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

Materials science and the sensor revolution

For the past decade, we have been investigating strategies to develop ways to provide chemical sensing platforms capable of long-term deployment in remote locations1-3. This key objective has been driven by the emergence of ubiquitous digital communications and the associated potential for widely deployed wireless sensor networks (WSNs). Understandably, in these early days of WSNs, deployments have been based on very reliable sensors, such as thermistors, accelerometers, flow meters, photodetectors, and digital cameras. Biosensors and chemical sensors (bio/chemo-sensors) are largely missing from this rapidly developing field, despite the obvious value offered by an ability to measure molecular targets at multiple locations in real-time. Interestingly, while this paper is focused on the issues with respect to wide area sensing of the environment, the core challenge is essentially the same for long-term implantable bio/chemo-sensors4, i.e.; how to maintain the integrity of the analytical method at a remote, inaccessible location

Autonomous valves in micro-fluidic manifolds based on versatile photoresponsive ionogels

Versatility in valve actuation within micro-fluidic devices is very desirable since precise flow control, provision of exact reagent amounts, contamination prevention between reagents, autonomy, disposability and low-cost manufacture are factors that cannot be found today for microfluidic valves. Valves made using photo-responsive gels are of great interest as functional materials within micro-fluidic systems since actuation can be controlled by light irradiation, without physical contact, unlike equivalent electroactuated valves. Nevertheless, their poor versatility, slow response times and limited robustness render them currently as scientific curiosities rather than ideally functioning devices.[1] The incorporation of photoresponsive gels with ionic liquids (ILs), ionogels, produces hybrid materials with many advantages over conventional materials. For example, through the tailoring of chemical and physical properties of ILs, robustness, acid/ base character, viscosity and other critical operational characteristics can be finely adjusted. Therefore, we can tune the characteristics of the ionogels by changing the IL and so more closely control the actuation behaviour of micro-valves made from these novel materials. In this paper, we present the preparation and performance of four different ionogels as micro-valves in microfluidic systems. It was found that simply varying the ILs, actuation can be modulated on demand

Photo-responsive ionogels: versatile flow control in micro-fluidic manifolds

This paper presents the synthesis, characterization and micro-valve actuation in a micro-fluidic device of novel polymeric materials based on phosphonium ionic liquids (ILs), ionogels. When photo-responsive gels are co-polymerised within different IL matrixes, high versatility in the ionogels actuation can be achieved when incorporated in a micro-fluidic system as micro-valves

Micro-patterning and actuation of phosphonium-based photo-responsive ionogels for micro-fluidic applications

The concept of “Micro-total-analysis-Systems” or “Lab-on-chip” has emerged over the past 20-years but, despite of the fact their incredible potential to revolutionise analytical science few outputs have reached the market so far[1]. Moreover, important issues like durability, disposability and cost of manufacture slow down the process of the integration of micro-fluidics into commercially relevant analytical products[2]. We believe that the next breakthroughs on micro-fluidic technology will come with the development of unconventional strategies in fundamental material science where ‘switchable’ or ‘stimuli-responsive’ materials, that can be remotely switched between forms with radically different properties, will substitute conventional fluid handling processes in analytical instrumentation[3]. We present the synthesis, surface patterning and characterisation of micro-valve structures and channel constrictors that underpin further movement towards the realization of next generation micro-fluidic components. The micro-structures are fabricated using novel materials (ionogels) based on phosphonium ionic liquids (ILs), and photo-responsive polymer gels with spiropyran moieties. Actuation can be achieved within seconds and easily controlled without the need for any physical contact between the stimulus source (light) and the resulting action, Figure-1. Furthermore, actuation time can be tuned by simply varying the IL-anion, for instance replacing [NTf2]- by [dca]- without changing the micro-fluidic device

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

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

Phosphonium dicyanamide ionogel incorporating bromophenol blue dye as a versatile platform for monitoring pH in solution

