Currently we are working to extend our research on chemical sensor technologies to more precisely refine sensing mechanisms and sensing devices based on integrated transduction principles such as EQCM, Magnetoelectronic, and optoelectronic devices. Particular challenges in this field is the sensing reliability in the real world conditions in the presence of ubiquitous gas species and humidity in case of gaseous detection and interfering molecules in case of biological fluids which will be dealt using orthogonality of transduction mechanisms and transduction materials. The final goal is the prototype development and device fabrications.

The following are specific examples of the projects we are pursuing in order to achieve the above targets, however, many more innovations can be inducted into the plans based on the outcomes of the research and from the lessons learned.

1: Inverted Mesa Electrochemical Quartz Crystal Microbalance (IM-EQCM) Sensors as Orthogonal Detection Platforms

In quest of accuracy and reliability for chemical sensors comparable to that of biosensors, we want to pursue the hyphenation of two highly successful probes in the sensing arena i.e., electrochemical (E) and QCM sensors, so as to obtain orthogonal signals that enhance accuracy and reliability through internal validation. The prerequisites for this design include efficient immobilization of sensing materials, no interference and coupling between adjacent sensors, non-interfering instrumental setups, and correct interpretation of combined data. These prerequisites will be accomplished in the course of this project firstly by fabrication and testing of innovative inverted mesa EQCM structures and finalizing the mesa and electrode geometries. Then the actual methodologies of data extraction will be established by combining nano-gravimetry to amperometric, voltammetric, and impedance analysis in various real life conditions. Various electrochemical control functions and the extension to impedance spectroscopy will extend the breadth for the accurate sensing systems for broad range of analytes including those that are not redox active. The final protocol will be benchmarked against individual electrochemical and QCM sensing as well as GC-MS to assess the real benefits and the probability to succeed in the future product development. The proposed sensor technology will not only make several significant contributions to the country’s capacity for work place safety and public security, but can also be extended to various biosensor applications for point of care diagnostics.

2: Optical QCM Sensor Technology for Endothelial Cell Activation and for Studying Cell-Cell Interactions

In this project, a monolithic O-QCM biosensor array will be fabricated and applied for various bioanalytical applications and will be demonstrated to provide more detailed and accurate information to reveal the mechanisms of complicated bio-interactions. For instance, O-QCM biosensor technology will be used to efficiently and rapidly differentiate, identify, and quantify activated ECs from normal ECs. Due to the high sensitivity of and complementary information provided by O-QCM biosensors, we expect the change of cell properties between normal ECs and activated ECs due to altered morphology, CAM expressions, and cell secretion (cytokines, chemokines, etc.) can be measured at an earlier stage than those using traditional in vitro tests. Following the EC activation, further interactions with various type of cancer cells can be studied with the same accuracy and reliability with the proposed designs. Furthermore, the same technology can be applied to understand various cellular interaction like antibody-antigen and carbohydrate-protein interactions and will form the basis of miniaturized and point-of-care bioanalytical tools for early and home diagnosis.

3: Nanomaterials based printable solid state electrolytes for multimodal detection of peroxide explosives

In this project, we aim to synthesize novel functional enzymatic nano-mimics that can serve both as transduction and sensing scaffolds for EQCM sensing and employ them to develop 3-D printable composites with ionic liquids (ILs) that can be casted onto various 2-D electrode designs of EQCM on single plane of a quartz wafer. Nanoscale films of this material are thus aimed to be utilized both as electrolyte and sensing element with the precision of few nanometers in deposition and without the problems of electrochemical disconnectivity for such films. Multiple data lines generated for the interaction events will include multiharmonic (n=1,3,5,…) frequencies from QCM part which are orthogonal to each other as well, QCM motional resistance, electrochemical parameters, and impedance data (useful in case of non-electroactive targets). In this manner, three way selectivity can be achieved: first, by the selective interaction of the functionalized nanomaterials with target; second, by the inherent selectivity for ionic liquid based responses; and third, by the orthogonal response mechanisms in the form of EQCM which will enhance the reliability and viability of detection for such high value targets and will serve as the first step in the development of wearable and versatile gadgets for the same purposes.

4: Optoelectrochemical Sensors based on Nanomaterial Mimics of Enzymes for Reliable Detection of Explosives

Recent developments in nanotechnology, especially in synthesizing nano-mimics of the enzymes provides an intriguing opportunity to design a sensor system that can overcome the stability and immobilization issues with much enhanced sensitivity, selectivity, dynamic range, and cost affectivity. The design and implementation of such a sensor for the detection will be the focus of the activities proposed in this project.

For this purpose, Palladium-Iridium (Pd-Ir) transparent electrodes composed of a network of these metals will be developed and immobilized on a variety of transparent substrates. The process of this fabrication will be based on templating ultra-long polymer nanofibres. Thus we will have electrodes materials which can have multiple orthogonal functions: (1) the electrode material is a highly efficient peroxidase mimic with a high catalytic constant ~ 3 orders of magnitude higher than HRP useful both for optical and electrochemical sensing; (2) the Ir surface can be readily modified with functional groups such as COOH, NH₂ via Ir-thiolate bonding allowing easier labeling of biotags for various detection protocols; (3) the porous metal network will be able to enhance the target adsorption leading to higher sensitivity; and (4) the transparency of the electrode will allow integration of optical and electrochemical detection platforms (multi-order sensing) which will enhance the detection range and selectivity by internal validation of the resulting data. Such higher order sensors thus constructed can simultaneously interrogate the same detection problem by multiple response mechanisms. These responses, being orthogonal to each other, increase the data acquisition channels thereby increasing the information content without increasing the number of sensors.