Photo-actuated ionogel microvalves for real-time water quality analysis in a micro-fluidic device

In the recent years, advances in micro-fluidic techniques for environmental applications have brought wide opportunities for improving of the capacity to monitor water quality. However, the development of fully integrated micro-fluidic devices capable of performing complex functions requires the integration of mico-valve with appropriate performance, since they are essential tools for the control and manipulation of flows in micro-channels.[1] The incorporation of ionic liquids within responsive gel matrices (ionogels) produces hybrid materials with many advantages over conventional materials. Depending on the ionic liquid, ionogels give the possibility of tuning several micro-valve actuation times and so independently control liquid flows within the channels under a common illumination source.[2] The undeniable advantage of these materials arise from the use of non invasive, non-contact stimuli such as light, offering improvements in versatility during manifold fabrication, and control of the actuation mechanism. Here we present an attractive approach for water quality analysis, nitrite determination, based on photo-switchable ionogel actuators wherein the micro-valve opening/closing mechanism is controlled by simply applying localised white light irradiation using optical fibres. The nitrite concentration of water samples is detected by a highly sensitive, low cost wireless paired emitter detector diode device. [1] M. Czugala et. al., “Materials Science: The Key to Revolutionary Breakthroughs in Micro-fluidic Devices”, Proceedings SPIE 8107, 81070C, (2011); doi:10.1117/12.895330. [2] F. Benito-Lopez et. al., Ionogel-based light-actuated valves for controlling liquid flow in micro-fluidic manifolds, Lab Chip 10, (2010), 195-20

Biofunctionalized all-polymer photonic lab on a chip with integrated solid-state light emitter

A photonic lab on a chip (PhLOC), comprising a solid-state light emitter (SSLE) aligned with a biofunctionalized optofluidic multiple internal reflection (MIR) system, is presented. The SSLE is obtained by filling a microfluidic structure with a phenyltrimethoxysilane (PhTMOS) aqueous sol solution containing a fluorophore organic dye. After curing, the resulting xerogel solid structure retains the emitting properties of the fluorophore, which is evenly distributed in the xerogel matrix. Photostability studies demonstrate that after a total dose (at l = 365 nm) greater than 24 J/cm2, the xerogel emission decay is only 4.1%. To re-direct the emitted light, the SSLE includes two sets of air mirrors that surround the xerogel. Emission mapping of the SSLE demonstrates that alignment variations of 150 mm (between the SSLE and the external pumping light source) provide fluctuations in emitted light smaller than 5%. After this verification, the SSLE is monolithically implemented with a MIR, forming the PhLOC. Its performance is assessed by measuring quinolone yellow, obtaining a limit of detection (LOD) of (0.60 +/- 0.01) mM. Finally, the MIR is selectively biofunctionalized with horseradish peroxidase (HRP) for the detection of hydrogen peroxide (H2O2) target analyte, obtaining a LOD of (0.7 +/- 0.1) mM for H2O2, confirming, for the first time, that solid-state xerogel-based emitters can be massively implemented in biofunctionalized PhLOCs

An In-Line photonic biosensor for monitoring of glucose concentrations

This paper presents two PDMS photonic biosensor designs that can be used for continuous monitoring of glucose concentrations. The first design, the internally immobilized sensor, consists of a reactor chamber, micro-lenses and self-alignment structures for fiber optics positioning. This sensor design allows optical detection of glucose concentrations under continuous glucose flow conditions of 33 μL/h based on internal co-immobilization of glucose oxidase (GOX) and horseradish peroxidase (HRP) on the internal PDMS surface of the reactor chamber. For this design, two co-immobilization methods, the simple adsorption and the covalent binding (PEG) methods were tested. Experiments showed successful results when using the covalent binding (PEG) method, where glucose concentrations up to 5 mM with a coefficient of determination (R2) of 0.99 and a limit of detection of 0.26 mM are detectable. The second design is a modified version of the internally immobilized sensor, where a microbead chamber and a beads filling channel are integrated into the sensor. This modification enabled external co-immobilization of enzymes covalently onto functionalized silica microbeads and allows binding a huge amount of HRP and GOX enzymes on the microbeads surfaces which increases the interaction area between immobilized enzymes and the analyte. This has a positive effect on the amount and rate of chemical reactions taking place inside the chamber. The sensor was tested under continuous glucose flow conditions and was found to be able to detect glucose concentrations up to 10 mM with R2 of 0.98 and a limit of detection of 0.7 mM. Such results are very promising for the application in photonic LOC systems used for online analysis © 2014 by the authors; licensee MDPI, Basel, Switzerland.This work has been funded by the German Research Foundation (DFG) within the framework of the Research Unit 856 Microsystems for Particulate Life-Science Products. One of the authors (S.B.) gratefully acknowledges the financial support of the Volkswagen Foundation. We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)Peer Reviewe

