measurements, which were comparable to those made in a commercially available cuvette. The size-exclusion filter also showed good and stable trapping capacity when using yeast cells of variable size (between 5 and 8 mu m diameter). For cell culture applications, vascular smooth muscle cells (VSMC), with sizes between 8 and 10 mu m diameter, were used as a mammalian cell model. These cells were efficiently trapped in the incubation chamber, where they proliferated with a classical spindle-shaped morphology and a traditional hill-and-valley phenotype. During cell proliferation, pH changes in the culture medium due to cell metabolism were monitored in real time and with high precision in the monitoring chamber without interference of the measurement by cells and other (cell) debris.

Microfluidics or lab-on-a-chip technology offer clear advantages over conventional systems such as a dramatic reduction of reagent consumption or a shorter analysis time, which are translated into cost-effective systems. In this work, we present a photonic enzymatic lab-on-a-chip reactor based on cross-linked enzyme crystals (CLECs), able to work in continuous flow, as a highly sensitive, robust, reusable, and stable platform for continuous sensing with superior performance as compared to the state of the art. The microreactor is designed to facilitate the in situ crystallization and crystal cross-linking generating enzymatically active material that can be stored for months/years. Thus, and by means of monolithically integrated micro-optics elements, continuous enzymatic reactions can be spectrophotometrically monitored. Lipase, an enzyme with industrial significance for catalyzed transesterification, hydrolysis, and esterification reactions, is used to demonstrate the potential of the microplatforms as both a continuous biosensor and a microreactor for the synthesis of high value compounds.

Photonic nanotences (PNFs) are introduced here as advanced high-sensitivity chemical sensors. They are based on sub-wavelength high aspect ratio structures and allow creating evanescent field (EF) higher than 70%, while keeping the light confined in a defined region. Thus unprecedented light-analyte interaction can be achieved. We demonstrate the waveguiding capabilities of these structures by presenting bent PNFs, proving their efficient light coupling and guiding. Finally, PNFs are implemented as absorbance sensor for lead (Pb2+) detection in water environment.

Elementary PDMS-based building blocks of fluidic, optical and optofluidic components for Lab on a chip (LOC) platforms has here been developed. All individual modules are compatible and can be anchored and released with the help of puzzle-type connectors This approach is a powerful toolbox to create modular optofluidic systems (MOPS), which can be modified/upgraded to user needs and in-situ reconfigurable. In addition, the PDMS can locally be functionalized, defining a modular biosensor. Measurements in absorbance and fluorescence have been pursued as demonstrator.

Stimuli-responsive materials undergo physicochemical and/or structural changes when a specific actuation is applied. They are heterogeneous composites, consisting of a non-responsive matrix where functionality is provided by the filler. Surprisingly, the synthesis of polydimethylsiloxane (PDMS)-based stimuli-responsive elastomers (SRE) has seldomly been presented. Here, we present the structural, biological, optical, magnetic, and mechanical properties of several magnetic SRE (M-SRE) obtained by combining PDMS and isoparafin-based ferrofluid (FF). Independently of the FF concentration, results have shown a similar aggregation level, with the nanoparticles mostly isolated (>60%). In addition to the superparamagnetic behavior, the samples show no cytotoxicity except the sample with the highest FF concentration. Spectral response shows FF concentrations where both optical readout and magnetic actuation can simultaneously be used. The Young’s modulus increases with the FF concentration until the highest FF concentration is used. Our results demonstrate that PDMS can host up to 24.6% FF (corresponding to 2.8% weight of Fe3O4 nanoparticles concentration). Such M-SRE are used to define microsystems – also called soft microsystems due to the use of soft materials as main mechanical structures. In that scenario, a large displacement for relatively low magnetic fields (, The research leading to these results has received funding from the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007-2013) ERC grant agreement no. 209243. Partial financial support from the 2014SGR-1015 (DGU) is acknowledged. Dr. XM-B was supported by the “Ramón y Cajal” program from the Spanish Government. MINAHE4:TEC2011-29140-C03-01.

