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

Development of fully functional microfluidic based platforms for rapid on-site water quality analysis

Environmental monitoring has grown substantially in recent years in response to increasing concerns over the contamination of natural, industrial, and urban areas with potentially harmful chemical agents. Traditional monitoring of water contamination is based upon manual in-situ ‘grab’ sampling followed by laboratory testing. Advantages of this strategy include high precision and accuracy of the measurements, however because of the expense involved in maintaining these facilities there are inherent restrictions in terms of spatial and temporal sampling. In contrast, in-situ measurements generated with portable instruments present a much more scalable model, enabling denser monitoring. The challenge is to develop inexpensive and reliable devices that can be used in-situ, with the capability to make the resulting data available remotely via web-databases, so that water quality can be monitored independently of location. Miniaturisation of analytical devices through the advent of microfluidics has brought wide opportunities for water analysis applications. The vision is to miniaturise processes typically performed in a central clinical lab into small, simple to use devices – so called lab-on-a-chip (LOC) systems. Microfludic systems are especially promising for point-of-care applications due to the low cost, low reagent consumption and portability, and the focus of this thesis is to provide novel microfluidic platforms towards an integrated system for water quality analysis. A main outcome of my work was the development and validation of innovative integrated systems that were designed and developed for quantitative analysis of turbidity and qualitative analysis of pH and nitrites in water samples. The microfluidic manifolds were designed and fabricated using rapid prototyping techniques such as soft lithography and CO2 laser cutting. For fluid propulsion, various methods were employed: back pressure, capillary forces (typical microfluidic manifolds) and centrifugal force (centrifugal discs). In the latter, fluid propulsion was performed by the forces induced due to the rotation of the disc, thus eliminating the need for external pumps since only a spindle motor is necessary to rotate the disc. Centrifugal discs systems are especially promising for point-of-care applications, and as a final output the fully integrated portable wireless system for in-situ colorimetric analysis was demonstrated. In all systems a low cost but highly sensitive paired emitter- detector diode (PEDD) method was employed to perform colorimetric measurements. Moreover, due to the wireless communication, acquisition parameters were controlled remotely and the results were downloaded from distant locations and displayed in real time. The autonomous capabilities of the system, combined with the portability and wireless communication, provide the basis for a flexible new approach for on-site water monitoring. In addition, their small size and low weight offered the advantage of portability. The suitability of the low-power analysers for the precise and continuous measurement of samples was established, since the analysers exhibited low limits of detection. Freshwater samples were analysed and the results were compared to those generated with a conventional bench-top instruments showing good agreement. Additionally, stimuli-responsive materials based on N- isopropylacrylamide (NIPAAm) phosphonium ionogels were characterised and incorporated within microfluidic platforms as sensors and actuators. The phase change NIPAAm ionogel functionalised with spirobenzopyran chromophores was characterised and applied for fluid control within microfluidic manifold. Microvalve actuation was performed by the localised white light irradiation, thus allowing for non-contact manipulation of the liquids inside of the microchannels. This is the first time that photoresponsive ionogel microvalves were incorporated within portable, wireless integrated microfluidic analytical platform. Moreover, phosphonium based ionogels incorporating pH sensing dye were used for pH sensing of water samples. This work presents the core technology for an integrated microfluidic platforms for fundamental research as well as for point-of-use applications.# The key outputs of my work are: 1.Design, fabrication and characterisation of novel microfluidic manifolds. 2.Stimuli-responsive ionogel materials were successfully employed within microfluidic devices for sensing and actuating applications. 3.Portable, wireless, integrated systems based on microfluidic platforms were developed and their successful application for analysis of pH, turbidity and nitrites was demonstrated

Materials science: the key to revolutionary breakthroughs in micro-fluidic devices

In microfluidics, valves and pumps that can combine specifications like precise flow control, provision of precise reagent quantities, minimal sample carryover, and low-cost manufacture, while also being inherently compatible with microfluidic system fabrication, are beyond the current state of the art. Actuators in micro-fluidics made using stimuli-responsive materials are therefore of great interest as functional materials since actuation can be controlled without physical contact, offering improvements in versatility during manifold fabrication, and control of the actuation mechanism. Herein we review the potential use of novel approaches to valving and pumping based on stimuli-responsive polymers for controlling fluid movement within micro-fluidic channels. This has the potential to dramatically simplify the design, fabrication and cost of microfluidic systems. In particular, stimuli-responsive gels incorporating ionic liquids (ILs) produce so-called ‘ionogels’ that have 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, the characteristics of the ionogels can be tuned by simply changing the IL and so the actuation behaviour of micro-valves made from these novel materials can be more closely controlled