Integrated Optical Interferometric Biosensors based on Microelectronics technology for biosensing applications

6 páginas, 8 figuras.-- Comunicación oral presentada al Ibersensors´2002 celebrado en Lima (Perú) en 2002.Integrated optical sensors have reached a great importance during last years since they can be used for the direct detection of biomolecular interactions. Moreover, Silicon microelectronics technology allows mass production as well as the fabrication of microsystems by hybrid integration of sources, sensors, photodelectors and CMOS electronics. For the fabrication of an evanescent field sensor with an integrated Mach-Zehnder interferometric (MZI) configuration, the optical waveguides must verify two main characteristics: monomode behaviour and high surface sensitivity. In this paper we present the development of a MZI sensor based on two different optical waveguides: TIR (Total Internal Reflection) and ARROW (Antiresonant Reflecting Optical Waveguides). The advantages of both structures are discussed and experimental results of the devices are presented.Peer reviewe

Development and integration of xerogel polymeric absorbance micro-filters into lab-on-chip systems

This work reports on the implementation of different absorption micro-filters based on a dye-doped hybrid organic-inorganic xerogel polymeric material synthesized by the sol-gel process. Microstructures containing eight different filter widths were fabricated in polydimethylsiloxane (PDMS), bonded to glass substrates and filled with the corresponding dye doped polymeric material by a soft lithography approach. The filtering capacity as a function of dye concentration and filter width was studied and revealed a linear dependence with both parameters, as expected according to the Beer-Lambert law. Zero passband transmittance values and relatively sharp stopband regions were achieved with all the filters, also showing rejection levels between −6 dB and −55 dB. Finally, such filters were monolithically integrated into a disposable fluorescence-based photonic lab-on-a-chip (PhLoC) approach. Calibration curves carried out with a model fluorophore target analyte showed an over two-fold increase in sensitivity and a thirty-fold decrease of the limit of detection (LOD) compared with the values recorded using the same PhLoC system but without the polymeric filter structure. The results presented herein clearly indicate the feasibility of these xerogel-based absorbance filtering structures for being applied as low-cost optical components that can be easily incorporated into disposable fluorescence-based photonic lab on a chip systems

McCLEC, a robust and stable enzymatic based microreactor platform

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

Critical Study on the Tube-to-Chip Luer Slip Connectors.

Luer slip is one of the gold standards for chip-to-world interface in microfluidics. They have outstanding mechanical and operational robustness in a broad range of applications using water and solvent-based liquids. Still, their main drawbacks are related to their size: they have relatively large dead volumes and require a significant footprint to assure a leak-free performance. Such aspects make their integration in systems with high microchannel density challenging. To date, there has been no geometrical optimization of the Luer slips to provide a solution to the mentioned drawbacks. This work aims to provide the rules toward downscaling the Luer slips. To this effect, seven variations of the Luer slip male connectors and five variations of Luer slip female connectors have been designed and manufactured focusing on the reduction of the size of connectors and minimization of the dead volumes. In all cases, female connectors have been developed to pair with the corresponding male connector. Characterization has been performed with a tailor-made test bench in which the closure force between male and female connectors has been varied between 7.9 and 55 N. For each applied closure force, the test bench allows liquid pressures to be tested between 0.5 and 2.0 bar. Finally, the analysis of a useful life determines the number of cycles that the connectors can withstand before leakage.The authors are grateful for the financial support from the Basque Country Government within the frame of the project BIKAINTEK 2018 (48-AF-W2-2018-00006)

Characterization of Ferrofluid-Based Stimuli-Responsive Elastomers

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 (<0.3 T) is achieved. The herein presented M-SRE characterization can be used for a large number of disciplines where magnetic actuation can be combined with optical detection, mechanical elements, and biological sample

Application of an E-Tongue to the Analysis of Monovarietal and Blends of White Wines

This work presents a multiparametric system capable of characterizing and classifying white wines according to the grape variety and geographical origin. Besides, it quantifies specific parameters of interest for quality control in wine. The system, known as a hybrid electronic tongue, consists of an array of electrochemical microsensors-six ISFET based sensors, a conductivity sensor, a redox potential sensor and two amperometric electrodes, a gold microelectrode and a microelectrode for sensing electrochemical oxygen demand-and a miniaturized optofluidic system. The test sample set comprised eighteen Catalan monovarietal white wines from four different grape varieties, two Croatian monovarietal white wines and seven bi- and trivarietal mixtures prepared from the Catalan varieties. Different chemometric tools were used to characterize (i.e., Principal Component Analysis), classify (i.e., Soft Independent Modeling Class Analogy) and quantify (i.e., Partial-Least Squares) some parameters of interest. The results demonstrate the usefulness of the multisensor system for analysis of wine