The one-step room-temperature micropatterning of a fluorophore-doped xerogel material on silicon oxide substrates is reported. The organo-alkoxysilane precursors and organic fluorescent dyes, as well as the polymerization experimental conditions, were tailored in order to obtain a highly homogeneous transparent material suitable for photonic applications. A thorough structural characterization was carried out by Fourier transform infrared (FT-IR) spectroscopy, (29)Si nuclear magnetic resonance ((29)Si NMR), thermogravimetric analysis (TGA), N(2) adsorption Brunauer-Emmett-Teller (BET) porosimetry, and confocal microscopy. These studies revealed a stable nonporous highly cross-linked polymer network containing evenly dispersed fluorescent molecules. Xerogel microstructures having thicknesses between 4 and 80 μm and height-to-width ratios between 0.04 and 4, as well as showing different geometries, from well arrays to waveguides, were patterned in a single step by micromolding in capillaries (MIMIC) soft lithographic technique. The reliability of the replication process was tested by bright-field optical microscopy and scanning electron microscopy (SEM) that show the close fidelity of the microstructures to the applied mold. The optical performance of the developed material was demonstrated by fabricating waveguides and evaluating their corresponding spectral response, obtaining absorption bands, at the expected excitation wavelengths of the corresponding fluorescent dyes and gain due to photonic re-emission (fluorescence) at their corresponding dye emission wavelengths. The hybrid xerogel material and the application of the simple fabrication technology presented herein can be directly applied to the development of cost-effective photonic components, as could be light emitters, to be readily integrated in single-use lab-on-chip devices and other polymeric microsystems.

Studies of photo-luminescence (PL) and X-ray Photoelectron Spectroscopy (XPS) were performed to silicon-rich silicon dioxide films (SRO) fabricated by implantation of Si ions on SiO2 deposited by plasma enhanced chemical vapor deposition (PECVD). Samples presented PL spectra formed by the contribution of two bands, respectively related to defects and quantum confinement (QC). The XPS results for the different samples presented significant differences in the density and types of Si-Si and Si-O bonds. A relation was observed between the types of Si bonds and the PL characteristics presented by the material, obtaining a modulation of the emission spectra trough the change of the implantation dose.

Rapid discrimination of avian vs. human phenotypes of emerging influenza A virus isolates with pandemic potential is an important issue in pathogenesis and epidemiology studies of the infection. In this work, functional architectures are tailored on the surface of a gold electrode, introducing receptor molecules as a sensing entity that mimics those found in the membrane of target cells of the influenza A virus and with the aim of developing an impedimetric-based detector for influenza A virus phenotyping. In a bottom-up approach, the artificial receptors are built by sequential assembly of a 1-octanethiol/octyl- galactoside hybrid bilayer, followed by an enzyme-mediated functionalization of the terminal galactoside groups with sialic acid molecules. The detection mechanism relies hence on the specific affinity between the sialic acid-galactose receptor moieties anchored on the modified electrode surface and the hemagglutinin (HA) viral surface protein. By using the appropriate type of sialyltransferase enzyme, sialylation of galactose residues is made through α-2,3 or α-2,6 linkages. This permits the envisaged impedimetric detector to discriminate rapidly between avian vs. human strains of influenza A virus with the absence of elaborate sample preparation steps. In contrast to immunosensors based on antibodies as bioreceptor, the sialylated modified gold electrode is also able to distinguish among influenza phenotypes, which could make the here presented detector a reagentless, label-free diagnostic device for influenza phenotyping. Biomimetic architectures for the impedimetric discrimination of influenza virus phenotypes are tailored by a self-assembly process on gold substrates. Incorporated sialic acid molecules as sensing entities mimic receptors found on target cells of the influenza A virus. The resulting detector rapidly discriminates between avian and human strains of influenza A virus, acting as a reagentless, label-free diagnostic device for influenza phenotyping, which is important in surveillance and prediction of pandemics. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., This work was supported by the CICYT (Spain, projects MAT2009-09960 and AGL2007-60274) and the CSIC (Spain, projects PIF08-018 and 201060I009). B.W. acknowledges a Personal Investigador contract of the Comunidad de Madrid. M.A.M.B. and M.Y. acknowledge a PIF08-018 contract.

Processing fl exibility and good mechanical properties are the two major reasons for SU-8 extensive applicability in the micro-fabrication of devices. In order to expand its usability down to the nanoscale, conductivity of ultra-thin SU-8 layers as well as its patterning by AFM are explored. By performing local electrical measurements outstanding insulating properties and a dielectric strength 100 times larger than that of SiO 2 are shown. It is also demonstrated that the resist can be nano-patterned using AFM, obtaining minimum dimensions below 40nm and that it can be combined with parallel lithographic methods like UV-lithography. The concurrence of excellent insulating properties and nanometer-scale patternability enables a valuable new approach for the fabrication of nanodevices. As a proof of principle, nano-electrode arrays for electrochemical measurements which show radial diffusion and no overlap between different diffusion layers are fabricated. This indicates the potential of the developed technique for the nanofabrication of devices.