Online monitoring of pH levels in different environments such as bio-engineering and chemistry is vital for effective control of many critical industrial processes. The most common chemical parameter monitored is pH, and there is an increasing interest in the fabrication of robust, cheap and versatile pH sensing materials that can be easily integrated within existing industrial technologies. Ideally these materials present low fouling and do not require calibration, thus minimising manual attention over long operational intervals. In this work we present an innovative material (ionogel) that integrates pH-sensing capabilities for continuously measuring pH during chemical or biological processes. The ionogel is a solid, flexible and easily to pattern material generated using tetrabutylphosponium dicyanamide ionic liquid, hydrogel polymer (N-isopropylacrylamide and N,N-methylene-bis(acrylamide)) and a pH sensitive dye (Bromophenol Blue). Figure 1 shows the UV spectra of the ionogel-dye in an acidic and a basic pH environment as well as the pictures of the ionogels. A substantial colour variation is observed as the pH changes that can be monitored visually or optically. We incorporated the photoresponsive dye during photo-polymerisation of the monomer to improve stability, for example, by preventing leaching of the dye from the ionogel into the sample phase. This strategy was not found to inhibit the sensitivity of the optical response

Molecular schizophrenics as sensors and actuators

‘Sensornets’ are large-scale distributed sensing networks comprised of many small sensing devices equipped with memory, processors, and short-range wireless communications capabilities.1 These devices, assembled from building blocks known as ‘Motes’ can gather and share sensor data from multiple locations through in-built wireless communications capabilities. The vision of incorporating chemical and biological sensing dimensions into these platforms is very appealing, and the potential applications in areas critical to society are truly revolutionary.2 For example, the environment; sensors monitoring air and water quality will be able to provide early warning of pollution events arising at industrial plants, landfill sites, reservoirs, and water distribution systems at remote locations. The crucial missing part in this scenario is the gateway through which these worlds will communicate; how can the digital world sense and respond to changes in the real world? Unfortunately, it would appear from the lack of field deployable devices in commercial production that attempts to integrate molecular sensor science into portable devices have failed to bear the fruits promised; this problem is what we call ‘the chemo-/ bio-sensing paradox’.3 In this work, we shall discuss how sensors and sensing systems are likely to develop in the coming years, with a particular focus on the critical importance of new concepts in fundamental materials science to the realisation of these futuristic chemo-/bio-sensing systems. This work focuses on the fundamental challenges, such as the ability to control the characteristics and behaviour of polymers and fluids, and processes occurring at solid-liquid interfaces. We will highlight the key role that stimuli-responsive materials can play in producing new “adaptive” materials capable of exhibiting dramatic changes in properties by external stimuli, such as, photon irradiation.4 In particular, the photochromic processes of spirobenzopyran, figure 1. These materials have the potential to revolutionise the way we design chemical and biological sensing systems

Analysis of water-soluble vitamins in biopharma raw materials by electrophoresis micro-chips with contactless conductivity detection

Detailed information concerning the composition of the raw materials employed in the production of biologics is important for the efficient control and optimization of bioprocesses. The analytical methods used in these applications must be simple and fast as well as be easily transferable from one site to another. In that context, microchip‐based electrophoresis represents a promising tool for application in the analysis of raw materials in biologics. Using electrophoresis micro‐chips, analysis times can be reduced to seconds and high separation efficiencies can be achieved using extremely low volume samples, minimal reagent consumption and waste generation, low cost/disposability, portability and ease of mass‐production [1]. Additionally the use of Capacitively Coupled Contactless Conductivity Detection (C4D) offers a rather simple and yet sensitive method for detection of ionic species. Recently, C4D has gained much popularity as on‐chip detection in electrophoresis micro‐chips [2]. The main reason for this is that there is no physical contact of the detection electrodes with the electrolyte solution. Therefore, the integration of this detection mode within the analytical system is rather simple. Furthermore, the background noise is significantly reduced leading to lower detection limits than the conventional contact conductivity detection. Vitamins are present at very low concentrations in biopharma raw materials and are usually determined using HPLC and CE methods [3]. Electrophoresis micro‐chips are a very good alternative to these techniques due to the shorter analysis time and yet very good resolution, among others. In this paper, we present the application of electrophoresis micro‐chips with C4D detection to the analysis of water‐soluble vitamins in raw materials used for the production of biologics in bioreactors. For that purpose, hybrid PDMS/glass chips were fabricated by using standard photolithographic techniques (Figure 1). The chip structure contains an extremely long channel of 101 mm (50 x 50 μm width x depth). Figure 2 shows the setup used for vitamins detection