One of the most important and recent trends in biosensor technology is continuous monitoring of metabolite using wearable biosensors. In parallel to the advancement in wearable electronics, wearable sensor-based systems for healthcare applications have attracted a significant interest both in industrial and academic research. Wearable biosensor applications aim to change centralised hospital-based care system to home-based personal medicine and reduce healthcare cost and time for diagnosis. Electrochemical transducers offer many advantages for wearable sensors for physiological monitoring, and can be easily integrated onto textile materials or directly on the skin.
These efforts have resulted in successful wearable physical sensors, such as temperature and pressure, for monitoring biophysical signals including heart rate, respiration rate, skin temperature, and brain activity. However, these physical sensors require external complementary measures to diagnose diseases precisely. On the other hand, wearable biosensors are able to give direct information about specific disease biomarkers and metabolite changes in bodily fluids. Our research focus is to develop wearable biosensing devices for specific disease biomarkers for continuous health monitoring.
Carbon-based Energy Devices
A great deal of interest has been paid to the application of carbon-based nano- and microstructured materials as electrodes due to their relatively low-cost production, abundance, large surface area, high chemical stability, wide operating temperature range, and ease of processing including many more excellent features. The nanostructured carbon materials usually offer various micro-textures due to their varying degrees of graphitisation, a rich variety in terms of dimensionality as well as morphologies, extremely large surface accessibility and high electrical conductivity, etc. The possibilities of activating them by chemical and physical methods allow these materials to be produced with a further higher surface area and controlled distribution of pores from nanoscale up to macroscopic dimensions, which actually play the most crucial role towards the construction of the efficient electrode/electrolyte interfaces for capacitive processes in energy storage applications. Development of new carbon materials with extremely high surface areas could exhibit significant potential in this context and motivated by this in recent work, we report for the first time the utilization of ultralight and extremely porous nano-microtubular Aerographite tetrapodal network as a functional interface to probe the electrochemical properties for capacitive energy storage. A simple and robust electrode fabrication strategy based on surface functionalized Aerographite with optimum porosity leads to the significantly high specific capacitance (640 F/g) with high energy (14.2 Wh/kg) and power densities (9.67×103 W/kg) have been developed.
Organic Electrochemical Transistors
Organic electrochemical transistors (OECTs) based on conducting polymers have undergone significant progress in recent years and are poised to become the device of choice for fabricating biosensors using semiconducting polymers. Due to their ability to support both efficient ionic and electronic transport, OECTs are able to transduce biological signals, which typically involve ion flux, into electrical signals with high gain. We are currently working on fundamental models to describe the performance of biosensors in which an OECT is integrated with an ion-blocking membrane (e.g., enzyme layers, ion-selective membranes, and other polymeric compositions). Some of our developments have provided guidelines on how to optimize biosensors in which OECTs transduce changes in the impedance of different types of membranes.
Interfacing 2D Materials for Bioelectronics
The integration of nanomaterials as a bridge between the biological and electronic worlds has revolutionised understanding of how to generate functional bioelectronic devices and has opened up new horizons for the future of bioelectronics. The use of nanomaterials as a versatile interface in the area of bioelectronics offers many practical solutions and has recently emerged as a highly promising route to overcome technical challenges in the control and regulation of communication between biological and electronics systems. Hence, the interfacing of nanomaterials is yielding a broad platform of functional units for bioelectronic interfaces and is beginning to have a significant impact on many fields within the life sciences.
In parallel with advancements in the successful combination of the fields of biology and electronics using nanotechnology in a conventional way, a new branch of switchable bioelectronics, based on signal-responsive materials and related interfaces, has begun to emerge. Switchable bioelectronics consists of functional interfaces equipped with molecular cues that are able to mimic and adapt to their natural environment and change physical and chemical properties on demand. These switchable interfaces are essential tools to develop a range of technologies to understand the function and properties of biological systems such as bio-catalysis, control of ion transfer and molecular recognition used in bioelectronics systems. For further reading, click here.
Even though designing of stimuli-responsive interfaces helps to control and regulate (bio)molecular interactions and eventually signal outputs, when the system involves many different inputs including different molecules or different reaction conditions, the overall system requires programming of each individual input and condition by segregating and/or putting all the parameters in order to maximise performance. However, current approaches are insufficient to satisfy these requirements. Recent studies, especially in the area of biotechnology, show that there is an obvious need to develop such systems with an ability to rearrange, control and order their functions. The programmable approach provides many opportunities to biotechnologists who specialise in artificial biological systems, such as mimicking living cells. It is well known that in nature, living reactions are naturally programmed, and attempts to construct artificial biological systems have generally resulted in vastly inferior performance. Because of this, in addition to advancement in the area of biotechnology to reach the target of the artificial biological system, the idea of biocomputing and/or programming is necessary.
DNA-sensors based Surface Plasmon Resonance
For this project, we have mainly worked on DNA hybridization on the gold surface by using a microcontact printing method and characterization of the surface with imagining surface plasmon resonance. In this work, we perform micro-contact printing of single-stranded DNA molecules on the gold surface and tried to sense hybridization by flowing complementary and non-complementary DNA solutions. Finally, we characterized the surface of gold based on the change in optical properties using imagining surface plasmon resonance (i-SPR) method.
Nanosized crystalline particles are of central importance to design novel optical composite materials where particulate pigments are added to a transparent matrix to develop optical features for instance absorption/emission at a desired wavelength of the optical spectrum, waveguiding the electromagnetic radiation, optical limiters, high/low refractive indices to control focusing power of the materials. However, there is often a trade-off between the development of one or more novel optical features and the optical transparency. Due to the sharp refractive index (RI) at the interface of particles and polymers, transparency suffers from strong light scattering and absorption and eventually, transparency is deteriorated. The reduction of the size of the scatterers (individual particles and particle domains) has been the commonly used approach to suppress optical scattering. When the size of scatters is smaller than one-tenth of the wavelength of electromagnetic radiation, the radiation propagates the materials without scattering according to Rayleigh scattering. In the visible region, the size of the particles should be in the range of 20-40 nm to maintain transparency. However, it is hard to keep these nanometer-sized particles isolated against the aggregation. Upon aggregation, the size of particle domains gets larger and strong scattering is unavoidable. In this study, we developed the index-matching technique in order to provide transparency of polymer nanocomposites at high-particle loading levels.