This article presents a polymeric micro-optical system that consists of two coupled miniaturized devices for spatially distributed characterization of microfluidic two-phase phenomena exploiting multiwavelength optical signals. The input device implements four optical windows (slits) which are superimposed on the centerline of a microfluidic serpentine channel and illuminate specific locations of the microchannel. The flow-related information is then collected by an ad hoc polymeric micro-optical output device that guides and merges the spatially distributed information into a single output signal, which maintains memory of the spatial coordinates by using the wavelengths as fingerprints of the slits’ position in the microfluidic channel. Both micro-optical devices were designed, simulated, and characterized in static and dynamic conditions. Experiments on two-phase (air and ethanol) flow were carried out by applying constant and periodic flow rate functions. In both cases, the system was proved to be efficient in capturing the spatial–temporal dynamics of flow profiles.

A multisensor system combined with multivariate analysis was applied to the characterization of red wines and to the quantification of the grape variety percentage. The proposed system, known as hybrid electronic tongue, consists of a colorimetric optofluidic system and an array of electrochemical sensors. Three monovarietal red wines were studied: Pinot Noir, Merlot and Cabernet Sauvignon. Homemade mixtures were elaborated from these wines according to a Simplex experimental design with 60 samples. The data obtained were treated using advanced chemometric tools like Principal Component Analysis (PCA) and Soft Independent Modeling Class Analogy (SIMCA) for the classification of the wine mixtures and Partial Least Squares (PLS) regression for the quantification of the grape variety composition. The results have shown a good classification of the grape varieties and the identification of the mixtures with Pinot Noir up to 75%. Besides, using the PLS regression, the system has demonstrated a high potential for quantifying the percentage of each grape variety.

We present the development of microbioreactors (MBRs) based on poly(dimethylsiloxane) (PDMS) segmented waveguides (SWG) for local absorbance measurements. Two different MBRs were studied, either using symmetric or asymmetric SWG (being defined as MBR-S and MBR-A, respectively). Their optical and fluidic performances were numerically analyzed, showing robustness from an optical point of view and distinct fluid flow profile. The optical characterization was done in two steps. Initially, the experimental limit of detection (LOD) and the sensitivity were determined for two different analytes (fluorescein and methylorange). With both systems, a similar limit of detection for both analytes was obtained, being in the micromolar level. Their sensitivities were 20.2±0.3 (×10⁻³) A.U./μM and 5.5±0.2 (×10⁻³) A.U./μM for fluorescein and methylorange, respectively. Once validated its applicability for local absorbance measurements, a continuous cultivation of Saccharomyces cerevisiae was done to test the viability of the proposed systems for photonic MBRs. Concretely, the cell growth was locally monitored inside the MBR during 33 h. Spectral analysis showed that the determination of the culture parameters were wavelength dependant, with a growth rate of 0.39±0.02 h⁻¹ and a doubling time of 1.65±0.09 h at an optimal wavelength of 469.9±0.3 nm. Besides the easy and monolithic integration of the SWG into poly(dimethylsiloxane) microfluidic systems, the results presented here are very promising for the application in any disposable photonic lab-on-a-chip systems used for online analysis or photonic MBRs.

A PDMS based tuneable microoptical system fabricated merging deep reactive ion etching, SU-8 and soft lithography, with a low-cost (mass-production), simple and highly repetitive technology, is presented. This system consists on a structure of two microlenses with uncoupled optical properties that can be mechanically actuated. This device was numerically simulated prior to its fabrication, to optimize its design and improve its behaviour. In addition, an optical characterization of the fabricated devices was carried out to provide a proof of concept of the presented devices and validate the proposed fabrication technology.

A low-cost photonic lab on a chip with three different working regimes for cell screening is presented. The proposed system is able to perform scattering, scattering + absorption, and absorption measurements without any modification. Opposite to the standard flow cytometers, in this proposed configuration, a single 30 ms scan allows to obtain information regarding the cell optical properties. An additional novelty is that the whole spectrum is obtained and analyzed, being then possible to determine for each regime which is the optimal working wavelength that would provide the best performance in terms of sensitivity and limit of detection (LOD). Experimental results have provided with an LOD of 54.9 +/- 0.7 cells (in the scattering regime using unlabeled cells), 53 +/- 1 cells (in the scattering + absorption regime using labeled cells), and 105 +/- 4 cells (in the absorption regime using labeled cells). Finally, the system has also been used for measuring the dead/live cell ratio, obtaining LODs between 7.6 +/- 0.4% and 6.7 +/- 0.3%, depending on the working regime used.

