Reusable Ionogel-based Photo-actuators in a Lab-on-a-disc

This paper describes the design, fabrication and performance of a reusable ionogel-based photo-actuator, in-situ photopolymerised into a lab-on-a-disc microfluidic device, for flow control. The ionogel provides an effective barrier to liquids during storage of reagents and spinning of the disc. A simple LED (white light) triggers actuation of the ionogel for selective and precise channel opening at a desired location and time. The mechanism of actuation is reversible, and regeneration of the actuator is possible with an acid chloride solution. In order to achieve regeneration, the Lab-on-a-Disc device was designed with a microchannel connected perpendicularly to the bottom of the ionogel actuator (regeneration channel). This configuration allows the acid solution to reach the actuator, independently from the main channel, which initiates ionogel swelling and main channel closure, and thereby enables reusability of the whole device.Economía y Competitividad), Spain. This project has receivedfunding from the European Union Seventh Framework Programme(FP7) for Research, Technological Development and Demonstrationunder grant agreement no. 604241. JS and FBL acknowledge fund-ing support from Gobierno de Espa˜na, Ministerio de Economía yCompetitividad, with Grant No. BIO2016-80417-P and personallyacknowledge to Marian M. De Pancorbo for letting them to use herlaboratory facilities at UPV/EHU. A.T., L.F., and D.D. are grateful forfinancial support from the Marie Curie Innovative Training Net-work OrgBIO (Marie Curie ITN, GA607896) and Science FoundationIreland (SFI) under the Insight Centre for Data Analytics initiative,Grant Number SFI/12/RC/2289

Versatile continuous pH monitoring barcode system based in ionogels

The online monitoring of pH level in different environments like bio-engineering [1] and chemistry [2] is vital for the control and well behaviour of the whole industrial process. Still exist the demand of miniaturised, versatile and autonomous systems which do not require of sensor calibration, replacement and manual attention over a long operational interval. In this abstract we present an innovative miniaturisable system for continuously measurement of pH solutions and vapours streams during chemical or biological processes. It consists on a simple barcode sensor with several pH dyes doped in an ionogel matrix. This ionogel is a hybrid material fabricated from an hydrogel polymer (N-isopropylacrylamide and N,N-methylene-bis(acrylamide) ratio 100:5) and an ionic liquid (Trihexyltetradecylphosphonium dicyanoamide). The barcode sensor consists of nineteen independent micro-wells (120 mm by 50 m) fabricated in poly(methyl methacrylate) and pressure-sensitive adhesive in three layers using a CO2 ablation laser. Different optically responsive molecular recognition ligands (pH-dyes) were incorporated in the ionogel matrix during monomers photo-polymerisation within each of the micro-wells generating a pH-sensor array for specific sensing applications like colorimetric, environmental or chemical sensing, Figure 1. It was observed that no leaching of pH dyes occurred during experiments and that the ionogel material was impressively robust under harsh conditions (pH:1 to pH: 14). The result is a sensing barcode which is able to generate a characteristic fingerprint-type colour of response within a single “snapshot” for different pH solutions and vapours. Moreover the pH response can be monitoring continuously and the barcode is reusable at least fifty times without sensitivity withdrawing

Novel multifunctional materials based on ionic liquids: on demand micro-valve actuation for lab-on-a-chip applications

We present the fabrication, characterization and performance as a micro-valve of four novel materials, ionogels, consisting in a polymeric structure with benzospiro-pyran units and phosphonium based ionic liquids. Each inonogel is photopolymerised in the channels of a poly(methyl methacrylate) microfluidic device generating four different micro-valves. The micro-valves are actuated by simply applying local white light irradiation and each of the micro-valves opens specifically at one particular time. Therefore, flows can be independently controlled by one single light source while the synthesis of ionogels with different ionic liquids enables distinct valve ac-tuation. Moreover, the microfluidic device can be reusable many times

Graphene-doped photo-patternable ionogels: tuning of conductivity and mechanical stability of 3D microstructures

