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

Wearable Electrochemical Sensors for Monitoring Performance Athletes

Nowadays, wearable sensors such as heart rate monitors and pedometers are in common use. The use of wearable systems such as these for personalized exercise regimes for health and rehabilitation is particularly interesting. In particular, the true potential of wearable chemical sensors, which for the real-time ambulatory monitoring of bodily fluids such as tears, sweat, urine and blood has not been realized. Here we present a brief introduction into the fields of ionogels and organic electrochemical transistors, and in particular, the concept of an OECT transistor incorporated into a sticking-plaster, along with a printable “ionogel” to provide a wearable biosensor platform

Stimuli Responsive Ionogels for Sensing Applications - An Overview.

This overview aims to summarise the exiting potential of “Ionogels” as a platform to develop stimuli responsive materials. Ionogels are a class of materials that contain an Ionic Liquid (IL) confined within a polymer matrix. Recently defined as “a solid interconnected network spreading throughout a liquid phase”, the ionogel therefore combines the properties of both its solid and liquid components. ILs are low melting salts that exist as liquids composed entirely of cations and anions at or around 100 0C. Important physical properties of these liquids such as viscosity, density, melting point and conductivity can be altered to suit a purpose by choice of the cation / anion. Here we provide an overview to highlight the literature thus far detailing the encapsulation of IL and responsive materials within these polymeric structures. Exciting applications in the areas of optical and electrochemical sensing, solid state electrolytes and actuating materials shall be discussed. Keywords: Stimuli Responsive Polymers; Ionogels; Ionic Liquids; Hybrid Materials; Molecular Photoswitches; Solid State Electrolytes

Wearable chemo/bio-sensors for sweat sensing in sports applications: combining micro-fluidics and novel materials

In the last decade, we have witnessed an exponential growth in the area of clinical diagnostic but surprisingly little has been done on the development of wearable chemo/bio-sensors in the field of sports science. In particular, the use of wearable wireless sensors capable of analysing sweat during physical exercise can provide access to new information sources that can be used to optimise and manage athletes’ performance. Lab-on-a-Chip technology provides a fascinating opportunity for the development of such wearable sensors. In this thesis two different colorimetric wearable microfluidic devices for real- time pH sensing were developed and used during athlete training activity. In one case a textile-based microfluidic platform employing cotton capillarity to drive sweat toward the pH sensitive area is presented that avoids the use of bulky fluid handling apparatus, i.e. pumps. The second case presents a wearable micro-fluidic device based on the use of pH responsive ionogels to obtain real-time sweat pH measurements through photo analysis of their colour variation. The thesis also presents the first example of sweat lactate sensing using an organic electrochemical transistor incorporating an ionogel as solid-state electrolyte. In this chapter, optimization of the lactate oxidase stability when dissolved in number of hydrated ionic liquids is investigated. Finally, a new fabrication protocol for paper-based microfluidic technology is presented, which may have important implications for future applications such as low-cost diagnostics and chemical sensing technologies

Multi-constrained mechanism for intra-body area network quality-of-service aware routing in wireless body sensor networks

Wireless Body Sensor Networks (WBSNs) have witnessed tremendous research interests in a wide range of medical and non-medical fields. In the delaysensitive application scenarios, the critical data packets are highly delay-sensitive which require some Quality-of-Service (QoS) to reach the intended destinations. The categorization of data packets and selection of poor links may have detrimental impacts on overall performance of the network. In WBSN, various biosensors transmit the sensed data towards a destination for further analysis. However, for an efficient data transmission, it is very important to transmit the sensed data towards the base station by satisfying the QoS multi-constrained requirements of the healthcare applications in terms of least end-to-end delay and high reliability, throughput, Packet Delivery Ratio (PDR), and route stability performance. Most of the existing WBSN routing schemes consider traffic prioritization to solve the slot allocation problem. Consequently, the data transmission may face high delays, packet losses, retransmissions, lack of bandwidth, and insufficient buffer space. On the other hand, an end-to-end route is discovered either using a single or composite metric for the data transmission. Thus, it affects the delivery of the critical data through a less privileged manner. Furthermore, a conventional route repair method is considered for the reporting of broken links which does not include surrounding interference. As such, this thesis presents the Multi-constrained mechanism for Intra- Body Area Network QoS aware routing (MIQoS) with Low Latency Traffic Prioritization (LLTP), Optimized Route Discovery (ORD), and Interference Adaptive Route Repair (IARR) schemes for the healthcare application of WBSN with an objective of improving performance in terms of end-to-end delay, route stability, and throughput. The proposed LLTP scheme considers various priority queues with an optimized scheduling mechanism that dynamically identifies and prioritizes the critical data traffic in an emergency situation to enhance the critical data transmission. Consequently, this will avoid unnecessary queuing delay. The ORD scheme incorporates an improved and multi-facet routing metric, Link Quality Metric (LQM) optimizes the route selection by considering link delay, link delivery ratio, and link interference ratio. The IARR scheme identifies the links experiencing transmission issues due to channel interference and makes a coherent decision about route breakage based on the long term link performance to avoid unnecessary route discovery notifications. The simulation results verified the improved performance in terms of reducing the end-to-end delay by 29%, increasing the throughput by 22% and route stability by 26% as compared to the existing routing schemes such as TTRP, PA-AODV and standard AODV. In conclusion, MIQoS proves to be a suitable routing mechanism for a wide range of interesting applications of WBSN that require fast, reliable and multi-hop communication in heavily loaded network traffic scenarios

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

Ionic Liquids and GUMBOS for Biomedical and Sensing Applications

This dissertation is a synopsis of advancements in the field of ionic liquids and a group of uniform materials based on organic salts (GUMBOS) in biomedical applications, especially with regard to cancer research. The toxicity of chemotherapeutic agents to normal tissues and drug resistance are a major concern in cancer treatment. In this dissertation, GUMBOS and nanoGUMBOS as well as ionic liquids and nanodroplets are explored as possible chemotherapeutic agents with minimal toxicity to normal cells. In the first part of my dissertation, exploitation of ionic liquid chemistry to modulate toxicity of rhodamine 6G is reported. Rhodamine 6G-based GUMBOS with varying counter-anions that are stable under physiological conditions, display excellent fluorescence photostability, and more importantly have tunable chemotherapeutic properties were synthesized. In vitro studies indicate that the hydrophobic compounds of this series allow production of nanoGUMBOS which are non-toxic to normal cells and toxic to cancer cells. Furthermore, the anions, in combination with cations such as sodium, were observed to be non-toxic to both normal and cancer cells. Thus, we demonstrate that both the cation and anion play an extremely important and cooperative role in the anticancer properties of these compounds. In the second part, the concept of multifunctional nanoparticles is introduced and exploited for theranostic applications. Nanoparticles possessing multiple properties such as luminescence, magnetism, and cancer targeting, were synthesized and explored for use in cancer therapy. In this regard, it is demonstrated that these nanoparticles can not only be used in diagnostics and as drug delivery agents, but also as active pharmacophores. Finally, the third part of this dissertation is a report of novel ionic liquid based pH sensitive colorimetric nanosensors based on phosphonium and fluorescein. The pH dependent size changes in the nanodroplets are demonstrated and potential applications in detecting acidic environment and anticancer activity are investigated