Microalgal cells were entrapped within two different sol–gel silica matrices with the aim of carrying out viability studies and developing active phases for sensor development. The first sol–gel system, based on methacryloxypropyltrimethoxysilane (MAPTS) and tetramethoxysilane (TMOS) monomers, was able to entrap lyophilized Chlorella vulgaris and Anabaena sp. PCC7120, but its rather non-porous nature limited the algal viability to the surface and fractures of the resulting hybrid material. However, this sol–gel material prepared with Chlorella tissue successfully performed as an active phase in the development of sensors for heavy-metal ions (e.g. Pb2+, Cu2+ and Cd2+) in water solution. The second sol–gel system was obtained using methyltrimethoxysilane (MTMOS), phenyltrimethoxysilane (PhTMOS) and TMOS monomers. Here, entrapped algae appeared to weakly interact with the resulting matrix probably due to its high hydrophobicity and also very low porosity. In this context, SEM and AFM studies carried out with the Anabaena-sol–gel material showed that algae could be removed from the polymeric network leaving traces having the algae’s peculiar three-dimensional shape. This opens the way to prepare imprinted materials using a soft lithographic approach, which could be potentially used as artificial receptors for electrochemical sensing of algae target species.

This paper presents the design, simulation, fabrication and characterization of a silicon hollow waveguide-based full-field absorbance biosensor and its application for the detection of hydrogen peroxidase (H 2 O 2 ) using a peroxidase enzyme as a model recognition element. Such a system merges into one single microstructure the transducer (waveguide) and the bioreactor (recognition element), achieving a high degree of integration with only one photolithographic step. Moreover, this configuration allows the interaction between the light confined into the hollow waveguide with the analyte. Hence, high sensitivities or small interaction lengths can be easily achieved. Numerical simulations and experimental results show a good agreement, with a linear behaviour ranging from 0.01 mM to 0.3 mM and sensitivities of 2.7 AU/mM and 3.0 ± 0.2 AU/mM, respectively. Furthermore, the experimental characterization shows a limit of detection of 0.020 ± 0.001 mM and a signal-to-noise ratio ranging from 20 dB to 14 dB on the linear range. These results, the simple design and technology proposed, together with the potential capability of the hollow waveguides to integrate microfluidic and microelectronics, present these structures as excellent candidates for the fabrication of ultra-compact, low-cost, micro total analysis systems (μTAS).

In this paper it is shown how the inclusion of the air mirrors allows both the enhancement of the performance of the Single Internal Reflection (SIR) systems and the implementation of a new type of highly sensitive absorbance-based biosensor, based on Multiple Internal Reflection (MIR). Both configurations are fabricated in a single-mask step and replicated using Poly(dimethylsiloxane) (PDMS) using soft lithographic techniques. Experimental results confirm the ray-tracing predictions: if the air mirror is accurately defined, the propagating light matches the conditions of Total Internal Reflection (TIR) at the PDMS–air interface, which results in a complete reflection of the light towards the flow cell. Hence, the inclusion of such microoptical components reduces the integration time more than 30 times while increasing the SNR and the sensitivity, reaching limits of detection (LOD) close to the μM level. On the other hand, in the MIR configuration, the shape of the air mirrors has been modified so as to allow the partial focusing of the light at adequate places of the flow cell. With the recursive positioning of air mirrors, the optical path length has been meaningfully lengthened without a dramatic increase of the volume. The experimental results also match with the ray-tracing predictions and have allowed obtaining LOD between 110 nM (PMIR-II) and 41 nM (RMIR) with sensitivities up to three times higher than the SIR configuration. The obtained results are auspicious for the implementation of the absorbance-based photonic lab-on-a-chip systems.

A new soft-lithography approach for direct silane nanopatterning, known as gas-transfer lithography, is presented and tested. Chemically active two-dimensional replicas of carbon nanotubes are attained (see image). Amplitude modulation atomic force microscopy reveals silane patterns with distinctive dimensions and chemical composition.

This paper presents the design, fabrication and characterization of polymer microoptoelectromechanical systems (MOEMS). An optical accelerometer and a variable optical attenuator (VOA) based on SU-8 are presented. Both devices consist on a quad-beam polymer structure and can be fabricated with a simple technology, requiring only two photolithographic steps. Self-alignment structures for fast and accurate fiber optic positioning have also been implemented in both devices. The accelerometer working principle consists on a misalignment between the three waveguides, which comprise the structure, as acceleration is applied. Experimental optical sensitivities of 13.1 dB/g for negative and 17.5 dB/g for positive accelerations, and a high repeatability in an uncontrolled atmosphere are observed. Using the same devices and taking advantage of the high thermal expansion (CTE) of the SU-8, it is possible to obtain a low-power consumption VOA. Experimental results show an attenuation of 20 dB for a power consumption of 12 mW.