Integrating stimulus responsive materials and microfluidics – The key to next generation chemical sensors

New generations of chemical sensors require both innovative (evolutionary) engineering concepts and (revolutionary) breakthroughs in fundamental materials chemistry, such as the emergence of new types of stimuli responsive materials. Intensive research in those fields in recent years have brought interesting new concepts and designs for microfluidic flow control and sample handling that integrate high quality engineering with new materials. In this paper we review recent developments in this fascinating area of science, with particular emphasis on photoswitchable soft actuators and their incorporation into fluidic devices that are increasingly biomimetic in nature

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

Next generation autonomous analytical platforms for remote environmental monitoring: Generation of fully functioning biomimetic analytical platforms for water quality

The Advanced Technologies for Water Resource Management (ATWARM) scientific programme involves 16 Marie Curie Fellows working on the performance and/or sustainability of water and wastewater treatment plants as well as on the development of novel advance technologies for analysis and monitoring of water quality. Increased demand for improved water management is a driving need for water quality monitoring systems with greatly improved price/performance characteristics. For a successful water treatment, rapid and reliable information on the sampling site are crucial. Furthermore, this information needs to be available in real time for any course of action to be implemented efficiently. In our laboratories, we believe that “Wireless Sensor Networks” is the key to obtain such monitoring capabilities. My project is focused on the development of novel chemo/bio-sensors based on functional materials integrated in micro-fluidic manifolds for environmental applications. These platforms should content a reliable sensing capability with low power wireless communication and remote control of the instrument status. In addition, the activity of the device, such as sampling, analysis, communication and power need to be integrated in the micro-fluidic platform. Special attention is given to the generation and control of liquid flow within the micro-channels using new materials that exhibit biomimetic behaviour [1]. I am using, in particular, stimuli-responsive gels that are of great interest as functional materials within micro-fluidic systems, since their actuation can be controlled remotely without physical contact (light or magnet), allowing for fast response times and versatility of fabrication. Up to now, I developed an optical sensor based on a wireless paired emitter detector diode device (PEDD) for colorimetric analysis of water quality integrated in a portable Lab-on-a-disc micro-fluidic platform. Its low power consumption, increasing spectral range coverage, excellent intensity and efficiency, small size, ease of fabrication and simplicity make PEDD a perfect optical detector for colorimetric assays [2]. In addition, the device is ideal for integration within micro-fluidic platforms based on the centrifugal Lab-on-a-Disc concept, in which detector integration is complicated due to the high rotation speeds typically used in this approach [3]. [1] F. Benito-Lopez, R. Byrne, A. M.Răduţă, N. E. Vrana, G. McGuinness, D. Diamond, Lab on a Chip, 10, 2010, pp. 195-201. [2] M. O’Toole, R. Shepherd, G. G. Wallace, D. Diamond, Anal. Chim. Acta, 652, 2009, pp. 308-314. [3] R. Gorkin, J. Park, J. Siegrist, M. Amasia, B. Lee, J. Park, J. Kim, H. Kim, M. Madou, Y. Cho, Lab Chip, 10, 2010, pp.1758-1773

Microfluidic system with a wireless paired emitter detector diode device as optical sensor for water quality monitoring

Increased demand for improved water management is driving need for water quality monitoring systems with greatly improved price/performance characteristics. This work presents the first use of wireless paired emitter detector diode device (PEDD) as an optical sensor for colorimetric analysis of water quality in a Lab-on-a-disc device format. The instrument detector involves using two light emitting diodes (LEDs), which act as both a light source and photo detector (Fig. 1a.). In comparison to the more commonly used method of coupling a LED to a photodiode, this technique achieves excellent sensitivity and signal-to-noise ratio, with very low cost fabrication and electronics. Furthermore, its low power consumption, increasing spectral range coverage, excellent intensity and efficiency, small size, ease of fabrication and simplicity of the PEDD make it a perfect optical detector for colorimetric assays [1]. In addition, the device is ideally suited for integration with microfluidic platforms based on the centrifugal Lab-on-a-Disc concept, in which detector difficulties can arise due to the high rotation speed typically used in this approach [2]. In this work the calibration of the system using bromocresol purple (BCP) is demonstrated. Concentration ranges were examined in parallel using UV-Vis spectroscopy as control, and the PEDD system. Similar limits of detection (ca. 2.5x10-4 M, Fig.1b.) were obtained in both cases. However, the PEDD system presented a linear trend over a wider range of concentrations. The experiments demonstrate the potential for the wireless PEDD to be a versatile and cheap alternative optical detector system for water quality monitoring in microfluidic applications