This work reports for the first time the development of enhanced conductivity, graphene- doped photo-patternable hybrid organic-inorganic ionogels and the effect of the subsequent materials condensation on the conductivity and mechanical stability of three- dimensional microstructures fabricated by multi-photon polymerisation (MPP). Ionogels were based on photocurable silicon/zirconium hybrid sol-gel materials and phosphonium (trihexyltetradecylphosphonium dicyanamide [P6,6,6,14][DCA] ionic liquid (IL). To optimise the dispersion of graphene within the ionogel matrices, aqueous solutions of graphene were prepared, as opposed to the conventional graphene powder approach, and employed as catalysts of hydrolysis and condensation reactions occurring in the sol-gel process. Ionogels were prepared via a two step process by varying the hydrolysis degree from 25 to 50%, IL content between 0-50 w/w%, and the inorganic modifier (zirconate complex) concentration from 30 to 60 mol.% against the photocurable ormosil and they were characterised via Raman, Electrochemical Impedance Spectroscopy and Transmission Electron Microscopy. MPP was performed on the hybrid ionogels, resulting in three- dimensional microstructures that were characterised using scanning electron microscopy. It is clearly demonstrated that the molecular formulation of the ionogels, including the concentration of graphene and the zirconate network modifier, play a critical role in the conductivity of the ionogels and influence the resulting mechanical stability of the fabricated three-dimensional microstructures. This work aims to establish for the first time the relationship between the molecular design and condensation of materials in the physico-chemistry and dynamic of ionogels

Schizophrenic molecules and materials with multiple personalities - how materials science could revolutionise how we do chemical sensing

Molecular photoswitches like spiropyrans derivatives offer exciting possibilities for the development of analytical platforms incorporating photo-responsive materials for functions such as light-activated guest uptake and release and optical reporting on status (passive form, free active form, guest bound to active form). In particular, these switchable materials hold tremendous promise for microflow-systems, in view of the fact that their behaviour can be controlled and interrogated remotely using light from LEDs, without the need for direct physical contact. We demonstrate the immobilisation of these materials on microbeads which can be incorporated into a microflow system to facilitate photoswitchable guest uptake and release. We also introduce novel hybrid materials based on spiropyrans derivatives grafted onto a polymer backbone which, in the presence of an ionic liquid, produces a gel-like material capable of significant photoactuation behaviour. We demonstrate how this material can be incorporated into microfluidic platforms to produce valve-like structures capable of controlling liquid movement using light

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

Real-time sweat pH monitoring based on a wearable chemical barcode micro-fluidic platform incorporating ionic liquids

This work presents the fabrication, characterisation and the performance of a wearable, robust, flexible and disposable chemical barcode device based on a micro-fluidic platform that incorporates ionic liquid polymer gels (ionogels). The device has been applied to the monitoring of the pH of sweat in real time during an exercise period. The device is an ideal wearable sensor for measuring the pH of sweat since it does not contents any electronic part for fluidic handle or pH detection and because it can be directly incorporated into clothing, head- or wristbands, which are in continuous contact with the skin. In addition, due to the micro-fluidic structure, fresh sweat is continuously passing through the sensing area providing the capability to perform continuous real time analysis. The approach presented here ensures immediate feedback regarding sweat composition. Sweat analysis is attractive for monitoring purposes as it can provide physiological information directly relevant to the health and performance of the wearer without the need for an invasive sampling approac

Beads, boats and switches: making things happen with molecular photoswitches

In this paper we present recent results obtained with a stimulus-responsive materials based on the photo-switchable behaviour exhibited by spiro-cyclic derivatives. Our results suggest that these highly novel materials offer unique capabilities hitherto inaccessible using conventional materials. In particular, we will focus on photocontrolled guest binding and release, inherent signalling of status, photo-actuation and solvent driven motion of small structures as examples of the fascinating behaviour of these exceptional materials

Micro-bioreactors controlled with photonic ionogel actuators

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 micro-valve with appropriate performance, since they are essential tools for the control and manipulation of flows in micro-channels.[1] Ionogels with incorporated spiropyran can be used as valves by photopolymerizing the gels in certain shapes. 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